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In memory of Simba
Feline leukemia virus (FelV) is a fatal virus afflicting cats. One of the most common infectious diseases among cats, FelV is present in approximately 2% of cats in the United States and 3% in Canada (1). It is the leading cause of cancer in cats and can cause a host of other health problems as well. As such, it is imperative that cat people of all stripes be aware of this dangerous disease and how to prevent and cope with it.
When a cat is infected with FelV, virus particles are shed in their saliva, urine, feces, and nasal secretions. Queens also shed the virus in their milk. Cats can become infected by fighting with and being bitten by an infected cat, engaging in grooming, or, more rarely, through sharing a litterbox or food/water dish. Kittens can be infected by their mothers both before and after birth. The virus cannot survive more than a few hours outside of its host, so cat-to-cat contact is usually required. Kittens are more vulnerable to infection than adult cats, as their immune systems are not fully developed. Cats with other illnesses are also at greater risk. However, even healthy adults can be infected, especially with repeated, prolonged exposure.
There is a FelV vaccine which has helped to reduce the prevalence of FelV over the past few decades. The American Association of Feline Practitioners recommends that all kittens receive the vaccine and the one-year booster, but considers it optional for indoor-only adult cats without other risk factors (2). The vaccine is recommended for at-risk adult cats, namely those with access to the outdoors, living with a known FelV+ cat, or living in a multi-cat household where the FelV status of all cats is not known (2). There are no major risks associated with the vaccine (2). Any cat may have an allergic reaction to any vaccine, so it’s best to keep on eye on them for a few hours afterwards.
The FelV vaccine has been refined over the years for increased effectiveness, but no vaccine is 100% effective, so the best strategy is to prevent exposure. Keeping cats indoors will make sure they avoid infected individuals outside. If you do allow your cat outside, supervising them or containing them can also do the trick. Walking them on a leash would count as both. Inside, it is important to separate FelV+ and uninfected cats. Ideally, FelV+ cats should be only cats or should live exclusively with other FelV+ cats so that there is no one to infect. Whenever bringing a new cat into the home, have your veterinarian test for FelV so that there are no surprises. If the new cat tests positive, it is recommended to separate them from your uninfected cats until you decide what to do next.
It can be difficult or impossible to tell by observing a cat whether they have FelV. FelV causes disease progressively and affects individuals differently, so a cat may show few or no symptoms early in their infection. However, there are some signs to keep an eye out for:
- Poor coat condition
- Pale gums, yellow color around mouth and whites of eyes (jaundice)
- Diarrhea
- Weight loss/poor appetite
- Lethargy
- Recurring infections
- Seizures, behavior changes, or other neurological symptoms
FelV gradually causes a cats immune system to deteriorate over time, leading to secondary infections and sometimes blood cancers. Cats may become anemic. Research continues, but so far there is still no cure for FelV. A veterinarian will instead treat the effects of FelV, the other diseases and symptoms it causes. The disease, or rather the problems it causes, will eventually prove fatal, but an infected cat can lead a normal life in the meantime. The median lifespan of a cat after diagnosis with FelV is 2.5 years, which may not seem long to us, but it is quite a chunk of time to a cat, and any time that they are able to enjoy is worth it if we are able to give it to them.
Works Cited
- Levy, J.K., et al. (2006). Seroprevalence of feline leukemia virus and feline immunodeficiency virus infection among cats in North America and risk factors for seropositivity. Journal of the American Veterinary Medical Association, 228(3), 371–376. DOI: 10.2460/javma.228.3.371.
- Scherk, M.A., et al. (2013). Disease information fact sheet: Feline leukemia virus. Journal of Feline Medicine and Surgery, 15, supplementary file. PDF
Published March 12, 2020
Updated April 23, 2020
