It is not yet clear whether dam construction in the Mekong Basin will increase the impact of schistosomiasis in the region (A. R. Blaazer Nature 479, 478; 2011). We need a better understanding of the parasite's transmission ecology to improve disease prediction and to determine the best dam locations.
Comparisons with dams in other countries can be misleading. In Africa, schistosome parasites are transmitted by snails with different habitat requirements from Neotricula aperta, a snail that is found only in calcium-rich waters in the Mekong Basin and the sole intermediate host of Schistosoma mekongi.
In fact, densities of N. aperta have declined to undetectable levels downstream of the Nam Theun 2 dam in Laos (S. W. Attwood et al. Ann. Trop. Med. Parasitol. 98, 221–230; 2004) — possibly as a result of flooding, decreased calcium levels and silting. Densities are also falling farther downstream in Thailand, even though habitats there are apparently unaffected (my unpublished observations).
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Attwood, S. Use snail ecology to assess dam impact. Nature 482, 162 (2012). https://doi.org/10.1038/482162d