Prevalence of gastrointestinal nematode resistance to avermectin anthelmintics on beef cattle operations in Georgia

Abstract

Anthelmintic resistance is a worldwide problem in all livestock systems, with most reports of resistance in cattle parasites being to the macrocyclic lactone (ML) drug class. Several prevalence studies performed internationally demonstrate that anthelmintic resistance in cattle parasites is a growing problem, however, no similar studies have been performed in the US. The primary objective of this study was to gain data on the prevalence of ML resistance in gastrointestinal nematode (GIN) parasites on beef cattle farms in Georgia. We also wanted to test the efficacy of combination anthelmintic therapy in these same herds, and use these data as a basis for educational outreach programs for beef producers in Georgia.