ETEC vaccination in pigs.

Enterotoxigenic Escherichia coli (ETEC) remain an important cause of neonatal and post-weaning diarrhoea in pigs. In general, neonatal infections can be prevented effectively by passive colostral and lactogenic immunity obtained by vaccination of the sow. In this respect, several maternal vaccines are on the market. These are applied mainly parenterally in the pregnant sow. However at weaning, lactogenic protection disappears. Strains involved in post-weaning diarrhoea mostly express F4 or F18 fimbriae. These fimbriae are important virulence factors since they allow the bacteria to bind to specific receptors on small intestinal enterocytes, resulting in colonization and subsequently the secretion of enterotoxins causing diarrhoea. Consequently, an active mucosal immunity, in which the local production of F4- and/or F18-specific sIgA plays an important role, is required to protect pigs against post-weaning diarrhoea. This review aims to give an overview of the immunization strategies applied in the pig model to prevent post-weaning diarrhoea caused by F4- and/or F18- positive ETEC in pigs. These include the use of oral live and subunit vaccines, encapsulation strategies and parenteral immunization.