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Modelling the short- and long-term impacts of drenching frequency and targeted selective treatment on the performance of grazing lambs and the emergence of anthelmintic resistance

Lookup NU author(s): Professor Ilias Kyriazakis

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Abstract

Refugia-based treatment strategies aim to prolong anthelmintic efficacy by maintaining a parasite population unexposed to anthelmintics. Targeted selective treatment (TST) achieves this by treating only animals that will benefit most from treatment, using a determinant criterion (DC). We developed a mathematical model to compare various traits proposed as DC, and investigate impacts of TST and drenching frequency on sheep performance and anthelmintic resistance. Short term, decreasing the proportion of animals drenched reduced benefits of anthelmintic treatment, assessed by empty body weight (EBW), but decreased the rate of anthelmintic resistance development; each consecutive drenching had a reduced impact on average EBW and an increased impact on the rate of anthelmintic resistance emergences. The optimal DC was fecal egg count, maintaining the highest average EBW when reducing the proportion of animals drenched. Long-term, reducing the proportion of animals drenched had little impact on total weight gain benefits, across animals and years, whilst reducing drenching frequency increased it. Decreasing the frequency and proportion of animals drenched were both predicted to increase the duration of anthelmintic efficacy but reduce the total number of drenches administered before resistance was observed. TST and frequency of drenching may lead to different benefits in the short versus long term.

Publication metadata

Author(s): Laurenson YC, Bishop SC, Forbes AB, Kyriazakis I

Publication type: Article

Publication status: Published

Journal: Parasitology

Year: 2013

Volume: 140

Issue: 6

Pages: 780-791

Print publication date: 01/02/2013

ISSN (print): 0031-1820

ISSN (electronic): 1469-8161

Publisher: Cambridge University Press

URL: http://dx.doi.org/10.1017/S0031182012002181

DOI: 10.1017/S0031182012002181

PubMed id: 23369535

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