Feline leukemia virus (FELV) is one of the most common and destructive of all cat viruses. It is highly contagious and is spread primarily by saliva during cat fights, grooming or mating. The virus may also spread by blood, urine and feces. Kittens may become infected while still in the womb, when the mother bites off the umbilical cord, or during nursing. The virus is not transmissible to humans.
Not all cats exposed to FELV become infected. About 40% of exposed cats have immune systems that destroy the invading virus. The remainder of exposed cats become persistently infected (60%). The latter group has inactive virus in the 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 1 year and 75% may have chronic illnesses and die within 3 years.
There are no signs specific for FELV infection. The main effect of the virus is to disrupt the cat’s immune system. Disorders commonly associated with FELV infection are: anemia; cancer; chronic respiratory infections; chronic infection of the mouth, gums; chronic eye infections; chronic skin disease; reproductive disease; frequent urinary tract infections; chronic vomiting and / or diarrhea; and other systemic diseases (feline infectious peritonitis, toxoplasmosis, hemobartonella…)
Feline Immunodeficiency Virus
Feline Immunodeficiency Virus (FIV) is another common feline retrovirus. It is similar to the human immunodefiency virus but is species specific – not transferable to humans. The primary route of transmission is thought to be through aggressive biting behavior. The virus is most commonly seen in older male cats. FIV infection generally carries a much more favourable prognosis than does FELV infection. FIV positive cats may live for years. They are usually presented for evaluation of non-specific illnesses which are a result of the viral effects or result from secondary infections subsequent to the immunodeficiency. Common abnormalities include dental, gum infections, upper and lower respiratory infections, chronic skin disease, urinary tract infection, eye diseases, cancer, etc.
Prevention of FELV/FIV
Vaccination before exposure to the virus is the best means of preventing FELV infection. Current vaccines are about 80% effective if given prior to exposure to the virus. Without vaccination, isolation from all cats with an unknown FELV/FIV status is the only means of prevention. There is currently no vaccine available for FIV. Infected cats should not be allowed to roam outdoors for fear of infecting other cats as well as placing the infected cat at risk of developing other infections.
There is currently no cure for either disease. Treatment is usually supportive in nature, controlling secondary infections etc. Once an FELV positive cat or kitten is clinically ill, treatment is usually not rewarding.
Which Cats are at Greatest Risk?
Cats with known or potential exposure to FELV/FIV are at greatest risk. These include outdoor cats, fighting cats, strays, cats with bite wounds, escapees, recently mated females if infection status of male is unknown, cats in multiple cat households in which the status of all cats is unknown or cats in households with an infected cat.
FELV/FIV Testing – Current Recommendations
The FELV/FIV status of all kittens/cats should be known. Since affected cats (FELV or FIV positive) can be clinically healthy for some time it is of paramount importance to know their retrovirus status to prevent exposure to other cats. For clinically ill animals, knowing their infection status is helpful both diagnostically and prognostically.
Testing and identifying FELV positive kittens/cats is the best means of preventing disease by preventing exposure to FELV infected kittens/cats.
Where the FELV status of the kittens/cats in the household is known, testing of all new kittens or cats prior to introduction into the household will prevent exposure to the virus. Even in a single cat household testing is recommended since the FELV status will be important information in regards to the pets future health. The ELISA antigen test is the preferred screening test for FELV. The test can be done at any age (no maternal antibody interference), is inexpensive, and requires only a small amount of blood. We are able to offer this test in house and the results will be available the same day. Should the test be positive for FELV we would recommend a confirmatory IFA blood test. We currently recommend testing all kittens and cats in the household – once there status is known, repeat testing would be based on their degree of risk of exposure (yearly screening at time of vaccination may be recommended for high risk cats). All new additions to the household should be tested prior to their admission into the house.
The FIV antibody status of all cats over 6 months of age should be known. Testing and identifying positive cats is the only means by which FIV disease can be controlled. The best means of preventing disease is to prevent exposure to FIV-infected cats. The preferred screening test for FIV is the ELISA antibody test. This test can be done in house with a small amount of blood and results are available the same day. Since maternal antibodies can affect this blood test, cats must be at least 6 months of age prior to testing. Should the ELISA test be positive we would recommend a confirmatory DNA blood test. Periodic (annual) testing may be recommended in those cats at high risk or those with known exposure. All new additions to the house should be tested prior to their admission.