Taylor Farms responds

Taylor Farms, in a separate statement, attributed the contamination cited by the FDA to an independent grower "who is no longer part of our supplier program."

"Our facility remains closed in central Mexico as we work with our research team to implement enhanced safety protocols from the field to the facility," the company said.

A tangled testing history

The investigation's final chapter follows a rocky road of conflicting results. Regulators from Mexico's food safety authority announced in August that their own investigation did not detect cyclospora in the lettuce or water at the facility.

That conclusion came days after the FDA was forced to retract a faulty test result. The test had incorrectly identified cyclospora in a sample of lettuce from Taylor Farms collected at the border.

What is cyclospora?

Cyclospora is a microscopic parasite that causes an illness called cyclosporiasis. According to the CDC, the infection commonly causes watery diarrhea "with frequent and sometimes explosive bowel movements."

Cyclosporiasis is less common than foodborne illnesses caused by other germs, such as salmonella and E. coli. The parasite spreads through human feces, which is why the presence of a wastewater tank and drainage ditch contamination at the farm points toward a possible sanitation failure — though the FDA has not confirmed the exact route.

The case also highlights a broader concern for food safety oversight. The FDA had not inspected this facility in more than seven years before the outbreak, a gap that reflects reduced international inspections since the pandemic.

With the investigation now closed, questions remain unanswered about how the contamination occurred. What the FDA does have is genetic and environmental evidence tying the outbreak to the Guanajuato site — and a lettuce facility that remains shut while its operator overhauls safety protocols.