After experiencing a blinding, throbbing headache, a 26-year-old man was rushed to a hospital. The cause: a life-threatening tapeworm in his brain.
While it might sound like a far-flung travel horror story, it actually happened in Napa, Calif. Fortunately, an adept surgeon was able to extract the parasite; if he hadn’t, the patient would likely have died within a half hour. According to doctors, this tapeworm, typically found in developing countries in Latin America, Asia, and Africa, could have been contracted while visiting one of those regions, swimming in a lake, or eating undercooked pork or dirty produce. The patient didn’t remember doing any of those things—although it’s not unlikely that he may have unwittingly consumed unwashed produce.
According to the Center for Disease Control and Prevention, about 1,000 hospitalizations occur yearly in the U.S. for brain infections caused by this particular tapeworm. Even more people contract parasites that affect muscle tissues and organs, leading to epilepsy, anaphylactic shock, amoebic dysentery, and more. The truth is, globalization and the ease of shipping foods internationally have made people of industrialized nations susceptible to parasitic infections as well. A report issued by the United Nations and World Health Organization declared that better farming and global food trade standards are needed in order to keep parasites out of the food chain.
At an individual level, the biggest keys to avoiding parasitic infections from food:
- Be a little more vigilant about learning more about the sources of your food.
- Wash all fruits and veggies thoroughly, including “pre-washed” greens.
- Cook all meat, especially pork, properly.
Of course, worms and protozoa (single-cell parasites) are not relegated to raw pork. Read on for more information about which foods are most at risk of containing parasites, compiled from the CDC.
Pork and Beef
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.
Illustration by Foley Wu