Tag: health

old brown tabby
Behavior

Cognitive Dysfunction Syndrome (CTS) in Elderly Cats

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Meredith Hemphill

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Encyclopaedia Felidae now has a Patreon! Go to www.patreon.com/EncyclopaediaFelidae if you want to help support this content!

Old brown tabby cat
Photo by Jonas Jaeken on Unsplash

As our cats get older, they can show a variety of signs of aging. Some, like arthritis and a graying muzzle, you probably expect. But did you know that cats (and dogs) can get dementia, just like humans? Cognitive dysfunction in cats is not uncommon in old age [4]. About 30% of cats 11-14 years old and 50% of cats 15+ have changes in behavior unrelated to another health problem [4-6]. This is called Feline Cognitive Decline or Cognitive Dysfunction Syndrome (CDS) in veterinary terms.

What Does Cognitive Dysfunction Syndrome Look Like?

Sordo and Gunn-Moore use the acronym VISHDAAL to help explain the typical indications of cognitive dysfunction in cats. The letters are in order of how common the symptoms are. [5]

  • V is for Vocalization: excessive meowing or yowling, especially at night [1-5]
  • I is for Interactions: changes in the way your cat interacts with members of the household, such as an increased or decreased interest in petting and attention, irritability, aggression toward people/pets, or decreased responsiveness [1, 3, 5, 6]
  • S is for Sleep-wake cycle: changes in the cat’s sleep-wake cycle, particularly being awake during hours of the night when they used to sleep [1-6]
  • H is for House-soiling: that is, urinating and/or defecating outside the litterbox [1-6]
  • D is for Disorientation: being confused about place or time, e.g. getting lost in familiar locations, becoming somehow stuck in places they should be able to get out of easily, not remembering that they’ve just been fed, staring blankly into space [1-6]
  • A is for Activity levels: either decreased activity, e.g. less grooming, lack of interest in food or play, or increased activity in the form of restlessness [1-6]
  • A is for Anxiety: this can manifest in a variety of ways depending upon the individual cat and may contribute to other symptoms [1-6]
  • L is for Learning and memory: forgetting routines, commands, and familiar people, pets, or places [2-6]

Not every cat will exhibit every symptom, and CTS is a condition that changes and progresses over time [5, 6]. Some of the first signs of CTS may be subtle, and many cat parents mistake them for a normal part of aging that they can’t do anything about [1, 5, 6]. However, if you notice any of these symptoms in your senior cat, you absolutely should tell your veterinarian [1, 3]. The vet can confirm a diagnosis and come up with a treatment plan to make your cat’s last years as peaceful as possible.

Cara’s Story

Cara was one of my childhood cats. She was born under our front porch when I was five or six years old, along with two sisters and a brother. We kept her and her brother, Milo, and they were with us into my college years. Cara was always sort of an odd duck. She wanted attention only rarely, stuck her head in shoes, and stared down into the floor vents for extended periods of time. But when she got to be maybe eight or nine years old, she started getting weirder.

The garage was the cats’ home base, and when they wanted out there they would stand at the door and meow. But Cara started going up to any closed door in the house and meowing to go out. She started actually rubbing against us and demanding attention. She started peeing in the bathtub. Cara had kidney problems, as many old cats do, but we never could figure out why it was just the bathtub. She became much more vocal, as well, although if she was meowing in the middle of night, we never heard it since they slept in the garage. No one in my family knew that pets could get dementia until we saw it with Cara.

Diagnosing Cognitive Dysfunction Syndrome

CDS is a diagnosis of exclusion because many of the symptoms can also be caused by medical problems that are common in senior cats [1-3, 5, 6]. For example, pain from arthritis might cause irritability or decreased activity [1, 2, 5]. Vision or hearing loss might cause a cat to become disoriented [1, 2]. It’s important to rule out other medical causes through testing [5]. Only then can your veterinarian be sure that CDS is the culprit.

What Causes Cognitive Dysfunction in Cats?

No one knows for sure what causes CDS. Just like Alzheimer’s disease in humans, it is still somewhat of a mystery. Veterinarians have a few ideas, however. As cats get older, their brains accumulate certain kinds of age-related damage [4-6]. Their brains eventually shrink and lose neural connections, just like ours do [5]. Toxic beta-amyloid plaques and abnormal tau proteins build up in the brain over time [4-6]. Impaired blood flow and oxidative damage are also age-related changes that contribute to cognitive dysfunction in cats [4-6]. The brain is expected to deteriorate with age, just like the rest of the body [3]. However, handling dementia in your elderly pet isn’t as straightforward as some of the other conditions common in senior cats because it isn’t one-size-fits all.

How is Feline Cognitive Dysfunction Treated?

Tan cat laying on sidewalk
Image by Anna Armbrust from Pixabay

There is no cure for CDS, but there are things you can do to make things easier for your cat if they are diagnosed with it [3, 5, 6]. A lot of it has to do with adjusting your cat’s environment to make things easier for them [1, 3]. Keeping to a strict routine makes everything easier to remember and less stressful [1, 5]. Avoid major changes, such as introducing a new pet, if at all possible [2, 3]. If your cat is up all night, you can make a point to keep them active during the day and play with them in the evening hours [1]. Cats that are soiling outside the litterbox may be forgetting where the litter box is or how they’re supposed to use it [1]. Add more litterboxes in easy-to-see places [1-3].

Anxiety may be helped by giving your cat more attention, playing the radio at night/when you’re not home, or using a calming pheromone diffuser like Feliway [1, 3, 5]. Every cat is different, though, so expect some trial-and-error. Ask your veterinarian for recommendations based upon your cats specific symptoms [1, 5]. It may help to consult a cat behaviorist, too [1].

A special diet can sometimes help with CDS [2, 3, 5, 6]. Vitamin E and antioxidants are believed to aid an aging cat’s brain [2, 3, 5]. There are cat foods available that are high in these nutrients [5]. Ask your veterinarian or local pet store for a recommendation. You can also buy supplements, but be careful, because they are usually formulated for dogs and may not be safe for cats [5]. Only use a supplement that is clearly labeled as safe for cats!

Medication

There aren’t any medications specifically for cognitive dysfunction in cats yet; nonetheless, there are some that your veterinarian may prescribe. Anti-anxiety medication is one option [1-3, 5]. The drug selegiline/Anipryl is approved for CDS in dogs and is sometimes prescribed for cats [1, 2, 5, 6]. Not all cats with CDS require medication, however, and their needs can change over time. Take your senior kitty into the vet for regular appointments to reassess what their needs are [6].

Sources

  1. American Society for the Prevention of Cruelty to Animals. (n.d.). Older cats with behavior problems. ASPCA. https://www.aspca.org/pet-care/cat-care/common-cat-behavior-issues/older-cats-behavior-problems
  2. Cornell Feline Health Center. (2018, July). Cognitive dysfunction. https://www.vet.cornell.edu/departments-centers-and-institutes/cornell-feline-health-center/health-information/feline-health-topics/cognitive-dysfunction
  3. International Cat Care. (2018, August 17). Senility, dementia or cognitive dysfunction syndrome. https://icatcare.org/advice/senility-dementia-or-cognitive-dysfunction-syndrome/
  4. Kornreich, B. (2022, September 27). Feline cognitive dysfunction syndrome (CTS). Cornell Feline Health Center Monthly Health Tips. [Email Newsletter]
  5. Sordo, L. and Gunn-Moore, D. A. (2021). Cognitive dysfunction in cats: Update on neuropathological and behavioural changes plus clinical management. VetRecord, 188(1), e3. https://doi.org/10.1002/vetr.3
  6. Stilwell, N. (2019). Unpacking feline dementia: A veterinary guide. Vetted, 115(5), 6-8. https://www.dvm360.com/view/unpacking-feline-dementia-veterinary-guide

Published October 1st, 2023

Science

Feline Calicivirus

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Meredith Hemphill

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Encyclopaedia Felidae now has a Patreon! Go to www.patreon.com/EncyclopaediaFelidae if you want to help support this content!

Shoutout to Dad for suggesting calicivirus as a topic.

Upper respiratory infections are common in cats. Often called cat flu, these infections are a lot like the colds and flus that humans get in the winter. Cat flu is highly contagious, but not very serious for most healthy adult cats. It can be dangerous for young kittens, seniors, and cats with chronic illnesses or weak immune systems. Like human colds, cat flu can be caused by more than one virus, but one of the most common culprits is feline calicivirus.

What is Feline Calicivirus?

Feline calicivirus particles
A calicivirus showing the characteristic chalice shapes on the surface – Photo by Marian C. Horzinek [2]

Feline calicivirus (FCV) is part of the Caliciviridae family of viruses [1, 2]. There are viruses from this family that afflict a wide range of vertebrate animals, including humans [1, 2]. Norovirus is a member of the Caliciviridae, as are some diseases of rabbits [1, 2]. The name calicivirus comes from the Greek work “calyx,” meaning “cup” or “goblet” [2]. This refers to the cup-shaped depressions on the surface of the hexagonal or star-shaped virus particles [2].

Feline calicivirus is specific to cats, both housecats and wild species [1, 2]. It is a single-stranded mRNA virus, a type which is particularly prone to mutation [2]. This has led to there being many different strains of FCV around the world.

How Are Cats Infected with Calicivirus?

FCV spreads most often in environments where a large number of cats live in close proximity to each other, such as boarding kennels, pet stores, shelters, breeding facilities, and dense feral colonies [1-5]. The risk begins to increase dramatically when as few as four cats are in close proximity [2]. In groups of fewer than four healthy cats, the infection rate is 2.5%, but groups of four or more healthy cats have an infection rate of 32% [2]! In colonies and shelters, the rate can range from 50-90% [2].

The virus is spread through direct contact with body fluids from an infected cat, primarily saliva and eye and nose secretions [1-5]. Blood, urine, and feces can also spread the virus, as can aerosolized droplets from sneezes [1-5]. This means sharing things like food bowls, water bowls, litterboxes, and bedding can spread FCV [1-3]. So can just sharing an environment, or human caretakers can accidentally spread the virus around by getting it on their hands or clothes [1-3]. Most infected cats shed virus for 2-3 weeks, but some become carriers and continue to spread FCV for months or years [1, 2].

Symptoms of Feline Calicivirus

The typical presentation of FCV is an upper respiratory infection [1-5]. The virus attacks the inside of the mouth and the lungs [1, 2]. The symptoms include the usual upper respiratory signs like sneezing, stuffy/runny nose, runny eyes, and sleepiness [1-3]. However, FCV may also cause ulcers inside the mouth, which may in turn lead to drooling and refusal to eat due to oral pain [1-5]. Occasionally vulnerable cats, usually young kittens, will develop pneumonia [2, 3]. It is rarely fatal, however, and most cats will recover in a week or so, although severe cases may take up to six weeks [1].

Some cats who become infected with feline calicivirus go on to develop chronic gingivitis [1-5]. Researches do not yet know why this happens, or why it only happens to certain cats [2]. If your cat has recently recovered from cat flu and is still having problems with their mouth, this is probably something to talk to your veterinarian about.

Limping Syndrome

FCV can sometimes attack the joints and result in a strange–and upsetting–manifestation known as limping syndrome [1-5]. It mostly occurs in kittens [3, 4], and it can look very scary. Affected kittens develop a fever as well as pain, stiffness, and lameness in their joints, but which limb(s) are affected may change over time [2-4]. Sometimes limping syndrome occurs as a side effect of an FCV vaccination, not from an infection [2, 3, 5]. Although it is painful, limping syndrome only lasts 2-3 days and usually clears up on its own [2-4]. However, during that time, your veterinarian may be able to prescribe anti-inflammatory and/or pain medication to make your kitten more comfortable [2, 3]. Kittens that are severely affected may be reluctant to move at all [3] and need your help getting to their food, water, and litterbox until they’re feeling better.

Advice from Kitten Lady Hannah Shaw on taking care of kittens with limping syndrome

Virulent Systemic Feline Calicivirus (VS-FCV)

In rare instances, the FCV virus mutates into a much, much more dangerous form called virulent systemic feline calicivirus (VS-FCV) [2, 3]. VS-FCV is able to infect multiple organ systems and the lining of blood vessels [2, 3]. It causes high fever, inflammation throughout the body, swelling of the head and limbs, sores on the face and feet, jaundice, and multiorgan failure [1-3]. About 60% of cats infected with VS-FCV die [1-3]. Fortunately, outbreaks are very rare [1-3] and have only been observed in some countries [3]. Researches have not found any genetic traits that distinguish VS-FCV strains from regular FCV strains, however, making it difficult to specifically vaccinate against VS-FCV until there’s a breakthrough [2].

