5 Common Foods That Can Harbor Parasites (And How to Protect Your Family)

They’re Not Just a Third-World Problem — These Everyday Foods Carry Real Risks Right Here at Home

When most Americans think about parasites, they picture something that happens “over there” — in developing countries with unsafe water or unsanitary food handling. It’s a comfortable assumption, but it’s wrong.

The truth is that parasites are far more common in the U.S. food supply than most people realize. The FAO and World Health Organization jointly ranked the top 24 foodborne parasites of global concern, and nearly all of them can be transmitted through foods you encounter every week at the grocery store, the farmer’s market, or your favorite restaurant (FAO/WHO, 2014). From the sushi counter to the produce aisle to your own kitchen faucet, the opportunities for parasitic exposure are hiding in plain sight.

This isn’t meant to make you paranoid. It’s meant to make you informed. Because with a few simple precautions — most of which take less than a minute — you can dramatically reduce your risk and protect your family from infections that range from mildly unpleasant to genuinely dangerous.

Here are five common foods that can harbor parasites, the specific organisms they carry, and exactly what to do about each one.

1. Raw or Undercooked Fish (Sushi, Sashimi, Ceviche) — Anisakis Worms

The Parasite

Anisakis simplex is a nematode (roundworm) that lives naturally in the gastrointestinal tracts of marine mammals like whales, dolphins, and seals. Its larvae infect fish and squid, where they coil up in the flesh and visceral cavity, waiting to be eaten by the next host in the food chain. When humans eat raw or undercooked infected seafood, they become accidental hosts — and the larvae can burrow into the walls of the esophagus, stomach, or intestine.

How Common Is It?

More common than you’d think. Using health insurance data from 2018–2019, researchers estimated the average annual incidence of anisakiasis in Japan to be nearly 20,000 cases. Japan accounts for the majority of reported cases because of the cultural prevalence of raw fish, but the problem is global and growing. Anisakidosis is still significantly underreported and misdiagnosed globally, making it a disease of rising public health concerns as raw fish consumption increases worldwide. Japan, Spain, South Korea, Italy, and the United States have the highest rates of reported cases.

The species most commonly found in sushi-grade fish include salmon, mackerel, squid, herring, and anchovies. A case published in 2023 documented a 19-year-old college student in the U.S. who coughed up a live Anisakis worm two days after eating raw salmon sushi (SHM Abstracts, 2023).

What It Does to You

Symptoms typically appear within hours of eating infected fish. They include sudden, severe abdominal pain, nausea, and vomiting. Some people experience a tingling sensation during or after eating raw or undercooked fish or squid — this is actually the worm moving in the mouth or throat. In some cases, the larvae burrow into the intestinal wall and cause an intense inflammatory reaction one to two weeks later, which can mimic appendicitis or Crohn’s disease. Some individuals also develop allergic reactions, including hives and even anaphylaxis.

How to Protect Yourself

The FDA recommends cooking seafood to an internal temperature of at least 145°F (63°C) to kill parasites. For raw preparations, proper freezing is the key. Commercial sushi in the U.S. is required to be frozen before serving, which kills Anisakis larvae. The FDA-recommended freezing protocols include holding fish at -4°F (-20°C) for 7 days, or at -31°F (-35°C) until solid and then storing at that temperature for 15 hours. If you buy fish to prepare raw at home, make sure it has been commercially frozen to these specifications — your home freezer may not get cold enough. When in doubt, cook it.

2. Undercooked Pork and Beef — Tapeworms (Taenia solium and Taenia saginata)

The Parasite

Tapeworms are among the oldest known human parasites, and two species are directly linked to the meat we eat. Taenia solium (the pork tapeworm) infects pigs, and Taenia saginata (the beef tapeworm) infects cattle. When humans eat raw or undercooked meat containing tapeworm larvae (called cysticerci), the larvae attach to the small intestine and develop into adult tapeworms — which can grow remarkably large. A tapeworm can grow to longer than 12 feet and can live for years. The beef tapeworm can reach up to 25 meters (over 80 feet).

