Longitudinal study to investigate VTEC O157 shedding patterns in young cattle

Individual animal samples were collected from ten VTEC O157 positive farms approximately monthly over 11 months to investigate the shedding of VTEC O157 by youngstock. VTEC O157 was isolated from 7.7% of the 6266 samples and 28.9% of the 1383 animals. On six of the farms VTEC O157 was isolated at multiple visits from several animals, whereas the remaining four farms had one or two positive animals at any one visit, with VTEC isolated from a maximum of four visits. A total of 92 animals were positive more than once (up to four sampling occasions) with a maximum of four negative samples between positive isolations. The results reveal a large variation in individual animal shedding patterns; the proportion of shedding animals on positive farms; and over time within the same farm. The lack of consistent shedding restricts the ability to target potential interventions to specific positive animals/groups or herds.