‘Super' or just ‘above average'? Supershedders and the transmission of Escherichia coli O157:H7 among feedlot cattle

Abstract

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 21 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 21 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.

The effect of transportation and lairage on faecal shedding and carcass contamination withEscherichia coliO157 and O26 in very young calves in New Zealand

“…In addition to transportation and lairage, there are also animal-related factors affecting the prevalence of hide contamination in cattle. For example, the presence of 'supershedders' in the pens of feedlot cattle can significantly increase transmission [42] and the prevalence of hide contamination [43]. Similarly, Jacob et al [44] found a significant correlation between hide prevalence within truckloads (a cohort of adult cattle transported and lairaged together) and the presence of high shedders (>5 × 10 4 CFU/g faeces) in truckloads, indicating that the levels of faecal E. coli shed during transportation and lairage also have an impact on the prevalence of hide contamination among slaughter cattle.…”

Age‐specific infectious period shapes dynamics of pneumonia in bighorn sheep

“…Moreover, inferences derived from cross-sectional studies can mislead control efforts. For example, longitudinal studies of Escherichia coli O157 in cattle, thought to be maintained by persistently infected supershedders, revealed that the pathogen may be serially shed by many individualsin other words, different individuals take turns at supershedding (Spencer et al 2015). If supershedding is not a stable individual-host characteristic, then targeted interventions based on specific individuals will fail.…”

Enterohaemorrhagic and other Shiga toxin-producingEscherichia coli(STEC): Where are we now regarding diagnostics and control strategies?

“…Such evidence supports suggestions that the diversity and composition of the cattle gut microbiome are important factors in controlling pathogen carriage (Munns et al., ). However, variation in feeds and administration of probiotics had little, if any, positive effect on “Super shedders” in other studies (Spencer, Besser, Cobbold, & French, ). Thus, the relationship between gut microbiome, diet and STEC carriage requires considerable further investigation.…”

“…(Munns et al, 2015). However, variation in feeds and administration of probiotics had little, if any, positive effect on "Super shedders" in other studies (Spencer, Besser, Cobbold, & French, 2015 Cattle hides are a particular source of carcass contamination, and the levels of STEC on hides at slaughter are a good predictor of meat contamination after processing (Wheeler, Kalchayanand, & Bosilevac, 2014). Interestingly, the diversity of the commensal microbial population of cattle hides appears to be important in determining the risk of contamination with STEC strains (Chopyk et al, 2016).…”