COMPARATIVE-STUDIES ON THE REDUCTION OF FECAL EGG COUNTS AND TREATMENT INTERVALS OF ENDOPARASITES IN THE HORSE

For a 44-week period the drugs moxidectin, ivermectin and pyrantel emb onate were comparatively tested for efficacy and persistency in horses under stud farm conditions. In the beginning all animals (100 %) harb oured small strongyles, and four (8,5 %) S. edentatus; the average num ber of epg was 2209. From the other intestinal parasites 13 (26 %) hor ses were also infected with P. equorum and two (4 %) of them with A. p erfoliata. Throughout the study moxidectin with an experimental gel fo rmulation of 2 per cent (0,4 mg/kg bodyweight) reduced strongyle egg o utput by more than 89 per cent for 16 weeks. A similar sufficient redu ced efficacy was shown by ivermectin (0,2 mg/kg bodyweight) and pyrant el embonate (19 mg/kg bobyweight) for eight and four weeks. Average tr eatment intervals were 20 weeks for moxidectin, twelve weeks for iverm ectin and seven weeks for pyrantel embonate. The reappearance of P. eq uorum was observed both in moxidectin and ivermectin-treated group in the 32th examination week. Anoplocephala eggs were found repeatedly in faeces of some horses treated both with moxidectin and ivermectin, bu t no Anoplocephala eggs were found in the pyrantel embonate-treated gr oup. Overwintering larvae were found in herbage samples in April, and at the end of May all pastures were free of larvae. Then an interrupte d increase of pasture larvae was observed caused by planned pasture ma nagement (change of pasture, other use of grass and therapy).