Feline leukemia virus: what you need to know

While the name is similar to the blood cancer which affects humans, feline leukemia virus (FeLV) is a retrovirus 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 The Merck Veterinary Manual Trusted provider of veterinary medicine. Go to source had the virus. The virus is a leading cause of illness and death in cats.

FeLV can weaken your cat’s immune system, leading to 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.

FeLV vs FIV: similarities and differences 

Feline immunodeficiency virus (FIV) and Feline leukemia (FeLV) are similar in many ways, aside from their acronyms. Understanding the differences can help better prepare you for seeking treatment. Since these two have such similar signs, it is best to have your cat vaccinated for both during their routine vet visits. If you suspect your cat of having signs of either virus, contact your veterinarian as soon as possible to get tested.

Similarities between FeLV and FIV

• Transmission method. Both viruses can be passed through saliva, in utero, or a mother cat’s milk.
• No cure. There is currently no known cure for either virus.
• Only found in cats. Neither virus is a risk to other animals or humans.
• Weakened immune system. Both viruses can suppress your cat’s immune system making them susceptible to secondary infections and diseases.
• Blood tests. Both can only be diagnosed by blood tests.
• Similar symptoms. A cat positive for either virus may experience diarrhea, vomiting, dental problems, eye infections, and skin issues.

Differences between FeLV and FIV

• Transmission sources. While FIV is only transmitted through saliva, FeLV can be transmitted in multiple ways.
• Bites. FIV transmission is usually the result of catfights involving a deep bite.

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. These are usually signs of anemia, which is commonly a secondary cause of FeLV.
• 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. Nodes are not normally visible. Since lymphoma is commonly caused by FeLV, this can cause your cat’s lymph nodes to swell and increase in size.
• Fever or diarrhea. Both are usually early signs of sickness that 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.

FeLV is only diagnosed through blood testing. There are two blood tests commonly performed, known as ELISA and IFA.

The ELISA test identifies the virus at its early stage — It determines whether the FeLV protein is within your cat. The test can usually be administered in your vet’s office.

The IFA test is usually administered after a positive ELISA test — This test will help evaluate the progress of the virus. According to the ASPCA, cats who are IFA-positive often do not clear the virus from their system, resulting in a poor prognosis in the long term.

Sadly, there is no cure for feline leukemia virus. Once your cat has tested positive, they will live with it for the rest of their lives. Treatments for a positive cat are mostly centered around addressing any secondary diseases that may present later. The good news is that even while your cat is positive, they can still lead a perfectly healthy, normal life.

Since there is no cure for FeLV, the best way to protect your cat is to prevent contact with the virus or vaccinate them against it.

• Keep your cat indoors — Infections can be harder to monitor if your cat comes into contact with cats that are infected.
• Avoid contact with multiple cats —  If you have a household with multiple cats and one that is infected, it’s best to keep them separated. Even with vaccinations, there is still a possibility your cat can still catch FeLV from an infected cat.
• Test any cat before bringing them home — When adopting or purchasing a new cat, it’s best to have them tested with your vet, with or without another cat at home. If you have another cat at home, this will protect them. If you don’t have a cat at home, it’s still a good idea, in case your new family member might be positive.
• Stay on schedule with regular vet checkups — Regular vet visits are important for your cat’s health. With an annual check-up, your vet will monitor your cat’s overall health and keep them updated with vaccinations.
• Vaccinate your cat — The best way to protect your cat from FeLV is for them to receive the initial vaccine. No vaccine is 100% effective, so it’s important to ensure your cat stays up to date with their annual booster shots.