Modelling the consequences of targeted selective treatment strategies on performance and emergence of anthelmintic resistance amongst grazing calves
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. Howe...
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| Format: | Article |
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Elsevier
2016-12-01
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| Series: | International Journal for Parasitology: Drugs and Drug Resistance |
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| Online Access: | http://www.sciencedirect.com/science/article/pii/S2211320716300641 |
| _version_ | 1811259406016315392 |
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| author | Zoe Berk Yan C.S.M. Laurenson Andrew B. Forbes Ilias Kyriazakis |
| author_facet | Zoe Berk Yan C.S.M. Laurenson Andrew B. Forbes Ilias Kyriazakis |
| author_sort | Zoe Berk |
| collection | DOAJ |
| description | 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. |
| first_indexed | 2024-04-12T18:30:55Z |
| format | Article |
| id | doaj.art-33d395092e2641a8a9afcf5dc369171d |
| institution | Directory Open Access Journal |
| issn | 2211-3207 |
| language | English |
| last_indexed | 2024-04-12T18:30:55Z |
| publishDate | 2016-12-01 |
| publisher | Elsevier |
| record_format | Article |
| series | International Journal for Parasitology: Drugs and Drug Resistance |
| spelling | doaj.art-33d395092e2641a8a9afcf5dc369171d2022-12-22T03:21:05ZengElsevierInternational Journal for Parasitology: Drugs and Drug Resistance2211-32072016-12-016325827110.1016/j.ijpddr.2016.11.002Modelling the consequences of targeted selective treatment strategies on performance and emergence of anthelmintic resistance amongst grazing calvesZoe Berk0Yan C.S.M. Laurenson1Andrew B. Forbes2Ilias Kyriazakis3School of Agriculture Food and Rural Development, Newcastle University, Newcastle Upon Tyne, NE1 7RU, UKAnimal Science, School of Environmental and Rural Science, University of New England, Armidale, New South Wales, 2351, AustraliaScottish Centre for Production Animal Health and Food Safety, School of Veterinary Medicine, University of Glasgow, G61 1QH, Scotland, UKSchool of Agriculture Food and Rural Development, Newcastle University, Newcastle Upon Tyne, NE1 7RU, UKThe 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.http://www.sciencedirect.com/science/article/pii/S2211320716300641CattleGastrointestinal parasitismOstertagia ostertagiTargeted selective treatment (TST)Anthelmintic resistanceMathematical modelling |
| spellingShingle | Zoe Berk Yan C.S.M. Laurenson Andrew B. Forbes Ilias Kyriazakis Modelling the consequences of targeted selective treatment strategies on performance and emergence of anthelmintic resistance amongst grazing calves International Journal for Parasitology: Drugs and Drug Resistance Cattle Gastrointestinal parasitism Ostertagia ostertagi Targeted selective treatment (TST) Anthelmintic resistance Mathematical modelling |
| title | Modelling the consequences of targeted selective treatment strategies on performance and emergence of anthelmintic resistance amongst grazing calves |
| title_full | Modelling the consequences of targeted selective treatment strategies on performance and emergence of anthelmintic resistance amongst grazing calves |
| title_fullStr | Modelling the consequences of targeted selective treatment strategies on performance and emergence of anthelmintic resistance amongst grazing calves |
| title_full_unstemmed | Modelling the consequences of targeted selective treatment strategies on performance and emergence of anthelmintic resistance amongst grazing calves |
| title_short | Modelling the consequences of targeted selective treatment strategies on performance and emergence of anthelmintic resistance amongst grazing calves |
| title_sort | modelling the consequences of targeted selective treatment strategies on performance and emergence of anthelmintic resistance amongst grazing calves |
| topic | Cattle Gastrointestinal parasitism Ostertagia ostertagi Targeted selective treatment (TST) Anthelmintic resistance Mathematical modelling |
| url | http://www.sciencedirect.com/science/article/pii/S2211320716300641 |
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