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:
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:
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.
Feline immunodeficiency virus is an infectious disease that can be prevented primarily by eliminating interactions with infected cats. Keeping your cat indoors is the most effective way to prevent FIV. Test all new cats prior to bringing them into your home and exposing them to your other cats. Recently, a vaccine has been developed that can help reduce the risk of acquiring FIV in at-risk cats. This is most beneficial in indoor/outdoor cats, outdoor cats or cats exposed to many new cats.
Other prevention methods include to neuter males (to minimize or prevent fighting). It is also recommended to isolate, test and treat infected cats.
In-depth Information on Feline Immunodeficiency Virus (FIV)
Other medical problems can lead to symptoms similar to those encountered in feline immunodeficiency virus. It is important to exclude these conditions before establishing a diagnosis of FIV infection. These conditions include:
Diagnostic tests must be performed to confirm the diagnosis of feline immunodeficiency virus and exclude other diseases that may cause similar symptoms. Some of the following diagnostic tests may be recommended:
Enzyme-lined immunosorbent assay (ELISA). The ELISA detects anti-FIV antibodies in the serum or saliva. As mentioned earlier, Results can be difficult to interpret in cats less than six 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.
If positive, a second test should be done to confirm FIV status using the Western blot or Polymerase chain reaction (PCR) test. The western blot test is considered to be definitive for FIV. If the initial screening test is positive but the western blot is negative, the cat is considered negative for FIV.
False positive ELISA tests can occur in cats less than 6 months of age that still have antiboidies from their mothers or from their mothers milk (maternal or colostral antibodies), in cats that have been vaccinated and a few from test error.
False negative ELISA tests can occur in cats that were recently infected and have not yet began to produce antibodies (it can take 8 weeks from exposure to have a positive test result). If you got your cat today and he is negative and he was exposed to a cat with FIV yesterday, it may be two months before he shows a positive test result. The other cause for false negative test results can occur in cats with end-stage FIV. These cats will have such severe immunodeficiency that their bodies will no longer make detectable antibody for the test.
Your veterinarian may recommend additional diagnostic tests to exclude or diagnose other conditions and to better understand the impact of FIV infection. These tests ensure optimal medical care and are selected on a case-by-case basis and may include:
Treatment of FIV infection must be individualized based on the severity of the condition and other factors that must be analyzed by your veterinarian. If your cat has no clinical signs, no treatment may be necessary. In this situation, regular follow-up visits to your veterinarian are important to ensure the condition does not progress. If immunodeficiency and secondary infection have developed, additional treatment will be necessary. Supportive care and symptomatic therapy are important and include:
Several drugs that are used to treat people with human immunodeficiency virus (HIV) infection have been used in cats with FIV infection. Drugs used may include the following:
Prognosis for Cats with FIV
Most cats with FIV will live for months to years without symptoms. Most cats will eventually have enough viral replication that they will go into the terminal phase of the disease and develop secondary illness.
Follow-up Care for Cats with Feline Immunodeficiency Virus
Optimal treatment for your cat requires a combination of home and professional veterinary care. Follow-up is crucial. Follow-up veterinary care for FIV often includes the following recommendations:
Use the “Test and Remove” program, which is a method to eliminate FIV-infected cats in a cattery or a multiple-cat household. The principles of this program are as follows:
Please note: Positive titers to FIV can occur from some vaccinations. This can produce a positive test result. If your cat tests positive to FIV and is NOT sick, please determine if your cat has been vaccinated recently. Titers to the vaccine can occur for up to 13 months after vaccination. Kittens born to vaccinated queens will also be positive to do passive transfer of antibodies.