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Online Journal of Veterinary Research

Volume 23 (4):315-320, 2019.

Nematode resistance to ivermectin, levamisole and fenbendazole in sheep flocks

determined by fecal egg count reduction test.*


A Varadharajan, R Gnansekar and S Kothandaraman.


Division of Animal Husbandry, Faculty of Agriculture, Annamalai University, Annamalai Nagar 608 002. Tamil Nadu, India. *Part of PhD research work submitted by the First Author.




Varadharajan A, Gnansekar R, Kothandaraman S., Nematode resistance to ivermectin, levamisole and fenbendazole in sheep flocks evaluated by fecal egg count reduction test, Onl J Vet Res., 23 (4):315-320, 2019. Resistance of gastrointestinal nematodes to ivermectin, levamisole, and fenbendazole treatments in 6 flocks of eighty, 5-15 month old male-female sheep in Cuddalore district, Tamil Nadu, India, was assessed by fecal egg count reduction tests (FECR). The sheep had not been treated with anthelmintics 2 months before and became infested by grazing on pasture. Faecal egg counts were done on day 0 before treatments and 10 days after. Before treatment, sheep were fasted 8h and then gavaged 5mg/kg fenbendazole or 15mg/kg levamisole Hydrochloride or injected subcutaneous 0.1mg ivermectin. Controls (n=20) were not treated. Ten gram feces were taken at day 0 before treatment and 10 days after for tube flotation nematode egg count. Resistance was determined according to WAAVP as < 95 % and fecal culture was done to identify nematode species. We found high levels of anthelmintic resistance to fenbendazole (50-89%) moderate to levamisole (93-95%) and low to ivermectin (94-97%). H. contortus was most frequent resistant nematode. We found high levels of resistance to fenbendazole in all flocks probably due to frequent routine use.


Key Words: Anthelmintic resistance, Sheep, ivermectin, levamisole, fenbendazole, Cuddalore, India.