Survey of anthelmintic resistance on Danish horse farms, using 5 different methods of calculating faecal egg count reduction.

This research examines the resistance of horse strongyles, a type of parasitic worm, to anthelmintic drugs on Danish farms, finding a high prevalence of the resistance. Of the different methods to calculate faecal egg count reduction (FECR), the study found the method recommended by the World Association for the Advancement of Veterinary Parasitology to be the most sensitive in detecting resistance.

Research Methods

• Researchers used 5 different methods to calculate FECR – a widely accepted measure of the effectiveness of deworming drugs.
• The study tested the resistance to 3 types of anthelmintic – benzimidazole and pyrantel as well as ivermectin – a type of new generation drugs.
• The study involved 42 horse farms in Denmark with varying degrees of incidence and treatment of parasitic infestations.

Key Findings

• Using the most sensitive method, the study discovered a staggering level of resistance to benzimidazole – 33 out of 42 or 79% of the farms showed drug resistance. This is a significant finding considering that benzimidazole is a commonly used horse dewormer.
• While pyrantel was tested on fewer farms (15), 3 of them (20%) showed resistance.
• The resistance to ivermectin – a potent and modern dewormer, was lower yet noticeable. Indications of resistance on one out of 16 farms (approximately 6%) was found.
• It’s notable that on two farms both benzimidazole and pyrantel resistance was detected raising concerns of wider resistance.

Significance & Recommendations

• The study highlights the high prevalence of anthelmintic resistance in Danish horse farms which, if left unchecked, could have profound health consequences for the equine population.
• The study emphasizes the need to conduct routine tests for anthelmintic efficacy to monitor and manage the effectiveness of parasite control programs.
• The researchers provide important insights about the necessity to develop strategies for effective nematode control in equine hosts, considering the widespread drug resistance.
• Also, the study underscores the importance of the careful use of anthelmintics in order to slow down the development of resistance.