New irrigation methods sustain malaria control in Sichuan Province, China.

Malaria appears to have been all but eradicated from certain areas of Sichuan Province mainly as a consequence of draining a sufficient proportion of rice paddy fields. The two main malaria vectors, both members of the Anopheles hyrcanus group, breed prolifically in rice paddy fields, which farmers have traditionally kept flooded all year round to ensure an adequate water supply. Over the last three decades, the irrigation network has been gradually extended, thus ensuring water security and increasing the area of arable land that could be farmed by intermittent wet/dry irrigation (IWDI). In addition, rice fields that had been left flooded but fallow throughout the winter are now under an annual cycle of wet crop/dry crop rotation (WDCR) to maximise productivity. Accordingly, vector breeding has been greatly reduced. It would appear that vector populations have now fallen below the level required to sustain malaria transmission.