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Title: Modelling the consequences of targeted selective treatment strategies on performance and emergence of anthelmintic resistance amongst grazing calves
Contributor(s): Berk, Zoe (author); Laurenson, Yan  (author); Forbes, Andrew B (author); Kyriazakis, Ilias (author)
Publication Date: 2016
Open Access: Yes
DOI: 10.1016/j.ijpddr.2016.11.002Open Access Link
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Abstract: The development of anthelmintic resistance by helminths can be slowed by maintaining refugia on pasture or in untreated hosts. Targeted selective treatments (TST) may achieve this through the treatment only of individuals that would benefit most from anthelmintic, according to certain criteria. However TST consequences on cattle are uncertain, mainly due to difficulties of comparison between alternative strategies. We developed a mathematical model to compare: 1) the most 'beneficial' indicator for treatment selection and 2) the method of selection of calves exposed to Ostertagia ostertagi, i.e. treating a fixed percentage of the population with the lowest (or highest) indicator values versus treating individuals who exceed (or are below) a given indicator threshold. The indicators evaluated were average daily gain (ADG), faecal egg counts (FEC), plasma pepsinogen, combined FEC and plasma pepsinogen, versus random selection of individuals. Treatment success was assessed in terms of benefit per R (BPR), the ratio of average benefit in weight gain to change in frequency of resistance alleles R (relative to an untreated population). The optimal indicator in terms of BPR for fixed percentages of calves treated was plasma pepsinogen and the worst ADG; in the latter case treatment was applied to some individuals who were not in need of treatment. The reverse was found when calves were treated according to threshold criteria, with ADG being the best target indicator for treatment. This was also the most beneficial strategy overall, with a significantly higher BPR value than any other strategy, but its degree of success depended on the chosen threshold of the indicator. The study shows strong support for TST, with all strategies showing improvements on calves treated selectively, compared with whole-herd treatment at 3, 8, 13 weeks post-turnout. The developed model appeared capable of assessing the consequences of other TST strategies on calf populations.
Publication Type: Journal Article
Source of Publication: International Journal for Parasitology: Drugs and Drug Resistance, 6(3), p. 258-271
Publisher: Elsevier Ltd
Place of Publication: United Kingdom
ISSN: 2211-3207
Fields of Research (FoR) 2008: 070708 Veterinary Parasitology
070202 Animal Growth and Development
070103 Agricultural Production Systems Simulation
Fields of Research (FoR) 2020: 300909 Veterinary parasitology
300301 Animal growth and development
300205 Agricultural production systems simulation
Socio-Economic Objective (SEO) 2008: 970107 Expanding Knowledge in the Agricultural and Veterinary Sciences
Socio-Economic Objective (SEO) 2020: 280101 Expanding knowledge in the agricultural, food and veterinary sciences
Peer Reviewed: Yes
HERDC Category Description: C1 Refereed Article in a Scholarly Journal
Appears in Collections:Journal Article

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