Resistance to a triple combination of broad-spectrum anthelmintics in naturally-acquired Ostertagia circumcincta infections in sheep.

Abstract

AIM:

To measure the efficacy of two macrocyclic lactone-levamisole-benzimidazole combination drenches against naturally-acquired abomasal nematode infections on a sheep farm in the North Island, New Zealand.

METHODS:

Eighteen lambs carrying naturally-acquired worm burdens were removed from pasture and randomly allocated to one of three equal-sized groups, consisting of an untreated control group and two treatment groups. One treatment group was given a single oral dose of a triple-combination anthelmintic administered at the manufacturer's recommended dose rate of 0.2 mg/kg ivermectin, 7.5 mg/kg levamisole and 5.0 mg/kg albendazole. The other treatment group received a similar dose of another triple-combination drench consisting of 0.2 mg/kg abamectin, 8.0 mg/kg levamisole and 4.5 mg/kg oxfendazole. Worm counts were carried out post mortem on the abomasa of all animals in all groups, 10 days after treatment.

RESULTS:

While the abamectin-levamisole-oxfendazole combination was highly effective against all three abomasal nematode species present, the ivermectin-levamisole-albendazole combination was not. In the latter instance, a reduction of only 78% was achieved against infections of Ostertagia (=Teladorsagia) circumcincta.

CONCLUSIONS:

These results provide evidence of resistance to an ivermectin-levamisole-albendazole combination drench by O. circumcincta.

CLINICAL RELEVANCE:

Besides representing the first confirmed report of resistance to a combination drench consisting of three broad-spectrum anthelmintics, the present results provide further evidence of the continuing escalation of multiple anthelmintic resistance in sheep nematodes in New Zealand.

• Authors: J Wrigley, M McArthur, P B McKenna, B Mariadass
• Journal: New Zealand veterinary journal (N Z Vet J) Vol. 54 Issue 1 Pg. 47-9 (Feb 2006) ISSN: 0048-0169 [Print] England
• PMID: 16528395 (Publication Type: Journal Article)

Chemical References

• Anthelmintics
• Benzimidazoles
• Levamisole
• abamectin
• Ivermectin
• Albendazole
• oxfendazole

Topics

• Albendazole (pharmacology, therapeutic use)
• Animals
• Anthelmintics (pharmacology, therapeutic use)
• Benzimidazoles (pharmacology, therapeutic use)
• Drug Resistance
• Drug Therapy, Combination
• Ivermectin (analogs & derivatives, pharmacology, therapeutic use)
• Levamisole (pharmacology, therapeutic use)
• Male
• New Zealand
• Ostertagiasis (drug therapy, veterinary)
• Parasitic Sensitivity Tests (veterinary)
• Random Allocation
• Sheep
• Sheep Diseases (drug therapy)
• Treatment Outcome