Integrated characterization of monogenean infestation in Tilapia zillii: cox1 barcoding, cytokine transcription, oxidative biomarkers, and histopathological insights

Abstract This study investigated monogenean infestations in Tilapia zillii collected from the Nile River in Kafr El-Sheikh Governorate, Egypt, using an integrated approach that combined morphological, molecular, immunological, and oxidative stress analyses to elucidate host-parasite interactions. Morphological examination identified Cichlidogyrus tilapiae as the predominant monogenean on gills, characterized by diagnostic haptoral armature and a sclerotized copulatory organ. Molecular confirmation via cytochrome c oxidase subunit I ( cox1 ) sequencing matched reference isolates with high similarity and moderate to strong support. All three cytokines showed significant upregulation in infested Tilapia zillii compared to controls: interferon gamma (IFN- γ) increased 3.30-fold, interleukin-1 (IL-1) 2.63-fold, and interleukin-10 (IL-10) 2.53-fold, with all changes being statistically highly significant. Oxidative stress biomarkers were concurrently elevated, indicating redox imbalance: catalase (CAT) increased 2.02-fold, superoxide dismutase (SOD) 2.03-fold, and reduced glutathione (GSH) 2.44-fold. Histopathology revealed distinct structural alterations in infected gills, including epithelial erosion, hyperplasia, lamellar fusion, edema, and inflammatory infiltration. Collectively, these findings provide quantitative evidence that C. tilapiae induces strong pro- and anti-inflammatory responses alongside oxidative stress in T. zillii . These results underscore the substantial histopathological impacts and support the value of integrated diagnostics in informing parasite management in Egyptian aquaculture.