Protozoa and Parasites

Some protozoa also cause foodborne illness. Parasites must live on or inside a living host to survive.

The most common foodborne parasites are Anisakis simplex, Cryptosporidium parvum, Toxoplasma gondii, Giardia lamblia, and Cyclospora cayetanensis.

Cyclospora was not known to cause human sickness until 1979, when the first cases were reported. Since then fresh produce has been associated with several outbreaks of food borne illness from Cyclospora in US and Canada, cases prolonged gastrointestinal disease in travelers and expatriates associated with southeast Asia and the rise of the immunocompromised population.

Giardia has been identified more than any other pathogen in waterborne disease outbreaks, but there also have been foodborne Giardia outbreaks.

Giardia was first describe by Lambl, who it the name intestinalis. Dogs pick up giardia by drinking water from streams and lakes or other contaminated sources. A person can contract giardia the same way or by failing to wash their hands after cleaning up after a Giardia infected dogs.

Cryptosporidium is also primarily a waterborne pathogen. An estimated 21 percent of waterborne outbreaks from drinking water are due to parasitic agents mainly Giardia and Cryptosporidium.

Waterborne Cryptosporidium oocysts can originate from cattle, swine, horses, deer, chicken, ducks, fish, turtles, guinea pigs, cats dogs or domestic sewage discharge.

Toxoplasma gondii is common in warm blooded animals, including cats, rats, pigs, cows, sheep, deer, chickens and birds.

It can be found in feces and raw meat from these animals.

Anisakis simplex and related worms are found in raw or undercooked seafood. These nematodes parasitizes fish and sea mammals, and thus humans ingest them by eating raw, pickled or smoked fish.

The most common clinical manifestations are those of acute gastric anisakiasis, characterized by epigastric pain, chills, nausea and vomiting within 12-24 of ingestion of parasitized food.

Trichinosis, caused by the parasitic worn Trichinella spiralis and associated with eating undercooked pork, is now relatively rare in the United States.

The parasites has a very broad host range; the major source of human infection are pork or bear meat.

Human infection can vary form subclinical (the majority of cases) to fatal.
Protozoa and Parasites