The efficacy of levamisole, and a mixture of oxfendazole and levamisole, against the arrested stages of benzimidazole-resistant Haemonchus contortus and Ostertagia circumcincta in sheep.
Sheep were allowed to graze pasture that had been seeded with benzimidazole-resistant Haemonchus contortus and Ostertagia circumcincta in order to acquire a burden of arrested larvae. Following housing, sheep were dosed orally with either oxfendazole at a dose rate of 4.7 mg/kg (to confirm the benzimidazole-resistant status of the species of nematode), levamisole at a dose rate of 7.5 mg/kg, or an oxfendazole/levamisole mixture at a dose rate of 4.6 mg/kg oxfendazole and 8.1 mg/kg levamisole. The efficacies of the treatments were assessed by estimation of the arrested larval burden in the abomasum of each sheep, either at 10 or 11 days (oxfendazole and oxfendazole/levamisole mixture), or 12 or 13 days (levamisole), after treatment. Compared to the untreated controls, the protection afforded by a single dose of either levamisole or the oxfendazole/levamisole mixture was >99% against the arrested stages of both Haemonchus contortus and Ostertagia circumcincta. Treatment with oxfendazole confirmed the benzimidazole-resistance status of the two species.
Andrews
S J
SJ
Schering-Plough Animal Health, Uxbridge, Middlesex, UK. stuart.andrews@spcorp.com
D000018:Abomasum / Q000469:parasitology; D000818:Animals; D000871:Anthelmintics / Q000008:administration & dosage / Q000592:standards / Q000627:therapeutic use*; D001562:Benzimidazoles / Q000008:administration & dosage / Q000592:standards / Q000627:therapeutic use*; D004351:Drug Resistance; D005243:Feces / Q000469:parasitology; D005260:Female; D005753:Gastric Mucosa / Q000469:parasitology; D006188:Haemonchiasis / Q000188:drug therapy / Q000469:parasitology / Q000662:veterinary*; D006189:Haemonchus / Q000187:drug effects / Q000254:growth & development; D007978:Levamisole / Q000008:administration & dosage / Q000592:standards / Q000627:therapeutic use*; D008297:Male; D010028:Ostertagia / Q000187:drug effects / Q000254:growth & development; D010029:Ostertagiasis / Q000188:drug therapy / Q000469:parasitology / Q000662:veterinary*; D010270:Parasite Egg Count / Q000662:veterinary; D011897:Random Allocation; D012756:Sheep; D012757:Sheep Diseases / Q000188:drug therapy / Q000469:parasitology*; D016037:Single-Blind Method
D000871:Anthelmintics; D001562:Benzimidazoles; D007978:Levamisole; C011030:oxfendazole