Which species poses the greatest risk for zoonosis of E.coli O157H7?

The greatest risk for zoonosis of E. coli O157:H7 is associated with cattle. This strain of E. coli is primarily found in the intestines of healthy cattle and can be shed in their feces without causing disease in the animals. Cattle are often asymptomatic carriers, which makes them a significant reservoir for the bacteria. The handling, consumption, or contamination of water and food sources with cattle manure can lead to transmission of E. coli O157:H7 to humans.

Infection in humans typically arises from undercooked beef, especially ground beef, or through contact with contaminated environments, including petting zoos or farms where cattle are present. The potential severity of infections caused by E. coli O157:H7 in humans, including severe gastrointestinal disease and complications like hemolytic uremic syndrome, emphasizes the importance of understanding the risks associated with this bacterium in cattle populations.

While other species such as pigs, sheep, and chickens can harbor E. coli, they are not considered major reservoirs for the O157:H7 strain when compared to cattle, thus highlighting why cattle pose the greatest risk for zoonosis related to this specific strain.