Drug resistant cyathostomins in donkey herds: lessons in management for all equids

Andrew F. Trawford
Faith A. Burden
Presentation date

The Donkey Sanctuary has over 2500 donkeys on its farms in the UK. Endoparasite control in these herds has been a major focus for the last 10 years. Monitoring of the herds has identified significant levels of anthelmintic resistance in the cyathostomins parasitising the donkey herds. Lack of efficacy of ivermectin, moxidectin, pyrantel and fenbendazole has been identified on multiple sites and in a number of cases treatment of donkeys harbouring such parasites is becoming increasingly challenging. Changes in management practices and approach to parasite treatment is discussed. Research to establish the extent of drug resistance and clinical significance of parasitism in donkeys is of primary concern; projects have focussed on identification of drug resistance, impacts of pasture management, validation of thresholds of faecal egg counts for treatment and alternatives to anthelmintics. Significant changes in management practices have been based upon results of these studies and new ideas and techniques are being developed. Treatment of all donkeys is carried out on the basis of a strongyle faecal egg count which is carried out on a 4-weekly basis throughout the year. Preliminary data and clinical experience has shown that increasing the FEC treatment threshold for healthy, mature donkeys to ≥ 1000 strongyle epg is sufficient to control clinical disease whilst reducing pasture contamination. Application of new treatment thresholds have reduced the reliance on chemical treatment. The mean number of anthelmintic treatments per year per animal was one in 2011; this is a significant reduction from previous dosing regimes where animals would be treated a minimum of four times per year. Animals are monitored frequently with problematic herds being 100% sampled every four weeks; such monitoring allows individualised treatment programmes and highlights reduced egg reappearance periods early. Reduced ERPs are investigated immediately with suspect animals undergoing a faecal egg count reduction test (FECRT) at the next treatment. Failed FECRTs trigger an alternative approach to treatment and further investigation. It is evident that some individual cases are becoming increasingly difficult to treat effectively; future trials of combinations of anthelmintics are being considered. Effective parasite control has also led to an increased emphasis on pasture management; dung is closely managed and carefully composted. Pasture is also rested in 6 month blocks with mixed species grazing instigated where possible. Good pasture management practices produce significant drops in pasture larval counts and is the primary mechanism used to reduce parasitism. Research and practical experience has emphasised the importance of good pasture management, treatment based upon faecal egg counts and routine assessment of efficacy of treatment. Researching and trialling higher dosing threshold has also led to significant decreases in the reliance of the organisation on anthelmintics with no recorded clinical effects. The lessons learnt from management of these large herds of donkeys may provide salient and important foundations for future equid herds that undoubtedly will experience similar problems in the future.

Not published as conference proceedings