Frequency of Escherichia coli virotypes in calf diarrhea and intestinal morphologic changes associated with these virotypes or other diarrheagenic pathogens.

Calf diarrhea is a common cause of pre-weaning morbidity and mortality in cattle operations. We evaluated the role of Escherichia coli by assessing the frequency of genes encoding virulence factors (virotypes) in E. coli from feces or intestinal contents, and the association of these virotypes or other diarrheagenic pathogens with intestinal morphologic changes in calves with or without diarrhea. E. coli was isolated from 408 feces and 105 intestines of calves with diarrhea and compared to those isolated from 635 feces and 100 intestines of calves without diarrhea, from 2002 to 2016. Virotype EAST1:F17, in combination with minor virotypes, was the most commonly detected type, but without differences in frequency between the 2 groups of calves. No significant intestinal morphologic changes were observed with the different E. coli virotypes in either group of calves, except for bacterial attachment to enterocytes for virotype STa:F5, which was detected only in calves with diarrhea. These observations suggest that E. coli, excluding virotype STa:F5, is not a significant diarrhea-causing agent in calves. However, the intestinal lesions observed in ~82% of calves with diarrhea were attributed to other diarrheagenic pathogens that include bovine coronavirus, Clostridium perfringens, Cryptosporidium spp., Eimeria spp., rotavirus, and Salmonella spp.