Abstract
BackgroundEscherichia coli O157 is a bacterial pathogen associated with severe disease in humans for which cattle are an important reservoir of infection. The identification of possible risk factors for infection in cattle could facilitate the development of control strategies and interventions to mitigate the risk to human health. The purpose of this study was to utilize data collected in 2014–2015 during the two contemporaneous cross-sectional surveys of the British E. coli O157 in Cattle Study (BECS) to investigate potential risk factors for E. coli O157 status in cattle destined for the food chain.ResultsIn the England & Wales survey only one variable, herd size, was associated with the outcome farm-level E. coli O157 positive status. The odds increased for each additional animal in the herd. In the Scotland survey, as well as a measure of herd size (the number of cattle aged 12–30 months), having brought breeding females on to the farm in the last year also increased the odds, whereas farms sampled in spring were less likely to be positive compared to those sampled in autumn.On the positive farms, in both surveys, an increase in the proportion of pats positive for E. coli O157 was associated with animals being housed at the time of sampling. However, the effect of housing on pat-level prevalence within positive groups was lower on farms from England & Wales than from Scotland (OR 0.45 (95% C.I. 0.24–0.86)).ConclusionFor the first time, factors associated with farm-level E. coli O157 status have been investigated in two contemporaneous surveys with comparable study design. Although factors associated with farm-level E. coli O157 status differed between the two surveys, one consistent factor was an association with a measure of herd size. Factors associated with the proportion of E. coli O157 positive pats within a positive farm were similar in both surveys but differed from those associated with farm-level status. These findings raise the hypothesis that measures to protect public health by reducing the risk from cattle may need to be tailored, rather than by assuming that a GB-wide protocol is the best approach.
Highlights
Escherichia coli O157 is a bacterial pathogen associated with severe disease in humans for which cattle are an important reservoir of infection
The mean proportion of pats testing positive for E. coli O157 on positive farms (Outcome 2 investigated in this study) was 0.46 (95% Confidence Interval (CI) 0.32– 0.60) in Scotland and 0.32 in England & Wales
The observation that farm-level risk factors for E. coli O157 presence in cattle intended for the food chain may differ between Scotland and England & Wales has further importance in relation to the Harmonised Epidemiological Indicators (HEI) for pathogenic verocytotoxin-producing E. coli (VTEC) for meat inspection, proposed by the European Food Safety Authority (EFSA) [32, 33]
Summary
Escherichia coli O157 is a bacterial pathogen associated with severe disease in humans for which cattle are an important reservoir of infection. Shiga toxin-producing Escherichia coli (STEC) – called verocytotoxin-producing E. coli (VTEC) – such as E. coli O157 are well-known human pathogens causing significant morbidity in both developed and developing countries. The main virulence characteristic of STEC strains is the production of Shiga toxins, of which there are two major types, stx and stx. The main virulence characteristic of STEC strains is the production of Shiga toxins, of which there are two major types, stx and stx2 These are further categorised into additional subtypes [2, 3]. Cattle – asymptomatic carriers of E. coli O157 – and other ruminant animals and their environment are important reservoirs for infection [4, 5]
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