Infection with Ostertagia circumcincta is a major constraint on sheep production in temperate areas of the world. A potential control strategy is the use of genetically resistant sheep. Therefore we examined the association between MHC-DRB1 alleles and faecal egg counts following natural, predominately O. circumcincta infection in a flock of Scottish Blackface sheep. Nineteen DRB1 alleles were identified by a combination of variation in the length of simple repetitive sequences within the intron between exons 2 and 3 and hybridisation of selected oligonucleotides to polymorphisms within exon 2. Faecal samples were taken from 200 lambs from one to six months of age at intervals of 4 weeks. Genetic effects were strongest at 6 months of age. Least-squares analysis indicated that substitution of the most common allele (I) by allele G2 would result in a 58-fold reduction in faecal egg counts in 6-month-old lambs and a 22-fold reduction in 5-month-old lambs. These results suggest that the major histocompatibility complex plays an important role in the development of resistance to O. circumcincta.
Schwaiger, F.W.; Gostomski, D.; Stear, M.J.; Duncan, J.L.; McKellar, Q.A.; Epplen, J.T.; Buitkamp, J. An ovine Major histocompatibility complex DRB1 allele is associated with low faecal egg counts following natural, predominantly Ostertagia circumcincta infection. International Journal for Parasitology (1995) 25 (7) 815-822. [DOI: 10.1016/0020-7519(94)00216-B]