Environmental Parameters and Biomphalaria Snail Distribution along River Kochi, West Nile Region, Uganda

Aims: To explore the abundance and distribution of the common fresh water mollusks in River Kochi, with a special focus on Biomphalaria species, a vector responsible for transmitting Schistosoma mansoni to humans.

Study Design: Across sectional study design was used.

Place and Duration of Study: This study was conducted between October 2007 and March 2008 along Kochi River in Koboko, Yumbe and Moyo in the West Nile region of Uganda.

Methodology: Five sites along the river approximately 20 km apart, were selected and data on snail abundance and various environmental variables thought to be influencing the distribution of snails along this river were collected. These variables included: altitude, season of the year, water flow velocity, water pH, water temperature and concentrations of total dissolved solids in the water.

Results: Findings indicate that numbers of Biomphalaria species of snails increased with decreasing altitude (mean numbers 0, 15.33, 19, 50 & 73.33 from highest to lowest altitude points) and no snails of this species were recorded during the wet season. The abundance of Biomphalaria showed a positive relationship with pH (r=0.614) but negative with water velocity (r=-0.749).

Conclusion: Altitude influences the distribution Biomphalaria snails and hence potential prevalence of schistosomiasis. Water users of Kochi River should therefore try to minimize contact with water in this river especially during the dry season. Local leaders should lobby to government for alternative sources of water during the dry season.