A comparative study of the effects of four treatment regimes on ivermectin efficacy, body weight and pasture contamination in lambs naturally infected with gastrointestinal nematodes in Scotland

Fiona Kenyon (Corresponding Author), David McBean, Andrew W Greer, Charlotte G S Burgess, Alison A Morrison, David J Bartley, Yvonne Bartley, Leigh Devin, Mintu Nath, Frank Jackson

Research output: Contribution to journalArticle

Abstract

Refugia-based drenching regimes have been widely recommended to slow development of anthelmintic resistance but there are few comparisons between different treatment approaches in the UK. The impact of four ivermectin treatment regimes on drug efficacy, lamb body weight and nematode contamination during a 154 day grazing season were evaluated in a consecutive five year field study. Regimes were whole-flock treatment every 4 weeks (NST), targeted selective treatment (TST) based on individual performance, strategic whole-flock treatments at pre-determined times (SPT) or whole-flock treatment when clinical signs were apparent (MT). Mean numbers of ivermectin drenches administered per season were 4.0, 1.8, 2.0 and 1.4 for NST, TST, SPT and MT groups, respectively. The mean anthelmintic efficacy (AE) for each treatment group was based on faecal egg count reduction post-treatment employing a bootstrap sampling based algorithm. Mean AE was 95-98% for all groups in 2006 and mean AE (95% confidence limits) for NST declined to 62% (55%, 68%) in 2010. In comparison, AE for TST, SPT and MT in 2010 were 86% (81%, 92%), 86% (83%, 90%) and 83% (78%, 88%), respectively. Body weight in TST and SPT was similar to NST in all years (p > 0.05), however MT lambs were lighter than NST in 2006-2008 (p ⩽ 0.04). Tracer lamb worm burdens was lowest in NST but was not significantly different between other groups. Overall, both the TST and SPT regimes appeared to maintain animal performance and conserve anthelmintic efficacy compared with a neo-suppressive anthelmintic treatment regime.

Original languageEnglish
Pages (from-to)77-84
Number of pages8
JournalInternational Journal for Parasitology: Drugs and Drug Resistance
Volume3
Early online date6 Mar 2013
DOIs
Publication statusPublished - Dec 2013

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Ivermectin
Anthelmintics
Scotland
Body Weight
Ovum
Pharmaceutical Preparations

Keywords

  • Sheep
  • Gastrointestinal nematodes
  • Anthelmintic resistance
  • Refugia

Cite this

A comparative study of the effects of four treatment regimes on ivermectin efficacy, body weight and pasture contamination in lambs naturally infected with gastrointestinal nematodes in Scotland. / Kenyon, Fiona (Corresponding Author); McBean, David; Greer, Andrew W; Burgess, Charlotte G S; Morrison, Alison A; Bartley, David J; Bartley, Yvonne; Devin, Leigh; Nath, Mintu; Jackson, Frank.

In: International Journal for Parasitology: Drugs and Drug Resistance, Vol. 3, 12.2013, p. 77-84.

Research output: Contribution to journalArticle

Kenyon, Fiona ; McBean, David ; Greer, Andrew W ; Burgess, Charlotte G S ; Morrison, Alison A ; Bartley, David J ; Bartley, Yvonne ; Devin, Leigh ; Nath, Mintu ; Jackson, Frank. / A comparative study of the effects of four treatment regimes on ivermectin efficacy, body weight and pasture contamination in lambs naturally infected with gastrointestinal nematodes in Scotland. In: International Journal for Parasitology: Drugs and Drug Resistance. 2013 ; Vol. 3. pp. 77-84.
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note = "This study was funded by the Scottish Government and the EU FP6 PARASOL Project (FOOD-CT-2005-022851). A.G. received funding from AGMARDT, NZ. The authors would also like to thank the following for their help with practical aspects of the study: Scott Roger, Jim Rayburn, Moredun Bioservices, Heather McDougal, Rachael Baker, Ailie Robinson, Claire McArthur, Karoliene Penders, Lottie Gaunt, Hazel Wilkie, Mark Lutton, Heather Laurie, Danielle Gordon, Frank Turnbull, Glen Lauder and Lynsey Melville. Authors are also grateful to Iain McKendrick, Giles Innocent and David Elston for their advices on statistical analyses of the data.",
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AU - Kenyon, Fiona

AU - McBean, David

AU - Greer, Andrew W

AU - Burgess, Charlotte G S

AU - Morrison, Alison A

AU - Bartley, David J

AU - Bartley, Yvonne

AU - Devin, Leigh

AU - Nath, Mintu

AU - Jackson, Frank

N1 - This study was funded by the Scottish Government and the EU FP6 PARASOL Project (FOOD-CT-2005-022851). A.G. received funding from AGMARDT, NZ. The authors would also like to thank the following for their help with practical aspects of the study: Scott Roger, Jim Rayburn, Moredun Bioservices, Heather McDougal, Rachael Baker, Ailie Robinson, Claire McArthur, Karoliene Penders, Lottie Gaunt, Hazel Wilkie, Mark Lutton, Heather Laurie, Danielle Gordon, Frank Turnbull, Glen Lauder and Lynsey Melville. Authors are also grateful to Iain McKendrick, Giles Innocent and David Elston for their advices on statistical analyses of the data.

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N2 - Refugia-based drenching regimes have been widely recommended to slow development of anthelmintic resistance but there are few comparisons between different treatment approaches in the UK. The impact of four ivermectin treatment regimes on drug efficacy, lamb body weight and nematode contamination during a 154 day grazing season were evaluated in a consecutive five year field study. Regimes were whole-flock treatment every 4 weeks (NST), targeted selective treatment (TST) based on individual performance, strategic whole-flock treatments at pre-determined times (SPT) or whole-flock treatment when clinical signs were apparent (MT). Mean numbers of ivermectin drenches administered per season were 4.0, 1.8, 2.0 and 1.4 for NST, TST, SPT and MT groups, respectively. The mean anthelmintic efficacy (AE) for each treatment group was based on faecal egg count reduction post-treatment employing a bootstrap sampling based algorithm. Mean AE was 95-98% for all groups in 2006 and mean AE (95% confidence limits) for NST declined to 62% (55%, 68%) in 2010. In comparison, AE for TST, SPT and MT in 2010 were 86% (81%, 92%), 86% (83%, 90%) and 83% (78%, 88%), respectively. Body weight in TST and SPT was similar to NST in all years (p > 0.05), however MT lambs were lighter than NST in 2006-2008 (p ⩽ 0.04). Tracer lamb worm burdens was lowest in NST but was not significantly different between other groups. Overall, both the TST and SPT regimes appeared to maintain animal performance and conserve anthelmintic efficacy compared with a neo-suppressive anthelmintic treatment regime.

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KW - Sheep

KW - Gastrointestinal nematodes

KW - Anthelmintic resistance

KW - Refugia

U2 - 10.1016/j.ijpddr.2013.02.001

DO - 10.1016/j.ijpddr.2013.02.001

M3 - Article

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EP - 84

JO - International Journal for Parasitology: Drugs and Drug Resistance

JF - International Journal for Parasitology: Drugs and Drug Resistance

SN - 2211-3207

ER -