Mapping the global potential distributions of two arboviral vectors Aedes aegypti and Ae. albopictus under changing climate

Background
Aedes aegypti and Ae. albopictus are
the primary vectors that transmit several arboviral diseases, including dengue,
chikungunya, and Zika. The world is presently experiencing a series of
outbreaks of these diseases, so, we still require to better understand the
current distributions and possible future shifts of their vectors for
successful surveillance and control programs. Few studies assessed the
influences of climate change on the spatial distributional patterns and
abundance of these important vectors, particularly using the most recent
climatic scenarios. Here, we updated the current potential distributions of
both vectors and assessed their distributional changes under future climate
conditions.

Methods
We
used ecological niche modeling approach to estimate the potential distributions
of Ae. aegypti and Ae. albopictus under
present-day and future climate conditions. This approach fits ecological niche
model from occurrence records of each species and environmental variables. For
each species, future projections were based on climatic data from 9 general
circulation models (GCMs) for each representative concentration pathway (RCP)
in each time period, with a total of 72 combinations in four RCPs in 2050 and
2070. All ENMs were tested using the partial receiver operating characteristic (pROC)
and a set of 2,048 and 2,003 additional independent records for Ae. aegypti and Ae. albopictus,
respectively. Finally, we used background similarity test to assess the
similarity between the ENMs of Ae. aegypti and Ae. albopictus.
Results
The predicted potential distribution of Ae. aegypti and Ae. albopictus coincided
with the current and historical known distributions of both species. Aedes
aegypti showed a markedly broader distributional potential across
tropical and subtropical regions than Ae. albopictus.
Interestingly, Ae. albopictus was markedly broader
in distributional potential across temperate Europe and the United States. All
ecological niche models (ENMs) were statistically robust (P < 0.001). ENMs
successfully anticipated 98% (1,999/2,048) and 99% (1,985/2,003) of additional
independent records for both Ae. aegypti and Ae. albopictus,
respectively (P < 0.001). ENMs based on future conditions showed similarity
between the overall distributional patterns of future-day and present-day
conditions; however, there was a northern range expansion in the continental
USA to include parts of Southern Canada in case of Ae. albopictus in
both 2050 and 2070. Future models also anticipated further expansion of Ae. albopictus to
the East to include most of Europe in both time periods. Aedes aegypti was
anticipated to expand to the South in East Australia in 2050 and 2070. The
predictions showed differences in distributional potential of both species
between diverse RCPs in 2050 and 2070. Finally, the background similarity test
comparing the ENMs of Ae. aegypti and Ae. albopictus was
unable to reject the null hypothesis of niche similarity between both species
(P > 0.05).

Conclusion

These
updated maps provided details to better guide surveillance and control programs
of Ae. aegypti and Ae. albopictus.
They have also significant public health importance as a baseline for
predicting the emergence of arboviral diseases transmitted by both vectors in
new areas across the world.
Citation: Kamal M, Kenawy MA, Rady MH, Khaled AS, Samy AM (2018) Mapping the global potential distributions of two arboviral vectors Aedes aegypti and Ae. albopictus under changing climate. PLoS ONE 13(12): e0210122. https://doi.org/10.1371/journal.pone.0210122