What Kinds of Intestinal Parasites Do Cats & Dogs Transmit?

There are two types of intestinal parasites common to both dogs and cats: worms and single-celled organisms called protozoans. The most common worms found in companion animals include the roundworm, hookworm, whipworm and tapeworm. These parasites can be transmitted to other companion animals and humans through direct or indirect contact with an infected animal. The eggs of these parasites are shed in the feces. Hookworms, tapeworms and roundworms are more commonly passed to people, whipworms less so. If a person were to put his hands where the eggs have been -- such as touching soil in a garden a street cat mistook for a litter box -- that person could transfer the eggs to his mouth if he touches his lips. Children who kiss an infected pet could ingest a flea carrying the tapeworm egg.

The other type of intestinal parasite that can be transmitted from infected animal to a pet or person is a protozoa. This is a single-celled organism similar to bacteria, but is not exactly the same. Protozoans that infect dogs and cats are giardia and coccidia. Cryptosporidium and toxoplasmosis are coccidia's evil cousins. With the exception of coccidia, all of these parasites can be transmitted to humans and other animals. The coccidia found in most infected cats is not the kind that can be passed on to humans. However, cryptosporidium and toxoplasmosis, two sub-species of the coccidia protozoan, are transmissible to humans.

The victim of Intestinal parasites is called a host. Parasites are transmitted from one host to the other via a number of methods, most having to do with not enough hand-washing. Some of the parasites are transmitted through the placenta or milk from the mother to the puppy or kitten. The infected puppy or kitten then sheds the eggs of the parasites in his stool. Pet owners who clean up after their pets -- such as picking up poo from the yard or on a walk, or scooping the litter box -- may get microscopic particles of feces on their hands. While it may just be an urban legend that the average human touches his face 2,000 times a day, the fact is, if you touch your face, particularly your lips, after becoming contaminated, you transmit the parasite. Congratulations! You are now a host!

Most often, if a person or animal is infected with an intestinal parasite, the problem can easily be eradicated with medications. The process involves keeping yourself and your pet's area very clean and ensuring all who come into contact with the contamination are treated aggressively. There are some cases, however, where an intestinal parasite problem may become a serious health problem. People who are immunocompromised, the very young or very old, and pregnant women are all at a higher risk of becoming seriously ill. Pregnant women should be especially careful when changing the litter box (or better yet, have someone else do it) if there is a chance their cat has toxoplasmosis. Having said that, it's important to mention that the average house cat who is being fed from a can is not at risk of toxoplasmosis as it comes from eating carrion -- and stray and outdoor cats don't generally use a litter box.