What Is the Feline Leukemia Virus (FeLV)?

First discovered in the 1960s, feline leukemia virus is a transmittable RNA retrovirus that can severely inhibit a cat’s immune system. It is one of the most commonly diagnosed causes of disease and death in domestic cats.

Because the virus doesn’t always manifest symptoms right away, any new cat entering a household—and any sick cat—should be tested for FeLV.

How Do Cats Get FeLV?

The FeLV virus is shed in many bodily fluids, including saliva, nasal secretions, urine, feces and blood. FeLV is most commonly transmitted through direct contact, mutual grooming and through sharing litter boxes, food and water bowls. It can also be passed in utero or through mother’s milk. Outdoor cats who get into fights with other cats can transmit the disease through bites and scratches. It should be noted that healthy cats over three months of age and vaccinated for FeLV are highly unlikely to contract the virus from another cat.

What Are the Signs of FeLV?

Cats can be infected and show no signs.
Loss of appetite and weight loss
Pale or inflamed gums
Poor coat condition
Upper respiratory infections
Diarrhea and vomiting
Changes in behavior
Vision or other eye problems
Enlarged lymph nodes
Reproductive problems (in females)
Chronic skin disease
Respiratory distress
How Is FeLV Diagnosed?

There are several types of tests available to diagnose FeLV. Most veterinarians and shelter professionals use the ELISA (enzyme-linked immunosorbent assay) test, which detects antigen to the FELV virus in the bloodstream. Other tests like the IFA (indirect fluorescent antibody) test or PCR (polymerase chain reaction) test are recommended to confirm positive ELISA test results.

What Happens to Cats Who Are Infected With FeLV?

FeLV weakens an animal’s immune system and predisposes cats to a variety of infections and diseases, including anemia, kidney disease and lymphosarcoma, a highly malignant and fatal cancer of the lymph system.

Which Cats Are Prone to FeLV?

Young kittens and cats less than one year of age are most susceptible to the virus. Cats who live with an infected cat, cats who are allowed outdoors where they may be bitten by an infected cat, and kittens who are born to a mother who is FeLV positive are most at risk for infection.

My Cat Has FeLV. How Can I Make Her Feel Better?

Feed your cat a nutritionally balanced diet, one free of raw meat, eggs and unpasteurized dairy products, which can harbor bacteria and parasites and lead to infection.
Provide a quiet place for your cat to rest indoors and away from other cats who could promote disease.
Bring your cat to the vet every six months—at the very least—for a wellness checkup and blood tests.
My Cat is FeLV-Positive But Symptom-Free. Can I Get Another Cat?

During the early stages of infection, a cat may not show any clinical signs, but he can still pass the virus to other cats. It’s not advisable to introduce a new uninfected cat into the household, even one who has been properly vaccinated against FeLV. Those living in close quarters with affected cats are most at risk for infection, and should be tested for the virus and, if negative, be housed separately.

Can Other Pets Catch FeLV?

Yes, FeLV is contagious to other cats, but not to humans or other species. Other cats in the house can acquire the virus from an infected cat. Though the virus doesn’t live long outside of the body, and is easily inactivated with common disinfectants, it can be passed through shared food and water as well as common litter boxes.

How Is FeLV Treated?

Sadly there is no cure for FeLV, and it is estimated that less than 20 percent of clinically infected cats survive more than three years of active infection. In the case of those cats who develop cancer, chemotherapy can help prolong life, but treatment often focuses on providing the best quality of life.

How Can FeLV Be Prevented?

There is a vaccine available for cats who are at risk of contracting FeLV. Like all vaccines, there are risks involved in vaccination, and the vaccine is not a 100-percent guarantee against infection. Your veterinarian can best evaluate whether this vaccine is right for your cat.

As with any infectious disease, the best prevention is eliminating sources of exposure. Routine FeLV testing and keeping your cat indoors and away from cats whose FeLV status is not known remain the best way to prevent your cat from becoming infected.