A case-control study investigating risk factors associated with postweaning Escherichia coli diarrhea in southern Ontario

Abstract

Objectives: To investigate management, housing, and nutrition factors and potential viral infections that might be associated with postweaning Escherichia coli diarrhea in pigs in southern Ontario. Methods: A case-control study involving 50 herds was conducted. Information on hygiene, management, facilities, management of diarrhea, porcine reproductive and respiratory syndrome virus (PRRSV) status, and nursery feed management was collected through a questionnaire. Rectal swabs and sera collected from ten weaned pigs in each herd were tested for F4+ (K88+) E coli and antibodies to two viral pathogens. Hemolytic E coli-like colonies were tested for agglutination in specific anti-F4 antiserum. Results: Twenty-six herds were designated as cases and 22 as controls. Escherichia coli positive for F4 were isolated from pigs in 15 case herds and 3 control herds. Postweaning diarrhea did not occur in the control herds during the study. In case herds, there were more feeder spaces per pen, the first rations offered in the nursery were more likely to be pelleted feed, and nursery pigs and gestating sows were more likely to be vaccinated against PRRSV than in control farms. Implications: Weaning age, weaning weight, and commingling of pigs, which are commonly considered risk factors for postweaning diarrhea, did not appear to be contributing factors in this study. Vaccination for PRRSV was associated with an increased risk of postweaning diarrhea, which occurred in a variety of herd types and sizes.