BACKGROUND: In May 2016, the Minnesota Department of Health (MDH) identified two cases of cryptosporidiosis. The cases reported visiting the same agritourism farm with different school field-trips, and that additional field-trip attendees were ill.
METHODS: Interviews about illness history, animal contact, and handwashing were conducted with teachers, chaperones and parents of students who visited the farm. A case was defined as a person who visited the farm during May 9-25 and experienced fever and diarrhea (≥3 loose stools in a 24-hour period), or diarrhea lasting ≥3 days, or had a laboratory-confirmed Cryptosporidium infection,within 2 weeks of their farm visit. Stool samples from cases were submitted to MDH for parasite and bacterial testing. MDH investigators visited the farm to assess safety measures and collect animal and environmental samples.
RESULTS: Animals present at the farm included chicks, other poultry, goats, sheep, pigs, a calf and a miniature horse. The farm was clean, did not allow visitors into pens, and signage covered most recommended messages. Adults held animals for children to pet. Other activities included hayrides, a hayloft swing and a playground. The handwashing station was a bathtub retro-fitted with 4 hot-water faucets, soap and paper towels. Hand sanitizer was available. Staff encouraged handwashing, and groups visited the tub as part of their itinerary. Five-hundred-fifty-five (25%) of 2256 visitors were interviewed. Seventy-two cases (13%) were identified; 20 were laboratory-confirmed. The mean age of cases was 13.6 years (range, 5-65); mean age of controls was 7.4 years (range, 3-68) (p<0.001). Cases were 5.5 times more likely to be adults than students (odds ratio [OR], 5.52; 95% confidence interval [CI], 2.86-10.6; p<0.001). Reporting contact with animals was not statistically associated with illness and handwashing was not statistically protective. Cases were 5.8 times more likely to have participated in other activities after interacting with the ruminants, rather than immediately handwashing (OR, 5.83; 95% CI, 1.71-19.9; p=0.002). The calf, one sheep and one pig tested positive for Cryptosporidium parvum which matched the C. parvum found in human cases (GP60 subgenotype IIaA15G2R1). The calf had scours 2-3 days before the field-trip season started.
CONCLUSIONS: This outbreak demonstrates that animal contact illnesses can occur even if handwashing facilities are adequate and staff promote their use. The critical factor was likely the prolonged time for some visitors between animal contact and handwashing. This emphasizes the need for handwashing immediately and a facility designed to promote this behavior.