Minnesota Valley Humane Society

Q: How is FeLV spread from cat to cat?
A: The feline leukemia virus is excreted in saliva and tears and possibly the urine and feces of infected cats. Prolonged, extensive cat-to-cat contact is required for efficient spread, because the virus is rapidly inactivated by warmth and drying.

Q: How long can a cat survive with FeLV disease?
A: A cat with FeLV disease may live for several weeks to several months, depending on how advanced the disease is at the time of diagnosis. However, it is impossible to tell how long any particular cat will survive.

Clinical Signs

Q: What are the clinical signs?
A: Common clinical signs produced by FeLV include anemia, jaundice, depression, weight loss, decreased appetite, diarrhea or constipation, blood in the stool, enlarged lymph nodes, respiratory distress, decreased stamina, excessive drinking and urination, fetal resorption, abortion, infertility, birth of "fading" kittens, and a syndrome resembling panleukopenia ("cat distemper"). FeLV also interferes with the cat's natural ability to ward off infectious disease agents, so that almost any severe, chronic illness may lead your veterinarian to suspect FeLV. Cancer occurs in some FeLV-infected cats. In those cats the tumor masses may cause such problems as respiratory distress; intestinal inflammation with diarrhea, vomiting or constipation; liver or kidney disease; cloudy eyes; and neurologic abnormalities.

FeLV Testing

Q:What do the FeLV test results mean?
A:The most common test is the enzyme-linked immunosorbent assay (ELISA or kit test) which can be performed in your veterinarian's office. This test detects a protein component of the virus as it circulates in the bloodstream. The feline leukemia virus is present in the blood (a condition known as viremia) during two different stages of the infection. The ELISA test can detect the primary viremia—the stage before the bone marrow has become infected, when the cat's immune system still has an opportunity to ward off the virus. The ELISA test can also detect the virus in the secondary viremia stage - when the virus has invaded the bone marrow, thus establishing a firm and lifelong foothold within the cat. A negative FeLV test does not imply immunity to FeLV, nor does it indicate that a cat has never been exposed to the virus (i.e., it is a test for virus, not the antibody to the virus).

A negative test can be found in cats that:

Have never been exposed to FeLV (which is what we all hope for)

Are incubating the virus at an earlier stage than either test can detect (such cats might test positive later on)

Have overcome a previous infection and thus have not become persistently viremic

Were infected with the virus previously and have developed disease, but for some reason do not have virus in the bloodstream at the time of testing

Treatment

Q: Is there any cure?
A: To date there is no cure for FeLV infection or disease. A variety of chemotherapeutic regimens have been developed, and in certain cases those regimens can produce a temporary remission, depending on the physical condition of the cat and the type of disease that is present. Those drug therapies may allow the cat to continue in a reasonably healthy state for a period of several weeks to several months. However, it must be understood that those are only remissions and not permanent cures. Chemotherapeutic drugs are very potent, and their effects must be monitored carefully, to avoid overdosing the patient.

Prevention

Q: Is there a vaccine to protect my cat against FeLV infection?
A: Several vaccines are now available to aid in the protection of your cat against FeLV infection. The vaccines are produced by various methods, and either contain the inactivated ("killed") whole virus, or a subunit protein of the virus. The principle of protection is the same for each of these vaccines.

Q: Are the FeLV vaccines safe?
A: The FeLV vaccines are as safe as other commonly used feline vaccines. As with any vaccine in animals or humans, some reaction to the vaccine may occur in a relatively small number of vaccinations. The vast majority of cats vaccinated with FeLV vaccines will experience no reaction at all. Occasionally, your cat will experience some malaise for a few hours or for a day or two after vaccination. On rare occasions, an allergic reaction to one of the components of the vaccine may occur which will result in fever, diarrhea, and malaise. This allergic reaction can be treated by your veterinarian.

Q: How effective are the FeLV vaccines?
A: The FeLV vaccines are reasonably effective in preventing persistent FeLV infection should your vaccinated cat be exposed to the virus. No vaccine is 100 percent effective, and this is true for the FeLV vaccines. The immune response produced by these vaccines will protect most exposed cats from becoming infected with the virus. Occasionally after exposure to the feline leukemia virus, a vaccinated cat will develop a transient viremia (temporarily become FeLV positive for up to 12 weeks), but the immune response produced by the vaccine will control the virus such that these cats will not develop clinical disease. Unfortunately, a small percentage of FeLV-vaccinated cats will not be protected against exposure to FeLV.

Q: What age should my cat be vaccinated for FeLV?
A: Kittens should be vaccinated twice starting at nine to ten weeks of age, with the second dose of the vaccine given three to four weeks later. Your cat should receive annual revaccinations ("booster" vaccinations) against FeLV.

Q: If my cat has been vaccinated, is it safe to have this cat live with a FeLV-positive cat?
A: The FeLV vaccines are not 100 percent effective, and thus a degree of risk occurs when a vaccinated cat is housed with a persistently-infected cat (FeLV-positive cat). It is recommended that FeLV-positive cats not be housed with FeLV-negative cats, even those that have been vaccinated. Certainly, a cat vaccinated against FeLV will have a far greater chance of successfully withstanding an exposure to FeLV than an unvaccinated cat.

Q: My one and only cat just died of FeLV. Is it safe to bring a new cat into my home?
A: Feline leukemia virus is relatively unstable and will not survive outside an infected cat for an appreciable length of time. A waiting period of at least thirty days after removal of an FeLV-positive cat is recommended before a new cat is acquired. Thoroughly disinfect or replace the food dishes, litter pans, and bedding that were used by the infected cat. Floors that are covered with tile or other hard surfaces should be cleaned and then disinfected with dilute bleach solution (4 oz. household bleach to 1 gal. water). Thorough vacuuming of rugs, plus the thirty-day quarantine, should be sufficient to eliminate the virus from carpeting in the household.

Q: Should FeLV-positive cats be euthanized?
A: Removal of persistently FeLV-positive (positive on the IFA test) cats from a household is the only proven effective method for FeLV control. The question naturally arises: what is to be done with such cats after their removal? In the past, some have recommended euthanasia (because there is no reliable means of eliminating the virus from the cat's body, the cat itself must be destroyed, to destroy the virus). Euthanasia has also been put forth as the only effective means for preventing further spread of FeLV within the cat population at large. The question of euthanizing a positive cat is one that must be addressed in each individual case, in consultation with the attending veterinarian. Vaccination against FeLV does not completely replace testing and removal as the method of choice for controlling FeLV.

If you own only one cat and it is FeLV-positive, euthanasia is not necessary from the standpoint of controlling virus transmission, so long as you keep your cat indoors and away from all other cats. You must remember, however, that in time the cat may develop an FeLV-related illness and become so uncomfortable that euthanasia becomes the only humane course of action.

If you have only a few cats and are reluctant to have a positive one destroyed, particularly if it is clinically healthy, a strict intrahousehold quarantine program may permit you to protect your other cats from infection. The FeLV-positive cat must be prevented from having any contact with the negative cats, perhaps by housing it in a separate room within the house. Separate feeding utensils and litter pans should be provided, and hands should be thoroughly washed and clothing (including shoes) after handling and caring for the positive cat. The positive cat should never be allowed outdoors, where it might come into contact with FeLV-negative cats and transmit the virus.

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