Hi Dr. Barchas,

I have two cats. Spike is an orange tabby, 7 years old. I adopted him about a year ago from a friend who moved out of town. Phoebe is 3, and I got her from the shelter when she was a kitten.

I took them to the vet for a checkup last week, and we ran some tests on Spike because he’s getting older. The tests showed that Spike has feline AIDS. This made me really scared about Phoebe as well as Spike. I took Phoebe in for an AIDS test, and she tested negative. When my friend owned Spike, he used to go outside and get in fights, but now both cats stay indoors. The vet said that Spike probably caught AIDS when my friend owned him.

My question is, how likely is it that Phoebe will catch the disease from her brother? I am really worried about her now.

Mary

Raleigh, NC

It is possible, but not likely.

Feline immunodeficiency virus, or FIV, is the virus that causes feline AIDS. It is related to HIV (the virus that causes AIDS in people), but it does not infect humans.

FIV weakens the immune system of cats. Cats that are infected with the virus are prone to infections throughout their body. In some cases, the virus damages the immune system so thoroughly that the cat cannot survive.

However, the news is not all bad for you and your cats.

First, FIV is not highly contagious. Cats usually contract the virus by fighting. And the fight has to be serious. For FIV to spread from Spike to Phoebe, he would need to bite her hard enough to break the skin. Although minor squabbles are common among cats that live together, they usually do not get into the sorts of fights that can spread FIV. Therefore, in my experience, FIV usually does not spread among cats that live in the same house.

As well, there is some good news for Spike. Most FIV-positive cats do not become sick until 5 – 10 years have passed. I have known several FIV-infected cats that never became sick from the virus. So, even though Spike has a serious disease, there is a good chance that he will live a normal life for a long time to come.