Feline Leukemia Virus

GENERAL DESCRIPTION

Feline leukemia virus (FeLV) is a common disease of cats that occurs in outdoor cats or multi-cat households. It is the most common cause of cancer in cats and is often fatal. FeLV is the cause of 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.

SOURCE & CAUSE

Feline leukemia is caused by a retrovirus 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 1-16 weeks.

SIGNS & SYMPTOMS

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 2-6 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. Others 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 these disease are typically severe and require intensive treatment. 

DIAGNOSIS & TESTS

Diagnosis begins with a complete history and a physical exam.  Your veterinarian will be 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 the amount and different kinds of red and white blood cells are present in the body. This will indicate the severity and presence of infection in your cat.
• ELISA testing - This stands for "enzyme-linked immunosorbent assay" is a test used to determine if a pet has been exposed to a certain pathogen by seeing if it’s 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 under 20 minutes at your vet 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 make expose your pet’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 is shedding virus and is infective to other cats. This test usually has to be analyzed at an outside veterinary lab, and may take 1-2 days to return results.
  

 

TREATMENT & MANAGEMENT

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 agaist 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 disease, 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 & HELPFUL HINTS

Prevention of feline leukemia virus is achieved by:

• Keep cats indoors and away from infected individuals, especially if they tend to fight with other cats.
• Get 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.
• Get all of your cats retested and revaccinated on a regular basis
  
• Bring 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 disease, no vaccine is 100% protective. Where possible, do not allow your cat, particularly if a kitten, to come into close contact with known FeLV-infected cats or cats without a known history of proper vaccination.