Why It Matters — Especially the Pork Tapeworm

While the beef tapeworm causes mostly mild digestive symptoms, the pork tapeworm carries a far more serious risk. Infection with T. solium tapeworms can result in human cysticercosis, which can be a very serious disease that can cause seizures and muscle or eye damage. Cysticercosis occurs when tapeworm eggs (rather than larvae) are ingested — often through contaminated food handled by someone carrying the adult tapeworm. When these eggs hatch, the larvae can migrate to the brain, eyes, muscles, or heart, forming cysts. Neurocysticercosis — cysts in the brain — is a leading cause of acquired epilepsy worldwide.

The WHO estimates that approximately 50 million people are infected with tapeworms globally, and about 50,000 die of cysticercosis annually. In the United States, T. solium taeniasis is seen primarily among Latin American immigrants, though domestically acquired cases do occur.

How to Protect Yourself

Cook all pork to an internal temperature of at least 145°F (63°C) for whole cuts, and 160°F (71°C) for ground pork. Cook ground beef to 160°F (71°C). Use a meat thermometer — color alone is not a reliable indicator of doneness. Avoid tasting raw meat mixtures. If you hunt your own game, the same temperature guidelines apply. Freezing pork at 5°F (-15°C) for 20 days also kills tapeworm cysticerci, though this is less reliable for beef.

Equally important: wash your hands thoroughly with soap and water after using the bathroom and before handling food. Because cysticercosis spreads through the fecal-oral route, good hygiene — particularly in households and food service — is a critical barrier.

3. Unwashed Leafy Greens and Fresh Produce — Cyclospora, Cryptosporidium, Toxoplasma, and Others

The Parasites

This is the one that surprises most people. Fresh salad greens, herbs, and raw vegetables can carry multiple parasitic organisms, including Cyclospora cayetanensis, Cryptosporidium, Giardia, and Toxoplasma gondii. These parasites arrive on produce through contaminated irrigation water, animal manure used as fertilizer, infected food handlers, or soil contamination.

A Canadian study that tested 544 packages of precut salads and leafy greens purchased at retail stores found Cryptosporidium in 5.9 percent of samples, Giardia in 1.8 percent, and Cyclospora in 1.7 percent (Dixon et al., PubMed, 2013). A Spanish study of organic leafy vegetables and strawberries found Toxoplasma gondii DNA in 37.2 percent of samples — the most prevalent parasitic protozoa detected (PMC, 2023).

The Outbreak History

Cyclospora outbreaks from fresh produce are a recurring problem in the United States. Past outbreaks have been associated with various types of imported fresh produce, including basil, cilantro, and raspberries. In 2018, two large multistate outbreaks sickened more than 761 people — one linked to prepackaged vegetable trays and another to fast-food restaurant salads. The 2023 and 2024 outbreak seasons involved more than 3,000 cases combined (Food Safety Magazine, 2025).

Toxoplasma gondii is particularly concerning. It is ranked as the third most important contributor to the global health burden from foodborne illness. While most healthy adults who become infected show no symptoms, Toxoplasma poses serious risks for pregnant women (it can cause miscarriage, stillbirth, or birth defects) and immunocompromised individuals.

How to Protect Yourself

Wash all produce thoroughly under running water before eating, even if it’s labeled “pre-washed.” Use a dedicated produce brush for firm-skinned vegetables. For leafy greens, separate the leaves and rinse each one individually. A solution of water with a small amount of white vinegar (roughly 1 part vinegar to 3 parts water) can help reduce surface contamination, though it won’t eliminate all parasites.

Grow your own produce when possible, and avoid using raw animal manure as fertilizer (composted manure that has reached high temperatures is much safer). If you’re pregnant or immunocompromised, be especially cautious with raw salads and unwashed herbs, and consider cooking vegetables when the source is uncertain.

4. Fresh Berries — Cyclospora and Toxoplasma

The Parasites

Berries deserve their own entry because their delicate, textured surfaces are particularly effective at trapping parasitic cysts and oocysts — and because they are almost always eaten raw.

Research has confirmed that Toxoplasma gondii oocysts can attach to and remain infectious on the surfaces of blueberries and raspberries (Kniel et al., 2002, referenced in PMC, 2020). A study published in Parasites & Vectors detected T. gondii oocysts in both vegetables and berry fruits purchased from local producers and supermarket suppliers (Lopes et al., PMC, 2020). The FAO/WHO comprehensive review on parasite contamination of berries noted that fresh produce items implicated in U.S. outbreaks include imported raspberries, which caused major Cyclospora outbreaks in 1996 and 1997.

