Factors Associated with Shiga Toxin-Producing Escherichia coli Shedding by Dairy and Beef Cattle

Abstract

Shiga toxin-producing Escherichia coli (STEC) is an important foodborne pathogen that can cause hemorrhagic colitis and hemolytic-uremic syndrome. Cattle are the primary reservoir for STEC, and food or water contaminated with cattle feces is the most common source of infections in humans. Consequently, we conducted a cross-sectional study of 1,096 cattle in six dairy herds (n ‫؍‬ 718 animals) and five beef herds (n ‫؍‬ 378 animals) in the summers of 2011 and 2012 to identify epidemiological factors associated with shedding. Fecal samples were obtained from each animal and cultured for STEC. Multivariate analyses were performed to identify risk factors associated with STEC positivity. The prevalence of STEC was higher in beef cattle (21%) than dairy cattle (13%) (odds ratio [OR], 1.76; 95% confidence interval [CI], 1.25, 2.47), with considerable variation occurring across herds (range, 6% to 54%). Dairy cattle were significantly more likely to shed STEC when the average temperature was >28.9°C 1 to 5 days prior to sampling (OR, 2.5; 95% CI, 1.25, 4.91), during their first lactation (OR, 1.8; 95% CI, 1.1, 2.8), and when they were <30 days in milk (OR, 3.9; 95% CI, 2.1, 7.2). These data suggest that the stress or the negative energy balance associated with lactation may result in increased STEC shedding frequencies in Michigan during the warm summer months. Future prevention strategies aimed at reducing stress during lactation or isolating high-risk animals could be implemented to reduce herdlevel shedding levels and avoid transmission of STEC to susceptible animals and people. IMPORTANCE STEC shedding frequencies vary considerably across cattle herds in Michigan, and the shedding frequency of strains belonging to non-O157 serotypes far exceeds the shedding frequency of O157 strains, which is congruent with human infections in the state. Dairy cattle sampled at higher temperatures, in their first lactation, and early in the milk production stage were significantly more likely to shed STEC, which could be due to stress or a negative energy balance. Future studies should focus on the isolation of high-risk animals to decrease herd shedding levels and the potential for contamination of the food supply. Shiga toxin-producing Escherichia coli (STEC) is an important foodborne pathogen in both developed and developing countries. STEC can cause hemorrhagic colitis and hemolytic-uremic syndrome (HUS), which can lead to kidney failure and death, particularly in young children (1). STEC strains belonging to serotype O157:H7 have been reported to cause human infections at the highest frequency, although there has been a steady increase in the detection of cases caused by STEC serotypes other than O157 (non-O157 STEC) (2-4). This increase is due in part to changes in laboratory diagnostic practices targeting non-O157 STEC (5). The incidence of non-O157 STEC infections in the United States increased from 0.12 per 100,000 population in 2000 to 0.95 per 100,000 in 2010, while the incidence of STEC O157 infections decreased...

Prevalence, virulence potential, and pulsed-field gel electrophoresis profiling of Shiga toxin-producing Escherichia coli strains from cattle

“…In this study, high temperature and rain were found to be associated with STEC prevalence. Similarly, a previous study reported higher STEC prevalence in hot seasons than in cold seasons [31–33]. In addition, rainfall has been considered an important transmission factor for STEC.…”

Pathogen Risks Related to the Movement of Birds Frequenting Livestock and Fresh Produce Growing Areas in the Southwestern U.S.

“…Prevalence ranges from 4% to 83% in feedlot cattle (Fegan et al 2004, Arthur et al 2009, Venegas-Vargas et al 2016). This marked difference in prevalence is likely due to a number of dynamic risk factors, including environment (Stanford et al 2016), animal age (Mir et al 2015), diet (Venegas-Vargas et al 2016), season (Stanford et al 2016), and year (Venegas-Vargas et al 2016). Contrary to STEC prevalence in cattle, the prevalence of STEC in wild birds is consistently lower.…”

Escherichia coli, cattle and the propagation of disease

“…Escherichia coli O157:H7 is a human pathogen that belongs to the Shiga toxin-producing E. coli or STEC group, an autonomous and serologically diverse group of bacteria that carry Shiga toxin-encoding genes on bacteriophages (Beutin et al 2004;Venegas-Vargas et al 2016). These strains synthesize Shiga toxin 1 (Stx1), Shiga toxin 2 (Stx2) or both (Obrig et al 2003;Rahal et al 2012), and additional toxin subtypes have also been described (Scheutz et al 2012).…”

“…In a study conducted in dairy cattle from Michigan farms, STEC shedding increased 2.5-fold when the average temperature during the 1-to 5-day period preceding sample collection exceeded 28.9 • C (Venegas-Vargas et al 2016). Cattle lactating for the first time had a 1.8-fold higher risk to shed STEC as compared to animals that have lactated at least twice, and animals that had been producing milk for less than 31 days had a 3.9-fold higher risk to shed the bacteria as compared to animals that had been producing milk for 31 days or longer (Venegas-Vargas et al 2016).…”