RESUMO
Ovine lymphocyte antigen is associated with reduced faecal egg counts in 4-month-old lambs following natural, predominantly Ostertagia circumcincta infection. International Journal for Parasitology 26: 423-428. Ten lymphocyte antigens were defined in a flock of Scottish Blackface sheep known to be naturally exposed to infection with Ostertagia circumcincta. Population and family studies suggested that the 10 antigens were products of class I loci. Antigen G13br was in linkage disequilibrium with allele g2 at the DRB1 locus. The g2 allele has previously been associated with reduced faecal egg counts in a different crop of lambs from the same farm. In this study antigen G13br was also associated with a reduction in faecal egg counts. The results provide partial confirmation of the role of the major histocompatibility complex in resistance to natural, predominantly O. circumcincta infection.
Assuntos
Antígenos HLA-DR/genética , Antígenos de Histocompatibilidade Classe I/genética , Linfócitos/imunologia , Complexo Principal de Histocompatibilidade , Ostertagia/imunologia , Ostertagíase/veterinária , Contagem de Ovos de Parasitas/veterinária , Doenças dos Ovinos , Alelos , Animais , Fezes/parasitologia , Feminino , Deleção de Genes , Marcadores Genéticos , Cadeias HLA-DRB1 , Desequilíbrio de Ligação , Ostertagíase/imunologia , Ostertagíase/fisiopatologia , OvinosRESUMO
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.