Horizontal transmission of Escherichia coli O157:H7 during cattle housing, survival kinetics in feces and water of Escherichia coli O157:H7 and characterisation of E. coli O157:H7 isolates from cattle faeces and a feedlot environment.

Abstract

Ruminant livestock, particularly cattle, are considered the primary reservoir of E. coli O157:H7. This study examined the transmission of E. coli O157:H7 within groups of cattle during winter housing. Holstein Friesian steers were grouped in 6 pens of 5 animals. An animal inoculated with, and proven to be shedding a marked strain of E. coli O157:H7 was introduced into each pen. Fecal (rectal swabs) and hide samples (900cm2 right rump) were taken from the thirty six animals throughout the study. Water, feed and gate/partition samples from each pen were also examined. Within 24h of introducing the inoculated animals into the pens, samples collected from the drinking water, pen barriers and animal hides were positive for the pathogen. Within 48h, the hides of 20 of 30 (66%) cohort animals from the 6 pens were contaminated with E. coli O157:H7. The first positive fecal samples from the non-inoculated cohort animals were detected three days after the introduction of the inoculated steers. Over the 23 days of the study 15 of 30 cohort animals shed the marked E. coli O157:H7 strain in their feces on at least one occasion. Animal behavior in the pens was monitored over a 12h period using CCTV cameras. The camera footage showed an average of 13 instances of animal grooming in each pen per hour. The study suggests that transmission of E. coli O157:H7 between animals may occur following ingestion of the pathogen at low levels, and that animal hide may be an important source of transmission.