title: Risk factors for Escherichia coli O157 shedding and super-shedding by dairy heifers at pasture.
abstract: We undertook a longitudinal study within a cohort of 52 dairy heifers maintained under constant management systems and sampled weekly to investigate a comprehensive range of risk factors which may influence shedding or super-shedding of E. coli O157 (detected by direct faecal culture and immunomagnetic separation). E. coli O157 was detected from 416/933 (44.6%) samples (faeces and recto-anal mucosal swabs) and 32 (3.4%) samples enumerated at >10000 c.f.u./g. Weekly point prevalence ranged from 9.4% to 94.3%. Higher temperature (P < 0.001), rainfall (P = 0.02), relative humidity (P < 0.001), pasture growth (P = 0.013) and body score (P = 0.029) were positively associated with increased shedding. Higher rainfall (P < 0.001), hide contamination (P = 0.002) and increased faecal consistency (P = 0.023) were positively associated with super-shedding. Increased solar exposure had a negative effect on both shedding and super-shedding within bivariate analyses but in the final multivariate model for shedding demonstrated a positive effect (P = 0.017). Results suggest that environmental factors are important in E. coli O157 shedding in cattle.
authors: Faculty of Veterinary Science,University of Sydney,Camden, NSW,Australia.
authors: K J
authors: KJ
authors: Williams
authors: Faculty of Veterinary Science,University of Sydney,Camden, NSW,Australia.
authors: M P
authors: MP
authors: Ward
authors: Faculty of Veterinary Science,University of Sydney,Camden, NSW,Australia.
authors: O P
authors: OP
authors: Dhungyel
authors: Faculty of Veterinary Science,University of Sydney,Camden, NSW,Australia.
authors: E J S
authors: EJ
authors: Hall
mesh_terms: D000818:Animals; D057138:Bacterial Shedding; D002417:Cattle; D002418:Cattle Diseases / Q000453:epidemiology / Q000382:microbiology*; D004927:Escherichia coli Infections / Q000453:epidemiology / Q000662:veterinary*; D019453:Escherichia coli O157; D005243:Feces / Q000382:microbiology; D005260:Female; D006813:Humidity; D008137:Longitudinal Studies; D015999:Multivariate Analysis; D015995:Prevalence; D011891:Rain; D012307:Risk Factors; D013696:Temperature
keywords: Shiga-like toxin-producing E. coli