FELINE LEUKEMIA VIRUS (FeLV)

Feline leukemia virus (FeLV) is one of the most common and destructive of all cat viruses.  It is highly contagious from cat to cat.  This disease cannot be transmitted to people or to other animals, other than cats.  This disease is similar to the human AIDS virus in that it suppresses the immune system, decreasing the resistance of the cat to other diseases.  FeLV is one of the MAJOR causes of death in cats today. 

Transmission is through the exchange of secretions:   saliva, blood, and fluids.  It is primarily spread by saliva during cat fights, grooming, mating, licking, sneezing, and sharing food and water bowls.  It can also be transferred from the mother cat to her kittens either during pregnancy or nursing.  The virus does not live outside the cat’s body over 2-3 days.  Research evidence to date shows NO possibility that Feline Leukemia is transmissible to humans.  

Not all cats exposed to FeLV become infected.  About 40% of exposed cats have immune systems capable of destroying the invading virus.   The remainder of exposed cats become persistently infected (30%) or develop a latent infection (30%).  The latter group has inactive virus in their bone marrow, and these virus particles may later become active when the cat becomes ill from another disease, stress or certain drugs.  Of the cats persistently infected, about 25% will die within the first year and 75% will die within 3 years.  Some may live a normal life, but tend to have various chronic illnesses.  It is estimated that 30% of all stray cats are infected today.

There are no signs specific for FeLV infection.  The main effect of the virus is to disrupt the cat’s immune system.  While anemia is the most common disorder caused by the virus, cancer and various other diseases are common.  Disorders commonly associated with FeLV infection include:  chronic respiratory disease;  chronic infection of the mouth, gums and tongue;  chronic eye disease;  frequent or chronic skin disease;  reproductive disease (abortion, stillbirths and kitten deaths);  frequent or chronic urinary tract infections;  chronic digestive tract disease;  loss of appetite;  weight loss;  fever;  lethargy;  and other systemic diseases (infectious peritonitis, hemobartonellosis, toxoplasmosis, polyarthritis).  Cats can have the feline leukemia virus for years before showing signs of the disease.

Cats at high risk are outdoor cats, intact male cats, cats in multi-cat households, and stray cats.  VACCINATION before exposure to the virus is the best means of protection (although no vaccine is 100% protective) other than absolute isolation from other cats.

Diagnosis is made by clinical signs and a positive blood test.  Testing is recommended for kittens at least 8-9 weeks of age, all stray cats, and ill cats.  Because of the incubation period and also the cat’s ability to fight off the disease, it is recommended to perform two tests at least two months apart.  A new kitten or stray cat could be incubating FeLV, and if tested too early in the disease, will receive a false negative result on the test.  A healthy cat that tests positive for FeLV should be re-tested in 2 months to see if that cat is capable of fighting off the virus.  Due to the high accuracy of the tests for feline leukemia, a positive test result is diagnostic for infection.  Some cats with the latent form of the infection may need to have further testing done to prove or disprove FeLV infection.

A diagnosis of FeLV is not an immediate death sentence for the infected cat.  For FeLV positive cats, the following recommendations are made:

1. Keep the cat indoors at all times.  This is beneficial for two reasons—the cat is not as exposed to other diseases, and therefore stays healthier; and the cat is not exposing other cats to FeLV infection.  

2. Bring the cat in for treatment at the first sign of illness.  FeLV positive cats will have a harder time combating infections.  

3. Keep FeLV positive cats on high quality diets, vitamins, and other medications recommended by the Doctor.  It is also very important that the cats not be put in stressful situations.  

4. Examinations performed every 6 months are recommended to monitor the cat’s general health.   It is common for infected cats to need frequent teeth cleanings.  

5. In a multi-cat household, it is not recommended to euthanize (put so sleep) the FeLV positive cat to protect the other cats.  These cats have all been exposed to feline leukemia already by eating out of the same utensils (exchange of secretions) and may also be positive for FeLV or are already incubating the disease.  It is recommended that these cats be tested for FeLV periodically.  

6. Once a case of FeLV is diagnosed in a multi-cat household, all of the cats need to be kept indoors.  This is so that they don’t potentially expose other cats to FeLV, and also so that they do not expose the infected cat to outside sources of disease.  

7. No new cats (strays or kittens) are to be introduced to the household until the following criteria are met:

a)     all positively tested cats are no longer there, and

b)     a follow-up two month testing of all cats achieves negative test results.

Euthanasia is considered for FeLV positive cats when:  the cat is severely ill and recovery is not expected;  the cat is an outdoor cat and cannot be made indoors;  or, the cat is a stray animal with no possibility of being placed in a home.

There is NO CURE for Feline Leukemia once the disease is contracted.

Due to the seriousness of this disease, we HIGHLY RECOMMEND that ALL cats be vaccinated!  This is even recommended for indoor cats due to the possibility of exposure at any time in the future—be it from another cat brought into the household, or the cat escapes outside.  Two booster vaccinations are recommended in the beginning to stimulate immunity.  It is then recommended that the cat receive a booster vaccination every three years to keep a high level of protection by the immune system.

Note: This article is provided by Claws & Paws Veterinary Hospital® for informational purposes only.