Potential climate change effects on the distribution of urban and sylvatic dengue and yellow fever vectors

Abstract

Climate change may increase the risk of dengue and yellow fever transmission by urban and sylvatic mosquito vectors. Previous research primarily focused on Aedes aegypti and Aedes albopictus. However, dengue and yellow fever have a complex transmission cycle involving sylvatic vectors. Our aim was to analyze how the distribution of areas favorable to both urban and sylvatic vectors could be modified as a consequence of climate change. We projected, to future scenarios, baseline distribution models already published for these vectors based on the favorability function, and mapped the areas where mosquitoes' favorability could increase, decrease or remain stable in the near (2041-2060) and distant (2061-2080) future. Favorable areas for the presence of dengue and yellow fever vectors show little differences in the future compared to the baseline models, with changes being perceptible only at regional scales. The model projections predict dengue vectors expanding in West and Central Africa and in South-East Asia, reaching Borneo. Yellow fever vectors could spread in West and Central Africa and in the Amazon. In some locations of Europe, the models suggest a reestablishment of Ae. aegypti, while Ae. albopictus will continue to find new favorable areas. The results underline the need to focus more on vectors Ae. vittatus, Ae. luteocephalus and Ae. africanus in West and Central sub-Saharan Africa, especially Cameroon, Central Africa Republic, and northern Democratic Republic of Congo; and underscore the importance of enhancing entomological monitoring in areas where populations of often overlooked vectors may thrive as a result of climate changes.

Keywords: Human health; mosquito species; spatial distribution; vector-borne diseases; zoonoses.

Figure 1.

Vector model future projections for the periods 2041–2060 and 2061–2080. Models of mosquitoes Ae. aegypti and Ae. albopictus, and of sylvatic species (Hg. janthinomys, Hg. leucocelaenus, Sa. chloropterus, Ae. luteocephalus, Ae. africanus, Ae. vittatus, Ae. niveus) for the current time (2001–2017) and average model projections into the future for the periods 2041–2060 and 2061–2080. Yellow triangles represent yellow fever vectors and red drops represent dengue vectors.

Figure 2.

Dengue vector model projections into the future for the periods 2041–2060 and 2061–2080. (a) Vector model for the current time (2001–2017), (b) average model projections into the future for the periods 2041–2060 and 2061–2080, (c) areas where favourability increases and decreases in the future relative to the present. Difference between the future projection and the current model. I: increment rate; M: maintenance rate. Positive values of I indicate a net increase in favourability, that is, a gain in favourable areas, whereas negative values of I mean a net loss of favourable areas. M indicates the degree to which the favourable areas in the current model overlap with the favourable forecasted areas. (d) Uncertainty of the vector model in the period 2041–2060 and 2061–2080. SD: standard deviation. Zoomed maps of a regional scale can be found in the Supplemental Material.

Figure 3.

Yellow fever vector model future projections for the periods 2041–2060 and 2061–2080. (a) Vector model for the current time (2001–2017), (b) average model projections into the future for the periods 2041–2060 and 2061–2080, (c) areas where favourability increases and decreases in the future relative to the present. Difference between the future projection and the current model. I: increment rate; M: maintenance rate. Positive values of I indicate a net increase in favourability, that is, a gain in favourable areas, whereas negative values of I mean a net loss of favourable areas. M indicates the degree to which the favourable areas in the current model overlap with the favourable forecasted areas. (d) Uncertainty of the vector model in the period 2041–2060 and 2061–2080. SD: standard deviation. Zoomed maps of a regional scale can be found in the Supplemental Material.