Treatment and Prevention

FCV usually goes away on its own in healthy cats [1-4]. There are currently no antiviral drugs that are proven to be effective against FCV, although a couple have shown promise in preliminary research [2]. As such, treatment focuses on relieving symptoms and supporting your cat’s body while it fights off the virus [1-4]. Your veterinarian might decide to prescribe medication like a non-steroidal anti-inflammatory drug or anticongestant [1, 2, 4]. Keeping the eyes and nose clean is important–nebulizers and saline eye or nose drops can help [1, 2, 4]. Some cats may need intravenous fluids [1, 2, 4]. Since many cats lose their appetite or simply find eating difficult, you may have to try different foods or ways of presenting their food to make sure they eat [1, 2, 4]. In severe cases, they may require a feeding tube [1, 2, 4].

Cat getting vaccine
Photo by Gustavo Fring on Pexels

The bad news is that FCV is extremely widespread. The good news is that there is a vaccine for it, which the American Association of Feline Practitioners [5] and European Advisory Board on Cat Diseases [2] both consider a core vaccine that all cats need to have. FCV is usually included in a combination vaccine with other common viruses [2].

Because there are so many different strains of FCV, the vaccine doesn’t always prevent a cat from becoming infected, but it is effective at preventing them from getting sick [2, 5]. Kittens lose the protection of the immune cells they get from their mothers somewhere between 6 and 14 weeks of age, so the American Association of Feline Practitioners recommends vaccinating kittens against FCV at 6 weeks, or as early as is allowed in your country [5]. Kittens should receive a primary vaccination series of 2-3 shots, and adult cats should receive a booster every 1-3 years, depending upon their risk level [2, 3, 5].

Works Cited

  1. Baker Institute for Animal Health. (2016). Feline calicivirus. Cornell University College of Veterinary Medicine. https://www.vet.cornell.edu/departments-centers-and-institutes/baker-institute/our-research/feline-calicivirus
  2. Hofmann-Lehmann, R., Hosie, M. J., Hartmann, K., Egberink, H., et al. (2022). Calicivirus infection in cats. Viruses, 14(5), 937. https://doi.org/10.3390%2Fv14050937
  3. International Cat Care. (2018, August 17). Feline calicivirus (FCV) infection. https://icatcare.org/advice/feline-calicivirus-fcv-infection/
  4. Kuehn, N. F. (2022, October). Feline respiratory disease complex (feline viral rhinotracheitis, feline calicivirus). Merck Veterinary Manual. https://www.merckvetmanual.com/cat-owners/lung-and-airway-disorders-of-cats/feline-respiratory-disease-complex-feline-viral-rhinotracheitis,-feline-calicivirus?query=calicivirus
  5. Scherk, M. A., Ford, R. B., Gaskell, R. M., Hartmann, K., et al. (2013). Disease information fact sheet: Feline calicivirus. Journal of Feline Medicine and Surgery, 15, supplementary file. https://catvets.com/public/PDFs/PracticeGuidelines/Guidelines/Vaccination/FelineCalicivirus_FactSheet.pdf

Published February 12th, 2023

Cat Care

Tick Prevention for Cats

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Meredith Hemphill

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Encyclopaedia Felidae now has a Patreon! Go to www.patreon.com/EncyclopaediaFelidae if you want to help support this content!

Summer in the Southeastern United States is Tick Season. Well, actually it’s just Bug Season, but one of the bugs you have to worry about is ticks. You don’t just have to worry about ticks crawling on you, but on your pets, too. Now that it’s hot and humid and creepy crawlies are everywhere, it’s high time we talked about tick prevention for cats and what to do if you find one of the little monsters attached to your furry friend.

The Life History of Ticks

Tick life cycle
Image from Beattie Pet Hospital

Ticks are little, creepy arachnids, relatives of spiders and scorpions. They need to feed on blood to proceed through each stage of their life cycle [2]. A female tick lays 3000-6000 eggs on the ground [6]. The eggs hatch into tiny larvae that feed and molt into nymphs [2, 6]. The nymphs do the same to develop into adults [2, 6]. Adult ticks feed and mate on a host animal [6].

Ticks cannot fly or jump–they must crawl or drop onto a passing animal [4, 6]. They sit on tall blades of grass or other vegetation and wait for a passing host to brush by [1, 2, 4, 6, 8]. They prefer to bite the head, neck, ears, and feet [1, 4, 8]. Once a tick bites, they bury their mouthparts in the skin [1, 8].

There are at least 15 species of ticks in North America and more than 800 in the world [2, 6]. The species likely to feed on cats in the United States are the deer or black-legged tick and American dog tick [6]. Ticks are most abundant during the late spring and summer.

Why Do Cats Need Tick Prevention?

Ticks carry a lot of diseases. Cats don’t get tick-borne illnesses very often, but they sometimes become very sick when they do [2, 4, 6, 8]. Below are tick-borne diseases of concern for cats.

  • Lyme Disease (USA, Canada, Europe, North Asia, East Asia)
  • Cytauxzoonosis (USA, Brazil, Europe)
  • Tick Paralysis (Australia)
  • Hemobartonellosis/Feline Hemotrophic Mycoplasmosis (Worldwide)
  • Tularemia (USA, Canada, Europe, North Asia)
  • Babeseosis (USA, Europe, South Africa, East Asia, Southeast Asia)
  • Ehrlichiosis (USA, Europe, South America, Africa, East Asia)

The more ticks that bite a cat, and the longer they remain attached for, the more likely it is that the ticks will infect the cat with a disease-causing pathogen [4, 7]. Tick bites may also become infected like any wound, and if a cat has a lot of ticks attached they could become anemic [1, 3].

Image from Texas A&M Agrilife Extension

What Kinds of Tick Prevention are Available for Cats?

These days, there are a lot of different types of tick prevention for cats. Some flea prevention products work for ticks, too. Others are tick-specific. Some are only effective against certain species of ticks [8]. Before using any tick prevention method, consult your veterinarian. They should know which ticks are present in your area and which preventatives will work best for your cat. For reference, these are the options available.

An important thing to remember: NEVER use an antiparasitic product meant for dogs on your cat. Make absolutely certain that the product you are using is labeled for use with cats, and that you use a dose that corresponds to your cat’s age and weight. Some of the flea and tick products made for dogs are very toxic to cats [4, 6, 7].

Spot-On Medications

Spot-on treatments are a type of topical medication that you squeeze out of a little tube onto the back of your cat’s neck [6]. They are a very popular form of tick prevention for cats–and dogs, too [2, 4-8]. Spot-on medications are highly effective and must be applied monthly [5].

Oral Medications

These monthly antiparasitic tablets are much more available for dogs than they are for cats, but you can sometimes find them [5, 7]. I suspect this is because many cats are so unwilling to take pills. Oral tick preventatives do have advantages if your cat will consume them. There is no need to worry about your cat rubbing the medication off onto you or your furniture [5]. Plus, with a medication that is meant to be eaten, there’s no concern about your cat grooming a chemical that isn’t safe for consumption off their fur. They aren’t supposed to be able to do that if you squirt a spot-on treatment in that magic place they can’t reach, but Joon finds a way.

Shampoos and Dips

Photo by Karin Chantanaprayura on Pexels

Famously, cats do not like baths. But, there are reasons these products could make sense for you. For example, your cat has a serious infestation, or your cat needs to take regular baths anyway. There are shampoos available that kill ticks on contact [5]. These shampoos are pretty inexpensive, but for ongoing protection your cat will need a medicated bath about every two weeks during peak tick season [5]. Just be careful not to get any in kitty’s eyes!

Dips are a bit different. The tick dip comes as a concentrated chemical that has to be diluted in water [5]. You then sponge it onto the cat’s fur or pour it over their back without rinsing [5]. These chemicals are strong, so they are not appropriate for all cats and cannot be used for kittens less than four months old [5].

Powders and Sprays

These topical products can sometimes be used in the cat’s environment and on their bedding as well as on your cat [3, 5]. Be sure to check the directions. Powders are rubbed into a cat’s fur and skin [5]. They can be irritating, so avoid kitty’s face and eyes [5]. Antiparasitic powders are not effective for very long and need to be applied once a week during peak tick season [5]. Sprays are also a topical treatment that must be kept away from a cat’s eyes [3, 5]. They kill ticks quickly but are short-acting [5, 6]. Some sprays, while considered pet-safe, are only meant for use around the house and not directly on animals. Again, always read the instructions.

Tick Collars

Medicated collars can help prevent ticks from attaching to your cat [2-7]. However, they work the best around the head and neck and are less effective elsewhere on the body [5]. That is one of the places where ticks tend to congregate, but they can and will attach anywhere. If ticks are only a minor problem in your area, however, this might be a reasonable solution.

Tick collars must have skin contact to be effective [5]. Make sure it fits so that two fingers just slide underneath [5]. Like any medication, cats can have allergic reactions to these collars, so watch for signs of discomfort like excessive scratching and remove the collar regularly to check for irritation [3, 5].

Environmental Control

There are things you can do to keep ticks off your cat in the first place, as well. Ticks like tall grass, brush, and wooded areas. Ideally, you would keep your cat away from these environments where ticks lay in wait [5]. Of course, if your cat has any access to the outdoors, that is probably easier said than done. You can, however, make your own property inhospitable to ticks. If you have a lawn, keep it mowed [1, 5, 8]. Get rid of tall weeds, brush piles, and unwieldy undergrowth [1, 5]. Whenever your cat comes in, go ahead and check them over with a flea comb [7].

How to Find and Remove Ticks from Your Cat

Unfortunately, parasites are wily, and sometimes they sneak past all our defenses. So what do you do if you find a tick that has already attached to your cat? First of all, don’t panic. Most tick bites do not result in an infection [2]. And you can get the gross little monster off.

Always wear disposable gloves when removing a tick, or at least put a paper towel between it and your skin [1, 2, 6]. Remember, humans can catch diseases from ticks, too, so it’s best to be safe. Also prepare a screw-top jar filled with rubbing alcohol before you remove the tick [1, 2, 6]. You are going to drop the tick in there. This is because you may want to preserve the tick to take to the veterinarian in case your cat becomes sick later, and a female tick is likely to have eggs inside that you want to make sure die with her [1, 2, 6].

With tweezers, grab the tick as close as possible to where it is attached to the skin. DO NOT jerk or twist it. This can cause the body to break off and leave the head behind, which is a serious infection risk. Rather, pull upward with steady pressure until the tick comes out. Drop it in the jar, screw the lid closed tightly, and label the jar with the date. Maybe write “TICK” on there too, just in case. You don’t want to mix that up with anything else. Disinfect the bite wound. Sterilize the tweezers with more rubbing alcohol. Wash your hands thoroughly after you throw your gloves away. Gloves are not perfect protection. [1-3, 6, 8]

If you do find a tick on your cat, Cornell Feline Health Center wants to know! They are conducting a Feline Lyme Disease Surveillance Program to test ticks that have been found on cats for the bacteria that cause Lyme disease. Visit the webpage to find out more.

Works Cited

  1. American Society for the Prevention of Cruelty to Animals. (n.d.). Fleas and ticks. https://www.aspca.org/pet-care/general-pet-care/fleas-and-ticks
  2. Cornell Feline Health Center. (n.d.). Ticks and your cat. Cornell University College of Veterinary Medicine. https://www.vet.cornell.edu/departments-centers-and-institutes/cornell-feline-health-center/health-information/feline-health-topics/ticks-and-your-cat
  3. Fogle, B. (1999). The complete illustrated guide to cat care and behavior. Thunder Bay Press: San Diego.
  4. Karwath, A. (2022, February 23). Cats and ticks. Blue Cross UK. https://www.bluecross.org.uk/advice/cat/cats-and-ticks
  5. Kvamme, J. (2011, June 14). 10 ways to stop ticks from biting your cat. PetMD. https://www.petmd.com/cat/parasites/evr_ct_10_ways_to_stop_ticks_from_biting_your_cat
  6. Llera, R. and Ward, E. (n.d.). Ticks in cats. VCA Animal Hospitals. https://vcahospitals.com/know-your-pet/ticks-in-cats
  7. Schwab, S. (2022, June 17). The best tick prevention for cats, according to a veterinarian. The Dodo. https://www.thedodo.com/dodowell/tick-prevention-for-cats
  8. Tick prevention for cats. (2018, August 8). Beattie Pet Hospital. https://beattiepethospitalhamilton.com/2018/08/08/tick-prevention-for-cats/

Published July 10, 2022

Updated July 11, 2022

Science

Feline Infectious Peritonitis (FIP)

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Meredith Hemphill

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Encyclopaedia Felidae now has a Patreon! Go to www.patreon.com/EncyclopaediaFelidae if you want to help support this content!

