Ask Dr. Richards: 10/02

Question: My daughter and I are more than average cat lovers. We really are suckers for the injured and homeless. But I have a question: Can people get worms from cats?

Answer: There are a number of zoonotic infections (meaning infections of animals that may be secondarily transmitted to humans), but lets talk about two types of intestinal-worm parasites that are particularly significant. Before I start, though, I must tell you that Im afraid that folks will become overly concerned about catching something from their cat(s). Bear in mind that although some infections can be transmitted from cats to humans, for the most part such occurrences are pretty uncommon, and they are usually very easy to prevent using a little common sense and good basic hygiene. One simple measure is to properly dispose used cat litter. Do not compost, which may place harmful organisms back into the environment.

Visceral larva migrans
First, lets talk about the disease, visceral larva migrans, which is caused by several species of roundworms. If eggs of the dog roundworm, Toxocara canis, and less commonly, the cat roundworm, T. cati, which are passed in the feces of an infected animal, are ingested by a person, they often just pass through and are eliminated in the feces. But they may hatch in the intestine. If so, the larvae can migrate through the body – hence the name – and create disease. Many times, the disease goes unnoticed. Depending on where the larvae migrate, however, the signs may include coughing, abdominal pain, muscle and joint pain, skin rashes or bumps, and even convulsions. Perhaps the most tragic consequence is blindness if the larvae reach the eye. It is estimated that in the United states up to 10,000 children are infected with dog or cat roundworms every year and between 700 and 800 of them become blind.

Cutaneous larva migrans
A second disease is cutaneous larva migrans. It is caused by the larvae of several species of hookworms that infect dogs and cats. Eggs passed in the feces of an infected animal will hatch, especially in warm, wet, sandy soil. People in contact with contaminated soil risk the larvae penetrating their skin. The larvae then tunnel through the skin and create an itchy, sometimes painful condition.

Both conditions are more common in children than in adults and are best prevented by appropriate and timely worming of cats (ask your veterinarian) and either instructing children not to play in areas you believe are likely to be contaminated with cat feces or preventing cats from defecating in areas where children are most likely to play. Keep your childs sandbox covered when not in use. Make sure you and your children wash your hands after working or playing in the soil.

Toxoplasmosis is not caused by a worm; it is caused by a single-celled protozoan. It is potentially of more concern than visceral or cutaneous larva migrans, particularly in immunosuppressed people (especially AIDS and cancer patients) and pregnant women. The way most people in this country become infected is by eating undercooked meat, by failing to wash their hands after handling raw meat, by eating unwashed raw vegetables, or by consuming unpasteurized dairy products.

However, direct contact with the feces of cats infected a few weeks earlier with Toxoplasma organisms is a potential source of infection too. Immunosuppressed people and pregnant women especially should wear gloves when gardening and, if possible, should have someone else take care of the litter box, particularly if the cats are allowed to go outside.

However, since Toxoplasma organisms require at least a day or more after being passed in the stool to become capable of infecting a person, cleaning the litter box at least once a day (while wearing rubber gloves, just to be sure) should be safe, even if done by an at-risk person..