Efficacy of abamectin against gastrointestinal tract nematodes and lungworms of cattle was determined in 4 experiments. The first 2 experiments were controlled trials in which efficacy was determined at necropsy in calves with either experimentally induced (n = 14) or naturally acquired (n = 16) infections. Half the calves in each experiment were treated with abamectin (200 micrograms/kg of body weight, sc), and half were left untreated as controls. Efficacy was > 99% against adult stages of Dictyocaulus viviparus, Haemonchus placei, Ostertagia ostertagi, Trichostrongylus axei, Cooperia punctata, Trichuris discolor, and C oncophora, and was 92.4% against Nematodirus helvetianus. The second 2 experiments were clinical trials in which efficacy was determined by fecal egg count reduction in naturally infected yearling heifers (n = 75) or 2-year-old heifers (n = 75). Within replicates of 5, 4 heifers were assigned at random to treatment with 200 Kg of abamectin/kg and 1 was left untreated as a control. Abamectin was 100% effective in eliminating strongylate nematode eggs from the feces of these heifers. In all experiments, adverse reactions were limited to small, clinically unimportant injection site swellings in 29% of abamectin-treated calves. Abamectin was judged to be safe and effective in these trials.

This study was done to evaluate the status of resistance to nematode populations on four major groups of anthelminthics. Nematode faecalegg count reduction tests (FECRT) were conducted on six free grazing small holder goat farms (namely Farms A-F) in Perak.The four drug groups tested in this study were Benzimidazoles, Imidazothiazoles,Macrocyclic Lactones and Salicylanilides. Faecal samples were subjected to the standard procedures of McMaster for worm egg estimation and also larval cultures for third stage larvae identification. Results of Farm A, Farm C and Farm D showed resistance to all 4 drugs groups of anthelminthic that were tested and the major worm population of this farm were Haemonchus contortus (49.75%), Trichostrongylus colubriformis (47.71%) and Cooperia sp. (2.53%). The results of Farm B and Farm F showed resistance to all the 3 groups of anthelminthics except Levamisole and the worm population of this farm was Haemonchus contortus (47.30%), Trichostrongylus sp. (38.44%), Oesophagostomum columbianum (13.50%) and Cooperia sp. (0.76%) Farm E was resistant to Benzimidazoles andsuspected resistance to 3 drugs groups; Levamisole, Macrocyclic Lactones and Closantel. The worm population for Farm E was Haemonchus contortus (71.35%), Trichostrongylus sp. (27.6%) and Oesophagostomum sp. (2%). These farms have a history of using the same anthelminthics over the past few years, thus leading to the severe case of anthelminthic resistance. Recommendations have beenmade to control helminths using alternative approaches such as cut and carry feeding, herbal medication using Neem leaves (Azadirachta indica) and rotational grazing as well as improvement in management of animals to increase their immunity.