Template-Type: ReDIF-Article 1.0 Author-Name: Z Mikulkova Author-Workplace-Name: Tekro, spol. s r.o., Prague, Czech Republic Author-Name: K Matejickova Author-Workplace-Name: Department of Infectious Diseases and Preventive Medicine, Veterinary Research Institute, Brno, Czech Republic Author-Name: J Motlova Author-Workplace-Name: Department of Infectious Diseases and Preventive Medicine, Veterinary Research Institute, Brno, Czech Republic Author-Name: P Ginterova Author-Workplace-Name: Tekro, spol. s r.o., Prague, Czech Republic Author-Name: M Jerabek Author-Workplace-Name: Tekro, spol. s r.o., Prague, Czech Republic Author-Name: L Pojezdal Author-Workplace-Name: Department of Infectious Diseases and Preventive Medicine, Veterinary Research Institute, Brno, Czech Republic Title: Oral efficacy of controlled-release doxycycline against Ichthyophthirius multifiliis infestation in salmonids Abstract:  Ichthyophthiriosis, caused by Ichthyophthirius multifiliis, is a major threat in salmonid aquaculture. This study evaluated the efficacy of orally administered standard doxycycline and controlled-release doxycycline formulations in experimentally infected brook trout (Salvelinus fontinalis). Fish received medicated feed for 10 days starting seven days post-infection. Controlled-release doxycycline achieved the highest survival rate (84.2%), followed by standard doxycycline (73.7%), while no control fish survived after day 25 post-infection. Both drug formulations eliminated trophonts from the skin and gills by 20 days post-treatment. Despite a 2.5-fold lower dietary dose, the controlled-release doxycycline achieved a tissue concentration equivalent to ~32% of that of standard doxycycline, with similar retention rates. Levels of doxycycline residues in water declined over time for both groups, indicating limited environmental release. These results demonstrate the effective mitigation of ichthyophthiriosis with orally administered doxycycline and the enhancement of antiparasitic efficacy and reduction of drug load in tissues and the environment via controlled-release technology, supporting its potential as a sustainable medicated feed strategy in salmonid aquaculture.  Keywords: brook trout, controlled release drug, medicated diet, rainbow trout Journal: Veterinární medicína Number: 47330 Volume: preprint DOI: 10.17221/104/2025-VETMED File-URL: http://vetmed.agriculturejournals.cz/doi/10.17221/104/2025-VETMED.html File-Format: text/html X-File-Ref: http://agriculturejournals.cz/RePEc/caa/references/vet-000004-7330.txt Handle: RePEc:caa:jnlvet:v:preprint:id:104-2025-VETMED Template-Type: ReDIF-Article 1.0 Author-Name: R Dobsikova Author-Workplace-Name: Department of Animal Breeding, Animal Nutrition and Biochemistry, Faculty of Veterinary Hygiene and Ecology, University of Veterinary Sciences Brno, Brno, Czech Republic Author-Name: P Marsalek Author-Workplace-Name: Department of Animal Protection and Welfare and Veterinary Public Health, Faculty of Veterinary Hygiene and Ecology, University of Veterinary Sciences Brno, Brno, Czech Republic Author-Name: J Velisek Author-Workplace-Name: Research Institute of Fish Culture and Hydrobiology, Faculty of Fisheries and Protection of Waters, University of South Bohemia, České Budějovice, Czech Republic Author-Name: J Blahova Author-Workplace-Name: Department of Animal Protection and Welfare and Veterinary Public Health, Faculty of Veterinary Hygiene and Ecology, University of Veterinary Sciences Brno, Brno, Czech Republic Title: Effect of a 24-hour praziquantel bath on the haematological and biochemical profile and selected parameters of oxidative stress in grass carp (Ctenopharyngodon idella) Abstract: This study assessed the effect of a 24-hour bath with praziquantel (2 and 4 mg/l) on grass carp (Ctenopharyngodon idella) by monitoring the haematological parameters, plasma biochemical profile, and oxidative stress indices. Fish were sampled at 24-, 48-, 72-, and 96-hours post-exposure (hpe). The haematological analysis revealed a significant increase (P < 0.05) in the white blood cell count immediately after treatment at both concentrations, with no subsequent changes. Within the plasma biochemical profile, a significant decrease (P < 0.05) was observed only in chloride (24 hpe at 2 mg/l; 72 hpe at both concentrations) and in magnesium (48 hpe at 2 mg/l). The oxidative stress responses indicated that the gill was the most responsive tissue. In the gill, the catalase and glutathione-S-transferase activities increased significantly (P < 0.05) at 48 hpe at 4 mg/l. Lipid peroxidation in the gill decreased at 48 hpe but increased at 72 hpe following exposure to 4 mg/l. In the hepatopancreas, the glutathione peroxidase activity significantly decreased at 48 hpe at 2 mg/l. In the plasma, significant changes (P < 0.05) were detected only in the ceruloplasmin activity, which decreased at 72 hpe in the 2 mg/l group. These findings provide essential baseline data supporting the potential future application of praziquantel in aquaculture. Keywords: antioxidant enzymes, blood, lipid peroxidation, quinoline antiparasitic Journal: Veterinární medicína Number: 47013 Volume: preprint DOI: 10.17221/89/2025-VETMED File-URL: http://vetmed.agriculturejournals.cz/doi/10.17221/89/2025-VETMED.html File-Format: text/html X-File-Ref: http://agriculturejournals.cz/RePEc/caa/references/vet-000004-7013.txt Handle: RePEc:caa:jnlvet:v:preprint:id:89-2025-VETMED