In memory of Sully

Gray cat with Christmas tree
Sully died of FIP at the end of 2021

Feline Infectious Peritonitis (FIP) is a severe multi-organ-system viral disease that affects domestic cats as well as other felines [2, 5]. Until very recently, a diagnosis of FIP was a death sentence for a cat. It is still often fatal. However, knowledge is power. Knowing when to go to the vet and what your options are can save a life.

What Causes FIP?

FIP starts with an intestinal virus called feline enteric coronavirus (FeCV or sometimes FCoV). You can’t catch this coronavirus; only felines can [1, 4, 5, 9]. FeCV is very common among cats, especially in places where many cats live close together like shelters and catteries [1, 2, 5, 8]. Most cats infected with FeCV experience no symptoms, mild diarrhea, or mild respiratory illness before defeating the infection on their own [1, 4, 5, 8, 9]. In the meantime, they can easily spread the infection through their fecal matter or, less often, saliva [1, 2, 4-6]. Cats usually become infected by getting the virus in their mouths [1, 5, 6]. Shared litter boxes are a typical culprit [1, 2, 4-6]. An uninfected cat needs only to step in the litterbox after an infected cat has used it, and then when they clean their paws later, they become infected themself.

But what does this benign virus have to do with FIP? It isn’t well understood, but in about 10% of cats a FeCV infection turns into FIP [1, 2]. This is believed to occur as a combination of two phenomena. First, FeCV undergoes a spontaneous mutation that enables it to infect macrophages, a type of white blood cell [1, 2, 5, 8, 9]. This is the feline infectious peritonitis virus (FIPV). Second, the immune systems of certain cats overreact to the mutated virus, causing out-of-control inflammation and damage [1, 4, 6]. Incidentally, it is an overblown immune reaction to the coronavirus of the moment, COVID-19, that makes it so dangerous for a proportion of the population.

In the bodies of cats where both of these things happen, FIP develops. Some cats are more prone to FIP than others. Although the specific genetic risk factors remain unclear, specific breeds are at greater risk: Abyssinians, Bengals, Birmans, Himalayans, Ragdolls, Cornish Rexes, and Devon Rexes [6, 8]. Younger cats and most especially kittens make up the majority of FIP cases [1, 4, 6]. Their weaker immune systems are less able to fight off a FeCV infection, giving it more time to mutate [5]. Unneutered cats also seem to be at greater risk, for unknown reasons [8].

FIP symptoms chart
Symptoms of FIP – Image from Cornell University eCommons

Symptoms and Subtypes

The most common and earliest symptoms of FIP are, frustratingly, not very specific. They may include fever, change in appetite, weight loss, and depression [1, 5, 6]. As FIP advances, it develops into one of two general forms: wet/effusive or dry/non-effusive. In the wet form, fluid builds up in the abdominal and chest cavities and may cause breathing difficulty [1, 4-6, 8]. The dry form causes neurological and eye symptoms such as seizures and uveitis (inflammation of the outer layers of the eye) in addition to the non-specific symptoms [1, 4-6, 8].

FIP diagnosis chart
Diagnostic Map for FIP (Hartmann, 2005)

Diagnosis

Diagnosing FIP is difficult and complicated. The symptoms can all be signs of other diseases. Once it is suspected, there is no definitive, foolproof test for FIP. At right is a diagnostic scheme for FIP from one scientific article as an example of the mental gymnastics veterinarians have to do when deciding how to pursue FIP testing.

The options include blood and fluid tests, genetic tests for FIPV, and the veterinarian’s observations during an exam [1, 2, 4-6]. Many of the tests are complicated by the fact that so many cats have been infected by FeCV [1, 2, 5]. A cat’s veterinarian has to determine the best course of testing based on their individual case.

Treatment

Until just a couple years ago, nothing could be done for cats with FIP except supportive care to ease their suffering and extend their life a short time. For many cats, that is still the case, for reasons I will get to shortly, or simply because their disease is too severe. Supportive care consists of subcutaneous or intravenous fluids, draining fluid from body cavities if applicable, steroids to control inflammation, and immunosuppressive medication [1, 2, 4-6].

GS-441524

GS-441524 is an antiviral drug that prevents viruses from synthesizing RNA, a molecule which many viruses, including FeCV/FIPV, use instead of DNA [3, 9]. It was created by the pharmaceutical company Gilead, which specializes in antivirals [9]. Gilead first tested GS-441524 against Ebola but was ineffective [9]. However, FIP researcher Niels Pedersen knew someone at Gilead and asked if they could send him anything to test [9]. His friend at Gilead obliged, and Pedersen found two promising candidates that killed FIP in cultured cat cells [9]. He moved on with testing one of them, GS-441524, in cats with FIP [9].

The results were incredible. In a laboratory study, ten of ten infected cats recovered [9]. In a field trial with 31 pet cats with non-neurological FIP, 25 recovered, still an unheard-of success rate for this otherwise inevitably fatal disease [7, 9]. A more recent pilot study suggests that GS-441524 is effective in neurological and ocular FIP, too [2]. Side effects were not too bad. Cats experienced pain and skin reactions at the injection site, sometimes developing sores or scars [7]. This may be because the formula is very acidic [7].

Gilead, however, has declined to license GS-441524 for animal use [9]. GS-441524 is almost identical, molecularly, to another one of their drugs, remdesivir, which they are trying to get licensed for human use, and they believe that licensing GS-441524 for FIP would harm their chances with remdesivir [9]. Cat people and Chinese entrepreneurs have gotten creative, however.

GS-441524 is not a difficult molecule to synthesize, so numerous outfits in China have chosen to manufacture and sell it, filling the gap Gilead left open [9]. Because GS-441524 is not FDA-approved, veterinarians cannot prescribe it, and it’s illegal for cat parents to purchase and administer it [1, 9]. That has not stopped desperate people who want to save their cats. Because it is a black market, there is a risk that the product will not be as advertised [1, 9]. And it is incredibly expensive: it costs 7,000-12,000 USD for the 12-week course of medication [9]. When people can manage to acquire it, however, GS-441524 seems to be as good as the research suggested [1, 9].

If your cat has been diagnosed with FIP, and you would like help accessing GS-441524 treatment, contact FIP Warriors.

Watch “Kitten Lady” Hannah Shaw’s journey through FIP with her cat Coco

Preventing FIP

Because FeCV is so common and easily spread, it’s hard to prevent FIP entirely. There are some things you can do, however. Keep litter boxes clean and far away from food and water dishes [1, 6]. Cats are more vulnerable to developing FIP if they have another disease like FeLV or FIV, so get your cats vaccinated against all those easily preventable diseases [1, 6]. There is one FDA-approved vaccine against FeCV, but it does not seem to be all that effective [1, 5, 6]. You can always ask your veterinarian about the FeCV/FIP vaccine if you’re concerned, however. Keep in mind that cats often get FeCV infections at animal shelters and catteries, so you may want to isolate any new cats for a couple weeks [1, 5].

Works Cited

  1. Cornell Feline Health Center. (2020). Feline infectious peritonitis. Cornell University College of Veterinary Medicine. Link
  2. Diaz, J. V. & Poma, R. (2009). Diagnosis and clinical signs of feline infectious peritonitis in the central nervous system. The Canadian Veterinary Journal, 50(1), 1091-1093. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2748294/
  3. Dickinson, P. J., Bannasch, M., Thomasy, S. M., Murthy, V. D., et al. (2020). Antiviral treatment using the adenosine nucleoside analogue GS-441524 in cats with clinically diagnosed neurological feline infectious peritonitis. Journal of Veterinary Internal Medicine, 34(4), 1587-1593. https://doi.org/10.1111/jvim.15780
  4. Feline infectious peritonitis (FIP). (n.d.). Veterinary Specialty Center. https://www.vetspecialty.com/feline-infectious-peritonitis-fip/
  5. Hartmann, K. (2005). Feline infectious peritonitis. Veterinary Clinics: Small Animals Practice, 35(1), 39-79. https://doi.org/10.1016/j.cvsm.2004.10.011
  6. Levy, J. K. & Hutsell, S. (2020, October). Feline infectious peritonitis (FIP). Merck Veterinary Manual. https://www.merckvetmanual.com/cat-owners/disorders-affecting-multiple-body-systems-of-cats/feline-infectious-peritonitis-fip
  7. Pedersen, N. C., Perron, M., Bannasch, M., Montgomery, E., et al. (2019). Efficacy and safety of the nucleoside analog GS-441524 for treatment of cats with naturally occurring feline infectious peritonitis. Journal of Feline Medicine and Surgery, 21(4), 271-281. https://doi.org/10.1177/1098612X19825701
  8. Pesteanu-Somogyi, L. D., Radzai, C., & Pressler, B. M. (2006). Prevalence of feline infectious peritonitis in specific cat breeds. Journal of Feline Medicine and Surgery, 8(1), 1-5. https://doi.org/10.1016/j.jfms.2005.04.003
  9. Zhang, S. (2020, May 8). A much-hyped COVID-19 drug Is almost identical to a black-market cat cure. The Atlantic. https://www.theatlantic.com/science/archive/2020/05/remdesivir-cats/611341/

Published June 15, 2022

Updated November 12, 2023

Cat Care

Are Essential Oils Safe for Your Cat?

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Meredith Hemphill

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Encyclopaedia Felidae now has a Patreon! Go to www.patreon.com/EncyclopaediaFelidae if you want to help support this content!

Essential oils and candle
Photo by Chelsea shapouri on Unsplash

Essential oils are a popular tool for home wellness and perfumery. Not only can they be bought bottled, but essential oils are now found in many personal care, cleaning, and scented products. We know that some substances which are safe for humans can be toxic to our pets, like certain foods, so should oil enthusiasts with cats be concerned?

Essential Oil Toxicity in Cats

The Swiss physician and alchemist Paracelsus is credited with the saying, “The dose makes the poison.” If taken the wrong way or in too great a quantity, essential oils are toxic to humans. Consider how much smaller your cat is than you [7, 9, 10, 14]. Their biology isn’t quite the same, either. Nature didn’t intend cats to consume a lot of plant materials. They have lower levels of the liver enzymes necessary to metabolize chemicals called phenols and terpenes that are found in certain essential oils [1-5, 9, 12]. The following oils are known to be toxic to cats:

  • Cinnamon
  • Citrus (lemon, lime, orange, bergamot)
  • Clove
  • Eucalyptus
  • Pennyroyal
  • Peppermint
  • Pine
  • Sweet Birch
  • Tea Tree/Melaleuca
  • Wintergreen
  • Ylang Ylang

Research on the effects of essential oils on cats is sparse, so there is no guarantee that oils which are not on this list are safe [5, 10]. Individual cats could be sensitive to oils that most cats are not, as well [7]. Therefore, use caution when trying out any essential oil around your cat for the first time.

The symptoms of essential oil toxicity in cats depend upon the oil, the dose, and the method of exposure, but there are things you can look out for. Common symptoms are watery nose or eyes, drooling, vomiting, difficulty breathing, tremors, wobbliness, low heart rate, and low body temperature [2-5, 8, 9, 12, 13]. In severe cases, essential oil poisonings can cause liver failure and death [2-5, 8, 12]. While there is no specific cure for essential oil toxicity, most cats recover well with supportive care such as bathing to remove the oil, intravenous fluids, medication, and heat [4, 5, 8, 12].

How To Keep Cats Safe Around Essential Oils

Tabby cat in box with bottles
Image by mrscaz from Pixabay

Cats may be exposed to oils by inhalation, absorption through the skin, or ingestion. Because of their fastidious grooming habits, cats are likely to ingest any oils that end up on their fur [2, 3, 5, 9-12]. You can use essential oils safely in a home with cats. You just need to be careful and keep all the possible routes of exposure in mind.