The 1996 Cyclospora outbreak was initially (and incorrectly) blamed on California strawberries, costing U.S. growers an estimated $16 million in losses before the true source — imported raspberries from Guatemala — was identified (FAO/WHO berry review, PMC, 2018).

Why Berries Are Higher Risk

Unlike smooth-skinned fruits like apples or bananas, berries have porous, uneven surfaces with tiny folds and cavities where parasitic cysts can lodge. They cannot be peeled, and vigorous scrubbing damages them. They are also typically eaten raw and are often consumed by children, who are especially vulnerable to parasitic infections.

How to Protect Yourself

Rinse all berries gently but thoroughly under running water before eating. Spread them in a single layer in a colander and let water flow over them for at least 30 seconds. A dilute vinegar soak (1 part white vinegar to 3 parts water for 5 minutes, then rinse) can help reduce parasite load, though no washing method eliminates 100 percent of surface contamination.

Know where your berries come from. Domestically grown berries from farms with good sanitation practices carry lower risk than some imported varieties. If you’re pregnant, consider cooking berries (in smoothies, baked goods, or sauces) rather than eating them raw during the high-risk season (spring and summer). Freezing berries does not reliably kill all parasites, though it reduces risk.

For homesteaders and gardeners who grow their own berries: avoid using untreated animal manure near berry patches, protect plants from contact with cat feces (a primary source of Toxoplasma oocysts in the environment), and wash everything before eating.

5. Unfiltered Tap Water — Giardia lamblia

The Parasite

Giardia duodenalis (also called G. lamblia or G. intestinalis) is the most commonly identified parasite causing waterborne disease outbreaks in U.S. public water systems. It’s a microscopic protozoan that forms hardy cysts capable of surviving in cold water for months and resisting standard chlorination levels.

How Common Is It?

During 2012–2017, public health officials from 26 states reported 111 giardiasis outbreaks with 760 primary cases, 28 hospitalizations, and 48 emergency department visits. Among waterborne outbreaks, tap water systems — including both municipal systems and private wells — were one of the leading exposure sources. Ingestion of as few as 10 cysts can cause disease.

The risk is higher for people who rely on private wells, rural water systems, or older municipal infrastructure. Aging pipes, distribution system deficiencies, and proximity between water lines and sewer lines can all create vulnerabilities. Research presented at a CDC panel on waterborne diseases noted that pressure fluctuations in aging pipe systems can draw contaminated groundwater into distribution lines through small leaks — particularly when sewer lines run close to water pipes (CDC, 2001).

What It Does to You

Giardiasis causes watery diarrhea, abdominal cramps, bloating, gas, nausea, and weight loss. About half of infections are asymptomatic, meaning you can carry and spread the parasite without knowing it. Symptoms can persist for weeks if untreated, and some people develop recurring symptoms or long-term digestive complications.

How to Protect Yourself

If your home uses municipal water, your supply is treated and monitored to meet EPA standards — but treatment system failures do occur. If you have concerns about your water quality, a point-of-use filter rated to remove cysts (look for NSF/ANSI Standard 53 or 58 certification, or filters with an absolute pore size of 1 micron or smaller) provides an extra layer of protection.

If your home uses a private well, have your water tested at least annually, especially if you live near agricultural land, septic systems, or surface water. Wells dug close to streams, ponds, or areas with wildlife activity (beavers, in particular, are known carriers) face higher contamination risk.

When camping, hiking, or traveling in areas without treated water, always filter, boil, or chemically treat water before drinking. Boiling for at least one minute (three minutes at elevations above 6,500 feet) kills Giardia cysts effectively.

Natural Support for Digestive Health After Exposure

If you’ve experienced a parasitic infection, or if you suspect past exposure, supporting your gut health afterward is important. Parasitic infections can disrupt the balance of gut bacteria, damage the intestinal lining, and leave lingering digestive symptoms even after the infection is cleared.

