Ask Dr. Richards: 04/03

Question: I recently read information on your website ( that states that humans can almost certainly not contract FIV from a cat and that there was no evidence in owners, researchers, etc.  However, were any of these people bitten or scratched by an infected cat? Also, can a human contract it by cleaning an infected cats litter box? What if a cat licks you? Almost certainly not is not 100%. I dont have a cat, but my HUGE concern is that my babysitter, who I just hired for my 23-month-old child, has a cat with FIV (and I had never heard of it until two days ago when she told me). Please help!

Answer: There are a number of reasons for putting your mind at ease, a few Ive which Ill mention here. First, feline immunodeficiency virus (FIV) is quite limited in the ways it can infect cats, the only animals the virus is known to infect. With few exceptions, the bite of an infected cat is required; that is, virus present in the saliva of an infected cat must be violently passed through the skin of another cat. (On rare occasions, the offspring of an infected mother cat may become infected, but obviously this doesnt apply to your specific concerns.)

Researchers have found that some laboratory strains of FIV can pass through mucus membranes (like those lining the oral cavity), perhaps putting cats that live peacefully with an infected cat at risk of infection (one can easily imagine that if an infected cat grooms another, the virus in his saliva could wind up in the mouth of his buddy). However, theres only scant evidence that FIV can be transmitted to cats by non-aggressive-that is, non-biting-behavior.

Second, FIV remains viable for only a short period of time outside the cat, so none could be tracked in on your sitter or her clothing, and its widely believed that sharing litter boxes, feeding dishes or living space with FIV-positive cats cant infect cats. Nor would people cleaning litter boxes or feeding dishes used by infected cats be placed at risk.

Why Not 100% Certain?
Its risky to say something like, humans can never, ever become infected with FIV, because no one will ever conduct a study in which every person on earth is injected with virus – and then check later to see if somebody got infected. So were left with other ways to determine whether the virus poses any risk to humans. One of the ways is to study people with a high risk of exposure to the virus, like veterinarians and lab personnel who work directly with the virus. At least one such study has been conducted (and I was one of the guinea pigs), and no evidence of infection was found in anyone, even those whod been bitten by FIV infected cats or accidentally injected with virus.   

There is absolutely no evidence that any person has ever been infected with FIV. Having said this, though, if FIV was to pose a problem, the people most likely at risk would be those most at risk of any kind of infection: the immunosuppressed (like people with AIDS or taking immunosuppressive medication), the very old, and the very young.

For this reason – and just to be on the safe side – I suggest that people who fit into any of these categories avoid close contact with FIV infected cats (like kissing on the nose or mouth), wash any areas of their body licked by the kitty, and avoid being bitten. These precautions are not based on a deep fear that FIV will infect the person; rather, theyre just common sense.


Question: I have a male tortoiseshell cat, approximately 12 weeks old. Can you tell me how much he is worth?

Answer: Yours is a fairly common question. The Cornell Feline Health Center receives calls from people with tricolored (tortoiseshell and calico) male cats fairly regularly. Realizing that such cats are uncommon, folks call in hopes that their cat will pave the way to fame and fortune. Well, don’t give up your day job just yet: These fellows have no greater monetary value than any other cat.

About One in 3,000
They are rare, though. Estimates vary, but one report gives odds of about one in 3,000. For clarification, tortoiseshell cats (torties) have a black coat with patches of yellow or orange. A calico cat is a tortie with patches of white. Torties and calicos can have a dilute coat pattern in which the black is replaced by gray and the orange is replaced by a cream color. For simplicity, all these cats are classified as tricolors.

It’s All In the Genes
For a genetically normal cat to have both red and black coat colors, it must have two X sex chromosomes: one to carry an orange gene, and one to carry a non-orange gene. Normal females carry two X sex chromosomes (XX) – and can have both orange and black. Genetically normal males are XY – and can’t be both orange and black. So for a male cat to be tricolored, something must be genetically amiss. One of the more common genetic abnormalities, called Klinefelter’s syndrome, results in sterility.

But don’t think you can skip having this little fellow neutered; some tricolored males are fertile, and I’ve personally seen some kittens sired by a calico Tom.