A foodborne outbreak of cyclosporiasis caused by imported raspberries

Cyclospora cayetanensis is a recently recognized parasite that causes prolonged diarrheal illness. Its modes of transmission have not been fully determined, although some investigations before 1996 implicated water. Outbreaks of cyclosporiasis in the United States in 1996 and 1997 are evidence of the increasing incidence of this disease. This report describes an outbreak of cyclosporiasis in persons who attended a luncheon on May 23, 1996, near Charleston, South Carolina.

In this retrospective cohort study, we interviewed all 64 luncheon attendees and the chef regarding food and beverage exposures. A case of cyclosporiasis was defined as diarrhea (> or = 3 loose stools per day or > or = 2 loose stools per day if using antimotility drugs) after attending the luncheon. We identified sporadic cases of cyclosporiasis and traced the implicated food.

Of 64 luncheon attendees, 38 (59%) met the case definition. Persons who ate raspberries (relative risk [RR] = 5.4; 95% confidence interval [CI], 2.2-13.2) or potato salad (RR = 1.8; 95% CI, 1.2-2.6) were at significantly increased risk for illness. The population attributable risk percentages were 73% for raspberries and 20% for potato salad. Cyclospora oocysts were found in stools from 11 (85%) of the 13 case patients submitting specimens for testing. Implicated raspberries originated in Guatemala.

Our investigation is one of the first studies to implicate a specific food (raspberries) as a vehicle for transmission of Cyclospora. Because of the apparent increasing incidence of cyclosporiasis in the United States, family physicians should consider testing for Cyclospora in any patient with prolonged, unexplained diarrhea.