Some Physico-chemical Parameters of Atavu River that Influence Gastropod Density at Amagunze Nigeria

Aims: The study was focused on the influence of some physico-chemical parameters of water on gastropod density at Atavu River waterlines, Amagunze south-eastern Nigeria.

Study Design: Cross-sectional prospective field study.

Place and Duration of Study: The study was carried out in Atavu River Amagunze, south-eastern Nigeria, between November 2018 and July 2019.

Methodology: Three 20 m2-quadrat stations were delineated from three respective communities on Atavu River water-lines for gastropod and water sampling for the determinations of some water parameters that could influence gastropod density. Gastropods were sampled with the scoop net for 9 months (November 2017-July 2018) while the species as well as cercariae shed in the laboratory were morphologically identified with Malacology Keys. Water was sampled for routine determination of water temperature, depth, current, electrical conductivity, dissolved oxygen (DO), total dissolved solids (TDS), calcium ions (Ca++) and hydrogen ion concentration (pH). Data on gastropod abundance and water parameters were subjected to descriptive statistics. Regression and correlation analysis were employed to determine the nature and degree of relationships between gastropod density and variable physico-chemical parameters of Atavu River.

Results: A total of 197 gastropods were collected from all sampled stations in 9 months, giving an overall mean density of 0.12 snails.m⁻². The percentages of identified species were Bulinus africanus (45.7), B. globosus (33.0), and B. truncatus (21.7). About 9.5% of the gastropods recovered shed the characteristic fork-tailed cercariae of Bulinus species in the laboratory. Regression of variables on gastropod density indicated positive correlation with Ca++, TDS, DO and electrical conductivity but negative with water current and depth. Water temperature and pH were not easily correlated with gastropod density. Human activities like bathing, swimming, washing, fetching of water for domestic use were observed at Atavu River-lines during the study period.

Conclusion: Fork-tailed cercariae-shedding Bulinus species have been recovered from Atavu river-lines where some water parameters influenced gastropod density. Bulinus species are known intermediate hosts of Schistosoma species that cause schistosomiasis. The on-going and unrestricted water-contact activities at Atavu river is a potential risk for schistosomiasis in Amagunze. This paper advocates for an innovative approach to schistosomiasis control in the study area and elsewhere in the country.