Experimental infection of weaned piglets with enterotoxigenic Escherichia coli O149:F4

Enterotoxigenic Escherichia coli is an important enteric pathogen causing post-weaning diarrhoea in piglets. Enterotoxins of E. coli induce the release of fluid into the intestines without apparent inflammation. Some serotypes of E. coli. especially O149:F4 can often be identified in association with haemorrhagic gastroenteritis. In this study we infected the weaned piglets (n = 53) by oral administration of enterotoxigenic E. coli O149:F4 strains isolated from piglets suffering from haemorrhagic gastroenteritis. The clinical course of infection and shedding of the challenge E. coli strain in the faeces of infected piglets was monitored for 14 days. The challenge strain soon outnumbered the other E. coli types in the intestines of most piglets. Diarrhoea developed in the majority of piglets and its severity varied. Severe diarrhoea was observed in 10% of the piglets but only one piglet died due to dehydration. No inflammatory lesions were detected in the intestines of the dead piglet and the other euthanized piglets. We assume that development of haemorrhagic gastroenteritis depends on the involvement of other factors that need to be identified. E. coli O149:F4 are only one of the causative factors of haemorrhagic gastroenteritis in piglets after weaning.