The current study aimed to investigate the most prevalent ectoparasites among some Egyptian tilapia hatcheries and find out the appropriate therapeutic and prophylactic doses. For that, 500 Nile tilapia fry weighing 0.02 g were collected from several hatcheries at Sharkia Governorate, Egypt, over the period of April to September 2017, examined for the presence of trichodinids and monogeneans. The prevalence and intensity of such parasites were recorded. LC₅₀ of the five selected chemicals was examined against 1000 healthy fry for 24 h. The therapeutic and prophylactic doses were evaluated against 360 heavily infested fry and 600 newly hatched ones for 72 h and 3 weeks of indefinite treatment, respectively. Infested fish exhibited erratic swimming, detached skins, and hemorrhagic gills. The most common parasites identified were Trichodina fultoni, T. salmincola, Cichlidogyrus sp., and Cichlidogyrus tubicirrus. The LC₅₀ was 81.31, 235.57, 7.19, and 15.48 ppm for formalin, hydrogen peroxide, potassium permanganate, and methylene blue, respectively. All chemicals were effective in treating trichodinids, while formalin was the only efficient chemical to treat monogeneans 72 h post-exposure. Potassium permanganate showed the best preventive activity against both types of parasites for successive 1 week post-exposure. This study highlighted the optimal use of chemical drugs for the control of ectoparasites from an economic perspective.

当前的研究旨在调查一些埃及罗非鱼孵化场中最普遍的外寄生物，并找出适当的治疗和预防剂量。为此，在2017年4月至2017年9月期间，从埃及Sharkia省的数家孵化场中收集了500份重0.02 g的尼罗罗非鱼鱼苗，检查了其中是否存在滴虫和单基因菌。记录了这种寄生虫的患病率和强度。LC ₅₀对这五种选定的化学药品中的24种进行了针对1000种健康鱼苗的检查。分别针对360个重度受感染的鱼苗和600个新孵化的鱼苗分别进行了72小时和3周的不确定时间的治疗和预防剂量。受感染的鱼表现出游动不规律，皮肤脱落和g出血。鉴定出的最常见的寄生虫是粉状毛线虫，沙门氏菌，Cichlidogyrus sp。和Cichlidogyrus tubicirrus。LC ₅₀福尔马林，过氧化氢，高锰酸钾和亚甲基蓝分别为81.31、235.57、7.19和15.48 ppm。所有化学品均能有效治疗滴虫病，而福尔马林是唯一可在暴露后72小时治疗单基因菌的有效化学品。高锰酸钾暴露后连续1周显示出对两种寄生虫的最佳预防活性。这项研究从经济角度突出了化学药物控制外寄生虫的最佳使用。