Global “worming”: Climate change and its projected general impact on human helminth infections

Projected climate changes in the coming decades are expected to affect the prevalence and incidence of some human helminth infections.Nearly one-fifth of the way through the 21st century, humanity is confronted by the realities of a quickly changing climate: warmer temperatures, alterations in rainfall patterns and distributions, floods and droughts, and other extreme weather events.All of these changes are expected to intensify in the coming decades.In concert with other global trends relevant to populations affected by neglected tropical diseases (NTDs), including social determinants such as urbanization, conflict, human migrations, and economic shifts [1,2], climate change will play a significant role in determining the future viability of helminth species and the emergence or decline of human helminthiases.Still another factor will be ongoing global efforts to control or eliminate human helminthiases through mass drug administration (MDA), vector control, and the delivery of new-generation biotechnologies.Because worms exist in dynamic relationships with their environments and, for some, with snail intermediate hosts or insect vectors, the effects of climate change will vary by species and could be multidimensional in nature.In addition, climate change may act synergistically or competitively with the major social determinants highlighted above, as well as MDA.Schistosomiasis in Africa is an example of the complexities of climate change interacting with urbanization and MDA.The hotter and drier conditions expected for many parts of Africa might reduce the continent's overall incidence of schistosome infections by decimating freshwater snail populations, which serve as intermediate hosts for the digenetic blood trematodes [3].However, not all species will suffer ill effects of environmental change, and these differential responses will influence disease burden.Ultimately, Africa's anticipated future economic development-together with expansion of praziquantel MDA and the possible development of a schistosomiasis vaccine-might eventually reinforce the effects of snail decimation due to climate change, thereby accelerating the elimination of schistosomiasis on the African continent.In contrast to the example above, in the case of lymphatic filariasis (LF), which has been slated for elimination via MDA [4], expanded ranges and extended breeding seasons of