Edema disease.

Edema disease is a common cause of illness and death loss in pigs during the first 2 weeks after weaning. The disease is an enterotoxemia caused by strains of E. coli that colonize the small intestine and produce Stx2e. Bacterial colonization is mediated by F18ab fimbriae. Susceptibility to disease is determined by presence of receptors for these fimbriae on small intestinal epithelial cells and is inherited as a dominant trait. Clinical signs and lesions are largely the result of Stx2e, which causes necrosis of endothelial and smooth muscle cells in small arteries and arterioles. Vascular damage in the brain stem with resultant infarction and malacia is the main cause of death in affected pigs. Studies conducted by veterinary researchers in the 1950s and 1960s identified the cause of the disease and provided future scientists with hypotheses to test regarding the pathogenesis. In the last two decades, studies using molecular-based techniques have allowed for the definitive identification of bacterial virulence factors that mediate intestinal colonization and vascular damage, that is, F18ab fimbriae and Stx2e. Identification of these virulence factors has provided a basis for current and future development of effective preventative measures, for example, vaccines.