Cyclospora outbreak spreads across 45 U.S. states, experts detail parasite's life cycle and health impact
Health officials report a record Cyclospora outbreak affecting thousands in 45 states, describing how the parasite reproduces in the human gut and the symptoms it causes.
The Centers for Disease Control and Prevention said on July 28 that cases of cyclosporiasis have been reported in 45 states, marking the largest known U.S. outbreak of the Cyclospora parasite. Michigan accounts for the highest number of reported illnesses, with investigators suspecting contaminated lettuce as a likely source.
Cyclospora oocysts, which are microscopic pods that can only reproduce inside the human digestive tract, attach to the surface of produce and become infectious after maturing in the environment. Professor Vernon Carruthers of the University of Michigan Medical School explained that the oocysts respond to gut signals such as temperature, bile and digestive enzymes, releasing parasites that invade the lining of the small intestine and multiply within host cells.
Molecular parasitologist Joel Barratt of Emory University noted that the parasites damage intestinal cells, reducing nutrient absorption and producing symptoms including nausea and diarrhea. He added that a milliliter of diarrheal fluid can contain roughly a thousand oocysts.
The parasites can survive in water and on crops despite exposure to chlorine, sunlight and cold temperatures, and may be spread through contaminated soil, irrigation water, or handling by workers. Infections can persist for weeks or months; Dr. Bobbi Pritt of the Mayo Clinic said treatment typically involves a combination of antibiotics sold under brand names such as Bactrim or Septra, which inhibit parasite replication.
While cyclosporiasis is rarely fatal, repeated exposure appears to confer partial immunity, especially in regions where the parasite is endemic. The current surge in the United States is linked to imported produce, including a recalled batch of shredded lettuce from Taylor Farms in Mexico that was associated with a nine-state cluster. State health departments are also investigating other possible sources, such as parsley and cilantro in North Carolina.