Cats may inhale essential oils that are aerosolized from lit scented candles, liquid potpourri, air fresheners, diffusers, or similar. Whenever you are using one of these products around your cat, make sure that your cat is able to leave the area if it gets to be too much for them [7, 9, 10]. Watch for signs of respiratory irritation like coughing, panting, or watery eyes and nose [3, 10]. If your cat shows symptoms, move them to fresh air immediately and bring them to a veterinarian if their condition does not improve within a few minutes [3, 9].

If your cat has asthma, allergies, or other respiratory conditions or is exposed to second-hand smoke, it is best not to diffuse essential oils or use essential oil-containing products that put particles into the air [3, 5, 9].

Always keep essential oils and products that contain them out of your cat’s reach, especially in the case of open diffusers or warmers. Cats are often repelled by the smell of substances that are toxic to them, but not always, and there have been cases of cats drinking essential oils [9]. Keeping oils, diffusers, etc. away from cats also prevents curious kitties from knocking over or breaking said containers and spilling the oil all over themself which can be very dangerous.

Of course, use extra caution with the essential oils that are known to be toxic to cats. And never apply concentrated essential oils to your cat’s skin or fur. Don’t use oils on your cat at all without consulting a veterinarian first.

Can Essential Oils Be Good for Cats?

That being said, there are times when essential oils can be used for your pet’s benefit. Unfortunately, as with oil toxicity, the research is scarce, so little can be said for certain. Proponents of using essential oils for pets say that they can be used to heal wounds and abscesses; get rid of fleas, ticks, and ear mites; treat upper respiratory infections; and treat Otitis externa, a.k.a. canker of the ear [1, 7, 10]. Sadly, irresponsible use of oils, particularly tea tree oil, for these purposes has caused suffering and occasionally death for the cats of well-meaning owners [4, 8, 13]. However, what little research there is has demonstrated that when used properly, certain essential oils show promise for the treatment of several conditions oil enthusiasts have claimed they do.

Ebani et al. found that the essential oils of oregano, clary sage, and rosemary showed promise in the treatment of Otitis externa, depending upon the strain of bacteria or fungus that caused it [6]. In testing plant oils against a fungus that causes ringworm, Mugnaini et al. determined that the oils of oregano and wild thyme showed strong antifungal activity [11]. Regarding ear mites, a study of ear mites in cats found garlic oil, marjoram oil, and ozonated olive oil to be effective at reducing the infestation [15]. While the oils were not as effective as the pharmaceutical medication, the authors concluded that they were “cheap, easily applicable, and safe alternatives to conventional treatments with no side effects” [15].

Works Cited

  1. Baser, K. H. C. & Franz, C. (2010). Essential oils used in veterinary medicine. In K. H. C. Baser & G Buchbauer (Eds.), Handbook of essentials oils: Science, technology, and applications (pp. 881-894). Taylor and Francis Group: Boca Raton, FL.
  2. Beck, A. (2019, August 30). Is it safe to use essential oils with cats? University Veterinary Hospital. https://uvhvets.com/is-it-safe-to-use-essential-oils-with-cats/
  3. Benson, K. (n.d.). Essential oils and cats. Pet Poison Helpline. https://www.petpoisonhelpline.com/blog/essential-oils-cats/
  4. Bischoff, K. & Guale, F. (1998). Australian tea tree (Melaleuca alternifolia) oil poisoning in three purebred cats. Journal of Veterinary Diagnostic Investigation, 10, 208-210. DOI: 10.1177/104063879801000223
  5. Cavanaugh, K. & Kornya, M. (2018, July 31). Cats and essential oils. Canadian Veterinary Medical Association. https://www.canadianveterinarians.net/documents/cats-and-essential-oils
  6. Ebani, V. V., Nardoni, S., Bertelloni, F., Najar, B., Pistelli, L., & Mancianti, F. (2017). Antibacterial and antifungal activity of essential oils against pathogens responsible for Otitis Externa in dogs and cats. Medicines, 4(2), 21. https://doi.org/10.3390/medicines4020021
  7. Essential oils a pets: A quick how-to. (2019, October 25). Young Living. https://www.youngliving.com/blog/essential-oils-for-pets-a-quick-how-to/
  8. Genovese, A. G., McLean, M., & Khan, S. A. (2012). Adverse reactions from essential oil-containing natural flea products exempted from Environmental Protection Agency regulations in dogs and cats. Journal of Veterinary Emergency and Critical Care, 22(4), 470-475. https://doi.org/10.1111/j.1476-4431.2012.00780.x
  9. Howard, B. (2020, August 24). How to keep cats safe around essential oils. Daily Paws. https://www.dailypaws.com/cats-kittens/health-care/cat-poisoning-toxins/essential-oils-safe-for-cats
  10. How I use essential oils safely for my pets. And you can, too! (n.d.). Capital Illini Veterinary Services. https://www.capitolillinivet.com/blog/how-i-use-essential-oils-safely-for-my-pets-and-you-can-too/
  11. Mugnaini, L., Nardoni, S., Pinto, L., Pistelli, L., Leonardi, M., Pisseri, F., et al. (2012). Activité antifongique de quelques huiles essentielles de plantes in vitro et in vivo sur Microsporum canis isolé chez le chat. Journal de Mycologie Médicale, 22(2), 179-184. https://doi.org/10.1016/j.mycmed.2012.04.003
  12. Schmid, R., Brutlag, A., & Flint, C. (n.d.). Essential oil and liquid potpourri poisoning in cats. VCA Hospitals. https://vcahospitals.com/know-your-pet/essential-oil-and-liquid-potpourri-poisoning-in-cats
  13. Villar, D., Knight, M. J., Hansen, S. R., & Buck, W. B. (1994). Toxicity of melaleuca oil and related essential oils applied topically on dogs and cats. Veterinary and Human Toxicology, 36(2), 139-142. https://europepmc.org/article/med/8197716
  14. Worwood, V. A. (2016). The complete book of essential oils and aromatherapy (25th anniversary edition). New World Library: Novato, CA.
  15. Yipel, F. A., Acar, A., & Yipel, M. (2016). Effect of some essential oils (Allium sativum L., Origanum majorana L.) and ozonated olive oil on the treatment of ear mites (Otodectes cynotis) in cats. Turkish Journal of Veterinary and Animal Sciences, 40, 782-787. DOI: 10.3906/vet-1508-10

Published January 9, 2022

Science

Hyperthyroidism

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Meredith Hemphill

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Encyclopaedia Felidae now has a Patreon! Go to www.patreon.com/EncyclopaediaFelidae if you want to help support this content!

Thyroid disease is fairly common in cats, especially as they get on in years. The most frequent type of thyroid disease in older cats is hyperthyroidism [1, 4]. My parents’ elderly cat, Rosie, has it. So did my roommate’s cat Coco. And so do my best friend’s two ancient gray ladies. Even though hyperthyroidism is a common illness, I will attest that it can still be mystifying at times. It can impact a cat’s entire body, and it isn’t completely understood even by scientists and veterinarians. It is diagnosable and treatable, however. Sometimes, hyperthyroidism can even be cured.

Graphic of cat thyroid gland
The thyroid gland – Image from Cornell Feline Health Center

What is Hyperthyroidism?

The thyroid gland is a small organ found in all vertebrates which produces the thyroxine (T4) and triiodothyronine (T3) hormones. In mammals, the thyroid is found in the throat and has two lobes. Thyroid hormones regulate a wide variety of bodily functions. When the thyroid produces too much T3 and T4, it’s called hyperthyroidism. Hyperthyroidism increases the body’s metabolism which can cause problems with many different organs and systems.

Cats typically develop hyperthyroidism when middle-aged or older [1, 2, 7, 8, 10]. Up to 10% of cats age 10 and older may have hyperthyroidism [1, 3, 8]. It’s uncommon in cats younger than that, however [1, 2, 7, 8]. Untreated hyperthyroidism is fatal, but today the prognosis for a cat with this disease is usually optimistic.

How is Hyperthyroidism Diagnosed?

If your veterinarian suspects hyperthyroidism, they will probably do a physical examination of your cat’s neck to see if they can feel that the thyroid is enlarged [1, 2, 4, 7]. The presence or absence of a suspicious lump isn’t enough for a diagnosis, however. Most of the time, the final diagnosis can be made with a total thyroxine, or TT4, blood serum test [10]. The vast majority of hyperthyroid cats will have very high T4 levels with a TT4 test, making the diagnosis clear right away [1, 2, 7, 10].

However, cats with hypothyroidism occasionally have T4 serum levels that fall within normal limits [1, 2, 7, 10]. T4 levels fluctuate, so your veterinarian may decide to try the test again in a few weeks [1, 7]. Or they might try other thyroid hormone blood tests. A thyroid scan is another option but must be performed at a specialty veterinary facility [7, 10].

What are the Symptoms?

Because thyroid hormones affect so many parts of the body, the symptoms of hyperthyroidism are varied and sometimes nonspecific. They include:

Graphic of cat with hyperthyroidism
Characteristic appearance of hyperthyroid cat – Image from Cornell Feline Health Center
  • Weight loss/muscle wasting
  • Increased appetite
  • Increased thirst and urination
  • Vomiting
  • Diarrhea
  • Hyperactivity
  • Unkempt fur
  • Aggression or irritability
  • Fast heartrate
  • Increased vocalization, especially at night
  • Weakness
  • Heat intolerance

Some cats demonstrate “apathetic hyperthyroidism,” where they are lethargic, anorexic, and depressed/dull instead of the more usual symptoms [1]. Hyperthyroidism is progressive, so symptoms may be very mild at first [2]. It’s also not uncommon for hyperthyroid cats to also have other diseases, especially since they tend to be older. Many of these symptoms can be symptoms of something else. The safest bet is to consult your veterinarian anytime your cat seems different or unwell.

Secondary Illnesses

An overactive thyroid can sometimes cause other organs to become diseased. The heart is particularly at risk. There is a form of heart disease known as thyrotoxic cardiomyopathy which is caused by the heart muscle working overtime to meet the demands of a metabolism on overdrive [10]. The heart muscle thickens as a result of pumping so hard, but then that makes it difficult for the heart to work properly [2, 4, 10]. This can lead to heart failure. Fortunately, successful treatment of the hyperthyroidism can improve and even reverse the cardiomyopathy [2, 7, 10].

Hyperthyroid cats frequently experience high blood pressure as a cardiac complication, too [2, 4, 10]. About 25% of the time, in fact [10]. In severe cases, the high blood pressure can damage their organs [2, 4, 10]. It can even lead to retinal detachment that renders them permanently blind [4, 10]. High blood pressure is no joke and needs to be managed alongside hyperthyroidism until the thyroid hormones are under control [2]. If the hyperthyroidism is resolved, the blood pressure usually takes care of itself [2, 10].

What Causes Hyperthyroidism?

Hyperthyroidism usually begins when the thyroid gland becomes enlarged [2, 10]. In cats, this is almost always the result of a benign tumor called an adenoma [2, 4]. In less than 2% of cases, the growth is cancerous [1, 10]. What causes the abnormal thyroid tissue growth to begin with, however, remains uncertain. Researchers have found evidence for both environmental and biological factors that may play a role.

Environment

There is a demonstrated association between diet and the chances of a cat developing hyperthyroidism. Too much iodine in the diet may make a cat susceptible [10]. Canned cat food is also associated with higher rates of hyperthyroidism [1, 5]. The results of a 1999 study suggest cats fed primarily canned food have a rate of hyperthyroidism 2 to 3 times higher than other cats [5]. Researchers still don’t know why canned food would lead to an overactive thyroid. Correlation is not causation, so there may be more going on here that we don’t understand yet.

Using cat litter has also been found to be a potential risk factor, with the same study showing triple the rate of hyperthyroidism in cats that use litter [5]. Again, although there is a potential link, there is as yet no explanation. From looking through a lot of research papers to write this article, I know that veterinary scientists are still hard at work trying to figure out feline hyperthyroidism. The disease just doesn’t want to give up its secrets easily.

Certain household chemicals are associated with higher rates of feline hyperthyroidism, too. Polybrominated diphenyl esters (PBDE), which are used as flame retardants, have been found in high levels in the blood serum of hyperthyroid cats [1]. According to the Environmental Protection Agency factsheet for PBDE, rodent studies have shown thyroid toxicity from PBDE exposure. Per- and polyfluoroalkyl substances (PFAS) are a versatile group of artificial chemicals with a wide variety of applications in industry and the home. Wang et al. found that PFAS levels, particularly perfluorooctanoic acid, were higher in hyperthyroid cats than the cats in the control group [9]. The Environmental Protection Agency lists tumor growth and thyroid hormone disruption among the effects of PFAS in animals.

