21.15109/ARP/8KFOKV Wan Sajiri, Wan Muhammad Hazim Wan Muhammad Hazim Wan Sajiri https://orcid.org/0000-0002-1364-2526 Veterinary Medical Research Institute Székely, Csaba Csaba Székely https://orcid.org/0000-0001-8831-9099 Veterinary Medical Research Institute Buchmann, Kurt Kurt Buchmann https://orcid.org/0000-0002-2747-237X Department of Veterinary and Animal Sciences, Faculty of Health and Medical Sciences, University of Copenhagen Sellyei, Boglárka Boglárka Sellyei https://orcid.org/0000-0002-1926-8256 Veterinary Medical Research Institute ARP 2026 Agricultural Sciences Monogenean control Fish parasitology Anthelmintic treatment Bath chemotherapeutants Parasite management Aquaculture health Sellyei, Boglárka Boglárka Sellyei Veterinary Medical Research Institute 2026-06-04 2026-06-04 10.1016/J.AQREP.2026.103653 21.15109/ARP/8KFOKV/I26T83 21.15109/ARP/8KFOKV/DJXYGT 21.15109/ARP/8KFOKV/NPL0OU 1167 19089 3677 text/csv application/vnd.openxmlformats-officedocument.wordprocessingml.document text/plain 1.0 Creative Commons Attribution-NonCommercial 4.0 International License. Severe infections with the gill monogenean Thaparocleidus vistulensis hinder the aquaculture of European catfish (Silurus glanis), promoting farmers to use broad-spectrum chemotherapeutants for control. This study aimed to describe the in vivo efficacy of specific anthelmintics, such as Praziquantel (PZQ) and Mebendazole (MBZ) (administered as bath treatments), against the infection. Initial toxicity tests exposed juvenile European catfish to PZQ and MBZ at concentrations of 0, 10, and 20 mg/L (24 h bath treatment) followed by a 14 days post-treatment (dpt) observation period. These tests demonstrated that European catfish could tolerate 10 mg/L of PZQ and MBZ without any signs of stress. In vivo treatment experiments were conducted by exposing experimentally infected catfish to 0, 1, 5, and 10 mg/L of PZQ or MBZ, after which fish were examined 1, 7, and 14 dpt. PZQ at the highest concentration eliminated 100% of parasites from the gills of juvenile European catfish within 24 h. MBZ displayed a delayed effect, with a 98% reduction in parasites at 14 dpt, even at the lowest concentration. Based on these results, it is possible to establish a strategy for treating European catfish against T. vistulensis infections, which can minimise the use of chemicals in aquaculture. Marie Sklodowska-Curie grant 956481