Evaluation of two anthelmintic treatment regimens (strategic vs selective) in donkeys naturally infected by intestinal strongyles

Introduction: equine worm programs are based on treatments applied at regular intervals during the year, often without diagnosis. These strategies led to the development of anthelmintic resistance worldwide. To reduce this phenomenon in horses, targeted selective treatments (TST), based on individual Fecal Egg Count (FEC), have been developed, treating only animals with a threshold value>200 eggs per gram (EPG). The present study evaluates during one year two anthelmintic regimes on donkeys naturally infected by intestinal strongyles (Cyathostominae and Strongylus vulgaris) in Italy. Materials and Methods: study animals were allocated in two treatment groups (strategic–ST and selective–TST) of 20 donkeys each, moreover a control group (C-group) of 10 animals were enrolled. Individual FECs were performed monthly using a modified McMaster technique. Results: at the beginning of the study in ST, TST and C-groups the mean EPG were 1585.5, 1627.0 and 1634.4, respectively, no statistical differences were observed (p=0.9815). In August 2015, donkeys belonging to ST and TST were dewormed with fenbendazole drench (7.5 mg/kg) showing a FEC reduction of 99.4% in both groups. All the donkeys of ST group were also treated with FBZ in February and July 2016, while monthly in TST group donkeys with an individual FEC>300EPG were treated. In the ST group after the first and the second treatment the mean EPG follow a progressive increase while remained almost constant in TST group allowing to treat a reduced number of donkeys per time-slot and avoiding high level of infestation (p<0.05). In the ST, TST and C-groups, the mean EPG during the study period was 347.0, 201.0 and 873.7, respectively. Discussion: the study showed that in the TST group the mean EPG of intestinal strongyles was lower than in ST; considering the high prevalence of S. vulgaris, TST in donkeys should be performed with specific parasitological surveillance.