Dual infection with attaching and effacing Escherichia coli and enterotoxigenic Escherichia coli in post-weaning pigs.

Post-weaning diarrhoea in pigs occurred on two farms in Hokkaido, Japan, in 1994. Four piglets aged 35 or 45 days were examined after death. At necropsy, ecchymotic haemorrhages were seen on the mucosal surface of the caecum and colon. Histopathologically, numerous Gram-negative bacilli adhered to the brush border of the small intestines, but the brush border itself was intact. Typical attaching and effacing (AE) lesions were seen in the caecum and colon. Immunohistochemically, the bacilli which adhered to the brush border gave positive results with antisera against serogroup O149 of Escherichia coli; the bacilli which caused the AE lesions, however, belonged to serogroup O45. It was concluded that the disease resulted from dual infection with attaching and effacing E. coli (AEEC) and enterotoxigenic E. coli (ETEC).