Feline leukemia virus (FeLV) is a highly infectious disease in cats. It does not spread to humans or other animals. Worldwide, about 1 to 2% of all cats have FeLV. The virus essentially attacks the cat’s immune system and makes the cat susceptible to infections, cancer, and severe anemia. Unfortunately, most cats who develop persistent FeLV die from the virus within 2.5 years.
There is no cure for FeLV, but a cat exposed to the virus can still live a happy and healthy life.
Some experts describe feline leukemia as a sneaky disease. That's because a cat might not show any symptoms in the early stages of FeLV infection. Some don’t show signs for years. Common symptoms of FeLV include:
More severe signs of infection include the development of cancer, like fibrosarcomas and lymphoma, the most common cancer associated with FeLV.
Not all cats exposed to FeLV experience the same outcomes. Some cats' immune systems are able to fight off and successfully eliminate the virus. Those cats can still spread the disease until the virus is out of their body.
However, about 70% of cats aren't able to clear the virus from their systems and develop persistent and life-long FeLV infections. Even when an infected cat doesn't show any symptoms, they still shed the virus and can infect other cats. Since it can take years for a cat with FeLV to get sick, that cat has plenty of time to interact normally with other cats and spread the disease.
Feline leukemia is mostly spread through a cat’s saliva and can pass from one cat to another through shared food or water bowls. Cats that groom each other can spread the disease that way, which is why some veterinarians say that FeLV is for lovers. Though less common, it is possible for cats to transmit FeLV through bites when they fight. The virus can also spread through shared litter boxes, and infected mother cats pass FeLV to their offspring.
Kittens are more likely to become infected than adult cats with the same level of exposure. Kittens also tend to get sick from the virus more quickly than adult cats.
Feline leukemia is diagnosed with a clinical exam, a review of a cat's medical history, and simple blood tests. A veterinarian usually requires 2 tests to confirm that the cat has FeLV because the initial test sometimes produces a false-positive result. The first screening test provides results quickly in the veterinarian's office. The second test that's done to confirm a positive first test has to be sent to a commercial lab because of the technology it uses, and those results can take a few weeks.
There’s no way to cure a persistent FeLV infection, so treatment focuses on managing symptoms. A cat that doesn’t have symptoms doesn’t need any special care besides the basic steps you’d take to keep any cat healthy at home.
A veterinarian might prescribe medications like steroids or administer blood transfusions to help a cat that’s showing signs of sickness. It’s not unusual for a cat with FeLV to need to stay at the veterinary hospital during treatment for severe secondary infections or other serious effects of the disease. The nature of feline leukemia makes it more difficult for a cat to respond to treatment, which is why they might need close observation by a veterinarian and hospitalization.
An FeLV diagnosis can seem scary, but cats with the virus can live normal, happy lives. It’s important to keep a close watch on the cat’s weight, energy level, litter box habits, and appearance. If a cat owner notices something abnormal, they should consult with a veterinarian right away. A cat with FeLV should visit a veterinarian every 6 months.
The only way to prevent feline leukemia is to keep infected cats away from ones that don’t have the virus. If you bring a new cat into your home and you don’t know it’s medical history, you should keep it separated from your other cats until a veterinarian has screened the new cat for FeLV.
Keep your cats indoors so that they won’t come into contact with infected cats. If you insist on letting the cat go outside, try to keep the cat in an enclosed area that’s away from strange felines.
Veterinarians recommend that all kittens are vaccinated against FeLV during the first year of their life. Beyond that, any cat that goes outdoors where it could be exposed to infected cats should continue to get the vaccine. The vaccine is usually not necessary for adult, indoor-only cats. The FeLV vaccine is not 100% protective. If you have a cat with the virus, you should still keep uninfected cats away from it even if they are vaccinated against FeLV.
You should have your cat tested for FeLV if it’s been in close contact with a cat that has the virus or is of an unknown health status. If the test comes back positive, the cat should be tested again in t3 months since some cats can clear the virus from their systems. It’s also essential to rule out false positives.
The good news is that the number of cats infected with the feline leukemia virus continues to drop in the United States because cat owners are vaccinating their cats against it, and more people keep their cat indoors today than in the past. Scientists are exploring the possible use of antiviral drugs to help treat this disease and give cats that have it better outcomes. Until a cure is found, the best approach is to try to prevent the spread of the disease.
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