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pen farms and petting zoos present children with sometimes unique access to both farm and wild animals. The experience provides opportunity to touch or feed animals not normally encountered in the domestic setting. Importantly, petting farms and zoos provide both entertainment and educational opportunities for children of all ages. However, in a small number of circumstances, contact with such animal hosts may give rise to zoonotic infections, including Salmonella, Campylobacter, Cryptosporidium, and Escherichia coli (E. coli), particularly E. coli O157. In the Netherlands it is estimated that there are approximately 450 petting zoos which are visited annually by 15-20 million people (Heuvelink et al., 2007). In the United Kingdom it is reported that there are between 5 and 10 million visitors to open farms each year (Walker, 2010). Petting farms typically have significant numbers of visitors between the months of May and September, coinciding with school holidays and vacation breaks. As a consequence, there is the potential for transmission of zoonotic organisms to many farm visitors in the absence of appropriate interventions and controls. However, overall the risk of infection is still perceived as proportionately low in context of the incidence of infection. Ordinarily, infection with E. coli O157 is most commonly associated with the consumption of contaminated foods such as meat, unpasteurized milk or cheeses. The consumption of faecally contaminated fresh produce, such as lettuce, has also been implicated in several outbreaks. Transmission can also take place via person-to-person contact through the faecal-oral route; this infective route is reported most commonly in child daycare centres. Recreational activities such as swimming in infected water bodies such as rivers or streams have also been reported as a transmission route. E. coli O157 can also be transmitted via contact with infected animals and such an infection route is most often associated with country fairs, petting zoos and petting/open farms (Rangel et al., 2005). Quite simply, people touching animals or contaminated surfaces associated with animals may contaminate their hands with E. coli O157 (Duffy, 2003) and infection may result from hand-to-mouth contact. 22
Escherichia coli O157: a wolf in petting farm clothing? In the last 10 years, several European countries and America have reported E. coli O157 outbreaks associated with petting farms and zoos, farmyard camps and country fairs. In the United States animal contact outbreaks were first reported in 1996, with most outbreaks subsequently associated with direct contact with cattle. The prevalence of E. coli O157 in farmed livestock has been reported by several groups but by contrast we still know relatively little about the prevalence in the diversity of species found on petting farms. Cattle are ordinarily perceived as the main reservoir of the organism, with E. coli O157 found in approximately 40% of herds in England and Wales (Paiba et al., 2003). The presence of E. coli O157 has also been reported in other
animals including pigs, sheep, horses, alpacas, llamas, deer and rabbits (reviewed by Pritchard et al., 2009). Several surveys would indicate that the prevalence of E. coli O157 in various species found on petting farms is actually quite high with some farms having between 50% and 70% positive samples (Heuvelink et al., 2007, Pritchard et al., 2009). Currently less is known about the colonization and persistence of E. coli O157 in small ruminants such as sheep compared with our current knowledge of the associations of this organism with cattle (La Ragione et al., 2009). One of the major issues in the control of E. coli O157 in animal species is that the organism survives in the gastrointestinal tract and does not cause