Abstract:

Objective  To explore advantages and disadvantages in systematically surveying the Oncomelania snail density by space sectioning approaches for improve the efficiency and reducing the costs in snail survey.  Methods  Liaodi village and Xiongdi village in Jiangling County were chosen as the pilot site, and the areas with presence of snails were initially spaced into 50m and 10m by 500m, and surveyed with systematic sampling method. GPS was applied to determine the starting and ending point within the natural environment decided.  The obtained snails were crushed to detect the infectious ones with cercaria shedding method. Then the average density of living snails and occurrence rate of frames with snails were calculated, and two different survey methods were compared for determining the effectiveness and efficiency. Results  A total of 39 sections were surveyed in the two villages. Systematic sampling of 2 584 frames by 10 m space revealed that the average density of living snails was 2.0406pcs/0.1m2. This consumed 209 hours in finishing tasks. Contrarily, sampling of 539 frames by 50 m space demonstrated an average density of living snails of 2.6067pcs/0.1m2, which consumed 73 hours of work that was three times as much as that of the former method. The difference was not significant regarding the snail status detected in the same space with diverse approaches(χ2=4.667, P>0.05). Conclusion  Space sectioning method for surveying the density in a typical environment with snail existence can reduce the labors and improve the work efficiency, as well as authentically reveal distribution of snails in specific surroundings.

Key words: Snail density, Snail investigation, Comparative method