Feline Leukemia

Feline Leukemia, also known as FeLV, is the most infectious disease agent producing fatal illness in domestic cats today. About 60 million cats in the U.S. have this virus. Once a cat has contracted FeLV its life span can range from several months to even years, but unfortunately the majority will last for only a few weeks.

FeLV is a retrovirus that interferes with the cat's natural ability to ward off infectious disease agents. A retrovirus is a virus that connects itself to a strand of DNA, tricking it into thinking that it’s just another normal strand, and then it begins to copy itself. FeLV is commonly compared to the Human virus HIV, which is also an immune system weakening retrovirus. People and animals other than felines are not susceptible to Feline Leukemia.

FeLV is spread through a cat’s direct contact with another infected cat. The reason this virus is so contagious is because it transfers itself in saliva, tears, urine and feces. For individuals who have seen two or more cats playing together, it is easy to see how easily the virus can be transferred. Since outdoor cats are more likely to get into fights, they are the most likely to come into close contact with a cat carrying the virus. It can be passed during normal activities as well, however, such as mutual grooming, sneezing, playing and nursing.

After a cat has come into contact with the virus, the virus will begin to replicate in the tonsils and pharyngeal lymph nodes. It then spreads via the bloodstream to other parts of the body, especially the bone marrow, and intestinal tissue, where it continues to replicate. It takes only 2 to 4 weeks after the initial infection for the virus to show up in the blood stream.

The best way to protect your cat from contracting FeLV is to keep him or her indoors. Because of the frequent contact with other cats, an outdoor cat is almost three times more likely to get the virus than an indoor cat.

Checking the signs

The only way to know for sure if a cat is FeLV positive is by having a veterinarian administer a series of blood tests. There are a few signs that you can look for in your cat that should throw up a red flag. If your feline exhibits any of the following symptoms, you should probably take him or her for a visit to the vet, who may decide to run blood work. These symptoms include, but are not limited to:

Depression
Decreased appetite
Diarrhea or constipation
Blood in the stool
Enlarged lymph nodes
Respiratory distress
Decreased stamina
Excessive drinking /urination
Weight loss
Decreased grooming
Abscesses that do not heal
Fevers (>103 degrees F)

Chances are (especially if you have a predominantly indoor cat) that these signs will not be caused by FeLV. Most of these symptoms can also be indicative of other, less serious conditions that your vet will be able to treat easily. Unfortunately, this virus can also be masked in some felines. In rare cases, cats who are infected will exhibit absolutely no symptoms and can, in fact, live a very healthy and normal life. These are carrier cats, and although they are not symptomatic, they can still infect other cats.

Testing your cat

There are currently two blood tests commonly used to check for FeLV: the enzyme-linked immunosorbent assay (ELISA) or the immunofluorescence assay (IFA). Both tests look for a specific protein within the virus. The ELISA test, also known as the kit test, can be performed in your veterinarian's office. The IFA, also called the slide test or Hardy test, must be sent out to a diagnostic laboratory. Both tests detect a protein component of the virus as it circulates in the bloodstream; the ELISA test finds the virus when it is free in the serum, the IFA will detect it within infected white blood cells. Interpretation of a positive or negative result will depend on which of these two tests your veterinarian has selected to use. If a positive diagnosis has been found using the ELISA test, your veterinarian will probable suggest sending a blood sample to a lab to run the IFA test.

Feline leukemia is present in the cat’s blood during two different stages of the infection. The ELISA test can detect the disease during the stage before the bone marrow has become infected (known as viremia) when the cat's immune system still has a chance to ward off the virus. The ELISA test can also detect the virus in the secondary viremia stage. This second stage means that the virus has invaded the cat’s bone marrow, which makes a positive prognosis much less likely.

By contrast, the IFA test only detects the virus once it has reached the second stage. Thus, the cats that test positive in an IFA test remain positive for life. Positive-testing cats in either case are considered infectious, as they are shedding FeLV in their saliva.

Vaccinating your cat

So far this year at Tree House, we have seen an overwhelming increase in the number of stray cats admitted with Feline Leukemia. This may be just a fluke, but you can help protect your cat by having him/her vaccinated. There are several vaccines now available to aid in the protection of your cat against Feline Leukemia. Although none of these vaccines are guaranteed to be100% effective, it’s still a good idea to talk to your veterinarian about getting your cat protected. Even if your cat has been vaccinated, it is still not recommended that he or she live with another cat who is FeLV positive. The vaccine will certainly increase the chance of your cat withstanding a prolonged exposure to an infected cat, but it is a chance that is not worth taking.

The current vaccine against FeLV is safe. Many people have heard that a cat who has been given a certain type of FIV vaccine will test positive for the disease. Since the FeLV vaccine does not contain a living virus, it will not cause your cat to show a false positive on the ELISA of IFA tests.

A Positive Test Result

If an indoor cat does have the virus, and you choose to help him or her, it is important to quarantine the cat from any other felines. The infected cat must have a separate litter box, bedding materials, and food and water bowls. A bleach/water mix (four ounces of household bleach per gallon of water) should be used to clean anything that has been in contact with the contagious cat, including the soles of your shoes. These simple precautions will allow you to control the virus.

The current procedures on treating FeLV positive cats involves knowing how to protect them from exposure to other diseases, ensuring good nutrition, making sure the cat is current on all vaccinations (but not the feline leukemia vaccine), controlling parasites, reducing stress, catching symptoms as they appear, and beginning aggressive treatments. There are currently no specific treatments for FeLV and no known cure for the virus. A large number of therapies have been investigated for FeLV positive cats, but most have not shown encouraging results. There are a few drugs that may help your cat live a little longer. The anti-viral drug AZT has shown some promise, but may cause many side effects. Another drug currently on the market is an oral drug called interferon. This particular drug has been shown to help stimulate the immune system, thus helping the cat to ward off upper respiratory viruses and other similar ailments.