The Fenbendazole Efficacy Against Parasitism of Cyathostomins in Horses in the Amur Region

In the Amur Region in 2021-2023, research was conducted to assess the fenbendazole efficacy against cyathostomins in 270 horses. The research was conducted by ovoscopic and larvoscopic methods, and the data obtained was processed mathematically. After the animals were dewormed at a dose of 7.5 mg/kg for the active substance, a reappearance period of cyathostomin eggs in feces was from 10 days with their number increased in further studies to day 19. Anthelminthic efficacy of fenbendazole as expressed in the ratio of the horses completely free of cyathostomins to the total number of infected animals in the experiment reduced from 70% in 2021 to 42% in 2023. Tests for the number of fecal eggs also showed stable dynamics of reduction in fenbendazole efficacy from 99.9% in 2021 to 89% in 2023. The analysis of all data obtained indicated the potential cyathostomin population resistance to fenbendazole in the horses of horse-riding clubs and stables in the Amur Region. Further studies are required to determine causes for a reduced egg reappearance period and to control the drug resistance status to anthelmintics of different classes in equine strongyles.