Leukemia Virus in Cats..What is FeLV?

Feline leukemia virus (FeLV) is a common disease that occurs in outdoor cats or multi-cat households, mainly. It is the most common cause of cancer in cats and is often fatal. FeLV is caused by a variety of diseases, not just leukemia. FeLV is specific to members of the cat family and does not pose a risk to other pets or people. FeLV infection is found worldwide. The proportion of cats infected differs according to the geographical location, environment, and the lifestyle of the cat.

Signs & Symptoms of FeLV

FeLV infection results in a moderate to severe suppression of the immune system. This means that the infected cat is less able to defend itself against a wide range of infections that would not normally cause a problem in healthy cats. A common occurrence in FeLV-infected cats is the development of a profound and life-threatening anemia, or pale tongue, gums, and nose. Other symptoms are usually seen two to six weeks after contact with an infected cat:

Fever
Loss of appetite
Vomiting
Constipation
Diarrhea
Enlarged lymph nodes
Infertility or other reproductive issues
Eye problems
Changes in behavior

Some cats will show no signs or symptoms due to inadequate exposure to the virus or good immune response. Other cats will fight off the majority of the virus, but still harbor it in their systems without shedding it or infecting other cats. Still others will not produce an adequate immune response, shed the virus, and will usually die from progression of symptoms.

Because this disease suppresses the immune system of your cat, it may lead to other infections and even cancer. Infections of the mouth and eyes are common. Cancers associated with this disease is typically severe and require intensive treatment.

Causes of FeLV

Feline leukemia is caused by a retrovirus cats can contract through direct contact with another cat’s saliva. Cat bites, grooming, and food and water dishes are the main routes of infection. The virus is also easily transmitted from a mother to her kittens, sometimes prior to birth. It may also be shed in the urine and feces, though this is not as common. Feline leukemia virus is not very resilient, and cannot survive outside of the cat host for more than a few hours.

There are three main subgroups of the feline leukemia virus. One cat can have one or more of these subgroups, which may change the route or severity of the disease.

Subgroup A - Most common, causes suppression of the immune system.
Subgroup B - Can be combined with subgroup A and cause the cancers that are related to this disease.
Subgroup C - Least common, causes a severe deficiency of red blood cells, as well as bone marrow damage.

Cats are capable of shedding the virus for long periods of time, but will most likely only shed the virus for 1 to 16 weeks.

Diagnosis of FeLV

Diagnosis begins with a complete history and a physical exam. Your veterinarian will most likely do the following:

CBC/Chemistry Panel - These blood tests will evaluate various internal organ functions, including the heart, liver, kidneys, pancreas, metabolism, and electrolyte balance. The CBC is a measure of the amount and different kinds of red and white blood cells that are present in the body. This will indicate the presence and severity of infection in your cat.
ELISA testing - This stands for "enzyme-linked immunosorbent assay," and is a test used to determine if a cat has been exposed to a certain pathogen by seeing if its body has produced antibodies against the pathogen. It can be used to test for viruses, bacteria, microbes, or other material. In this case, the veterinarian would take a blood sample and test the serum for the antibodies to feline leukemia. The ELISA test is a fast, economical test that is good for detecting early or weak feline leukemia infections. This test can likely be done in less than 20 minutes at your veterinarian’s clinic.
Immunofluorescence - This is a technique used to illuminate either viruses or their antibodies in a tissue or culture using a fluorescent dye. It is typically used to confirm a positive ELISA test. In this case, your veterinarian will expose your cat’s white blood cells to the feline leukemia antigen. The virus will attach to any cell displayed in the sample and show under a microscope as a bright green spot on the slide. If your cat tests positive in this test, it means he/she is shedding virus and is infective to other cats. This test usually has to be analyzed at an outside veterinary lab, and may take one to two days to return results.

Treatment for FeLV

Your veterinarian may treat feline leukemia based on the symptoms your cat shows. They may administer drugs that stimulate your cat’s immune system to fight against the virus. They may prescribe antibiotics or other medications to treat secondary infections. Cancers may be treated using an extensive program of chemotherapy or anti-viral drugs.
There is not a cure for this FeLV, but transmission can be managed by keeping your infected cat away from other cats. Spaying and neutering your infected cat will prevent them from having reproductive disorders or producing infected kittens. Infected cats should be protected from secondary infection by avoiding uncooked food, keeping the environment stress-free, maintaining sanitary conditions in your home, and closely monitoring their symptoms.

Prevention of FeLV

Prevention of feline leukemia virus is achieved by:

Keeping cats indoors and away from infected individuals, especially if they tend to fight with other cats.
Getting all of your cats vaccinated for feline leukemia at a young age. Your veterinarian will require that your cat test negative for feline leukemia before vaccinating.
Getting all of your cats retested and revaccinated on a regular basis.
Bringing only vaccinated kittens that have tested negative for the disease into your home.

Vaccines are available to protect cats against FeLV infection. Their use is highly recommended for any cat that goes outside at any time, and therefore could have contact with FeLV-infected cats. As with other vaccines, an initial course of two injections is required, and regular boosters are necessary to maintain immunity. Your veterinarian will discuss the most appropriate options for your cat with you. All cats should be tested for FeLV prior to vaccination.

Although vaccination is very helpful in preventing infection with FeLV and controlling FeLV-related diseases, no vaccine is 100 percent protective. Where possible, do not allow your cat, particularly kittens, to come into close contact with known FeLV-infected cats, or cats without a known history of proper vaccination.