Siamese cat in meadow
Siamese have a reduced rate of hyperthyroidism – Image by rihaij from Pixabay

Biology

Hyperthyroid cats may have defects in the way their cells communicate that lead to the adenomas and other tissue abnormalities that overproduce thyroid hormones. Cats with thyroid nodules sometimes have low levels of the G protein in their thyroids [1]. A lack of G protein can decrease the inhibition of cell growth [1]. Some cats with thyroid nodules or adenomas have a cancer-causing mutation, known as an oncogene, which could cause the excessive cell growth [1].

Certain breeds of cat are less likely to develop the disease: Siamese, Burmese, Tonkinese, Himalayan, Persian, Abyssinian, and British Shorthair [3, 5, 9, 10]. At one time, only the Siamese, Burmese, and Persian/Himalayan were known to have these decreased risk, so the benefit was thought to be associated with the color-point pattern or lighter coat colors [3]. This hypothesis ultimately didn’t hold up [3], but perhaps there is something special these breeds have in common which will one day come to light. The same study which discovered the three new resistant breeds also found that long-haired, nonpedigree cats have higher rates of hyperthyroidism [3]. This despite the extremely long-haired Persian and Himalayan’s decreased rate.

What Treatments are Available?

Radioactive Iodine

It might sound a little scary, but radioactive iodine is actually the gold standard for treating feline hyperthyroidism. This treatment can only be done in specialized veterinary clinics that are authorized to work with radioactive materials, so it may not be accessible or affordable for everyone [2, 7, 10]. It’s a great option if you can take it, though, because for about 95% of cats it cures their hyperthyroidism–even those few with cancerous thyroid tumors [1, 2].

Radioactive iodine therapy relies on the fact that the thyroid takes up iodine to synthesize thyroid hormones. The cat is injected with the radioactive version of iodine, I-131 [1, 2, 7, 10]. No anesthesia is required [2, 7, 10]. The cat’s thyroid absorbs the I-131, just like it would normal iodine, but the abnormal thyroid tissue that’s churning out T3 and T4 like crazy is hogging the iodine. So the radioactive molecules get sucked into the abnormal tissue and kill it, leaving alone the cat’s healthy tissues, including any healthy thyroid tissue [1, 2, 7, 10].

Although the procedure is quite safe for the cat, it can be dangerous for the people around the cat which is now shedding radioactive particles [2]. Cats have to be hospitalized for a week or two after radioactive iodine therapy so that their radiation levels can get low enough for release [1, 2, 7, 10]. Even then, special care has to be taken at home for a two weeks after [1].

Radioactive iodine therapy may be a good option for cats that cannot undergo anesthesia. It also works well for cats with ectopic thyroid [7]. Ectopic thyroid is thyroid tissue somewhere other than the usual location of the thyroid gland such as under the tongue or in the chest [10]. It can be in locations that would be difficult to remove surgically. Radioactive iodine therapy doesn’t usually have complications, but for the rare cat it works too well and they become hypothyroid instead [2]. The solution to this is medication with thyroid hormones.

Medication

Hyperthyroidism cannot be cured with medication, but it can be managed with it. The medicine is called methimazole [1, 4, 7, 10]. Its brand names are Felimazole and Tapazole [4, 7, 10]. Methimazole is available as an oral tablet or a gel applied to the skin [1, 2]. It works by decreasing the production and release of hormones from the thyroid [2, 4]. It’s usually given twice a day [1, 4].

Cats may be given methimazole as a long-term method of managing their disease or to stabilize them before trying a more permanent solution [1, 4, 7]. Like all drugs, methimazole can have side effects. According to the Food and Drug Administration, the most common side effects of methimazole in cats are changes in appetite, lethargy, vomiting, diarrhea, skin lesions, itchiness, unusual vocalizations, weight loss, fur abnormalities, weakness, and agitation [4]. However, a small percentage of cats develop severe side effects with methimazole [1, 4]. Namely, liver disease, anemia, low blood platelets, and low white blood cell counts [1, 4, 7, 10]. Always report medication side effects, even seemingly small ones, to your veterinarian.

Two veterinarians holding white cat
Photo by Gustavo Fring from Pexels

Surgery

When Dr. Jean Holzworth first recognized feline hyperthyroidism in 1978, the only way to treat it was to remove the offending thyroid gland [1]. Although there are now other options, for some cats this is still the chosen course of treatment. For most cats, surgery cures their hyperthyroidism [2]. It can also be done at a regular veterinary surgery rather than the special facility required for radioactive iodine therapy, making it accessible to more people. Surgery requires a cat to go under anesthesia, however, and for older cats who often have other health problems, that can be a risky proposition [2, 10].

Surgery also carries a chance of complications. Complications aren’t likely, but they do happen. Most cats still have enough thyroid cells left after the surgery to keep up their T3 and T4 hormone levels, but some become hypothyroid and require medication [7]. Another possible complication is damage to the parathyroid glands, which are near or within the thyroid are necessary for maintaining normal calcium levels in the blood [2, 7]. If the parathyroid glands become damaged, the cat may develop low blood calcium and require supplemental calcium or vitamin D [1, 7]. Other complications include damage to nearby nerves or the larynx [1, 7].

Due to the risks associated with surgery and the availability of alternatives, it isn’t a very common choice anymore [2]. That being said, it might still be the right option for you and your cat. That’s something you would have to figure out with your veterinarian.

Diet

The research is still ongoing for diet as a means of controlling hyperthyroidism in cats [2]. For cats with health concerns that make other treatment options difficult or impossible, however, it can be the best–or only–choice despite being somewhat controversial. The principle is that limiting the amount of iodine in the cat’s diet to a small, controlled amount restricts the amount of hormones the thyroid can make. Cats fed a prescription iodine-restricted diet and nothing else should return to normal thyroid function [1, 7, 10]. Nothing else really means NOTHING else. No treats, don’t even put the prescription food in a bowl that has been used for other food or untreated water [1, 10]. The iodine-restricted diet contains only 0.2 parts per million of iodine [10]. That is a really, really small amount. It would not take much to throw off the balance.

In memory of Coco and Rosenberg

Works Cited

  1. Brewer, W. G., Jr. (2020, July 6). Treating feline hyperthyroidism. Blue Pearl. https://bluepearlvet.com/medical-library-for-dvms/treating-feline-hyperthyroidism/
  2. Cornell Feline Health Center. (2017, January). Hyperthyroidism in cats. Cornell University Collège of Veterinary Medicine. https://www.vet.cornell.edu/departments-centers-and-institutes/cornell-feline-health-center/health-information/feline-health-topics/hyperthyroidism-cats
  3. Crossley, V. J., Debnath, A., Chang, Y. M., Fowkes, R. C., et al. (2017). Breed, coat color, and hair length as risk factors for hyperthyroidism in cats. Journal of Veterinary Internal Medicine, 31(4), 1028-1034. https://doi.org/10.1111/jvim.14737
  4. Food and Drug Administration. (2019, December 3). Hyperthyroidism in cats: There’s an FDA-approved drug to treat it. FDA.gov. https://www.fda.gov/animal-veterinary/animal-health-literacy/hyperthyroidism-cats-theres-fda-approved-drug-treat-it
  5. Kass, P. H., Peterson, M. E., Levy, J., James, K., et al. (1999). Evaluation of environmental, nutritional, and host factors in cats with hyperthyroidism. Journal of Veterinary Internal Medicine, 13(4), 323-329. https://doi.org/10.1111/j.1939-1676.1999.tb02189.x
  6. Peterson, M. E., Castellano, C. A., and Rishniw, M. (2016). Evaluation of body weight, body condition, and muscle condition in cats with hyperthyroidism. Journal of Veterinary Internal Medicine, 30(6), 1780-1789. https://doi.org/10.1111/jvim.14591
  7. Pet Health Topics. (n.d.). Hyperthyroidism in cats. Washington State University College of Veterinary Medicine. https://www.vetmed.wsu.edu/outreach/Pet-Health-Topics/categories/diseases/hyperthyroidism-in-cats
  8. Stephens, M. J., O’Neill, D. G., Church, D. B., McGreevy, P. D., et al. (2014). Feline hyperthyroidism reported in primary-care veterinary practices in England: Prevalence, associated factors and spatial distribution. Veterinary Record, 175(18), 458. https://doi.org/10.1136/vr.102431
  9. Wang, M., Guo, W., Gardner, S., Petreas, M., et al. (2018). Per- and polyfluoroalkyl substances in Northern California cats: Temporal comparison and a possible link to cat hyperthyroidism. Environmental Toxicology and Chemistry, 37(10), 2523-2529. https://doi.org/10.1002/etc.4239
  10. Williams, K., Downing, R., and Ward, E. (n.d.). Hyperthyroidism in cats. VCA Hospitals. https://vcahospitals.com/know-your-pet/hyperthyroidism-in-cats

Published April 25th, 2021

Updated June 14th, 2023

Cat Care

How to Choose the Best Cat Litter

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Meredith Hemphill

mehshadoweye

Encyclopaedia Felidae now has a Patreon! Go to www.patreon.com/EncyclopaediaFelidae if you want to help support this content!

Gray cat beside litterbox
Photo by Litter Robot on Unsplash

I was recently forced to switch brands of cat litter because the place I shop stopped carrying the one I had been using for most of Joon’s life. Upon searching for a suitable replacement, I was immediately confronted with the overwhelming variety of cat litter options available on the market today. What I thought would be, at most, a ten minute task took an hour-and-a-half as I fell down a rabbit hole of customer reviews and “best cat litters” rankings. No one deserves to suffer as I have suffered. Instead, I am putting together a handy guide to the types of cat litter and the factors about them that matter.

Material Matters

Before World War II, there was no such thing as cat litter. Most cats were outdoor or indoor-outdoor and didn’t have litterboxes at all (10). Increased urbanization had brought more cats inside as family pets, however, creating a need for the litterbox. So people with indoor cats would fill boxes with sand or ashes and keep them somewhere out-of-the-way (10). It was a solution, but not a great one. Sand and ash do nothing for absorption and little for odor control, and they track everywhere. They are horrible substances when it comes to tracking. My last apartment had a wood-burning fireplace. We never used it, yet the whole apartment was gray by the time we moved out thanks to my cat. But pre-war homeowners had nothing better to use. Those of us who live in the era of cat litter have a man named Edward Lowe to thank.

Ed was a former sailor whose father had a company that manufactured absorbent clay (10). This clay was used to clean up oil and grease spills in wartime factories (10) and civilian garages alike (5). Ed realized those same absorbent properties might work in litterboxes, and he was right (4, 5, 10). In 1947, he registered his invention under the name Kitty Litter (9). Granulated clay litters are still used today, but a lot of other materials have been added since Ed Lowe created the litter market. We’ll start with the old stand-by.

Clay

The original type of cat litter made from granulated clay is still an option. It’s usually the cheapest kind of litter (4, 5). It has good absorption but doesn’t clump, so the whole pan needs to be thrown out and refilled once it’s too soiled (4, 5). That usually takes about a week for a single cat (5, 10). Granulated clay tends to have good odor control (7). These days, many formulations include additives like carbon or plant extracts to boost the odor control properties (7). Granulated clay litter usually doesn’t track too bad (10), but it can be pretty dusty (4, 7).

In the 1980s, biochemist and cat person Thomas Nelson, on a quest for a better litter, discovered that bentonite clay forms clumps when wet (5,10). Now waste could simply be scooped out of the litterbox instead of the whole box being dumped all the time. Thus, clumping clay cat litter was born. Obviously the biggest advantage of clumping clay litter is the ease of clean-up (2-5, 7, 10). Those clumps also lend themselves to greener pet care. Since the box doesn’t need to be completely emptied as often as it does with granulated clay, clumping clay litter causes less waste and is better for the environment (5, 10). It also tends to be better for odor control (5, 10). Bentonite clay is still dusty, though (3, 4, 7). It’s also quite heavy (3, 4).

There are now lightweight formulas to mitigate that last issue (4, 9). These mix bentonite clay with less weighty mineral particles (4). There are also lightweight granulated clay litters that use a different, lighter-weight type of clay (4). These have much the same advantages and disadvantages as the heavier cat litters they are derived from. The bags or boxes are just easier to lift and transport.

