Anthelmintic resistance and the control of ovine ostertagiasis: a drug action model for genetic selection.

A site-specific genetic prediction model is presented, which examines the influences of different anthelmintic treatment regimens on selecting for drug resistance within a sheep management system. The model exploits the power of modern microcomputers to integrate factors such as parasite strain, geographic location, management practice and genetic fitness to identify effective control regimens which do not lead to resistant Ostertagia circumcincta strains over a 30-year horizon. The potential use of the model as a farm level management-support tool is discussed.