Feline Immunodeficiency Virus (FIV)


What is Feline Immunodeficiency Virus?

The feline immunodeficiency virus (FIV) causes immunodeficiency disease in domestic cats. This makes the cat’s body unable to develop a normal immune response. Once a cat is infected by the virus their immune system becomes severely weakened. This is a slow acting virus and an infected cat may not show symptoms until years after the initial infection has occurred. Cats with FIV that are kept in a stress-free environment, with proper supportive and medical care tend to not show symptoms and do live a normal, comfortable life. When the disease does reach its terminal phase, the cat becomes prone to developing secondary infections or cancer. This disease is primarily spread by deep bite wounds via saliva. It also has the potential to be spread from an infected mother to the kittens during passage through the birth canal or when the newborn kittens ingest infected milk.


What are the symptoms of FIV?

Initially, most FIV-positive cats develop a mild stage of illness roughly 4 to 6 weeks after infection with the virus. The virus spreads to the lymph nodes, resulting in a generalized but usually temporary enlargement of the lymph nodes and a fever.  This may be accompanied by other general or non-specific symptoms such as lethargy, weight loss or lack of appetite. However, these early symptoms may not be noticed since most cats act normal. This initial infection is followed by a latent period where only mild or no clinical signs will be seen. This period can last for months to years. Eventually, FIV enters the terminal phase where the virus starts to replicate profusely. This causes suppression of the cat’s immune system leading to secondary bacterial infections of the urinary, gastrointestinal and respiratory tracts, as well as infection in and around the mouth and eyes. FIV positive cats should be monitored for signs of infection, cancer or progression of the primary disease as this is what becomes fatal if it can’t be treated or resolved.

How is FIV diagnosed?

Blood testing is available for FIV. The enzyme-linked immunosorbent assay (ELISA) detects the antigens in the blood serum. This test is quick and convenient, as most veterinary clinics can run them in clinic. A negative test usually means the cat does not have FIV, but if there is still suspicion the cat should be retested in 8-12 weeks as this is the time needed for antibodies to develop post exposure to the virus. A positive FIV ELISA test can be confirmed with the Western Blot. This send out test is considered the confirmatory test for FIV. If the Western Blot result shows positive, the cat is considered FIV positive.

A general blood test may also give some insight to the cat’s FIV status. Cats with FIV can also show signs of anemia (low red blood cells), hypergammaglobulinemia (abnormally high level of gamma globulin), lymphopenia (abnormally low level of lymphocytes in the blood) and/or neutropenia (abnormally low level of a type of white blood cell).


How is FIV managed and prevented?

Vaccination for FIV is available, however it is somewhat controversial and many veterinarians do not recommend using it. The problem with the vaccine is that there multiple strains of the virus, so even with vaccination your cat can still be at risk of acquiring the virus. Also if your FIV-vaccinated cat is showing symptoms of FIV, the blood testing can not differentiate between antibodies from the vaccine or from an actual infection, making diagnosis difficult.

Ideally, FIV-positive cats should be separated from other cats and kept in a single cat household. If an FIV-positive cat is part of a multi-cat household make sure to use separate food and water bowls (the virus can be spread by saliva) and routine disinfection of bowls and litter boxes is recommended.

Preventing the spread of FIV is the most important part of controlling this virus. This can be accomplished by:

  • Keeping cats indoors- they will not be involved with fights with other cats with unknown medical history.

  • Spay and neuter your cat- this will reduce the urge to roam and fight if outdoors.

  • FIV test any new cat being introduced to your group of existing house cats.