Eco-Friendly

This is a new but fast-growing slice of the cat litter market. More people are trying to make earth-conscious decisions, and that includes their pets. Clay litter is not biodegradable (7). So, there has been a push for sustainably sourced cat litter that is. There are a lot of types of eco-friendly litter now, which is great, but we don’t want to be here all day. Instead, I’m just going to summarize them.

  • Wheat: Utilizes the starches and enzymes in wheat to clump and control odor. Low-dust and low-tracking. (4, 7)
  • Corn: Most common natural cat litter. Utilizes the starches and enzymes in corn to clump and control odor. Low-dust. Can be expensive. (4, 7)
  • Pine/wood: May be made from recycled lumber scraps for added eco-friendliness. Comes in pellet, granule, or crushed form. Wood scents aid odor control. Low-dust. Naturally absorbent but does not clump. (4, 7)
  • Paper: Recycled paper made into pellets or granules. Highly absorbent and essentially dust-free. Granule form clumps. Lacking on odor control. (4, 7)
  • Grass: Made from one of several types of grass. Good clumping and odor control. (4)
  • Coconut husk: Made from the outside part of coconuts. Clumps, but not tightly. Low-dust. Natural coconut scent aids odor control. Not the most widely available option. (7)
  • Walnut shells: Crushed walnut shells, makes for a dark brown litter. Good clumping and odor control. Low-dust and low-tracking. (4, 7)
Cat litter pellets
Some cat litter comes in pellets – Photo by Michal Zacharzewski from FreeImages

I’ve also heard of more niche eco-friendly cat litters made of hemp, peas, green tea, yuca, sugarcane, and even tofu. Some eco-friendly cat litter is compostable or even flushable, although personally I’m not sure flushing cat litter is a great idea (5, 10). Because cats will ingest small amounts of litter while grooming and come into skin contact with their litter, it is important to make sure any cat with allergies is not given an eco-friendly litter containing an ingredient(s) they are allergic to (3). Some of these cat litters contain a lot of different plant ingredients, so check carefully. It’s also important to note that these plant-based litters can attract insects if not stored properly (7).

Silica

Silica is perhaps the latest and greatest when it comes to cat litter. This type of cat litter is made of tiny silica gel crystals or beads (4, 5, 7, 10). Silica is a naturally-occurring mineral that happens to be highly-absorbent (7). These litters are the most expensive, but some say they’re worth the price (3-5, 7). Silica cat litter is famously dust-free and low-tracking (3-5). It has great odor-control (3, 4, 7). It’s so absorptive, it can, in theory, last up to a month for one cat before needing to be changed out (7). It doesn’t clump, though, so that does mean throwing the whole litterbox-full out at the end of the month, or sooner if you have multiple cats (5).

It is the diagnostic cat litters that have really put silica at the front of the pack lately, however. Diagnostic litter contains pH indicators that change color in response to urine (1, 9). By indicating the pH of a cat’s urine, diagnostic litter can be a powerful tool for monitoring kitty’s health (1, 9). Urinary tract infections, kidney disease, and diabetes are some of the diseases that can affect the pH of a cat’s urine (9). For cat’s that have chronic urinary complaints, diagnostic cat litter could be especially helpful (9).

It is important to keep in mind that nothing matters more when choosing a cat litter than what your cat thinks. If something about their litter distresses a cat, there’s a good chance they won’t use it. That said, some cats do not like the sharp, gritty texture of silica crystals under their paws (4, 5, 7).

Clumping or Non-Clumping?

Cats may not go out and buy their litter, but they will make the final decision on whether they use it or not. Their opinion is the most important. So what do they prefer? Certainly their waste would be unlikely to form neat little clumps out in the wild. But that is actually what they prefer. Maybe it’s because the clumping action instantly helps clean up the place. Whatever the reason, cats prefer clumping litter to non-clumping litter (1, 3, 5, 9).

Scented or Unscented?

Some cat litter is scented to cover up the smell of cat waste. Lavender seems to be a favorite, by my observation. This has never appealed to me, but I can see why it might. Who would want to smell cat urine when they could smell flowers? Well, cats disagree. Cats generally don’t like strong smells (1, 3, 7). Even if that scented litter doesn’t smell very strong to you, it might to your cat’s much more sensitive nose. Those scents can linger on your cat after they’ve left the litterbox, too, which they really won’t like (3). Of course, all cats are individuals, so some will tolerate scented litter, but it’s best to avoid it. The litterbox should be scooped/cleaned often enough that it doesn’t reek, anyway.

Cat behaviorist Jackson Galaxy gives his tips for a litterbox your cat will want to visit

Special Considerations

Kittens and Trainees

There are some things to keep in mind when deciding what to put in the litterbox of kittens, especially very young ones. Years ago, a magazine article sounded the alarm that clumping cat litter might be dangerous for kittens (10). The concern is that kittens may eat litter because they explore with their mouths, and the clumping litter would clog their intestines (2, 10). Veterinarians don’t see evidence that this is something that really happens much if ever (2, 10). Still, it may be a good idea to stick with non-clumping cat litter while young kittens are getting used to the litter box (2, 10).

When it comes to litterbox training, both kittens and adult cats that haven’t used the box before can benefit from special litter (1, 6). Cat attractant litters and litter additives are formulated to emit a scent that gets cats’ attention and draws them to the litterbox (1, 6). Kerrie McKeon, designated cat expert for the Greater NYC animal rescue Bideawee, swears by this stuff (1). When Bideawee rescued a large group of cats, none of which had ever used a litterbox, she filled their litterboxes with cat attractant litter (1). All of the cats learned how to use a litterbox without the need for medication (1).

Asthma and Respiratory Disease

For cats with asthma or other respiratory ailments, litter dust can be a big problem (1, 9). It’s right in their faces! “Imagine trying to use the bathroom in a dust storm,” explains feline training-and-behavior specialist Cathy Bosley (1). All that dust can be a serious respiratory irritant and cause or worsen an asthma attack (9). There’s probably no such thing as a truly dust-free litter. Still, the goal is minimal dust. Litter specifically meant for cats with respiratory ailments or paper-based litter can be good options (9).

Surgical Recovery

Cats that are recovering from surgery, even a routine spay/neuter, need special consideration. Their litter might not be the first thing to come to mind as part of their aftercare, but it can make a difference. Some types of litter can get stuck and build up on sutures, bandages, wounds, etc. (1, 9). Clumping litter is the primary culprit for this problem (1). Besides being gross, stuck litter can irritate sensitive tissue (1). I can only imagine what kind of infection risk it poses. Pelleted paper cat litter is the gold standard for surgical recovery because it does not stick (1, 9). Cats are not fans of sudden changes, though, so if you have the time before a scheduled surgery, it’s best to start switching litters beforehand.

Declawed Cats

Never, ever declaw a cat. Ever. But maybe you already have a declawed cat. My former roommate and I once adopted an abandoned cat and discovered that all four of his paws had been declawed, which is almost never done. So if you’ve already got a furry friend who is missing the ends of their digits, they may have some issues that other cats don’t. Litterbox trouble is a common one. Declawed cats have chronic foot pain, and the litterbox can make this worse (8). The act of digging can be difficult and/or painful (8). Also, the dust and particles of litter between their toes, as well as grooming it out later, can really hurt declawed cats (8). The right cat litter can alleviate the discomfort, however.

The key is to find the softest cat litter possible (8). Pelleted litter is usually a bad idea–it’s too hard and bumpy (8). Look for lightweight, fine-grained litter (8). Eco-friendly litters can be softest, depending upon what they’re made of and the texture, so maybe give them a try (8). My roommate used a wheat litter for the declawed rescue cat. He was equally happy with the grass litter in Joon’s boxes.

Works Cited

  1. Adelson, K. I. (2020, October 1). The best cat litter, according to vets. The Strategist. https://nymag.com/strategist/article/best-cat-litter.html
  2. CatHealth. (n.d.). Best litter for kittens: Is clumping litter safe? CatHealth.com. https://www.cathealth.com/cat-care/safety/2300-best-litter-for-kittens-is-clumping-litter-safe
  3. CatHealth. (n.d.). What is the best type of cat litter? CatHealth.com. https://www.cathealth.com/cat-care/accessories/2439-what-is-the-best-type-of-cat-litter
  4. Golon, C. (2014, August 5). The cat owner’s guide to kitty litter options. VetStreet. http://www.vetstreet.com/our-pet-experts/the-cat-owners-guide-to-kitty-litter-options
  5. Lee, J. A. (2008). Kitty litter: Does it really matter what type I buy? Pet Health Network. https://www.pethealthnetwork.com/cat-health/cat-behavior/kitty-litter-does-it-really-matter-what-type-i-buy
  6. Nicholas, J. (2021, March 21). Litter box 101: What type of litter is best for your cat. Preventive Vet. https://www.preventivevet.com/cats/what-type-of-litter-is-best-for-your-cat
  7. Petco. (n.d.). Choosing the best cat litter for your household. https://www.petco.com/content/petco/PetcoStore/en_US/pet-services/resource-center/new-pet/Choosing-the-Right-Cat-Litter.html
  8. PetMD Editorial. (2019, April 9). What’s the best litter for declawed cats? PetMD. https://www.petmd.com/cat/care/whats-best-litter-declawed-cats
  9. Robins, S. (2020, January 26). Finding the right litter. Catster. E-newsletter.
  10. Schultz, J. L. (2003). How to choose a cat litter. Petfinder. https://www.petfinder.com/cats/bringing-a-cat-home/choose-cat-litter/

Published March 28, 2021

Behavior

Why do cats purr?

mehshadoweye

Meredith Hemphill

mehshadoweye

Encyclopaedia Felidae now has a Patreon! Go to www.patreon.com/EncyclopaediaFelidae if you want to help support this content!

Brown tabby cat in lap
Image by Hans Braxmeier from Pixabay

What could bring more joy than a purring kitty curled up in your lap? And there are so many different kinds of purrs. Some cats purr like a lawn mower engine, and some are so quiet you could barely hear them with your ear on their chest. Purring is a uniquely feline behavior. We associate it with happy kitties, but cats actually purr under a lot of different circumstances. This rather odd sound must serve a purpose besides being adorable. So why do cats purr?

Anatomy of the Purr

First things first: what even is purring? As someone who used to try it for myself as a child, I promise it doesn’t come naturally if you aren’t a cat. There was a lot of debate about how cats purred for a long time. One prominent theory was that the purring sound came from a change in the cat’s blood flow [1, 4, 6]. Now, biologists are generally agreed that cats purr using the muscles of their larynx and diaphragm [1, 3-5, 7]. By vibrating their larynx, which in turn vibrates their hyoid bone [5], a cat causes the air in their throat to vibrate as well, creating the sound we know as purring [1, 6].

Most vocalizations can only be made when exhaling. It just makes sense. You need air in your lungs to push through your larynx to talk, sing, laugh, etc. The same is true of other animals. However, cats can purr on the exhale and the inhale, which is what enables them to purr constantly [1-5, 7]. This is due to the continual vibration of the larynx as they breathe in and out through it [1].

Cats Purr to Communicate

Cats first start to purr by the time they are a week old [1, 2, 4]. The purring of her newborns may signal to a queen their location and wellbeing [1, 2, 4]. It is thought that each kitten has a unique purr their mother can recognize so that she can tell which of her babies is communicating with her [2].

Queens will also purr for their kittens [5, 6]. One reason may be to provide a tactile cue to help blind and deaf newborn kittens locate the milk supply [6]. Even though very young kittens can’t hear the purring yet, they can feel the vibrations because they are, ideally, never far away. Alternatively, the mother’s purring may disguise the soft mews of the kittens from the ears of predators [5]. Whatever the evolutionary reason, purring cements the bond between queen and kittens [5].

Some adult cats purr when feeding, possibly a throwback to that kittenhood behavior [1]. Cats may also purr to inform their person that they want their food, now please [1]! The purr of solicitation sounds different from the snuggly purr [1]. What’s the difference? It’s hard to say for sure. Our lack of knowledge about how cats communicate with each other makes it harder to understand the nuances of how they communicate with us.

One thing that’s certain is cats in the wild purr when they groom each other [1]. Grooming is an important part of a cat’s daily life and a positive social interaction between cats who have a bond. Perhaps this comes closest to the contended purring of a cat that is lying in a warm lap or being petted.

