Efficacy of two Anthelmintic Products on Strongyles in Horses from Stud Farms in Romania

Nematodes belonging to the group of equine strongyles have a huge impact on equine health. Studies in horse establishments world-wide have shown a tremendous occurrence of these parasites under largely different geographic and climatic conditions. Accordingly, decades of strongyle control have been based on regular and frequent preventive treatments with anthelmintics and, subsequently, this has led to increasing levels of anthelmintic resistance. Therefore, it is essential that investigations into the efficacy of current anthelmintics in different locations are performed to help future reliable control programmes. This paper reports preliminary data of a survey conducted in Romania to evaluate the efficacy of two commonly used anthelmintics (fenbendazole - FBZ and ivermectin - IVM) against horse strongyles, using a faecal egg count reduction test (FECRT). Horses with a strongyle faecal egg count (FEC) of ≥50 eggs per gram (EPG) were enrolled into the study. The anthelmintic efficacy was determined by calculating the percentage of reduction in FEC between the group mean at Day 0 and Days 14 post-treatment. Individual strongyle faecal egg count reduction tests (n=137) were performed on three stud farms (R, S, C) in which 108 and 29 horses were administered ivermectin and fenbendazole, respectively. The results of the study have shown that the efficacy was within the expected range with no signs of anthelmintic resistance for IVM (98.2-100%). However, FBZ resistance was suspected in one stud (the group mean FECR of 75.4%). Thus, further studies are planned to investigate extension of the anthelmintic resistance in horse parasites including an increased number and different horse establishments in Romania, in order to design realistic control programmes carrying a limited risk of selection for anthelmintic resistance and improve overall health of the horses.