Research Article | 11 Jan 2026

Seasonal dynamics of fish-borne pathogens and water quality in Lake Nasser, Egypt: Environmental correlates and One Health implications

Nady Khairy Elbarbary1,2 ORCID, Elena Kravchenko3, Kirill Tarasov3, and Mounir M. Bekhit2,4Show more

1. Department of Food Hygiene and Control, Faculty of Veterinary Medicine, Aswan University, Aswan, Egypt.

2. Academy of Scientific Research and Technology (ASRT), Cairo, Egypt.

3. Dzhelepov Laboratory of Nuclear Problems, Joint Institute for Nuclear Research, Dubna, Russia.

4. Department of Pharmaceutics, College of Pharmacy, King Saud University, Riyadh, Saudi Arabia.

Corresponding author: Nady Khairy Elbarbary (nadykhairy@vet.aswu.edu.eg)

Received: 2025-07-15, Accepted: 2025-11-07, Published: 2026-01-11

INTERNATIONAL JOURNAL OF ONE HEALTH | pg no. 1-16 | Vol. 12, Issue 1 | DOI: 10.14202/IJOH.2026.1-16
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Abstract

          
Background and Aim: Seasonal variation profoundly influences aquatic ecosystems, altering water quality, microbial ecology, and food safety. In Egypt’s Lake Nasser, one of the world’s largest artificial freshwater reservoirs, climatic fluctuations may shape pathogen dynamics, affecting fish health and public safety. This study investigated the seasonal variations in physicochemical parameters, heavy metals, and the phenotypic and genotypic profiles of major fish-borne pathogens in Lake Nasser, Egypt, within a One Health framework. 
Materials and Methods: A total of 300 water and 300 Nile tilapia (Oreochromis niloticus) samples were collected seasonally from five lake sectors. Physicochemical indicators (temperature, pH, dissolved oxygen [DO], electrical conductivity, and six heavy metals) were analyzed following the American Public Health Association and the Association of Official Analytical Collaboration standards. Bacteriological examinations were performed according to ISO protocols to enumerate total bacterial counts (TBCs) and to isolate Staphylococcus aureus, Vibrio cholerae, Pseudomonas aeruginosa, and Aeromonas hydrophila. Molecular confirmation of species and virulence determinants was achieved using polymerase chain reaction (PCR) assays targeting 16S ribosomal RNA and virulence genes. Correlations between environmental parameters and pathogen prevalence were evaluated using Pearson’s analysis (p < 0.05). 
Results: Water temperature peaked in summer (29.7°C) while DO and pH were highest in winter (8.05 mg/L and 8.7, respectively). While zinc, copper, cadmium, and lead exceeded the Canadian Council of Ministers of the Environment thresholds for aquatic life, all heavy metals were below World Health Organization limits for drinking water. TBCs increased significantly during summer (3.59×105 Colony Forming Unit/g). S. aureus and V. cholerae predominated in summer, P. aeruginosa in spring, and A. hydrophila in autumn. Temperature positively correlated with bacterial counts (r = 0.82, p < 0.001), whereas DO showed a negative association (r = –0.71, p = 0.001). PCR confirmed multiple virulence genes in all isolates. 
Conclusion: Seasonal climatic fluctuations strongly influence microbial contamination in Lake Nasser. Although water quality remains within acceptable limits, elevated temperatures and reduced oxygen during summer promote pathogen proliferation, posing food safety risks. Continuous One Health-based surveillance integrating environmental, microbiological, and climatic indicators is recommended to safeguard aquatic ecosystems and public health under changing climate conditions. 

         
Keywords: Egypt, fish-borne pathogens, Lake Nasser, One Health, seasonal variation, water quality.