Lettuce probe into largest foodborne illness outbreak of parasite in US history: Mexico's Health Ministry investigation finds shocking results

Mexico's Health Ministry said on Saturday that a US Food and Drug Administration investigation into the cyclospora parasite outbreak linked to shredded iceberg lettuce from Taylor Farms in Mexico did not conclusively identify the source of contamination. Mexico's food-safety regulator Cofepris said tests conducted by its national reference laboratory on raw materials, finished products and water from the facility investigated in the outbreak were negative for the cyclospora parasite.

The regulator added that environmental findings alone do not constitute conclusive evidence that agricultural products were the source of contamination. The FDA said on Friday it found a strong epidemiological and traceback link between the outbreak and recalled shredded iceberg lettuce produced by Taylor Farms in Mexico, but said there was insufficient evidence to determine how contamination occurred.

The agency reported two environmental samples positive for cyclospora in Mexico, one from wastewater leaving a processing facility and another from a drainage ditch at an iceberg lettuce farm. The Centers for Disease Control and Prevention declared the outbreak over on September 11. The outbreak sickened 12,883 people in 21 states, hospitalized 570 and was linked to two deaths.


Mexico said it cooperated throughout the investigation, providing traceability information, inspections and samples, and would continue technical cooperation with US health authorities.

The Food and Drug Administration said on Friday that its inspectors detected cyclospora at the Mexican farm blamed for the largest foodborne illness outbreak of the parasite in U.S. history.

Despite the finding, the FDA said it’s unclear how the parasite got into lettuce at Taylor Farms’ facility. The agency has now closed its investigation into the outbreak, which led to nearly 13,000 cases of diarrhea and other illnesses across the U.S.

The announcement comes more than six weeks after the agency sent its investigators to the farm in Guanajuato, Mexico. The visit was the agency’s first time there in more than seven years following a steep drop in international food safety inspections after the COVID-19 pandemic.

FDA inspectors said Friday they found cyclospora in two places: a wastewater tank and a drainage ditch used for lettuce cultivation. While it’s unclear how the contamination took place, the FDA said the samples provide “strong epidemiological data” linking the outbreak to the Taylor Farms site.

Cyclospora is a microscopic parasite that commonly causes watery diarrhea “with frequent and sometimes explosive bowel movements,” according to the CDC. The illness, called cyclosporiasis, is less common than foodborne illnesses caused by other germs, including salmonella and E. coli.

The parasite is spread through human feces, and it still isn’t clear how sewage could have contaminated enough food to sicken so many people.