These things keep happening, and we know why, but the worst is the way it affects kids and their families.
BBC News is reporting that two children from Kent who visited Cantref Adventure Farm 
have been sickened by E. coli O157 and are recovering at home.
Two family members of one of the infected children have also tested positive.
One is believed to have contracted the illness through contact with the child. The farm has been asked to comment.
A table of petting zoo outbreaks is available at http://bites.ksu.edu/petting-zoos-outbreaks.
Erdozain G, Kukanich K, Chapman B, Powell D. 2012. Observation of public health risk behaviours, risk communication and hand hygiene at Kansas and Missouri petting zoos – 2010-2011. Zoonoses Public Health. 2012 Jul 30. doi: 10.1111/j.1863-2378.2012.01531.x. [Epub ahead of print]
Abstract below:
Observation of public health risk behaviors, risk communication and hand hygiene at Kansas and Missouri petting zoos – 2010-2011Outbreaks of human illness have been linked to visiting settings with animal contact throughout developed countries. This paper details an observational study of hand hygiene tool availability and recommendations; 
frequency of risky behavior; and, handwashing attempts by visitors in Kansas (9) and Missouri (4), U.S., petting zoos. Handwashing signs and hand hygiene stations were available at the exit of animal-contact areas in 10/13 and 8/13 petting zoos respectively. Risky behaviors were observed being performed at all petting zoos by at least one visitor. Frequently observed behaviors were: children (10/13 petting zoos) and adults (9/13 petting zoos) touching hands to face within animal-contact areas; animals licking children’s and adults’ hands (7/13 and 4/13 petting zoos, respectively); and children and adults drinking within animal-contact areas (5/13 petting zoos each). Of 574 visitors observed for hand hygiene when exiting animal-contact areas, 37% (n=214) of individuals attempted some type of hand hygiene, with male adults, female adults, and children attempting at similar rates (32%, 40%, and 37% respectively). Visitors were 4.8x more likely to wash their hands when a staff member was present within or at the exit to the animal-contact area (136/231, 59%) than when no staff member was present (78/343, 23%; p<0.001, OR=4.863, 95% C.I.=3.380-6.998). Visitors at zoos with a fence as a partial barrier to human-animal contact were 2.3x more likely to wash their hands (188/460, 40.9%) than visitors allowed to enter the animals’ yard for contact (26/114, 22.8%; p<0.001, OR= 2.339, 95% CI= 1.454-3.763). Inconsistencies existed in tool availability, signage, and supervision of animal-contact. Risk communication was poor, with few petting zoos outlining risks associated with animal-contact, or providing recommendations for precautions to be taken to reduce these risks.