While the name is similar to human blood cancer, feline leukemia virus (FeLV) is a retrovirus — a type of illness that integrates into the host’s genome — commonly known and widespread among felines, both wild and domestic. Just how common is FeLV? In 2010, 3.1% of cats tested in the U.S. (Trusted Source) had the virus. The virus is a leading cause of illness, cancer, and death in cats. But fortunately, due to advances in testing and vaccination, the prevalence of FeLV has decreased over the last 25 years.
FeLV can weaken your cat’s immune system, leading to infections, blood disorders, and some cancers. Cats positive for FeLV also experience the side effects of the virus, making them more prone to abscesses, gingivitis, and other dental problems, and additional health issues.
Many diagnostic tests are covered by pet insurance—find out what is (and isn’t) covered by reading our comprehensive pet insurance coverage guide.
Feline immunodeficiency virus (Trusted Source) (FIV) and Feline leukemia (FeLV) can be similar beyond their acronyms. However, understanding the differences can help better prepare you for seeking treatment. If you suspect your cat of having signs of either virus, contact your veterinarian as soon as possible to get tested.
Both conditions are retroviruses and affect the immune system. They can have similar transmission methods (namely through bite wounds) and some similar symptoms like diarrhea, vomiting, infection, and loss of appetite..
However, FIV can only be transmitted through saliva while FeLV can be transmitted through other means like urine and feces. Cats who have direct contact with these bodily fluids — whether during grooming, shared litter boxes, or food—can contract FeLV. FeLV also has a higher rate of transmission and is easily transferable from cat to cat, even through casual contact. FeLV is also considered a more serious condition.
FeLV can infect a cat of any age and can be passed through several different sources. These include:
FeLV is often known as the "friendly cat disease" as it is often spread between social cats who share food, toys, and groom each other. FIV on the other hand is the "unfriendly cat disease", spread mostly through bite wounds.
Dr. Liza Cahn
Early signs of FeLV are not easily detected as most cats don’t display any symptoms. As the virus moves through your cat’s system, symptoms will begin to show.
There are several blood tests needed to diagnose and confirm the presence of FeLV. Vets will often start with an ELISA test, (Trusted Source) which is quick and routine at vet offices. If your cat’s blood comes back positive, your vet may administer an IFA test to detect the presence of virus within the white blood cells and confirm an active infection. Positive cats should be retested in 6-12 weeks to distinguish between regressive and progressive infections. A PCR test may also be recommended.
There are several ways that a cat’s body can handle exposure to FeLV:
If your cat hasn’t eliminated the virus, it will spread to other parts of their body like the intestines and lymph nodes. During the more advanced stages, the virus can work itself into your cat’s bone marrow and at that point, clearing of the virus is highly unlikely and they will be infected (and able to transmit disease) for life.
Feline leukemia doesn’t have a cure. Since the virus can cause secondary infections, treatment is often given for those infections that may occur in the upper respiratory tract, urinary tract, or skin. If your cat does experience a secondary infection due to their weakened immune system, vets will prescribe antibiotics. Sometimes, illness can cause fever or poor appetite in which case your vet may prescribe appetite stimulants, special foods, or anti-inflammatory medications. Less commonly, cats with feline leukemia may experience anemia requiring a blood transfusion. (Trusted Source)
Preventing secondary infections is an important way to keep your cat’s quality of life high. Some ways to do that may include limiting their access to the outdoors or their exposure to other cats. Unfortunately, any illness can be a tremendous threat to your immunocompromised cat’s life.
Unfortunately most cats with the virus will not have the same lifespan as a noninfected cat. Often, the lifespan following diagnosis can be 6 months to 6 years, with a median of 2.5 years. Cats with regressive disease can have normal lives for much longer, but the virus may reactivate.
There are ways to minimize their risks of secondary infection such as limited time outdoors (consider a catio or cat harness), keeping them away from potentially ill cats, preventing fighting/scraps with other animals, washing your hands before handling them, and ensuring they don’t share food or water with other pets. Other ways to manage your cat with FeLV include:
Since there is no cure for FeLV, the best way to protect your cat from FeLV is to prevent their exposure in the first place. The easiest way to do this is to ensure they receive the initial vaccine series. No vaccine is 100% effective, so it’s important to ensure your cat stays up to date with their annual booster shots. This is especially important for kittens and cats that are exposed to the outdoors or who have contact with cats that may be potentially infected. Cats should be tested for FeLV prior to vaccination.
This depends on when they were diagnosed, the type of infection they have, and many other factors. The average lifespan after diagnosis may range from 6 months to 6 years.
The symptoms vary but can include pale gums, enlarged lymph nodes, fever, infections, and weight loss.
The virus will only survive for a few hours outside of a cat. Surfaces and households can be easily disinfected without the worry of risk.
The prognosis of FeLV is not necessarily fatal. Some cats live for years with FeLV, but once infected, death is usually caused by FeLV. The cause of death can be directly or indirectly related to FeLV since FeLV can cause infections, other diseases, and some cancers. Some of these issues may not occur until later in life.
Unfortunately, there is currently no cure for FeLV. Prevention is often the best plan for pet parents.
