Lack of efficacy of monepantel against trichostrongyle nematodes in a UK sheep flock

Hamer, K., Bartley, D., Jennings, A., Morrison, A. and Sargison, N. (2018) Lack of efficacy of monepantel against trichostrongyle nematodes in a UK sheep flock. Veterinary Parasitology, 257, pp. 48-53. (doi: 10.1016/j.vetpar.2018.05.013) (PMID:29907192)

Abstract

Monepantel resistance was diagnosed during routine monitoring of the effectiveness of a farm’s roundworm control strategy. Weaned lambs had become ill thrifty and developed diarrhoea, despite the routine use of monepantel. This clinical presentation was caused by trichostrongylosis. The faecal egg count reduction was 76.7% (95% CI: 55.1–82.2%) following treatment with 2.5 mg/kg monepantel. Predominantly Trichostrongylus vitrinus along with small proportions of Oesophagostomum venulosum and Trichostrongylus vitrinus were identified by deep amplicon sequencing of pools of larvae recovered from pre and post monepantel treatment coprocultures and on postmortem examinations. The undifferentiated FECRT showed resistance to monepantel, but not to levamisole, ivermectin, or moxidectin. Examination of farm anthelmintic treatment and animal movement records suggested that treatments before movement onto silage aftermaths, putatively with low numbers of susceptible nematodes in refugia, may have placed a high selection pressure on monepantel resistance. Effective control of parasitic gastroenteritis using anthelmintic drugs is a prerequisite for sustainable sheep production. This case reiterates the need for care when combining anthelmintic treatments with movements to safe grazing, and the value of monitoring of anthelmintic efficacy as part of iterative planned animal health management.

• Item Type: Articles
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Hamer, Miss Kim
• Authors: Hamer, K., Bartley, D., Jennings, A., Morrison, A., and Sargison, N.
• College/School: College of Medical Veterinary and Life Sciences > School of Biodiversity, One Health & Veterinary Medicine
• Journal Name: Veterinary Parasitology
• Publisher: Elsevier
• ISSN: 0304-4017
• ISSN (Online): 1873-2550
• Published Online: 01 June 2018
• Copyright Holders: Copyright © 2018 Elsevier B.V.
• First Published: First published in Veterinary Parasitology 257:48-53
• Publisher Policy: Reproduced in accordance with the copyright policy of the publisher