Mother cat and kittens in barn
Queens and their kittens purr to communicate – Image by Franz W. from Pixabay

Healing Vibrations

Cats don’t just purr for happy reasons. They sometimes purr when they’re stressed, scared, injured, or dying [1, 3-5, 7, 8]. Cats have sometimes been seen lying alongside another, injured cat, both purring [7]. This is called “purr therapy” because the purring is believed to be a way of comforting the injured cat [7]. In stressful situations, purring can serve as a method of self-soothing [7]. However, it may be an even more powerful tool than that.

Cats purr at a frequency of 20-150 Hertz [1, 3]. These low-frequency vibrations have demonstrated healing benefits [1, 3, 4, 7, 8]. 25 and 50 Hz frequencies promote bone growth and fracture healing [8]. 100 Hz has therapeutic use for pain, wound healing, swelling, and difficulty breathing [8]. It may seem far-fetched, but bones do respond to pressure by hardening [1, 7]. And there is a good evolutionary reason why cats might vibrate their way to good health.

Cats are ambush predators. This means they spend a lot of their time resting and waiting in-between hunts. Purring could have evolved as a low-energy way to stimulate their muscles and bones while stationary [3, 7]. Then their bones wouldn’t weaken or become brittle over time from lack of use [7]. Interestingly, researchers have proposed just such a fix for astronauts. Muscle atrophy and bone density loss are a big problem on long space missions where the lack of gravity prevents normal exercise. Vibrating foot plates have been suggested to stimulate astronauts’ bones and prevent them from losing density [7]. It seems the cats had that figured out a long time ago.

Do All Cats Purr?

Probably not, but it kind of depends upon how you define purring, apparently. Once upon a time in the early 1800s, biologists believed that cats could either roar or purr, but it was impossible to do both [7]. This is how cats came to be divided into the “big cats,” or subfamily Pantherinae, and the “small cats,” subfamily Felinae [6, 7]. Although most big cats are larger than most small cats, those names are actually a misnomer, since the smallest of the “big cats,” the clouded leopard, is smaller than the biggest of the small cats, the puma [7]. The basis of the division on roaring vs. purring is also probably inaccurate.

Two sleepy bobcats
Housecats aren’t the only ones that purr! – Image by Amber Stevens from Pixabay

The Pantherinae cats have a rope of tough, flexible cartilage where the Felinae have only the hyoid bone [5, 6]. This gives the larynx greater flexibility so that roaring is possible, although lions are the only ones to make regular use of this ability [5, 6]. Does this mean they can’t purr, though? These days, biologists tend to believe than most cats can purr, or at least something like it [3, 7]. Some call it a purr-like vocalization or a hum rather than a true purr [3, 4, 6].

Even granting that most cats can actually purr, some of the Pantherinae are usually believed to be exceptions: lions, leopards, jaguars, tigers, snow leopards, and clouded leopards [7]. But that may yet prove untrue. The anthropologist and animal behaviorist Elizabeth Marshall Thomas suggests that big cats may reserve purring for their cubs and that is why people think they don’t purr at all [6]. We simply aren’t around when they do.

Works Cited

  1. Dowling, S. (2018, July 25). The complicated truth about a cat’s purr. BBC Future. https://www.bbc.com/future/article/20180724-the-complicated-truth-about-a-cats-purr
  2. Edwards, A. (2006). The ultimate encyclopedia of cat, cat breeds, and cat care. Hermes House: London.
  3. Lyons, L. A. (2006, April 3). Why do cats purr? Scientific American. https://www.scientificamerican.com/article/why-do-cats-purr/
  4. Science Reference Section. (2019, November 19). Why and how do cats purr? Library of Congress. https://www.loc.gov/everyday-mysteries/item/why-and-how-do-cats-purr/
  5. Stewart, D. (1995, April 1). Do lions purr? And why are there no green mammals? The National Wildlife Federation. https://www.nwf.org/Magazines/National-Wildlife/1995/Questions-and-Answers-About-Wildlife
  6. Thomas, E. M. (1994). The tribe of tiger: Cats and their culture. Simon & Schuster: New York.
  7. Venton, D. (2015, May 8). Why do cats purr? It’s not just because they’re happy. Wired. https://www.wired.com/2015/05/why-do-cats-purr/
  8. von Muggenthaler, E. (2001). The felid purr: A healing mechanism? The Journal of the Acoustical Society of America 110(5), 2666. https://doi.org/10.1121/1.4777098

Published February 7, 2021

Updated June 20, 2022

Cat Care

In Search of the Best Cat Food, Part IV: Grain-Free, L.I.D., & Raw Diets

mehshadoweye

Meredith Hemphill

mehshadoweye

Encyclopaedia Felidae now has a Patreon! Go to www.patreon.com/EncyclopaediaFelidae if you want to help support this content!

There are trends in pet food just like there are among humans. Increasingly, there has been a movement toward more “natural” pet foods. The idea is to feed pets a diet in line with what they would eat in the wild or what their ancestors ate. However, as my mother is fond of saying, arsenic is natural, too. We need to look past the marketing and make sure that these diets are really all they’re cracked up to be.

Grain-Free Diets

Photo by Nick Fewings on Unsplash

Grain-free diets are fairly self-explanatory. They contain no grains, i.e. wheat, corn, oats, rice, or any other crop in the group. These foods are also gluten-free, but not all gluten-free cat foods are grain-free, as gluten is a protein found in wheat, so other grains may still be included in some gluten-free diets. The concept behind grain-free cat food is that cats, as obligate carnivores, would not include grains in their native diet, which is mostly true. Cats would not chow down on grains in the wild, but they do eat their prey in its entirety, including the stomach contents, which can certainly include grains or other vegetation. The argument that a high-carbohydrate diet is unhealthy for cats still stands nonetheless, and this has largely been the appeal of grain-free cat food.

A Tufts University Study compared 35 grain-free dry cat diets to 42 regular dry cat diets and found that the average carbohydrate content of the grain-free diets was 12 g/1000 kcal lower (1). The individual carbohydrate contents varied widely, however, so it depends a lot upon the food in question (5). The carbohydrate levels are not all that matters, however. Cats are known to be able to digest grains and obtain nutrition from them (2, 3). Considering that cats evolved eating lots of rodents and rodents eat lots of grains, this makes sense.

Grain-free foods don’t simply ditch the carbohydrates–they replace the grains with starchy vegetables like potatoes, lentils, cassava, or peas. There isn’t much research on how digestible these plants are or how bioavailable their nutrients (3). At least some cats get gastrointestinal symptoms from consuming them (4, 5).

Some owners may choose grain-free diets over concerns about food allergies. But food allergies are uncommon in cats. A 2018 study found that only 0.1% of cats had them (10). When food allergies do develop, it is usually to animal products like beef or dairy, not plants (2, 3, 4). Gluten intolerance has not been documented in cats, so that’s no reason to avoid grains (3). Obviously, if your cat really does have a documented allergy to a grain, then you want to make sure their diet is at least free of that grain. If you suspect an allergy, talk to your veterinarian before you do anything else.

I would be remiss if I didn’t mention the concerns about grain-free diets and heart problems that have been brought up in the last several years. Although the connections are primarily being investigated in dogs, it has been impossible not to wonder if there is reason to be worried about cats. Around 2017-18, veterinarians began to raise concerns over cases they saw of dogs fed grain-free diets developing dilated cardiomyopathy, a form of heart disease causing an enlarged heart (6).

The US Food and Drug Administration (FDA) decided to investigate, and they still are. It’s thought that taurine deficiency might play a part, and diets containing legumes or potatoes as the primary carbohydrate might be the culprits, but it remains unclear (7). There were only a handful of reports on cats, so the FDA chose to focus on dogs, and there has been no further word on whether there may be a link between a grain-free diet and heart problems in cats (6).

Grain-free diets, at least the way they are manufactured today, are probably not as beneficial as we may have been led to believe. They may even be harmful, although more research will have to be done for us to know for sure. I’ll admit, I used to be one of those people who thought I had to feed my cats grain-free food. It sounds so much healthier for them! But that’s what marketing is for, isn’t it?

Limited Ingredient Diets

Limited ingredient diets, or L.I.D., are not just one thing. L.I.D. is a bit of an umbrella term, encompassing a group of diets that have a narrower range of ingredients than usual. They are generally meant for cats with known or suspected food allergies, and in fact they can be helpful for such cats. L.I.D. often contain only single protein and carbohydrate sources, i.e. lamb and rice or salmon and potato (8, 9). This makes is easy to be sure that a cat with food allergies or sensitivities is not eating an ingredient they are allergic to.

Novel source of protein? – Image by sven kopping from Pixabay

Many L.I.D. are made with “novel” sources of protein and/or carbohydrates that pets are unlikely to have encountered before, and therefore probably won’t have developed an allergy to (8, 9). These range from the rather mundane–duck, rabbit, sweet potato–to the very out in left field–alligator, kangaroo (8, 9). L.I.D. may also be used as part of a series of elimination diets to figure out what a cat with suspected food allergies is allergic to, under veterinary supervision (9).

Aside from cats with food allergies, some L.I.D.s may be helpful for cats with sensitive digestion as well (8). Otherwise, there is really no particular need for a healthy cat to be on a L.I.D. If you think your cat might benefit from one, especially if you suspect your cat may be suffering from allergies, talk to your veterinarian about it. Most cats with allergies are allergic to fleas or something else in their environment, not their food (10). If food allergies are suspected, there is a long process of testing via elimination diets to determine what, if anything, in the diet your cat is allergic to (9).

Raw Diets

This is a tough nut to crack. While I was doing my research, I read a particular article which was harshly critical of raw diets for cats. One of the drawbacks they listed was that there has been very little research done on these diets. As someone who was lately a research scientist, I kind of want to bash my head against a wall. The solution to a lack of research is to do the research, not to declare that the under-researched thing is bad.

But the fact that there is currently a lot of anecdotal information and not much in the way of scientific studies is a lot of the problem with raw diets, I think. It’s difficult to decide whether the proponents or the detractors have the firmer position because both have only a handful of studies to back them up. The rest is a matter of logic, tangential information, and beliefs.

Before we go any further down this rabbit hole, let’s talk about what a raw diet is. The definition can be a bit variable, but the basic principle is that the food is made of uncooked ingredients. A raw pet diet is mostly muscle meat, organs, ground bone, eggs, and sometimes vegetables, fruits, and dairy (11). Some people make homemade raw diets, but they can be purchased in a variety of forms as well. The goal is to simulate the natural diet of the pet, or its ancestors in the case of dogs, which are highly domesticated animals and don’t really have a natural diet. For cats, their diet in the wild, ideally, is whole prey animals like mice, birds, fish, and small reptiles.

Image by A_Different_Perspective from Pixabay

Proponents of raw diets for cats say that raw meat is more nutritionally sound, having not been exposed to heat that might break down or alter nutrients, and it’s more biologically appropriate for cats anyway (12, 13). They claim that the diet can prevent or alleviate many feline ailments (13, 14). The evidence for this remains anecdotal, but this will necessarily be the case until rigorous research is done to investigate. Nonetheless, some veterinarians have begun to recommend raw diets based on their experience with them, but most fall into the other camp.

The detractors of raw diets, and there are many, say that raw diets are dangerous and have no major benefits. The American Veterinary Medical Association, American Animal Hospital Association, Companion Animal Parasite Council, and Centers for Disease Control have all taken a position against feeding pets raw diets (15). The primary concern is food-borne infections. This is the reason public health authorities tell us humans not to eat undercooked meat and to carefully avoid cross-contamination. Raw food, especially raw animal products, can carry bacteria and parasites. And studies have shown that raw pet foods do (12, 15), which is to be expected, really. The professionals who decry raw pet foods take the position that the risk of disease to both pets and humans outweighs what little benefit, if any, they see in these diets.

Even here there are two sides: those in favor point out that cats, being carnivores, have short, acidic digestive tracts designed for digesting meaty meals without allowing pathogens to proliferate in their guts (13, 14). Not to mention that cooked pet foods have been found to be contaminated with pathogens or toxins before, so perhaps to say raw foods are unsafe draws a false comparison (13)? That’s another case where I doubt anyone has crunched enough data to be sure. Even raw diet cheerleaders readily say that owners need to be careful not to give themselves food poisoning if they feed their cats a raw diet. Using proper food-handling technique should prevent any problems. It’s also important to dispose of uneaten food promptly and cleaning and sanitizing the food dish, as well as the area around it if any food gets on the floor.

