NEMATODE EGG RE-APPEARANCE PERIOD AFTER ANTHELMINTIC THERAPY IN HORSES IN THE MOSCOW REGION

The research purpose is studying early signs of the anthelmintic resistance development in equine nematode population on horse farms. This is possible with reference to the egg-reappearance period (ERP) after the treatment. The study was performed in the Moscow Region in 2020–2021. The horses were examined by the flotation method before the therapy. The data obtained made it possible to divide the animals into 5 experimental groups. Groups 1–2 included horses infected by strongyles. The treatment was given with Albendazole and Ivermectin. Groups 3–5 included horses infected with Parascaris equorum; they were treated with Fenbendazole, Ivermectin and Aversectin C. All horses from the experimental groups were examined on days 14, 42 and 84. Benzimidazoles and Aversectin C showed no ERP reduction. Despite the fact that Albendazole did not show 100% efficacy and an increase in eggs appeared in faeces of the horses began from day 42 (from week 6), these data correspond to the literature data on the ERP during the Albendazole therapy and do not indicate the development of any anthelmintic resistance. After Ivermectin, the growth of Strongylid and Parascaris eggs was detected in faeces of the horses on day 42 (from week 6), which was an ERP reduction as compared with the literature data at 9 weeks. The study was supported by the grant from the Russian Science Foundation (Project No. 20-76-00035).