by Kaylee Anderson
The global distribution of human cases of dengue and other mosquito-transmitted disease presents a serious health problem, especially considering the diseases have spread significantly in recent years. Although there is considerable research on the global distribution of these diseases, there is a second concern: range expansion by vector species. In recent years, the two main mosquito vectors, Aedes aegypti and albopictus have spread to more regions, including lower and middle latitudes, introducing ‘forest diseases’ to humans. Ae. aegypti is thought to be responsible for most massive outbreaks of dengue, so its future geographical distribution is important to predict.
Campbell et al. (2015) use a correlative niche modeling approach to evaluate the growing potential distribution of these two species based on the influence of current and future climate conditions.
The authors found that models for present day distributions are accurate and indicate that these two mosquito species have fulfilled their invasive potential globally. Although for a few apparently suitable areas, neither species had been detected. Recent searches have revealed their presence of these species in almost all climatically suitable areas. The expansion of climatically suitable areas is what Campbell et al.’s models predict. There were strong indications of Ae. albopictus spreading to larger areas, including, East Asia, Eastern North America, and possibly across Africa and Southern South America. Ae. albopictus has the broadest potential in North America, whereas Ae. aegypti appears to be stronger in Africa and Australia.
Although these models show great potential and accuracy for the predicted climate changes, these models lack the power to predict non-ideal conditions for the species. Due to the short life-cycles and environmental sensitivity of these mosquitos, the geographical expansion of these vectors will be dramatically different than the predicted, if non-ideal climatic conditions occur in the future.
While the distribution of Aedes-borne viruses has received needed attention in scientific literature about human infection, the distributional shifts in vector species have not been studied heavily. While vector populations can exist without the virus present, the range expansion of these vectors suggests that there will be disease introduction in response to climate change.
Campbell, L., Luther, C., Moo-Llanes, D., Ramsey, J., Danis-Lozano, R., et al. 2015. Climate change influences on global distributions of dengue and chikungunya virus vectors. Phil. Trans. R. Soc. B 370:1665. DOI: 10.1098/rstb.2014.0135