My aunt lives in Dallas and recently told me about an article that you wrote that said dogs should not eat grapes. Can you please let me know if this is true and to what extent. How many grapes would my dog need to eat for there to be a problem? I have a grapevine that is just starting to produce growing on my dogs’ kennel. She is a 43-pound Spitz mix, the other a 128-pound Malamute mix, and both love fruit.

There are sporadic cases reported of dogs experiencing toxicity from eating grapes or raisins. This is a new toxicity, and a lot is not yet known about it. As a result, I discourage the practice and would try to prevent your dogs from eating this fruit. However, an occasional grape or raisin as a treat is unlikely to be harmful. As with anything, moderation is the key.

My cat Regan recently died of FIP. I have another cat that I want to have tested to make sure she doesn’t come down with this horrible disease, but I have heard mixed ideas about this test.

Some of the opinions I got said the test should be done so I can treat her if she is positive, but I’ve also heard the test is not very good if the cat is healthy. What do you think?

First let me express my condolences on losing Regan. Losing a pet is never easy, and sudden death from FIP is particularly traumatic.

Regarding the feline infectious peritonitis test, realize that this blood test detects antibody to corona virus, NOT FIP virus (although FIP virus is a mutated corona virus).

It is a difficult test to interpret. Here are some things to keep in mind. Any vaccinated cat may have a false positive FIP titer. Since testing methods can vary, corona virus antibody titers obtained from different laboratories cannot be accurately compared.

The outcome of infection and symptoms of disease exhibited by individual cats are determined by immune status rather than presence of the FIP virus in the cat, so PCR (Polymerase Chain Reaction) testing for virus is irrelevant in most cases. No test can distinguish between nonpathogenic coronavirus and FIP.

Coronavirus antibody titers in purebred cats are particularly difficult to interpret because very high titers can frequently be found in clinically healthy cats. As a result of all of this confusion, it is hard to recommend routine testing of healthy cats, and I certainly would not eliminate cats from the household simply based on a positive test.

Shawn P. Messonnier, author of the “Natural Health Bible for Dogs & Cats” (Prima, $24.95). is a veterinarian and pet care advocate.