[Dynamics and diffusion of Oncomelania snails in Danyang City, Jiangsu Province]

To understand the dynamics and the diffusion trend of Oncomelania snails in Danyang City, Jiangsu Province, so as to explore effective control measures.

The data of historical records and routine surveillance of snails were collected and analyzed according to the river systems.

The snails were imported from external river systems and spread from the rivers to inland. The diffusion trend was from the upstream to downstream and from the rivers to irrigation canals.

The inland rivers connecting with the Yangtze River are the main routes where marshland snails can spread from outside to the inland. The irrigation system plays an important role in snail spreading to the irrigation areas. The regular surveillance in combination with the basic construction of farmland and irrigation system is needed to prevent the spread of the snails and the retransmission of schistosomiasis japonica in Danyang.