Inheritance of resistance to oedema disease in the pig: experiments with an Escherichia coli strain expressing fimbriae 107.

Inheritance of resistance to intestinal colonization with E. coli causing oedema disease is hypothesized to be under the control of one locus consisting of two alleles with susceptibility (S) dominating resistance (s). This mode of inheritance was investigated by mating pigs, resistant and susceptible to the disease, and examining the offspring. Weaned piglets were repeatedly inoculated orally with 5 x 10(5) CFU per pig per day of a streptomycin resistant strain of E. coli serotype O139:K12(B):H1:F(107) and susceptibility determined by daily semiquantitative cultural examination of rectal swabs. Using results obtained from offspring, 5 boars were retrospectively assigned the genotype ss, 1 was assigned Ss, and 2 were assigned SS. Nine sows were designated ss, 8 classified Ss and 4 SS. Ninety two pigs resulted from matings regarded as ss x ss; 89 (97%) of these were resistant to colonization and oedema disease. Of the 168 pigs from Ss x ss matings, 83 (49%) were resistant, while only 13 (9%) of 146 pigs from matings with at least one SS parent were classified resistant. The results are compatible with inheritance being controlled by one locus and with susceptibility dominating resistance to oedema disease.