Hybridization between Haemonchus contortus and Haemonchus placei in field populations provides a potential mechanism for interspecies transmission of anthelmintic resistance mutations Overall conclusions (confirmed with 3 independent markers) Graphical representation of Genescan of five hybrid worms with three microsatellite markers (1st Anthelmintics Drug Resistance Conference San Francisco, California,USA)

  • Umer Naveed Chaudhry (Speaker)

Activity: Academic talk or presentation typesOral presentation


Resistance to the all class of anthelmintic has been observed in parasitic nematodes of livestock. There are many aspects of the genetics of anthelmintic resistance that remain poorly understood. It is still unclear how resistance mutations originate and spread in parasite populations in the field. Resistance is widespread in the highly pathogenic small ruminant parasitic nematode H. contortus and this parasite provides us a valuable model system in which to study such questions. For this parasite, three different mutations (P200, P198 and P167) in the isotype-1 β-tubulin gene have been associated with benzimidazole (BZ) resistance [1, 2]. We are studying these mutations to investigate whether one parasite species can serve as a source of resistance mutations for another species by virtue of interspecies hybridization and genetic introgression. Although, H. contortus and the related species H. placei have strong host preferences, they can infect multiple host species and co-infections occur. H. contortus is commonly found in sheep and goats, whereas H. placei is common in cattle. In contrast, the extent of anthelmintic resistance in H. placei is currently unknown. The two parasite species are phylogenetically close and experimental co-transplantation of adult parasites can result in hybridization between two species. H. contortus and H. placei are sympatric in many regions of the world especially where large and small ruminants share the same pasture. In the present study, we have shown that co-infection of sheep and goats are common in some regions. We use a number of genetic markers to demonstrate interspecies hybridization does occur in field populations suggesting the potential for introgression of BZ resistance mutations between these species. This has major implications for the spread of anthelmintic resistance from small ruminants to large ruminants and for the potential emergence of anthelmintic resistance in the important cattle parasite H. placei
Event titleAnthelmintic Resistance I USA
Event typeConference
Degree of RecognitionNational