Feline Immunodeficiency Virus (FIV)


Overview of Feline Immunodeficiency Virus (FIV)

Feline immunodeficiency virus (FIV) is a viral infection that attacks the immune system of cats. It is also known as Feline acquired immunodeficiency syndrome (Feline AIDS) and commonly referred to by the letters “F-I-V”. The immunodeficiency caused by the virus can promote a variety of symptoms including: infections caused by the poorly functioning immune system, anemia and low blood-cell counts, infections of the gums and mouth, cancer or neurologic disease.

Below is an overview of Feline Immunodeficiency Virus (FIV) followed by in-depth information about the diagnosis and treatment of this disease. 

FIV is a retrovirus similar to the Human Immunodeficiency Virus (HIV also known as AIDS). FIV is not contagious to people; it is an infectious disease spread from cat to cat, primarily by biting and scratch wounds. FIV has been found in the mother’s milk and can be transmitted from mother to kitten. Experimentally, FIV can also be transmitted through semen however this is not thought to be a significant method of transmission in nature. Transmission among household cats through normal contact is thought to be unlikely. Outdoor, adult, and male cats are predisposed. Male cats are twice as likely to be infected as female cats. Adult cats are more common infected than kittens.

FIV has three stages of infection. They include an acute phase associated with various symptoms, which includes infections, fever and lymph node (gland) enlargement. The second phase is called the subclinical phase, which lasts from months to years, during which time many cats appear healthy and shows no clinical signs. The third phase is chronic infection, also known as the terminal phase, which is associated with deterioration of the immune function and that predisposes cats to a variety of infections. Clinical signs of the terminal phase are determined by how the virus affects the individual cat. Signs can be secondary to infections, tumors or neurologic dysfunction.

Infection is thought to involve between one and 14 percent of the cat population. In the United States, the prevalence is 2.5% to 6% in client owned cats and 3.5% to 23 % in stray cats.

Cats with FIV are more susceptible to stomatitis, upper respiratory tract infections, co-infection with feline leukemia virus (FeLV), toxoplasmosis, feline infectious peritonitis (FIP) and fungal infections.

What to Watch For

Many cats are diagnosed on a routine blood screening and are asymptomatic. If the FIV is causing active infections, sign will vary depending on the secondary problem caused.

Nonspecific signs of lethargy, anorexia, weight loss, depression or those associated with an infection can be seen. Infections can occur to any site including the skin, respiratory tract, neurologic system, eyes, mouth, and/or intestines.

Neurologic dysfunction can cause clinical signs of trouble walking, weakness, difficulty using a leg, seizures, and/or behavioral changes.

Diagnosis of Feline Immunodeficiency Virus 

Veterinary care should include diagnostic tests and subsequent treatments. Diagnostic tests are needed to recognize FIV and exclude other diseases. Tests may include:

  • Complete medical history and physical examination
  • Blood test called the Enzyme-lined immunosorbent assay (ELISA) test should be done. The ELISA detects anti-FIV antibodies in the serum or saliva.

    Results can be difficult to interpret in cats less than six months of age because some cats may still carry antibodies from their mother that is positive for FIV without actually being infected. These antibodies are generally gone from kitten by 6-months of age.

    These tests will also be positive if the cat has been vaccinated for FIV. For this reason, only unvaccinated cats should be tested and every cat should be tested before the first FIV vaccination.

    All positive test results should be confirmed with a second test called the Western blot or Polymerase chain reaction (PCR) test. Feline leukemia testing should also be completed to determine if this infection also exists.

  • Treatment of Feline Immunodeficiency Virus (FIV)

    There has been no proven cure for FIV infection, several treatment options, supportive care, and symptomatic therapies are important, including:

  • Antibiotics for bacterial infections
  • Nutritional support
  • Parasite control
  • Keeping the cat indoors and isolated from other cats
  • Biopsy and removal of tumors
  • Home Care

    Administer prescribed medications and monitor your cat’s general activity level, body weight, appetite and attitude. Provide quality nutrition and schedule veterinary visits to monitor the condition.

    Keep all FIV infected cats indoors to decrease exposure to other cats. It is ideal to isolate FIV infected cats from negative cats, however, as mentioned earlier transmission among household cats through normal contact is thought to be unlikely although it is possible.

    For cats with FIV, preventative health care and dental care with antibiotic coverage prior to the procedure is often recommended in infected cats. Vaccination for other diseases should be discussed with your veterinarian. If yearly vaccinations are given, only killed vaccines, which are vaccines made up of killed virus, as opposed to other types where live virus may have been modified, should be utilized to protect a potentially inadequate immune system in infected cats.


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