Anthelmintic resistance in gastrointestinal nematodes of goats

Abstract

Investigation on the prevalence of gastrointestinal nematodes of goats in Thrissur Corporation area was carried out by detecting faecal eggs and larvae after coprological examination and coproculture respectively. The faecal samples for coprological examination were collected from animals brought to the University Veterinary hospitals, Kokkalai and Mannuthy, University Goat and Sheep farm and from nearby houses around Mannuthy. Screening of faecal samples of 320 goats during the period of study from June 2004 to May 2005 revealed 114 as positive (35.63 per cent). The type of positive infection noted were Strongyle (95.61 per cent) and Strongyloides (4.38 per cent) infection. Monthwise prevalence of gastrointestinal nematodes showed maximum infection in May (48 per cent) while a lower prevalence in August (28 per cent). Seasonwise, the prevalence of gastrointestinal nematodes was found to be 30.7 per cent, 33.33 per cent and 39.13 per cent during cold wet South West monsoon (heavy rainfall), warm wet North East monsoon (low rainfall) and dry season respectively. The prevalence of gastrointestinal nematodes was observed to be higher in young goats below one year (42.10 per cent) and in females (85.96 per cent ) than males (14.03 per cent). There was no significant variation between breeds and management . The species of nematodes encountered were Haemonchus contortus (55.26 per cent), Oesophagostomum columbianum (13.15per cent), Trichostrongylus colubriformis (21.05 per cent), Bunostomum trigonocephalum (6.14 per cent) and Strongyloides papillosus (4.38 per cent). The comparative biometry of various infective larvae of the commonly found nematodes were noted. Resistance to various anthelmintics by the nematodes in goats of the University Goat and Sheep farm, Mannuthy were detected by the methods namely Faecal Egg Count Reduction Test (FECRT) and Egg Hatch Test (EHT). Forty kids aged between three to six months were used for this purpose. Faecal Egg Count Reduction Test revealed resistance to albendazole, ivermectin and morantel citrate by the gastrointestinal nematodes. The drugs namely albendazole, ivermectin and morantel citrate showed a per cent worm reductions of 30, 53, 45 with 52, 34 and 62 as lower 95 per cent confidence limits. Specific resistance to benzimidazole group by EHT showed the ED50 value of albendazole (µg per ml) in EHT to be 0.211556 which further established resistance to albendazole by the gastrointestinal nematodes of goats. Anthelmintic resistance is best controlled in the ground level by the use of correct type of anthelmintics at the correct dose against nematodes in goats. Breeding for disease resistance, development and use of vaccines and biological control using nematophagous fungi are the prospective methods for the control of anthelmintic resistance.