Repellent activity of icaridin-impregnated horsecloth against horse flies

Horseflies are pests that cause discomfort from blood-sucking and disease transmission, and economic losses in the equine industry. This study evaluated the efficacy of horsecloth impregnated with icaridin in reducing horsefly attacks and deterring horseflies. Repellent activities were evaluated under three conditions: treatment 1 (no horsecloth), 2 (horsecloth without icaridin), and 3 (horsecloth impregnated with icaridin), using three native Hokkaido horses (Dosanko) and three mixed-breed horses (Dosanko and Haflinger) in July 2023 at a riding horse club in Hokkaido, Japan. Treatment 3 significantly reduced the number of horseflies. Treatment 2 did not significantly reduce horsefly numbers. Treatments 2 and 3 significantly reduced the number of avoidance actions. The reduction in avoidance actions in treatment 3 was greater than that in treatment 2. Lighter-colored horses experienced fewer fly attacks and avoidance actions than darker-colored horses. Overall, using icaridin-impregnated horsecloths (treatment 3) was more effective for repelling horseflies than the use of physical barriers alone (treatment 2). This study suggests that integrating chemical repellents with physical protection can enhance horsefly control strategies, improve horse welfare, and improve the safety of horses interacting with them. Further research is recommended to assess the generalizability of these findings to different horse breeds and environments with a greater number of horses.