Nematode control in spring-born suckler beef calves using targeted selective anthelmintic treatments

O'Shaughnessy, J.; Earley, Bernadette; Mee, JF; Doherty, Michael L.; Crosson, P.; Barrett, Damien; Macrelli, Michele; Waal, Theo de

doi:10.1016/j.vetpar.2014.07.009

Cited by 12 publications

(21 citation statements)

References 33 publications

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“…Elevated pepsinogen levels occur from around 2–3 weeks as young adult worms emerge from the gastric glands (Jennings et al., 1966, Ritchie et al., 1966). All these traits have shown promising outcomes for the success of TST in practice (Greer et al., 2010, McAnulty et al., 2011, Höglund et al., 2013, O'Shaughnessy et al., 2014a, O'Shaughnessy et al., 2015a, O'Shaughnessy et al., 2015b), therefore relationships for these traits had to be defined within the model.…”

Section: Methodsmentioning

confidence: 99%

“…Calves within a population were treated at the specified times, subject to a determinant criterion: for ADG the calves with the lowest gains were preferentially treated; for FEC and pepsinogen the calves with the highest values were preferentially treated. A total of 2 days was allowed for processing and analysis of the samples; ivermectin was then assumed to be administered the following day at 200 μg/kg bodyweight (Höglund et al., 2013, O'Shaughnessy et al., 2014a). An additional comparison group was included whereby calves were selected for treatment at random by generating random pseudo-numbers relating to calf ID numbers; as such, the other determinant criteria were evaluated in relation to this.…”

Section: Methodsmentioning

confidence: 99%

“…The same 3 determinant criteria were investigated, with the addition of a group of calves treated according to a combination of FEC and pepsinogen, as this strategy has been investigated in the field (O'Shaughnessy et al., 2014a, O'Shaughnessy et al., 2015a, O'Shaughnessy et al., 2015b). Available literature was used to define threshold values for each determinant criterion.…”

Section: Methodsmentioning

confidence: 99%

“…The threshold for FECs was considered to be 80 eggs/g. A trigger of 200 eggs/g has been used previously, however this was defined for mixed infections (O'Shaughnessy et al., 2014a). Although seasonal variation in egg ratios is observed in temperate regions (Dorny et al., 1988, Vercruysse et al., 1988, Verschave et al., 2014), for simplicity it was assumed that an average proportion of 0.4 was O. ostertagi eggs (Dorny et al., 1988, Vercruysse et al., 1988, Hilderson et al., 1990, Ploeger and Kloosterman, 1993, Almería et al., 1996, Areskog et al., 2013, Verschave et al., 2015).…”

Section: Methodsmentioning

confidence: 99%

“…Individuals are generally identified as needing to receive treatment on the basis of their level of parasitism or performance (Charlier et al., 2014). Although TST strategies have been developed and applied successfully in lambs (Greer et al., 2009, Kenyon et al., 2009, Kenyon et al., 2013), there are considerably fewer studies on cattle, with the first insights into the application of TST having occurred relatively recently (Greer et al., 2010, McAnulty et al., 2011, Höglund et al., 2013, O'Shaughnessy et al., 2014a, O'Shaughnessy et al., 2015a, O'Shaughnessy et al., 2015b). As there are important differences in host-parasite interactions and parasite epidemiology between cattle and sheep, differences in the methodology and application of TST in cattle can be expected.…”

Section: Introductionmentioning

confidence: 99%

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Modelling the consequences of targeted selective treatment strategies on performance and emergence of anthelmintic resistance amongst grazing calves

Berk

Laurenson

Forbes

et al. 2016

International Journal for Parasitology: Drugs and Drug Resistan

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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.

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