The largest tapeworm that can infect humans, Taenia solium, can be contracted through larval cysts in undercooked pork. Once in the stomach, they hatch and feed on nutrients from food in the intestines, leading to malnourishment. Taenia solium can also cause issues in the central nervous system, including epileptic seizures.

Toxoplasma gondii, one of the most widespread human parasites, can contaminate meat and organs from pork, beef, and other game. Although toxoplasma gondii can stay dormant in the tissues of a host for a lifetime without ever showing symptoms, it’s extremely dangerous for pregnant women because it could penetrate the placenta and cause fetal abnormalities or miscarriage. These protozoa may also lurk in the feces of cats and rodents—which is the reason expectant mothers are told to avoid scooping cat litter.


Transmitted through contaminated soil, Ascaris are intestinal roundworms—the largest and most common in humans, with 25 percent of the world infected. (Although the infection is very rare in the United States—most of these occurrences happen in developing countries.) Some fruits and vegetables may also come from soil contaminated with dog feces containing eggs from a dog tapeworm called Echinococcus granulosus. This slow-growing parasite can migrate from the digestive tract to the liver; symptoms may not appear for several years.

Cryptosporidium can occur from fecal contamination of water supplies by infected livestock—yet another reason why getting more familiar with the source of your produce is important.


Some raw or undercooked freshwater fish contain Opisthorchiidae (a family of flatworms) larvae. When eaten by humans, they grow into adult worms that inhabit the bile duct and gallbladder. Long-term infections have been linked to cancer of the liver. Freezing or cooking fish can kill this parasite, but preservation through pickling, drying, salting, or smoking won’t. Stick to saltwater fish as much as possible; for lox, look for wild-caught Pacific salmon in order to avoid any fish that were caught from rivers or streams.


Like produce, fruit juice is susceptible to Cryptosporidium through contaminated water. Unpasteurized cider, as well as milk, have been cited as sources of recent parasitic outbreaks.

Even more severe are Trypanosoma cruzi, protozoa that progress slowly, infecting cells and organs within the body, including the heart. Over time, this parasite could lead to severe, and sometimes fatal, cardiac or intestinal issues. In recent years, several outbreaks were linked to contaminated fruit and sugar cane juices.

Consumers may want to trace the origins of fresh juices or other unpasteurized liquids more closely. Whenever possible, make your own juice from fresh fruit from a trusted farmer. The CDC also recommends opting for canned or bottled fruit drinks, or ones that are pasteurized.

Want to learn more about food safety and avoiding parasites? Follow these additional tips for avoiding foodborne illnesses as best practices for also minimizing risk of contracting parasites.