培养红罗非鱼（Oreochromis spp.）中Trichodina spp的形态学和分子特征以及生姜（Zingiber officinale）的体外和体内抗寄生虫作用的探索

The present study aimed to identify Trichodina species infesting red tilapia (Oreochromis spp.) at a fish farm in Alexandria, Egypt, using integrated morphological and molecular approaches, and to evaluate the in vitro and in vivo antiparasitic efficacy of ginger (Zingiber officinale) extracts. Three trichodinid species T. truttae, T. acuta, and T. compacta were identified morphologically and characterized by partial 18S rRNA gene sequencing. The obtained sequences were deposited in GenBank under accession numbers OQ559682.1, OQ456130.1, and OQ368745.1, respectively. The in vitro trials showed concentration-dependent antiparasitic activity for both aqueous and ethanolic ginger extracts. Complete cessation of parasite motility occurred after mean exposure times of 22.8, 16.0, 7.2, and 4.3 min at ethanolic extract concentrations of 5, 7.5, 10, and 20 ppt, respectively, compared with 48.5, 35.7, 19.8, and 10.4 min at aqueous extract concentrations of 50, 100, 150, and 200 ppt, respectively. In the in vivo bath-treatment trial, infection prevalence was 3.33% after exposure to the 5 ppt ethanolic extract for 90 min and 0% after exposure to the 7.5 ppt extract for 30 min, compared with 90.0% in the water control and 0% in the formalin-treated group. Mean parasite intensity in the skin and gills was reduced to 0.6 and 0.4 parasites per microscopic field, respectively, after treatment with the 5 ppt extract, whereas no parasites were detected following treatment with the 7.5 ppt extract under the conditions investigated. HPLC analysis identified gingerols and shogaols in the ethanolic extract, including 6-gingerol, 8-gingerol, 10-gingerol, and 6-shogaol. Short-term toxicity observations indicated that the selected treatment conditions were better tolerated than the higher concentrations and longer exposure periods that were tested. These findings support further investigation of ethanolic ginger extract as a candidate bath treatment for trichodinid infestation in red tilapia. Further research should address extract standardization, treatment safety, and efficacy under larger-scale aquaculture conditions.