thiophanate and Haemonchiasis

Multiple resistance to albendazole, thiophanate, levamisole and orally administered invermectin was detected in an isolate of Haemonchus contortus in sheep on a farm where benzimidazole resistance had already been identified. Following a faecal egg count reduction test, this was confirmed by both critical and controlled anthelmintic tests. Different groups of sheep infected naturally or given an experimental infection with the benzimidazole-resistant isolate were treated with the recommended doses of various anthelmintics. Compared to the control group, the percentage reductions in the faecal egg counts of sheep treated with albendazole, thiophanate, levamisole and ivermectin varied between 38.2% and 79.1% and the residual worm counts between 27.3% and 57.5%. The results indicate the presence of multiple anthelmintic resistance in this isolate of H. contortus. Sheep treated with closantel showed 100% reductions in faecal egg and worm counts, indicating that this drug was very effective against the population of H. contortus on the farm.

Topics: Administration, Oral; Albendazole; Animals; Anthelmintics; Benzimidazoles; Dose-Response Relationship, Drug; Drug Resistance, Multiple; Feces; Haemonchiasis; Haemonchus; Ivermectin; Kenya; Levamisole; Parasite Egg Count; Salicylanilides; Sheep; Sheep Diseases; Thiophanate

Forty-nine sheep artificially exposed to a thiabendazole (TBZ) resistant isolate of Haemonchus contortus were assigned to 7 groups of 7 animals each and used to conduct a controlled anthelmintic trial. One group of sheep served as untreated infected controls and 6 groups were treated as follows: closantel, 5.0 mg kg-1; ivermectin, 0.2 mg kg-1; oxfendazole, 5.0 mg kg-1; thiophanate, 50 mg kg-1, levamisole, 7.5 mgkg-1 and thiabendazole, 66 mg kg-1. Eggs per gram of faeces were determined on days 21, 24 and day 34 (10 days post-treatment) after infection and all animals were necropsied for residual worm counts. The calculated efficacies of the treatments against H. contortus as indicated by worm reduction were closantel (100%), ivermectin (99.3%), oxfendazole (35.2%), thiophanate (56.7%), levamisole (98.6%) and thiabendazole (24.3%). The data therefore indicate that the TBZ-resistant isolate of H. contortus used was highly resistant to the 2 benzimidazole (BZ) anthelmintics, oxfendazole and thiophanate. This is the first report in Kenya of a field strain of H. contortus resistant to thiophanate.

Topics: Animals; Anthelmintics; Benzimidazoles; Drug Resistance; Feces; Female; Haemonchiasis; Ivermectin; Levamisole; Male; Parasite Egg Count; Salicylanilides; Sheep; Sheep Diseases; Thiabendazole; Thiophanate

Following reports of suspected gastrointestinal strongylid nematode resistance to thiophanate in sheep and goats at Sokoine University of Agriculture (SUA), Tanzania, field strains of Haemonchus contortus, one from SUA and another from Kimamba, Tanzania, were selected for a critical controlled test to evaluate the efficacy of thiophanate. The SUA H. contortus strain in goats showed a marked resistance to thiophanate at an oral dose of 50 mg kg-1 liveweight (efficacy = 24.1%), while the Kimamba H. contortus strain showed very marked susceptibility (efficacy = 99.7%) to thiophanate at the same oral dose. This is the first report from East Africa of a field strain of H. contortus resistant to thiophanate. The incidence of resistant strains of strongyloid parasites to benzimidazole anthelmintics in sheep and goats in East Africa is on the increase. The magnitude of this problem should be evaluated and remedial solutions sought.

Topics: Abomasum; Animals; Carbamates; Drug Resistance; Feces; Female; Goat Diseases; Goats; Haemonchiasis; Haemonchus; Parasite Egg Count; Random Allocation; Tanzania; Thiophanate; Trichostrongyloidea; Trichostrongyloidiasis

The occurrence of a field strain of Haemonchus contortus which was resistant to thiophanate and susceptible to thiabendazole and levamisole is reported. The LD95 of thiophanate for the strain was found to be 156.1 mg/kg and its resistance factor was 6.7. In possessing specific thiophanate resistance it differed from previously reported thiophanate resistant strains of H contortus which have been benzimidazole resistant worms that have possessed cross resistance to thiophanate.

Topics: Animals; Carbamates; Drug Resistance; Feces; Haemonchiasis; Haemonchus; Levamisole; Male; Sheep; Sheep Diseases; Thiabendazole; Thiophanate; Trichostrongyloidea; Trichostrongyloidiasis

Topics: Animals; Carbamates; Cattle; Cattle Diseases; Haemonchiasis; Thiophanate; Trichostrongyloidiasis

Thiophanate administered daily at low dosages reduced nematode faecal egg output, egg hatchability and parasitic worm burdens in treated lambs and ewes. Six daily doses of 1 or 3 mg per kg thiophanate (approximately 1/25th to 1/75th of the median therapeutic dose), given to lambs experimently infected with Trichostrongylus colubriformis, were partially effective in suppressing faecal egg output and egg hatchability. Six doses of 5 mg per kg per day were effective in lambs infected with Haemonchus contortus and Nematodirus spathiger. Daily doses of thiophanate (50 or 200 mg per head) given over 14 weeks to lambs grazing contaminated pasture resulted in improved productivity (the higher dosage) and suppression of output of viable eggs and reduced worm burdens (both dosages). Reduced output of viable eggs was also obtained in housed, lactating ewes receiving 5 or 7 mg per kg thiophanate dispersed daily in the feed for 11 or nine weeks respectively after lambing.

Topics: Animals; Antinematodal Agents; Carbamates; Haemonchiasis; Ostertagiasis; Sheep; Sheep Diseases; Thiophanate; Trichostrongyloidiasis

Topics: Animals; Carbamates; Cattle; Cattle Diseases; Haemonchiasis; Nematode Infections; Ostertagiasis; Sheep; Sheep Diseases; Thiophanate; Trichostrongyloidiasis