Feline Immunodeficiency Virus

Snowball was a big white tomcat that had cruised the neighborhood for a couple of years.  One of my clients felt sorry for the cat without an apparent home, so she began to feed and befriend him.  Surprisingly, Snowball enjoyed human touch and companionship.  His scars and notched ears attested to the territorial battles that he had survived.  My client became very attached to the cat and wanted to bring him into her home.  Her concern was whether Snowball could be carrying anything that would be dangerous to her precious house cats.

To her surprise, my client was able to get Snowball into a cat carrier, and she brought him in to my clinic.  She wanted him tested for Feline Leukemia (FeLV) and Feline Immunodeficiency Viruses (FIV), and then have him neutered if negative.  She was nervous because Snowball’s previous lifestyle had placed him at high risk for contracting these viruses.  We were able to perform a blood test in the clinic, and were happy to report that Snowball was negative for both viruses.  He did not have a microchip when scanned.   Snowball was allowed to become a pampered pet and enter a new household.

FIV is also known as feline AIDS.  It is not transmissible to humans, but is passed between cats through biting and experimentally from a queen to her kittens.  Since Snowball had an assortment of battle scars, he was a prime suspect for the virus. FIV positive cats may be problem free for years and even live normal life spans, which is not typical for FeLV positive cats.  Studies show that 1.5-3% of healthy cats in the United States are infected with FIV.  Cats that are kept exclusively indoors are not at risk for exposure.

FIV is similar to HIV in its mode of action in the body.  Initially the virus enters the lymph nodes.  Fevers can follow, as can drops in white and red blood cells counts.  The virus targets a type of white blood cell called T-lymphocytes.  These cells play roles in fighting infection and in general immunity, so FIV affected cats are less resistant to other diseases.  Some veterinary diagnostic laboratories have the ability to test ratios of lymphocytes in FIV affected cats.  If the ratio of CD4+:CD8+ lymphocytes is low, the cat’s prognosis is poor.

Bad gums (gingivitis) and oral inflammation (stomatitis) are seen frequently in FIV positive cats—but these signs are common in other cats too.  When cats with FIV contract another type of infection, such as a bacterial infection, they do not respond as quickly or as completely to a normal course of antibiotics.  Often additional nursing care or longer treatment periods are needed.

My client was very happy with Snowball’s test results, but I did caution her that if this cat had been recently exposed to FIV, it would take 8-12 weeks before a test would yield a positive result.  This is because it takes time between virus exposure and development of antibodies in the blood. The screening test for FIV is called an ELISA test, which tests for antibodies.  If it is positive, another test called a Western Blot should be performed to confirm the diagnosis.  Snowball was tested again 3 months later and was still FIV negative.

The general prognosis for an FIV cat is much better than for an HIV human.  Rapid immunosuppression and death is uncommon.  Researchers hypothesize that this may be because cats have relatively short life spans and they do not live long enough to suffer the consequences of the virus.

Currently there is a vaccine that helps protect cats from FIV.  One problem with the vaccine is that it is not known whether it protects cats against all 5 subtypes of the FIV virus.  Another problem with the vaccine is that vaccinated cats test positively for FIV on routine screening tests, so it is not currently possible to differentiate between a vaccinated cat and an infected one.  I do not use this vaccine in my practice.  If someone chooses to use this vaccine, I would highly recommend having their cat microchipped, so that if the cat gets picked up by Animal Control or taken to a vet, it can be identified as an “owned” cat and not just a stray.

Treatment is aimed at controlling clinical signs and secondary problems.  Healthy FIV positive cats should be kept indoors to decrease their exposure to disease agents and to reduce their likelihood of infecting other cats.  When possible, FIV positive cats should be homed with other FIV cats.  A study from Glasgow University found that the risk of FIV being passed from one cat to another in the same household is 1-2%.  If there is no aggressive contact between cats, the risk is extremely low.

To prevent FIV infection, keep your cats indoors and test all cats’ viral status when introduced into your home.  If you have an outdoor cat, periodic testing is suggested, especially if oral disease or poor response to treatment for a routine problem is present.

Written by Dr. Wexler-Mitchell of The Cat Care Clinic in Orange, CA
Copyright © 2011 The Cat Care Clinic

About Dr. Elaine Wexler-Mitchell

Dr. Elaine Wexler-Mitchell is the owner of The Cat Care Clinic in Orange, CA
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