'Super' or just 'above average'? Supershedders and the transmission of Escherichia coli O157:H7 among feedlot cattle.
Supershedders have been suggested to be major drivers of transmission of Escherichia coli O157:H7 (E. coli O157:H7) among cattle in feedlot environments, despite our relatively limited knowledge of the processes that govern periods of high shedding within an individual animal. In this study, we attempt a data-driven approach, estimating the key characteristics of high shedding behaviour, including effects on transmission to other animals, directly from a study of natural E. coli O157:H7 infection of cattle in a research feedlot, in order to develop an evidence-based definition of supershedding. In contrast to the hypothesized role of supershedders, we found that high shedding individuals only modestly increased the risk of transmission: individuals shedding over 10(3) cfu g(-1) faeces were estimated to pose a risk of transmission only 2.45 times greater than those shedding below that level. The data suggested that shedding above 10(3) cfu g(-1) faeces was the most appropriate definition of supershedding behaviour and under this definition supershedding was surprisingly common, with an estimated prevalence of 31.3% in colonized individuals. We found no evidence that environmental contamination by faeces of shedding cattle contributed to transmission over timescales longer than 3 days and preliminary evidence that higher stocking density increased the risk of transmission.
Department of Statistics, University of Warwick, Coventry, UK s.e.f.spencer@warwick.ac.uk.
Simon E F
SE
Spencer
Department Veterinary Microbiology and Pathology, Washington State University, Pullman, WA 99164, USA.
Thomas E
TE
Besser
School of Veterinary Science, University of Queensland, Gatton, Queensland, Australia 4343.
Rowland N
RN
Cobbold
mEpiLab, Infectious Disease Research Centre, Institute of Veterinary Animal and Biomedical Sciences, Massey University, Palmerston North, New Zealand.
Nigel P
NP
French
D000818:Animals; D002417:Cattle; D002418:Cattle Diseases / Q000635:transmission*; D004927:Escherichia coli Infections / Q000635:transmission* / Q000662:veterinary*; D019453:Escherichia coli O157 / Q000472:pathogenicity*; D008954:Models, Biological
Bayesian statistics; Escherichia coli infections/veterinary; cattle diseases/epidemiology; supershedder