Millions of illnesses linked to foodborne parasites, new study warns

Hundreds of millions of illnesses worldwide may be linked to foodborne invasive parasites each year, according to a new analysis that researchers say highlights a major but often overlooked public health challenge.

The research, published this month in The Lancet Global Health, estimated that 277 million illnesses were caused by potentially foodborne invasive parasites, with approximately 171 million attributable to foodborne transmission.

Researchers examined the burden of 14 parasitic diseases from 2000 to 2021.

“Over 10 years ago, WHO estimates of hazard-specific foodborne disease burdens showed that parasites exert considerable health burdens globally,” the authors wrote. “We updated these estimates, focusing on 14 invasive parasitic diseases.”

Professor Lucy Robertson of the Norwegian University of Life Sciences (NMBU), a lead author of the study, told Newsweek that “invasive parasites result in hundreds of millions of foodborne diseases annually.”

The researchers found considerable variation among different parasites. Of the estimated 4.89 million foodborne disability-adjusted life-years (DALYs) associated with the diseases studied, the largest contributions came from Taenia solium and Clonorchis sinensis, the two parasites linked to the highest numbers of foodborne deaths, according to the study.

Robertson warned that “greater recognition that these parasites affect human health and welfare should be a key public health message,” noting that “food poisoning is not only bacteria.”

The study’s authors concluded that foodborne parasitic diseases continue to cause “considerable suffering,” with some populations and regions facing particularly high risks.

According to the study, the overall burden was greatest in the Americas, largely because of Chagas disease—which is spread through insects known as triatomine, or "kissing" bugs, a subfamily within the Reduviidae family, that bite and suck blood from animals or people carrying the parasite. The Americas were followed by Africa, where much of the burden stemmed from epilepsy associated with neurocysticercosis, an infection caused by larval cysts.

Robertson said that although Chagas disease is often associated with transmission by Reduviid bugs, foodborne transmission is also significant, acquired through contaminated food or drinks. “It is worth noting that Chagas disease caused by the foodborne route tends to result in more severe disease,” she said.

The study also found that while the global burden of foodborne parasitic diseases fell between 2000 and 2021, one parasite moved in the opposite direction.

Robertson said she was encouraged that the burden from invasive foodborne parasites was generally declining. However, she described the apparent increase in disease burden associated with the fishborne helminth Clonorchis sinensis as unexpected, noting it “should be a wakeup call for relevant authorities in those countries where this parasite occurs.” Clonorchis sinensis is a fishborne parasitic worm, commonly known as the Chinese liver fluke, that can infect people who eat raw or undercooked freshwater fish.

Professor Dr. Vedat Turhan, an infectious diseases specialist at Medicana Health Group, noted that the study shows the Western Pacific region also experienced an increase in foodborne parasitic illnesses during the study period.

Turhan told Newsweek that factors that may influence disease trends include changes in food production and distribution, increasing international travel and migration, and greater consumption of raw or undercooked foods.

Both experts emphasized that prevention measures must address the complex life cycles of parasites.

Robertson said thorough cooking can help reduce risk, but stressed that many parasites are zoonotic, infecting humans and animals, and typically involve environmental, animal, and human factors. She said a "One Health" approach that considers all three is essential.

Turhan said many foodborne parasitic diseases can be prevented through thorough cooking of meat, fish, and other potentially contaminated foods. He also highlighted safe water, proper food preparation, hand hygiene, and adequate waste disposal as important preventive measures.

At a broader level, Turhan said that “a strong food-safety system, veterinary surveillance of animal hosts for foodborne parasites and control of infection in animal hosts is required,” while greater awareness among both the public and healthcare workers could help support earlier diagnosis and treatment.

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