endoparasite

The Donkey Sanctuary is a UK based charity in Sidmouth, Devon. Its mission is to transform the quality of life for donkeys, mules and people worldwide through greater understanding, collaboration and support, and by promoting lasting, mutually life-enhancing relationships. The Donkey Sanctuary has a total of seven farms in the UK including a reception farm for new arrivals (quarantine) where the study is based. The relinquished and rescued donkeys by can arrive to the quarantine farm from different origins, for that reason, it is important to follow a health control program on arrival which includes a full coprological exam; this will determine the need of using an specific worming protocol. One of the most prevalent parasites is Strongylus spp. and it is very common to find animals with a moderate egg count who are asymtomathyc. The general recommendation is to treat donkeys with an egg count of 300 to 400 eggs per gram (The two antihelmintics used during the isolation period were two endectocides: moxidectin (Equest, 0,4 mg/Kg) and ivermectin (Eqvalan, 0,2 mg/Kg).

The worming protocol used for those animals that have been considered healthy on arrival and that they did not have received a recent antihelmintic treatment was to recieve an initial treatment with Moxidectin with a quarantine period of 48 hour without access to pasture. Those animals that have recieved a recent worming treatment( within the last 6 weeks) with ivermectin or moxidectin, they were only treated if the faecal egg count was higher than 50 epg or a different type of parasite was found (for example pulmonary nematodes). No other actions were taken in those animals with Strongylus spp. after the first faecal egg count results if they had been treated with moxidectin, otherwise the previous described protocol had been followed. 

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.

Donkeys and horses share several parasites including the small strongyles, Cyathostominae. Moxidectin (MOX), a compound of macrocyclic lactones, has a wide range of ecto and endoparasitic activity in many species. For horses, MOX is available as oral gel formulation that provides excellent and long-lasting efficacy against nematodes such as large and small strongyles. There is a paucity of data available on the efficacy of anthelmintics used in donkeys (Veneziano et al., 2011). Therapeutics, such as antiparasitic compounds, are often administered to donkeys on the basis of dosage and intervals recommended for horses, because very few drugs have donkey-specific label indications (Grosenbaugh et al., 2011). The objective of the present study was to evaluate the field efficacy and Egg Reappearance Period (ERP) of MOX oral gel up to 84 days at horse dose against natural infection of Cyathostominae in donkeys.