Abstract
Cholera is a negative public health event caused by Vibrio cholerae. Although V. cholerae is abundant in natural environments, its pattern and transmission between different niches remain puzzling and interrelated. Our study aimed to investigate the occurrence of nonpathogenic V. cholerae in the natural environment during endemicity periods. It also aimed to highlight the role of molecular ecoepidemiology in mapping the routes of spread, transmission, and prevention of possible future cholera outbreaks. V. cholerae was detected in different aquatic environments, waterfowl, and poultry farms located along the length of the Nile River in Giza, Cairo, and Delta provinces, Egypt. After polymerase chain reaction amplification of the specific target outer membrane gene (Omp W) of suspected isolates, we performed sequence analysis, eventually using phylogenetic tree analysis to illustrate the possible epidemiological relationships between different sequences. Data revealed a significant variation in the physicochemical conditions of the examined Nile districts related to temporal, spatial, and anthropogenic activities. Moreover, data showed an evident association between V. cholerae and the clinically diseased Synodontis schall fish. We found that the environmental distress triggered by the salinity shift and elevated temperature in the Middle Delta of the Nile River affects the pathogenesis of V. cholerae, in addition to the characteristics of fish host inhabiting the Rosetta Branch at Kafr El-Zayat, El-Gharbia province, Egypt. In addition, we noted a significant relationship between V. cholerae and poultry sources that feed on the Nile dikes close to the examined districts. Sequence analysis revealed clustering of the waterfowl and broiler chicken isolates with human and aquatic isolated sequences retrieved from the GenBank databases. From the obtained data, we hypothesized that waterfowl act as a potential vector for the intermediate transmission of cholera. Therefore, continuous monitoring of Nile water quality and mitigation of Nile River pollution, in addition to following good managemental practices (GMPs), general hygienic guidelines, and biosecurity in the field of animal production and industry, might be the way to break this cyclic transmission between human, aquatic, and animal sectors.
Highlights
There has been a massive increase in data published regarding public health events that emphasize the role of epidemiology and the environment in the transmission cycle of many threatened zoonotic diseases
V. cholerae has the unique capability to persist in two forms: viable but not culturable (VBNC) and conditionally viable environmental cells (CVEC)
The data revealed that V. cholerae was abundant in the examined aquatic and poultry sources
Summary
There has been a massive increase in data published regarding public health events that emphasize the role of epidemiology and the environment in the transmission cycle of many threatened zoonotic diseases. The VBNC is the latent endemic form of V. cholerae that occurs in the natural environment in response to temporal, seasonal, and geographical variations and/or nutrient deprivation [2,4,5]. This state of endemicity has been hypothesized to be based on four theories: animal reservoirs theory (nonhuman persistence), chronicity theory (human persistence), human continuous transmission theory, and environmental persistence (aquatic environment as a reservoir) [6,7,8,9,10]
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