BACKGROUND: On March 24, 2016, the Connecticut Department of Public Health (CDPH) identified a cluster of seven culture-confirmed Shiga toxin-producing Escherichia coli (STEC) infections. Six of the first seven patients reported visiting the same dairy goat farm. A joint investigation involving the CDPH, Centers for Disease Control and Prevention, Connecticut Department of Agriculture, and the local health district was initiated.
METHODS: : A case was defined as a laboratory-confirmed E. coli O157 infection in an individual with the outbreak pulsed-field gel electrophoresis (PFGE) strains or someone with hemolytic uremic syndrome (HUS) during March - May 2016, with an epidemiologic link to the goat farm. Active case-finding was conducted, and all identified case-patients were interviewed by telephone using a standard questionnaire. Environmental and goat fecal samples were collected and tested at the CDPH State Public Health Laboratory. PFGE and whole genome sequencing were performed on isolates recovered from case-patient, animal, and environmental samples.
RESULTS: A total of 51 confirmed E. coli O157 cases were linked to the outbreak with onset dates ranging from 3/7/2016 to 5/14/2016. All case-patients were interviewed, 39 (76%) visited the same goat farm or had contact with goats originating from the farm, and 6 (12%) had contact with someone who visited the farm. Case-patients ranged in age from 10 months to 50 years; 55% were ≤ 5 years of age. Eleven (22%) case-patients were hospitalized and 3 (6%) developed HUS. Forty-one (84%) O157 clinical isolates yielded primary outbreak PFGE patterns; the remaining isolates demonstrated closely-related patterns. Among 61 environmental samples collected, 28 (46%) yielded STEC isolates including 18 O157, 9 O103, and 1 O-undetermined. Among the 17 goat fecal pellet samples/swabs collected, 16 (94%) yielded STEC isolates including 11 O157 and 7 O103. All sequenced human, environment, animal STEC O157 isolates were highly related differing by 0-6 single nucleotide polymorphisms.
CONCLUSIONS: E. coli O157 is known to colonize the gastrointestinal tract of healthy ruminants, and STEC illness resulting from direct contact with shedding animals or their environment has been reported. In this outbreak, greater than half of the case-patients were 5 years of age or younger. This age group is at increased risk for severe illness. Restricting young children’s (<5 years) access to ruminants should be considered in the future to minimize risk to this vulnerable population.