What is Feline Leukemia Virus?

Feline leukemia virus, also known as “FeLV,” is a retrovirus that attacks the immune system and red blood cells. It is the cause of a variety of diseases. FeLV is specific to cats and does not pose a risk to other animals or people.

How do I know if my cat is showing signs of FeLV?

In many cats, FeLV infection results in suppression of the immune system. This means that the cat is less able to defend itself against a wide range of infections that would not normally cause a problem in healthy cats. These secondary infections are responsible for many of the diseases associated with FeLV. Owners should be aware of their cat’s normal behaviors and bring them to the vet right away if anything changes. Some common symptoms of illness include:

• Decreased appetite or anorexia
• Lethargy
• Progressive weight loss
• Frequent sneezing or coughing
• Green discharge from the eyes or nose
• Diarrhea or vomiting
• Poor coat
• Pale gums
• A variety of eye conditions
• Inflammation of the mouth or gums

During the early stages of infection, it is common for cats to exhibit no signs of disease at all. Over time, however, (weeks, months, or even years) an infected cat's health may progressively deteriorate or they may experience repeating cycles of illness and relative health. FeLV is also a common cause of cancer in cats.

How is FeLV transmitted or spread?

Contact with saliva from infected cats is a primary mode of transmission, because the concentration of virus is high in saliva. Transmission most commonly occurs through close, social contact between cats. Behaviors such as mutual grooming, sharing of food and water bowls and litter boxes, and fighting can contribute to transmission. The virus is also shed in blood, urine, feces, nasal secretions, and milk. Infected mothers can pass the disease to their kittens through milk or grooming.

Susceptible cats are kittens and adult cats with weakened immune systems. Healthy adult cats are essentially immune to the disease. The virus cannot survive longer than a few minutes in the environment outside of the cat. This means that if you pet a cat with FeLV and then pet another cat, the risk of transmission is essentially zero.

Diagnostic Tests

The test for FeLV is performed at your vet’s office and usually takes about 10 minutes. A positive test should be confirmed with a second, more sensitive test that is sent to the lab and can take 3-4 days.

Kittens may be tested at any age. However, infection in newborn kittens may not be detected until weeks to months after birth. Therefore, several FeLV tests during the first six months of life may be necessary to feel completely "safe" about a negative test result.

Treatment

Unfortunately, there is currently no definitive cure for FeLV. Veterinarians treating and managing FeLV-positive cats showing signs of disease usually treat specific problems (like prescribing antibiotics for bacterial infections or performing blood transfusions for severe anemia). A relatively effective vaccine against FeLV is available, although it will not protect 100% of cats vaccinated. Cats are most vulnerable to the virus as kittens. Kittens should be vaccinated with a recombinant vaccine. Leukemia is almost-entirely preventable with just two kitten vaccines and a booster one year later. After that, even if the cat is exposed, the vaccines will help protect it -- plus the cat will naturally be more resistant to infection because of its age. Since not all vaccinated cats will be protected by vaccination, preventing exposure remains important even for vaccinated pets.

How can infection of FeLV be prevented?

• Have your cats spayed and neutered.
• Keep cats indoors.
• Don’t allow your cats to interact with cats that are unknown to you and could carry disease.
• If your kitten goes outside, consider vaccination. Speak with your veterinarian.

All cats should be tested for FeLV prior to introducing them into a home, and infection-free cats should be housed separately from infected cats. Food and water bowls and litter boxes should not be shared between FeLV-infected cats and noninfected cats. Unfortunately, many FeLV-infected cats are not diagnosed until after they have lived with other cats. In such cases, all other cats in the household should be tested for FeLV. Ideally, infected and non-infected cats should then be separated to eliminate the potential for FeLV transmission.

The FeLV virus can only live for only minutes outside the cat's body, and is readily destroyed by most disinfectants, so a new, healthy cat can be brought safely into a "contaminated" house within days of the departure of an FeLV-infected cat.

Prognosis

Although many FeLV cats live shorter lives, they will have several great years in their new home. Cats live on average 3 years after diagnosis, but each cat is different. Once a cat has been diagnosed with FeLV, careful monitoring of weight, appetite, activity level, elimination habits, appearance of the mouth and eyes, and behavior is an important part of managing this disease. Any signs of abnormality in any of these areas should prompt immediate consultation with a veterinarian.

How do I keep my FeLV cat healthy?

• Healthy FeLV-infected cats should be housed indoors and kept away from other cats to limit the risk of disease transmission; veterinary checks should be performed at least every six months.
• Keep your cat up to date on routine vaccinations and preventives (such as parasite medications).
• Bring your cat to the veterinarian as soon as you notice they are not feeling well.
• Feed a high-quality diet.

Public Health Implications

There is no evidence that FeLV can be transmitted to humans. The Immune-suppressed owner Immune-suppressed cats and immune-suppressed owners do not mix well. Those who are immune suppressed, be they human or non-human, can be easily infected with common organisms and in turn shed larger numbers of those organisms. This means that someone who is immune suppressed (human or not) can serve as an amplifier for infectious agents. An immune-suppressed cat can increase an immune-suppressed human’s exposure to infectious agents and vice versa. This is obviously not a good situation. The same is true for multiple immune-suppressed cats living together. If possible, there should be only one immune-suppressed individual per home.