Feline leukemia virus (FeLV) is an infectious disease of cats that suppresses their immune system, making them susceptible to infections. Because it can be easily spread from one cat to another, it's one of the most common infectious feline diseases, affecting 3.1% of all cats in the United States. It's a disease that can go undetected for quite a while, and there's no cure. FeLV can ultimately cause cancer in cats, and it’s one of the few cancers in any species that can be prevented via vaccination.
FeLV is transmitted from other infected cats "shedding" the virus — a time when the virus is replicating in the body and released into the environment through their saliva, nasal secretions, urine, feces, and milk. This means cat-to-cat transfer may occur during grooming, through bite wounds, and even by simply sharing feeding dishes and litter boxes. It can also be transmitted from infected mother cats to their kittens while still in the womb or nursing.
Beyond cats who have close contact with infected cats, the American Association of Feline Practitioners (AAFP) has identified several other risk factors for FeLV:
It's important to remember that indoor cats can be infected with FeLV; they're just less likely due to the reduced chances of being exposed to another cat who is already infected with FeLV. The risk increases if they spend any time outside or with other cats who have not tested negative (even cats that hang out in screened in rooms or catios may have saliva contacts with other cats).
Age can also play a role in a cat's susceptibility to infection and the severity of symptoms. Kittens have the highest risk of infection and progressively worsening symptoms over the course of their lives. However, adult cats may be susceptible to FeLV infection after long-term exposure.
It's common for cats to show no signs of the disease during the early stages of an FeLV infection. Over time, which can be weeks, months, and even years, symptoms may surface, including:
If your cat shows any of these symptoms, it's essential to have them checked out by your veterinarian.
Because this disease is highly contagious and infection comes with serious health consequences, the AAFP recommends that cats should be tested when they are:
Testing is done using a small blood sample. The first test is typically used as a screening tool and can be performed at your veterinary clinic with results in as little as 20 minutes. A negative result from the first screening test is highly reliable. However, if the result is positive, the next step is to have a confirmatory test done by an outside laboratory, which takes a couple of days.
FeLV can usually be detected in the blood within 30 days of exposure (though sometimes it can take longer). If your cat tests negative, but they could have been exposed to FeLV less than 30 days ago, your veterinarian will likely want to repeat the test at least 30 days after their last potential exposure.
Unfortunately, there is no cure for FeLV. But that doesn't mean hope is lost. For FeLV-positive cats, long term management should focus on the treatment of secondary diseases. Prompt attention should be given to any medical problems that your FeLV-infected cat develops, and preventive healthcare is paramount. Veterinary checkups should be done every six months.
Fortunately, there is a vaccine for FeLV. Talk to your veterinarian about your cat's risk factors and whether they should receive the vaccine. The AAFP recommends FeLV vaccination for: