SURVEY OF ANTHELMINTIC RESISTANCE ON DANISH HORSE FARMS, USING 5 DIFFERENT METHODS OF CALCULATING FECAL EGG COUNT REDUCTION

This study reports on the prevalence of anthelmintic resistance in str ongyles of horses in Denmark; Of 5 methods used for the calculation of faecal egg count reduction (FECR) the method recommended by the World Association for the Advancement of Veterinary Parasitology, for the d etection of resistance in sheep was the most sensitive procedure for d etecting resistance. Using this method benzimidazole resistance was de tected on 33 of 42 farms (79%) examined. Pyrantel was tested on 15 far ms and FECR tests indicate resistance on 3 (30%) farms. On 2 farms on which resistance to pyrantel was detected resistance to benzimidazoles was also detected. On one of 16 farms examined ivermectin resistance was indicated at Day 14 but not at Day 19. On the 15 remaining farms i vermectin was effective. Due to the high prevalence of anthelmintic re sistance in Danish horse herds it is recommended that tests of anthelm intic efficacy be conducted routinely to monitor the effectiveness of the strongyle control programmes.