Distribution of K88-Adhesive and Non-Adhesive Phenotypes Among Four Popular Breeds of Pigs

Abstract

Enterotoxigenic Escherichia coli expressing K88 fimbrial adhesins cause diarrhea and death in piglets by colonizing the small intestine and excreting enterotoxins that stimulate electrolyte fluid transport to the intestinal lumen. The E. coli colonize the small intestine by adhering to receptor(s) on the epithelial brush borders by means of fimbrial adhesins. K88ab, K88ac, and K88ad adhesins are the three distinct antigenic variants of K88 E. coli adhesins. Each variant exhibits a different adhesion specificity, suggesting differences in the receptors to which they bind. Differences in K88 variant binding, and presumably receptor expression in pigs is inherited in a simple Mendelian fashion with adhesive activity being dominant over nonadhesive activity. When the bacteria adhere they gain time to multiply and cause disease, specifically, colibacillosis. Thus, piglets whose intestinal brush borders contain these specific receptors are susceptible to diarrhea caused by one or more of the antigenic adhesin variants. Piglets whose intestines lack the receptors are resistant to diarrhea caused by K88 E. coli. The animals can be grouped into phenotypes according to the variants that adhere or fail to adhere to their brush borders. Phenotypes of pigs relative to the binding of the fimbrial variants K88ab, K88ac, and K88ad to these brush borders were previously established by Bijlsma et al (1982) as A: adhesive to all three variants, B: adhesive to K88ab and ac variants, C: adhesive to K88ab and ad variants, D: adhesive to the K88ad variant only, and E: nonadhesive. However, the distribution of these phenotypes in the swine population has not been established. Thus, the magnitude of risk to colibacillosis caused by K88 E. coli cannot be determined. Further, without knowledge of the availability of disease resistant breeding stock, strategies of genetic selection for resistance cannot be devised. The purpose of the present study was to determine the prevalence of the various K88 adhesive phenotypes in several popular breeds of pigs.