Population dynamics of planktonic and symbiotic Vibrio spp. associated with the freshwater invasive snail Physa acuta (Gastropoda: Physidae) in Wouri estuary (Douala, Cameroon)

Abstract

In Cameroon, the coastal city of Douala is seriously confronted with major epidemics of waterborne diseases, especially cholera, caused by pathogenic bacteria. However, the related environmental factors are poorly understood. This study aimed to investigates the population dynamics of planktonic and symbiotic Vibrio spp. associated with the freshwater invasive snail Physa acuta in Wouri estuary, focusing on the impact of selected abiotic factors. Abiotic parameters were analyzed using standardardized methods. Microbiological analyses involved isolating, identifying and counting planktonic and symbiotic Vibrio spp. cells associated with Physa acuta. The Wouri Estuary streams exhibit hypoxia, with dissolved oxygen levels as low as 1 % at certain stations and characterized by high organic matter loads. Total symbiotic Vibrio spp. abundance peaked during the rainy season and increased from freshwater saltwater gradient. The survival of both planktonic and symbiotic Vibrio spp. cells associated with Physa acuta is influenced by several abiotic factors including precipitation, salinity, suspended solids and dissolved organic matter. The species of Vibrio spp. potentially pathogen to human were isolated in both planktonic and symbiotic forms. Vibrio parahaemolyticus was provisionally identified in this study as indigenous to Physa acuta, while V. alginolyticus, V. vulnificus, V. cholerae, V. fluvialis and V. mimicus, which may be responsible for public health problems, are present accidentally in both study environments. All the evidence suggests that the bacteria present in the digestive tract of Physa acuta accumulate indiscriminately from the natural environment and constitute transient populations. Based on this study, decisions on the management of public health problems can be envisaged to avoid the emergence and re-emergence of certain zoonotic diseases.