Journal article
A multi-species model to assess the effect of refugia on worm control and anthelmintic resistance in sheep grazing systems
Australian Veterinary Journal, Vol.89(6), pp.200-208
2011
Abstract
Develop a computer simulation model that uses daily meteorological data and farm management practices to predict populations of Trichostrongylus colubriformis, Haemonchus contortus and Teladorsagia (Ostertagia) circumcincta and the evolution of anthelmintic resistance within a sheep flock. Use the model to explore if increased refugia, provided by leaving some adult sheep untreated, would delay development of anthelmintic resistance without compromising nematode control.
Procedures
Compare model predictions with field observations from a breeding flock in Armidale, NSW. Simulate the impact of leaving 1-10% of adult sheep untreated in diverse sheep-grazing systems.
Results
Predicted populations of Tr. colubriformis and T. circumcincta were less than those observed in the field, attributed to nutritional stress experienced by the sheep during drought and not accounted for by the model. Observed variation in faecal egg counts explained by the model (R2) for these species was 40-50%. The H. contortus populations and R2 were both low. Leaving some sheep untreated worked best in situations where animals were already grazing or were moved onto pastures with low populations of infective larvae. In those cases, anthelmintic resistance was delayed and nematode control was maintained when 1-4% of adult stock remained untreated.
Conclusions
In general, the model predicted that leaving more than 4% of adults untreated did not sufficiently delay the development of anthelmintic resistance to justify the increased production risk from such a strategy. The choice of a drug rotation strategy had an equal or larger effect on nematode control, and selection for resistance, than leaving 1-10% of adults untreated.
Details
- Title
- A multi-species model to assess the effect of refugia on worm control and anthelmintic resistance in sheep grazing systems
- Authors/Creators
- R.J. Dobson (Author/Creator) - Murdoch UniversityE.H. Barnes (Author/Creator) - The University of SydneyK.L. Tyrrell (Author/Creator) - Commonwealth Scientific and Industrial Research OrganisationB.C. Hosking (Author/Creator) - Novartis Animal Health Australasia Pty Limited, Yarrandoo R & D Centre, Kemps Creek, NSW, AustraliaJ.W.A. Larsen (Author/Creator) - The University of MelbourneR.B. Besier (Author/Creator) - Agriculture and FoodS. Love (Author/Creator) - University of New EnglandP.F. Rolfe (Author/Creator) - Novartis Animal Health Australasia Pty Limited, Yarrandoo R & D Centre, Kemps Creek, NSW, AustraliaJ.N. Bailey (Author/Creator) - Novartis Animal Health Australasia Pty Limited, Yarrandoo R & D Centre, Kemps Creek, NSW, Australia
- Publication Details
- Australian Veterinary Journal, Vol.89(6), pp.200-208
- Publisher
- Wiley-Blackwell
- Identifiers
- 991005540618707891
- Copyright
- 2011 The Authors
- Murdoch Affiliation
- School of Veterinary and Biomedical Sciences
- Language
- English
- Resource Type
- Journal article
- Note
- ‘The definitive version is available at www.interscience.wiley.com’
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- Collaboration types
- Industry collaboration
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- Citation topics
- 1 Clinical & Life Sciences
- 1.163 Parasitology - General
- 1.163.1022 Anthelmintic Resistance
- Web Of Science research areas
- Veterinary Sciences
- ESI research areas
- Plant & Animal Science