Feline leukemia virus: what you need to know

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 This is an approved Trusted Source for betterpet. Learn more about Trusted Sources 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.

The difference between FeLV and FIV

Feline immunodeficiency virus Trusted Source This is an approved Trusted Source for betterpet. Learn more about Trusted Sources (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.

How FeLV is transmitted

FeLV can infect a cat of any age and can be passed through several different sources. These include:

• Bodily fluids. FeLV can be passed through saliva, blood, nasal secretion, urine, and feces. That means cats who share toys, bowls, and litter boxes, and groom each other are at risk if one is infected.
• Mother to kitten. Kittens can get infected in utero and through their mother’s milk.
• Proximity to infected cats. Outdoor cats or cats in a shelter or foster care are most at risk since it is harder to detect when or if they come into contact with a FeLV-positive cat.

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.

• Pale or inflamed gums. Pale gums are usually signs of anemia, which commonly occurs as a result of  FeLV. These cats are also predisposed to developing gingivitis or stomatitis (inflammation of the gums and mouth).
• Weight loss or loss of appetite. Your cat may stop eating their food or find no interest in their treats. Your cat may also display a drastic loss in their weight.
• Chronic illness. Due to the virus suppressing your cat’s immune system, they may consistently be sick.
• Enlarged lymph nodes. Your cat’s lymph nodes can be found on their neck as well as other parts of the body. Since lymphoma is commonly caused by FeLV, this can cause your cat’s lymph nodes to swell and increase in size.
• Fever, vomiting, or diarrhea. These early signs of sickness might signal viral infection.
• Infections. Due to your cat’s weakened immune system, they may start developing infections on their skin, upper respiratory area, nose, eyes, and urinary tract.
• Unkempt coat. If you notice your cat’s coat is unkempt or increasingly dry, this can be a sign that they’re unable to clean themselves or that they’re becoming deficient nutrients.

There are several blood tests needed to diagnose and confirm the presence of FeLV. Vets will often start with an ELISA test, Trusted Source This is an approved Trusted Source for betterpet. Learn more about Trusted Sources 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.

Possible outcomes of FeLV infection

There are several ways that a cat’s body can handle exposure to FeLV:

• Abortive. At least 20-30% of cats who are exposed to the FeLV virus are able to fight it off naturally before it spreads.
• Regressive. In this case, the infection has spread to organs and/or bone marrow before it’s removed by the body. Typically, these cats aren’t infectious to others but anything that suppresses their immune system can trigger the virus’ recirculation. This accounts for around 30-40% of cases.
• Progressive. With this type of FeLV exposure, the body is unable to get rid of the virus. They will be permanently infected and infectious to other cats accounting for 30-40% of cases.

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 This is an approved Trusted Source for betterpet. Learn more about Trusted Sources

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:

• Keeping them clean. Secondary infections can be serious so keeping their eyes and ears free of debris and dirt can help prevent eye, ear, and respiratory infections.
• Regular brushing. Manual grooming can keep their skin and coat healthy and can also cue you into any subtle skin infections that might be hiding in their fur.
• Watch for signs of infection. Vigilance when checking them for lethargy, decreased appetite, coughing, drainage, etc. can be vital in preventing a serious infection.
• Preventative care. Keep up to date with routine vet visits as well as flea/parasite/and tick prevention. Similarly, dental care is equally as important.

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.