Evaluation of anthelmintic efficacy in goats in Savannakhet province, Lao PDR

Gastrointestinal nematode infection is prevalent in grazing goats in Laos and is controlled, when required, by administration of locally purchased anthelmintic. This study aimed to test the efficacy of the three locally available anthelmintics albendazole (ALB, Abentel® Atlantic Labs, Thailand), ivermectin (IVM, Ivomec® Boehringer Ingelheim, South Africa) and levamisole (LEV, Lemisol® Life Biopharma Malaysia) to determine whether anthelmintic resistance is compromising worm control. A faecal egg count reduction (FECR) test was conducted on 127 goats in four villages in two districts of Savannakhet province. The pre-treatment (day 0) mean faecal egg count (FEC) was 489 eggs per gram (range 0 to 2880 eggs/g) and goats were allocated to 4 treatments (ALB 5.625 mg/kg oral, IVM 0.2 mg/kg subcutaneous, LEV 7.5mg/kg subcutaneous, untreated control) giving 31-32 goats per treatment. FEC was determined at 7 and 14 days later for all groups. FECR for each anthelmintic was determined by comparison with the untreated control group using the RESO calculation spreadsheet. The overall reductions in strongyle FEC at days 7 and 14 post treatment were 96 and 99 % for ALB, 96 and 95 % for IVM and 98 and 98 %for LEV treatments indicating mean efficacy 95%. These data suggest adequate efficacy of the currently used anthelmintics with possible emerging resistance to IVM.This situation should be monitored into the future. It is likely that low levels of anthelmintic treatment coupled with communal grazing results in a large population of nematodes “in refugia” from treatment, thus slowing the development of anthelmintic resistance.