Pathophysiological and Molecular Characterization of Streptococcus agalactiae in Farmed Nile Tilapia | ||
| Egyptian Journal of Veterinary Sciences | ||
| Articles in Press, Corrected Proof, Available Online from 08 September 2025 PDF (1.5 M) | ||
| Document Type: Original Article | ||
| DOI: 10.21608/ejvs.2025.395469.2912 | ||
| Authors | ||
| Rania M. Attia1; Mai A.M. El-Son* 2; Saleh shafik3; Nevien K. Abdelkhalek4 | ||
| 1Department of Aquatic Animal Medicine, Faculty of Veterinary Medicine, Mansoura University, Egypt. | ||
| 2Department of aquatic animal medicine,faculty of veterinary medicine , Mansoura university, Egypt | ||
| 3Animal Health Research Institute, Mansoura branch, Egypt | ||
| 4Department of Aquatic Animal Medicine, Faculty of Veterinary Medicine, Mansoura University, Mansoura 35516, Egypt. | ||
| Abstract | ||
| This study investigated an outbreak of Streptococcus agalactiae infection in Nile tilapia (Oreochromis niloticus) farmed in Egypt, with a focus on pathogen identification and the resulting pathophysiological impacts. The investigation was carried out at a private aquaculture facility in the Manzala region, Dakahlia Governorate, during the summer of 2021. Clinically, affected fish showed signs of exophthalmia, skin haemorrhages, and marked congestion of internal organs. Bacteriological and molecular characterization using 16S rRNA gene sequencing confirmed S. agalactiae as the causative agent, with an overall prevalence of 15% among examined specimens. Experimental infection trials demonstrated significant oxidative stress responses, evidenced by increased levels of nitric oxide and malondialdehyde, and decreased antioxidant biomarkers including catalase (CAT), superoxide dismutase (SOD), glutathione (GSH), and glutathione peroxidase (GPx). Histopathological lesions were observed in multiple organs, including hepatic degeneration, renal tubular necrosis, splenic congestion, and meningoencephalitis. These findings highlight the systemic nature of S. agalactiae infection and underscore the urgent need for preventive strategies, early diagnostic protocols, and improved biosecurity measures to mitigate fish losses and safeguard aquaculture sustainability. | ||
| Keywords | ||
| Streptococcus agalactiae; Nile tilapia; Molecular diagnosis; Oxidative stress; Histopathology | ||
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