While the following approaches are not treatments for active parasitic infections (see a doctor for that), they can support gut recovery:

• Probiotics and fermented foods. Reintroducing beneficial bacteria through yogurt, kefir, sauerkraut, kimchi, and quality probiotic supplements can help restore microbial balance after infection.
• Bone broth. Rich in collagen, glycine, and glutamine, bone broth has been used traditionally to support intestinal lining repair. While clinical evidence is limited, the amino acid profile supports the tissue repair process.
• Pumpkin seeds. These have been used in folk medicine across many cultures as a natural antiparasitic. Some research supports the traditional use, particularly against tapeworms, though the evidence is preliminary and should not replace medical treatment.
• Anti-inflammatory foods. Turmeric, ginger, garlic, and omega-3-rich foods help reduce the gut inflammation that often persists after parasitic damage.
• Digestive bitters and fiber. Bitter herbs (dandelion root, gentian) stimulate digestive secretion, and adequate fiber supports the regular elimination that keeps the digestive tract moving.

The Bottom Line: Knowledge Is the Best Protection

Parasites aren’t exotic. They’re in the sushi restaurant downtown, the salad mix at the supermarket, the undercooked burger at the backyard cookout, and — in some cases — the water running through your pipes. That doesn’t mean you need to live in fear. It means you need to live with awareness.

The protective steps are simple and consistent: cook meat to proper temperatures, freeze fish before eating it raw, wash all produce thoroughly, know your water source, and practice good hand hygiene. These aren’t complicated or expensive. They’re just habits — and they work.

For families who are growing their own food, hunting their own game, or living on well water, the stakes are a little higher and the knowledge matters a little more. But the same principles apply: know the risks, take the precautions, and trust that informed, consistent action is the best medicine of all.

 

Important Disclaimer: This article is for educational purposes only. If you suspect you have a parasitic infection, consult a healthcare provider for proper diagnosis and treatment. Do not attempt to self-treat parasitic infections with home remedies.

 

 

 

 

 

References

Centers for Disease Control and Prevention (CDC). About Anisakiasis. https://www.cdc.gov/anisakiasis/about/index.html

Centers for Disease Control and Prevention (CDC). About Human Tapeworm (Taeniasis). https://www.cdc.gov/taeniasis/about/index.html

Centers for Disease Control and Prevention (CDC). Giardiasis Outbreaks — United States, 2012–2017. MMWR, 70(9). https://pmc.ncbi.nlm.nih.gov/articles/PMC7948938/

Dixon, B., et al. (2013). Detection of Cyclospora, Cryptosporidium, and Giardia in ready-to-eat packaged leafy greens in Ontario, Canada. Journal of Food Protection. https://pubmed.ncbi.nlm.nih.gov/23433379/

FAO/WHO. (2014). Multicriteria-based ranking for risk management of foodborne parasites. Microbiological Risk Assessment Series, No. 23.

Food Safety Magazine. (2025). Cyclospora cayetanensis: An emergent public health threat and an enigma for traceback investigation. https://www.food-safety.com/articles/10770

Lopes, A. P., et al. (2020). Detection of Toxoplasma gondii oocysts in fresh vegetables and berry fruits. Parasites & Vectors, 13, 180. https://pmc.ncbi.nlm.nih.gov/articles/PMC7140358/

Martín-Escolano, R., et al. (2023). Protozoan parasites and free-living amoebae contamination in organic leafy green vegetables and strawberries from Spain. Food Microbiology. https://pmc.ncbi.nlm.nih.gov/articles/PMC10316001/

Merck Manual Professional Edition. (2025). Anisakiasis. https://www.merckmanuals.com/professional/infectious-diseases/nematodes-roundworms/anisakiasis

MedlinePlus. Tapeworm infection — beef or pork. https://medlineplus.gov/ency/article/001391.htm

Robertson, L., & Gjerde, B. (2018). Parasite contamination of berries: Risk, occurrence, and approaches for mitigation. Food and Waterborne Parasitology. https://pmc.ncbi.nlm.nih.gov/articles/PMC7033989/

Sugiyama, H., et al. (2022). Anisakiasis annual incidence and causative species, Japan, 2018–2019. Emerging Infectious Diseases, 28(10). https://pmc.ncbi.nlm.nih.gov/articles/PMC9514333/

World Health Organization (WHO). Taeniasis/Cysticercosis Fact Sheet. https://www.who.int/news-room/fact-sheets/detail/taeniasis-cysticercosis