Evaluation of Efficacy of Albendazole 2.5% Drench Formulation and Possible Multi-drug Resistance for Treatment of Gastrointestinal Nematodes in Naturally Infected Sheep

Abstract

Following several reports indicating reduced efficacy of some anthelmintics in sheep in different parts of the Sudan; faecal egg count reduction test was used to report on therapeutic efficacy of four anthelmintics common in use in sheep health care procedures in the field. In the current study, 16 male sheep with confirmed gastrointestinal nematodes (GINs) infection were used to evaluate the efficacy of Albendazole 2.5% drench formulation and to compare obtained results with that of Ivermectin 0.8% drench formulation. Samples of the drugs (the same batch) were randomly selected and tested before the start of the experiment to ensure satisfaction of finished product specification. Animals were divided into two groups each of eight animals; sheep in the first group (A) were drenched orally with albendazole at 5mg/kg body weight (bwt) as single dose, while animals in the second group (B) received ivermectin oral solution at dose rate of 0.2mg/kg bwt. Faecal samples were collected at the following intervals: 0 (before treatment), and then at 2, 3, 4, 7, 10, 14, and 21 days (post treatment). Blood samples were collected from sheep before and following treatment to evaluate the effect of treatment on some blood metabolites namely: total proteins, albumin, urea, aspartate aminotransferases, alanine aminotransferases, calcium and phosphorus. Results obtained indicated that there is no evidence of efficacy in the two treatment groups (albendazole and Ivermectin). Therapeutic doses of albendazole, and ivermectin did not induce clinically important adverse reactions in sheep. One week later same animals were re-arranged again into two treatment groups each of eight sheep. Animals in the first group (C) were treated with Tetamisole 5% at dose rate 3mg/kg bwt and animals in the second group (D) were treated with Levamisole 2.5% at dose rate 7.5mg/kg bwt. Results indicated that the two anthelmintics (Tetramisole 5% and Levamisole 2.5%) appeared equally ineffective as the first two drugs (Albendazole 2.5% and Ivermectin 0.8%). Likewise, there were no significant reductions in egg count in the four drugs used in the current study. These findings represent the first report in Sudan from the field of multiple anthelmintics resistance having developed in more than one drug after being administered to sheep. The study recommends further evaluation of the status of anthelmintic resistance in sheep using in vitro methods and molecular techniques.