A controlled study on efficacy and egg reappearance period of Ivermectin in donkeys naturally infected with small strongyles

The aim of the present study was to investigate the efficacy and the egg reappearance period (ERP) of ivermectin (IVM) in donkeys during a 13-week period. The study involved a total of 14 adult Amiata breed donkeys, 7 – 13 years of age, and naturally infected with small strongyles. A group of 10 don- keys was treated with IVM oral paste at a dose rate of 200 mcg/kg BW. Another group of 4 donkeys was kept as untreated control group. Faecal samples were collected and examined for strongyle eggs on day 0 before treatment. IVM efficacy was based on the faecal egg count reduction test (FECRT) on day 14 post-treatment. Then individual faecal samples were collected and examined by FECRT at weekly intervals. A FECRT of 100 % was found after treatment with IVM and its ERP, defined as the week when the mean FECRT decreased until to become lower than 90 % efficacy, was estimated to be 11 weeks without signs of developing anthelmintic resistance. No adverse reac- tions were observed during the study period. Our findings may be useful to veterinary practitioners and breeders as they show that IVM, at the recommended dose rate, can be still considered a highly effective and safe pharmacological tool for the treatment of small strongyles in donkeys. Therefore, it is strongly recommended that all possible strategies are undertaken to avoid the risk of emergence of anthelmintic resistance to IVM in donkeys.