Source:Crump JA, Sulka AC, Langer AJ, et al. An outbreak of Escherichia coli 0157:H7 infections among visitors to a dairy farm.
New Engl J Med.

In a case-controlled study conducted by both state and national health agencies, visitors to a farm in Pennsylvania were surveyed at home within 10 days after their visit to ascertain rates of diarrheal disease. Fifty-one patients (median age 4 years; 92% less than 10 years) with confirmed (15) or suspected (36) Escherichia coli O157:H7 infection were identified. Hemolytic uremic syndrome (HUS) developed in 8, all 10 years or younger. Bloody diarrhea occurred in 37%, fever in 45% and vomiting in 45%. Contact with calves and/or their immediate environment was associated with an increased risk of E coli O157:H7 infection. Hand washing approached statistical significance with respect to a protective effect. E coli O157:H7 was found in 28 of 216 cattle (13%) and on surfaces that were accessible to the public. All of the isolates had a similar pattern on pulsed-field gel electrophoresis. Controls were obtained through a phone survey of 19,698 telephone numbers in the region of the study. Of the 3,497 households contacted, 134 (4%) had a household member who visited the farm in the same time period as the affected children. Twenty-two (16%) of the controls reported diarrhea in the 10 days following the visit. This contrasts with an expected diarrheal rate of 7% per 10 days in the general population (CDC; unpublished data, 1998–1999). Transmission of infection to patients was thought to occur from touching animal hides and/or sites in the immediate environment of the cattle.

This study extends previous observations that E coli O157: H7 can be spread by direct contact between cows and people and that people can become infected after the organisms have been shed by cattle. E coli can survive in the environment for many months.1 The organism is also known to be spread by contamination of food and water. Moreover, the use of antibiotics to treat diarrheal disease in children is associated with an increased risk of developing HUS.2 Cows do not become sick from this organism because their endothelium lacks the receptor for the endotoxin elaborated by E coli O157:H7. Young children, rather than adults, are more likely to develop HUS because they have a greater number of E coli endotoxin receptors on their glomerular vascular endothelium.3 Once again, we find that one of the best preventative measures to avoid the spread of infectious disease is hand washing. Should children stop going to petting farms or “children’s zoos?” I hope not since such activities are rewarding.

Steps are needed to reduce the risk of developing serious infection. Perhaps consideration ought to be given to public health measures such as culturing animals that serve as reservoirs, separating eating areas from visiting areas, and increased surveillance of the interactions between children and pets. Anticipatory guidance about hand washing before visitation, teaching children to avoid putting their fingers into...

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