Abstract
BackgroundThe level of anthelmintic resistance within some cyathostomin parasite populations has increased to the level where sole reliance on anthelmintic-based control protocols is not possible. Management-based nematode control methods, including removal of faeces from pasture, are widely recommended for use in association with a reduction in anthelmintic use to reduce selection pressure for drug resistance; however, very little work has been performed to quantitatively assess the effectiveness of such methods.MethodsWe analysed data obtained from 345 donkeys at The Donkey Sanctuary (Devon, UK), managed under three different pasture management techniques, to investigate the effectiveness of faeces removal in strongyle control in equids. The management groups were as follows: no removal of faeces from pasture, manual, twice-weekly removal of faeces from pasture and automatic, twice-weekly removal of faeces from pasture (using a mechanical pasture sweeper). From turn-out onto pasture in May, monthly faecal egg counts were obtained for each donkey and the dataset subjected to an auto regressive moving average model.ResultsThere was little to no difference in faecal egg counts between the two methods of faecal removal; both resulted in significantly improved cyathostomin control compared to the results obtained from the donkeys that grazed pasture from which there was no faecal removal.ConclusionsThis study represents a valuable and unique assessment of the effectiveness of the removal of equine faeces from pasture, and provides an evidence base from which to advocate twice-weekly removal of faeces from pasture as an adjunct for equid nematode control. Widespread adoption of this practice could substantially reduce anthelmintic usage, and hence reduce selection pressure for nematode resistance to the currently effective anthelmintic products.
Highlights
The level of anthelmintic resistance within some cyathostomin parasite populations has increased to the level where sole reliance on anthelmintic-based control protocols is not possible
Helminth control varies slightly between the farms, the general routine involves taking faecal samples from every animal at four-weekly intervals, faecal worm egg counts (FWEC) analysis for strongyle eggs and anthelmintic dosing based on varying FWEC thresholds
To ensure that the welfare of the donkeys involved in the study was not compromised, any individuals with a FWEC of 2,000 eggs per gram (EPG) or over at any sampling received a clinical examination by a veterinary surgeon and where appropriate an immediate dose with pyrantel embonate at a dosage of 19 mg/kg was administered
Summary
The level of anthelmintic resistance within some cyathostomin parasite populations has increased to the level where sole reliance on anthelmintic-based control protocols is not possible. Targeted threshold dosing involves selecting which animals to dose using faecal worm egg counts (FWEC), typically using an arbitrary lower threshold of 200 eggs per gram (EPG) [2,10] This strategy is appealing because of the high levels of over-dispersion of nematodes within populations [10,11]. Adopted practices aim to break the transmission cycle of the parasites by preventing or reducing re-infection of animals through grazing Methods such as dung removal from pasture [7,17,18], strip grazing and resting pasture have been advocated [19], few quantitative studies have been undertaken to truly demonstrate their effectiveness
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