A zoonotic disease is one that can be passed from pets to people. People often worry about the possibility of infection for themselves or family when a pet is diagnosed with intestinal parasites, such as worms. This concern is valid because there are several intestinal parasites that are considered to be zoonoses.
Which Intestinal Parasites Are Zoonotic?
Roundworms, more properly known as ascarids, are one of the most common intestinal parasites seen in both dogs and cats. In fact, many (if not most) puppies and kittens are born with roundworms. Roundworms, however, do have the potential to be passed to people. They are considered a zoonotic disease. Children are at highest risk for infection with roundworms.
Tapeworms also are considered to be a zoonotic parasite. However, typically, they are not passed from dogs or cats directly to people, even though dogs and cats are commonly infected with them.
In order to infect a dog or cat, tapeworms require an intermediate host, which is usually a flea or a small prey animal that is ingested. The intermediate host is necessary for transmissal of tapeworms to people also and dogs and cats do not serve as intermediate hosts. However, eating uncooked meat or fish that is infected can pass certain types of tapeworms to people.
Trichenella is another intestinal parasite that has the ability to infect people. However, dogs here in the US are seldom the cause of trichinellosis (infection with Trichenella) in people. This disease is transmitted only by eating uncooked or undercooked meat infected with the parasite, most often pork or wild animals.
Another intestinal parasite that can be passed from people to pets is Giardia. Giardia is different from many other intestinal parasites because it a protozoan (a single-celled organism) rather than a worm. Nevertheless, it can infect both dogs and cats and can also potentially be passed to people.
Toxoplasma gondii, the cause of toxoplasmosis, is a parasite that is frequently found in cats. It can infect people as well and can be quite serious under certain circumstances, particularly for a pregnant woman and her fetus. Toxoplasma is also a protozoan parasite and not a worm. Pregnant women can take precautions to protect their unborn baby from this disease, however.
How Are Intestinal Parasites Passed From Animals to People?
Intestinal parasites can be passed to people in several different ways. The primary means of transmission depends on the type of parasite.
- Some intestinal parasites can be passed to people through ingestion of feces from infected animals or ingestion of contaminated soil or water. Examples include roundworms, hookworms, Giardia and Toxoplasma.
- Some can be passed when the larvae of the parasite contact uncovered skin. Hookworms can be transmitted this way.
- Other intestinal parasites are transmitted by eating uncooked or uncooked meat that is infected. Certain types of tapeworms as well as Trichenella can be passed in this fashion.
Fortunately, in most cases, by taking simple precautions like practicing good hygiene and making sure all meat is cooked thoroughly before eating it, infection with zoonotic intestinal parasites can be avoided.