The activity of ivermectin against common nematode parasites of sheep was examined in 2 experiments. In the 1st experiment, 14 sheep with naturally acquired infections were assigned to 2 groups of 7 sheep each. Sheep in 1 group were treated with 200 micrograms of ivermectin/kg of body weight and the remainder served as nontreated controls. In the 2nd experiment, 15 sheep with experimentally supplemented infections (including a benzimidazole-resistant strain of Haemonchus contortus) were assigned to 3 groups of 5 each. The 1st group was treated with 200 micrograms of ivermectin/kg, the 2nd was treated with 88 mg of thiabendazole/kg, and the 3rd served as nontreated controls. Ten to 12 days after treatment, all sheep were euthanatized and necropsied, and the parasites they harbored were recovered and identified. Efficacy of ivermectin was excellent (greater than 96%) against Dictyocaulus filaria, H contortus, Ostertagia circumcinta, Marshallagia marshalli, Trichostrongylus axei, T colubriformis, and T vitrinus. Treatment was not as uniformly effective for Nematodirus spathiger (73% to 85%), N filicollis (80% to 96%), Cooperia curticei (92% to 100%), immature nematodes (92% to 100%), and early 4th-stage larvae (46% to 100%). Efficacy of thiabendazole was poor for H contortus (42%) and early 4th-stage larvae in the abomasum (52%), but approached 100% for most of the other parasites.

The sheep lungworm Dictyocaulus filaria is of world-wide distribution and causes verminous pneumonia which may result in weight loss and death of the infected sheep. The current investigation was carried out in an organized farm in the Nilgiris district of Tamil Nadu, India during the period from 2012 to 2014. Infected sheep showed clinical illness varying from dullness, depression, moderate coughing, dyspnoea and labored breathing with little mortality. On necropsy, both larval and adult stages of lungworm were recovered from trachea, bronchi and bronchioles. The identity of the nematodes was confirmed as D. filaria based on the socks shaped spicules in males and anterior knob in the larva. Of the 55 animals, including 17 lambs examined during the study period, eight animals were confirmed to have died due to verminous pneumonia. Apart from that, in a few lambs, lung abscess was noticed. Though the infection was present throughout the year, the clinical illness was pronounced in dry summer (n=23) and rainy season of south west monsoon (n=19). The disease was managed by minimizing the exposure of lambs to the contaminated pasture and by deworming with two doses of levamisole hydrochloride @ 7.5 mg/ kg body weight at 21 day interval to control the lungworm infection in sheep.