The effect of transportation and lairage on faecal shedding and carcass contamination with Escherichia coli O157 and O26 in very young calves in New Zealand

Abstract

The effect of transportation and lairage on the faecal shedding and post-slaughter contamination of carcasses with Escherichia coli O157 and O26 in young calves (4-7-day-old) was assessed in a cohort study at a regional calf-processing plant in the North Island of New Zealand, following 60 calves as cohorts from six dairy farms to slaughter. Multiple samples from each animal at pre-slaughter (recto-anal mucosal swab) and carcass at post-slaughter (sponge swab) were collected and screened using real-time PCR and culture isolation methods for the presence of E. coli O157 and O26 (Shiga toxin-producing E. coli (STEC) and non-STEC). Genotype analysis of E. coli O157 and O26 isolates provided little evidence of faecal-oral transmission of infection between calves during transportation and lairage. Increased cross-contamination of hides and carcasses with E. coli O157 and O26 between co-transported calves was confirmed at pre-hide removal and post-evisceration stages but not at pre-boning (at the end of dressing prior to chilling), indicating that good hygiene practices and application of an approved intervention effectively controlled carcass contamination. This study was the first of its kind to assess the impact of transportation and lairage on the faecal carriage and post-harvest contamination of carcasses with E. coli O157 and O26 in very young calves.

Keywords: Shiga-like toxin-producing E. coli; calves; lairage; transport.

Fig. 1.

Diversity of PFGE profiles of Escherichia coli O157 isolates (n = 56) recovered from different samples collected from 60 calves at pre-slaughter (RAMS: on-farm and on-plant) and post-slaughter (swab: hide, pre- and post-intervention). Only samples from animals with one or more recovered isolates are shown (each row), with split cells representing two characteristically different PFGE profiles of isolates, coloured by farm of origin. Black cells represent PFGE profiles prevalent on high-prevalence farms on study day, dark grey on low-prevalence farms and pale grey on neither low- or high-prevalence farms included in the study and therefore likely of different origin. Numbers in cells represent assigned PFGE cluster numbers and * identifies STEC isolates (see Supplementary Figure S1).

Fig. 2.

Diversity of PFGE profiles of Escherichia coli O26 isolates (n = 115) recovered from different samples collected from 60 calves at pre-slaughter (RAMS: on-farm and on-plant) and post-slaughter (swabs: hide, pre- and post-intervention). Only samples from animals with one or more recovered isolates are shown (each row), with split cells representing up to three characteristically different PFGE profiles of isolates, coloured by farm of origin. Black cells represent PFGE profiles prevalent on high-prevalence farms on study day, dark grey on low-prevalence farms and pale grey on neither low- or high-prevalence farms included in the study and therefore likely of different origin. Numbers in cells represent assigned PFGE cluster numbers and * identifies STEC isolates (see Supplementary Figure S2).