Berks County, PA –  Dear Christopher Cat: I mentioned to my veterinarian that I am switching my cats to a raw diet, and she objected, saying many were contaminated with bacteria. I don’t see her point, since free-roaming cats eat raw mice without having problems.

Christopher responds: The difference is that outdoor cats kill their prey and eat it immediately, before bacteria levels can rise.

Food-borne bacteria have ample opportunity to flourish when raw food is sorted, ground or cut up and packaged. These bacteria can sicken not only your cats, but also you and other family members.

In a recent two-year study, the Food and Drug Administration’s Center for Veterinary Medicine tested 1,056 samples of pet food for salmonella and listeria bacteria, two common foodborne pathogens.

Of the samples tested, 196 were commercial raw cat and dog foods, most of which were frozen. Fifteen (8 percent) of the samples tested positive for salmonella, and 32 (16 percent) contained listeria.

Only one of the 860 nonraw diets carried these bacteria.

Salmonella can contaminate raw fruits and vegetables, unpasteurized dairy products and raw or undercooked meat, poultry and eggs. These bacteria cause bloody diarrhea, vomiting, lethargy, fever, loss of appetite and stomach pain, in both pets and their people.

Listeria causes even more serious disease; 90 percent of the people sickened by foodborne listeria require hospitalization. Despite intensive care, 20 percent to 30 percent die.

So stick with a major manufacturer’s processed food, preferably one whose label states it was tested in cats.