What You Should Know About Feline AIDS


Feline immunodeficiency virus, or FIV, is a widespread viral infection that attacks the immune system of cats. It is caused by the same family of viruses that triggers AIDS in humans and has much the same devastating impact on infected cats. It is often referred to as “feline AIDS.”

The virus devastates a cat’s immune system, stopping it from effectively combating other diseases and infections. Infected cats eventually fall prey to a wide variety of secondary illnesses that overwhelmingly prove fatal. There is no cure, but cats can live for up to 10 years – much of it in seeming good health – before succumbing.

It is estimated that between one percent and 14 percent of the cat population is infected with FIV. The disease is transmitted from cat to cat by blood and saliva. This happens primarily through biting and scratching so outdoor and male cats that fight with other cats are at greatest risk. FIV has also been found in milk and can be transmitted from mother to kitten. Transmission among household cats through normal contact is thought to be unlikely. Nor can the disease be transmitted to humans.

How FIV Progresses

FIV has three stages of infection:

  • Stage 1 – In the first stage the virus first causes infections, fever and swollen lymph nodes.
  • Stage 2 – During this stage, the virus is in effect dormant and many cats appear “healthy.” This is called the sub-clinical phase and lasts from months to years.
  • Stage 3 – In the final, often referred to as “terminal” stage, the cat suffers the infections and diseases that are often fatal within a year. It is called the chronic infection stage.
  • Diagnosis

    An infected cat will often suffer from numerous diseases and infections, including anemia, infections of the gums and mouth, cancer and skin disorders. The cat may also suffer neurological problems that cause seizures, problems maintaining balance and dementia, as well as behavioral changes like inappropriate elimination. Co-infection with feline leukemia virus can occur. Many cats may seem healthy but they are still infected.

    The key to diagnosing FIV is determining whether these problems are the result of a suppressed immune system caused by the virus. Your veterinarian will take a medical history, do a complete physical examination and administer an FIV blood test designed to see whether a cat has developed antibodies to the virus. If antibodies are present, it indicates the virus is present in the body. This test is called ELISA or IFA.

    It is a good idea to test kittens because they contract the virus when nursing, but it is also possible for a test to show wrongly that a kitten is infected; a nursing kitten can also carry the antibodies of an infected mother without being infected itself. A kitten that tests positive should be retested after six months of age, when it carries its own antibodies and test results will be more reliable.

    A cat that tests positive or appears to have FIV will likely undergo further tests to measure its general health and the impact the disease is having on individual organs.



    There has been no proven effective treatment for FIV infection. If your cat has no clinical signs, no treatment may be recommended. In this situation, regular follow-up visits to your veterinarian are important to insure the condition does not progress. If immunodeficiency and secondary infections have developed, your veterinarian will choose treatments to combat them. These are likely to consist of antibiotics for bacterial infections, nutritional support, fluid therapy for dehydrated cats and parasite control.

    Several therapies used to treat people with AIDS have been used in cats with FIV infection with the goal of boosting their immune systems and slowing the progress of the disease. These treatments include:

  • AZT, a well-known AIDS drug. Treatment with AZT may result in clinical improvement, immune function and quality of life, but AZT has some potentially serious adverse effects and should be administered to FIV-infected cats under the supervision of a veterinarian experienced with its use.
  • Alpha interferon. This drug may reduce viral replication in some infected cats. It is not licensed for use in cats, but some clinical studies found increased activity, increased appetite, improvement of blood abnormalities, increased clearance of virus and prolonged survival in treated cats.
  • Bone marrow transplantation. This procedure has been performed in a limited number of FIV-infected cats and is successful in restoring white blood cell counts in some instances. Infected cats, however, remain infected with FIV. This procedure is available only at a limited number of referral research institutions.
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