Is raw food a good idea for your cat? In general, there’s so little concrete information that it’s hard to say. My instinct is that cats are carnivores, so it should be fine, as long as the diet is well-balanced. It needs to be either an approved commercial diet (AAFCO-approved in the United States) or a homemade diet using a recipe designed by a veterinarian or veterinary nutritionist. If you are thinking about going the homemade route, be very careful about looking for recipes on the internet, because there are lots of them, and many are just made up by people with cats, not experts in cat nutrition.

Also, some cats and some households should not use raw diets. Cats on immunosuppressants (like chemotherapy drugs) or high doses of steroids should not be feed raw food diets, as their immune systems may be more vulnerable to the pathogens in raw animal products (13). Households with very young children or elderly people, or anyone with a compromised immune system, probably shouldn’t use a raw cat food, either (11, 12, 13). Pathogens from their food can pass into a cat’s stool and even remain on the cat, especially on their face, in addition to the aforementioned concerns of pathogens being on food prep and feeding surfaces (12). In a home where there are people–or pets–with weak immune systems, this could be very dangerous. The jury may be out on raw diets in general, but there is definitely a subset of households where they will never be appropriate.

Works Cited

  1. Prantil, L.R., Heinze, C.R., and Freeman, L.M. (2017). Comparison of carbohydrate content between grain-containing and grain-free dry cat diets and between reported and calculated carbohydrate values. Journal of Feline Medicine and Surgery, 20(4), 349-355. https://journals.sagepub.com/doi/full/10.1177/1098612X17710842
  2. Freeman, L.M., Linder, D.E., and Heinze, C.R. (2016, June 14). Grain-free diets: Big on marketing, small on truth. Petfoodology. https://vetnutrition.tufts.edu/2016/06/grain-free-diets-big-on-marketing-small-on-truth/
  3. Cats Only Vet Hospital. (2019, June 3). Grain free and other marketing trends. https://catsonlyvethosp.com/grain-free-other-marketing-trends/
  4. Buzhardt, L. (n.d.) What’s in my cat’s food?: Designer diets, grain free diets. VCA Hospitals. https://vcahospitals.com/know-your-pet/whats-in-my-cats-food-designer-diets-grain-free-diets
  5. Heinze, C.R. (2017, July 3). Research update: New insight into grain-free cat diets. Petfoodology. https://vetnutrition.tufts.edu/2017/07/research-update-new-insight-into-grain-free-cat-diets/
  6. Cats Herd You. (2018, August 22). What do grain-free pet food warnings mean for cats? https://catsherdyou.com/what-do-grain-free-pet-food-warnings-mean-for-cats/
  7. US Food and Drug Administration. (2018, July 12). FDA investigating potential connection between diet and cases of canine heart disease. https://www.fda.gov/animal-veterinary/cvm-updates/fda-investigating-potential-connection-between-diet-and-cases-canine-heart-disease
  8. LID diets for dogs and cats. (2017, June 26). Pet Central, Chewy. https://petcentral.chewy.com/lid-diets-dogs-cats/
  9. Anderson, K. (2020, July 2). Meals that heal: The best food for cats with allergies. The Dog People, Rover. https://www.rover.com/blog/best-food-cats-with-allergies/
  10. Burns, K. (2018, June 27). Banfield: Few pets allergic to food; flea, environmental allergies rise. American Veterinary Medical Association. https://www.avma.org/javma-news/2018-07-15/banfield-few-pets-allergic-food-flea-environmental-allergies-rise
  11. Association of American Feed Council Officials. (2012). Raw foods. https://talkspetfood.aafco.org/rawfoods
  12. Stregowski, J. (2020, April 30). Should you feed your cat a raw diet? The Spruce Pets. https://www.thesprucepets.com/raw-food-diet-for-cats-552329
  13. Tasi, A. (2020, January 6). Feeding raw: A veterinarian’s view. The Conscious Cat with Ingrid King. https://consciouscat.net/2020/01/06/feeding-raw-a-veterinarians-view/
  14. Pierson, L.A. (2016, November). Feeding your cat: Knowing the basics of feline nutrition. Cat Info. https://catinfo.org/#Home-Prepared_Diets
  15. Paul, M. (2014, September 24). The dangers of a raw diet for your cat. Pet Health Network. http://www.pethealthnetwork.com/cat-health/cat-diet-nutrition/dangers-a-raw-diet-your-cat

Published August 9th, 2020

Updated October 29th, 2020

Cat Care

Feline Heartworm Disease

mehshadoweye

Meredith Hemphill

mehshadoweye

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To quote Cats the musical, “A cat is not a dog.” This is a fact that is both obvious and often overlooked. Sometimes, cats and dogs are subject to the same illnesses, but that does not mean that they will have the same symptoms or can receive the same treatments. Heartworm disease is a prime example.

Heartworm lifecycle
Heartworm lifecycle – American Heartworm Society

Heartworm is the common name for a blood-borne parasite, Dirofilaria immitis, which normally resides in the heart or attached large blood vessels of an infected animal (1). Mature female worms are 6-14 inches (15-36 centimetres) long and 1/8 inch (3 millimetres) wide, with mature males about half that size (1). They can infect dogs, cats, ferrets, and even, rarely, humans (2). Wild hosts include wolves, coyotes, foxes, and sea lions (2). The heartworm lifecycle begins when a mosquito bites an infected animal. The mosquito sucks up larvae circulating in the bloodstream, called microfilaria (2). The larvae develop into an infectious stage in the mosquito and then enter a new host animal when the mosquito bites it (2). The larvae migrate to the right side of the new host’s heart, where they will mature into adult worms over the next six months.

Heartworms can only be transmitted by mosquitos, not between individual animals, although having a significant population of infected hosts increases the likelihood of infection. Heartworms can live for 5-7 years in dogs and 2-4 years in cats (3), so the infection burden in an animal population can increase quickly over several mosquito seasons, and individuals can be infected multiple times. Heartworm infection is possible throughout the United States and in many other countries throughout the world. Thirty species of mosquito can carry the larvae (1). Infected wildlife or mosquitoes can travel great distances, and infected pets may be moved or adopted to new areas (1), so it is safest to assume that if there are mosquitoes where you live, there is a risk of heartworm.

Worms in plastic container
Preserved heartworms (I know, gross) – Image by Mirko Sajkov from Pixabay

Cats are not a very good host for heartworms. Canines are more hospitable to the parasites. Cats are infected 5-20% as often as dogs in the United State, depending upon the location (4), and the worms often fail to mature inside their bodies. Cats also are unlikely to have circulating microfilaria, and about a third of infections in cats have mature worms of the same sex and therefore produce no larvae at all (5). However, just because cats are an imperfect host does not mean that they cannot suffer severe or sometimes fatal symptoms.

Because cats are so much smaller than most dogs, they don’t have space for nearly as many of the parasites. They usually have only 1-3 mature worms, if they have any adults at all (2). Even a few worms is still considered a heavy infection, however, due to a cat’s size (3). And even a cat with only immature worms can still have significant disease. Although the term “heartworm disease” would suggest that the symptoms primarily affect the heart, in cats heartworms tend to cause respiratory problems. Heartworms, once mature, often take up residence in the pulmonary arteries that take blood from the heart to the lungs (6). There, worms can block the arteries, and dead and dying worms cause inflammation that compounds the problem (6).

Cats are subject to a complication known as heartworm-associated respiratory disease (HARD). The symptoms of HARD are rapid and labored breathing, coughing, and gagging. Unfortunately, these symptoms are also indicators of asthma or bronchitis, making it difficult to distinguish a heartworm infection from other forms of respiratory distress. Other symptoms of heartworm infection are also non-specific: vomiting, loss of appetite, and weight loss. In more severe cases, cats may have seizures, faint, struggle to walk, or accumulate fluid in their abdomens. Sometimes, the first sign that something is wrong is sudden death.

If heartworm is suspected in a cat, it is much harder to diagnose an infection than in a dog. It is typical to have to use multiple tests, often more than once (7). This is because the unusual nature of heartworm infection in cats makes many tests less reliable, including the antigen blood test which is the gold standard for dogs (7). The antigen test detects mature female worms, but will not detect an infection with only male or only immature worms (5). Because both of those types of infection are likely in cats, there is a high rate of false negative results. Still, 50-70% of cats are estimated to have at least one female worm, so the test is worth a try (7).

The antibody test is another blood test which detects the cat’s immune response to the parasite. While antigen tests can only detect an infection after 6-8 months, once the parasites are mature, the antibody test is effective as early as two months after infection (7). The antibody test can be highly sensitive, but it’s reliability decreases over time and may be affected by the use of certain medications to treat the infection (7). It can also still be positive after a cat has fought off an infection but the antibodies are still in their blood (7). As the antigen and antibody tests are both useful but have major pitfalls for cats, they are best used together.

If the results of the antigen and antibody blood tests are inconclusive, there are other options. The blood can be tested for circulating microfilaria, but less than 20% of cats will have microfilaria, and then only for 1-4 weeks, so the chances of finding them are low (1). X-rays and ultrasounds of the heart and its vessels can look for changes in the shape of the heart and pulmonary arteries (1). Sometimes an ultrasound will even find the mature worms themselves, although this is uncommon since cats have so few worms (1).

When a heartworm infection can be diagnosed, treatment is its own challenge. The medication used to treat heartworm in dogs, melarsomine dihydrochloride, has been shown to be toxic to cats (8, 9). Cats that appear to be doing well or have no symptoms at all may be allowed to continue fighting the infection on their own while being continually monitored and routinely re-tested (7). A course of steroids is a common treatment for cats that need more support.

If a cat is in need of acute care, a veterinarian will step in with treatments for shock and symptoms, such as oxygen, intravenous fluids and steroids, or bronchodilator drugs to open up their airways (7). The goal is to stabilize the cat until they can eliminate the infection on their own. As measures of last resort when an otherwise stable cat seems to have trouble doing this, the drug ivermectin can be given to kill adult worms, or worms may even be surgically removed (7).

Gray and white cat in red window box
Take care of your cat’s heart <3 – Image by Melinda Rózsa from Pixabay

Obviously, heartworm disease in cats is a complicated and difficult matter. The best treatment is prevention. Heartworm preventatives are available as monthly oral or topical medications, or an injection given every six months by your veterinarian (2). In the United States, heartworm medication is available by prescription only, but on the bright side, most heartworm medications also prevent intestinal parasites, and some are effective against external parasites like fleas and ticks (2). The American Heartworm Society recommends using year-round prevention even in places with cold winters, just in case (2). Indoor cats should be treated as well. Mosquitoes have a knack for making their way inside. About a third of cats with heartworm infections are indoor-only (1). You can’t underestimate the diabolical sneakiness of mosquitoes.

For more information about heartworms, visit the American Heartworm Society at https://www.heartwormsociety.org/ or any of the resources below.

Works Cited

  1. Barnette, C. and Ward, E. (n.d.). Heartworm disease in cats. VCA Animal Hospitals. https://vcahospitals.com/know-your-pet/heartworm-disease-in-cats
  2. American Heartworm Society. (n.d.). Heartworm in cats. https://www.heartwormsociety.org/heartworms-in-cats
  3. U.S. Food and Drug Administration. (2019, August 22). Keep the worms out of your pet’s heart! The facts about heartworm disease. link here
  4. Ryan, W.G., et al. (1995). Prevalence of feline heartworm disease – a global review. American Heartworm Society. Proceedings of the heartworm symposium 1995, 79-86. https://www.cabdirect.org/cabdirect/abstract/19960805975
  5. Stannard, R. (n.d.). The facts about feline heartworm disease. Today’s Veterinary Practice. https://todaysveterinarypractice.com/the-facts-about-feline-heartworm-disease/
  6. Cornell Feline Health Center. (n.d.). Heartworm in cats. Cornell University College of Veterinary Medicine. link here
  7. Jones, S., et al. (2014, October). Current feline guidelines for the prevention, diagnosis, and management of heartworm (Dirofilaria immitis) infection in cats. American Heartworm Society. PDF
  8. McLeroy, L.W. (1998). Evaluation of melarsomine dihydrochloride for adulticidal activity against Dirofilaria immitis in cats with intravenously transplanted adult heartworms. MS Thesis, 95. University of Georgia, Athens, GA.
  9. Goodman, D.A. (1996). Evaluation of a single dose of melarsomine dihydrochloride for adulticidal activity against Dirofilaria immitis in cats. MS Thesis, 95. University of Georgia, Athens, GA.

Published June 21st, 2020

Updated November 4th, 2020