Multiple-species resistance to avermectin anthelmintics on beef cattle farms in Georgia, USA.

Anthelmintic resistance (AR) in gastrointestinal nematodes (GIN) is a worldwide problem in all livestock production systems. Several prevalence studies performed internationally demonstrate that AR in cattle parasites is a growing problem; however, there are no published studies on prevalence in the United States (USA). In this study, we performed fecal egg count reduction tests (FECRT) on twelve cow-calf farms in Georgia, USA.