RESUMO
The objective of this study was to determine sources of Shiga toxin-producing Escherichia coli O157 (STEC O157) infection among visitors to Farm X and develop public health recommendations. A case-control study was conducted. Case-patients were defined as the first ill child (aged <18 years) in the household with laboratory-confirmed STEC O157, or physician-diagnosed hemolytic uremic syndrome with laboratory confirmation by serology, who visited Farm X in the 10 days prior to illness. Controls were selected from Farm X visitors aged <18 years, without symptoms during the same time period as case-patients. Environment and animal fecal samples collected from Farm X were cultured; isolates from Farm X were compared with patient isolates using whole genome sequencing (WGS). Case-patients were more likely than controls to have sat on hay bales at the doe barn (adjusted odds ratio: 4.55; 95% confidence interval: 1.41-16.13). No handwashing stations were available; limited hand sanitizer was provided. Overall, 37% (29 of 78) of animal and environmental samples collected were positive for STEC; of these, 62% (18 of 29) yielded STEC O157 highly related by WGS to patient isolates. STEC O157 environmental contamination and fecal shedding by goats at Farm X was extensive. Farms should provide handwashing stations with soap, running water, and disposable towels. Access to animal areas, including animal pens and enclosures, should be limited for young children who are at risk for severe outcomes from STEC O157 infection. National recommendations should be adopted to reduce disease transmission.
RESUMO
BACKGROUND: In Connecticut, despite hazards of raw milk consumption, attempts to ban raw milk sales have been unsuccessful. In July 2008, 2 children experienced Escherichia coli O157-associated hemolytic uremic syndrome (HUS) after consuming raw milk purchased at a retail market and a farm (farm X). We investigated to determine the outbreak source and control measures. METHODS: Confirmed cases were HUS diagnosis or E. coli O157:NM infections with isolates matching outbreak strains among patients during June to July 2008. Probable cases were diarrheal illness among farm X customers during the same period. We conducted case-control studies to determine the source of E. coli O157 exposure and assess for dose-response relation between illness and frequency of raw milk consumption. Farm X dairy practices were evaluated; stool specimens of humans and animals were cultured for E. coli O157. Staff time and laboratory and medical costs were calculated. RESULTS: We identified 14 cases (7 confirmed). Five (36%) case patients required hospitalization; 3 (21%) experienced HUS. No deaths were reported. Raw milk consumption was associated with illness (P = .008); a dose-response relation was demonstrated (P = .01). Dairy practices reflected industry standards. E. coli O157:NM outbreak strains were isolated from stool specimens of 6 case patients and 1 milking cow. The total estimated outbreak cost was $413,402. CONCLUSIONS: Farm X's raw milk was the outbreak source despite no violations of current raw milk regulatory standards. This outbreak resulted in substantial costs and proposed legislation to prohibit nonfarm retail sale, strengthen advisory labels, and increase raw milk testing for pathogens.