The effect of climate change on malaria transmission in the southeast of Iran

Projected impact of climate change on human health in low- and middle-income countries: a systematic review

Low- and middle-income countries (LMICs) contribute relatively little to global carbon emissions but are recognised to be among the most vulnerable parts of the world to health-related consequences of climate change. To help inform resilient health systems and health policy strategies, we sought to systematically analyse published projections of the impact of rising global temperatures and other weather-related events on human health in LMICs. A systematic search involving multiple databases was conducted in accordance with Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines to identify studies with modelled projections of the future impact of climate change on human health. Qualitative studies, reviews and meta-analyses were excluded. The search yielded more than 2500 articles, of which 70 studies involving 37 countries met criteria for inclusion. China, Brazil and India were the most studied countries while the sub-Saharan African region was represented in only 9% of studies. Forty specific health outcomes were grouped into eight categories. Non-disease-specific temperature-related mortality was the most studied health outcome, followed by neglected tropical infections (predominantly dengue), malaria and cardiovascular diseases. Nearly all health outcomes studied were projected to increase in burden and/or experience a geographic shift in prevalence over the next century due to climate change. Progressively severe climate change scenarios were associated with worse health outcomes. Knowledge gaps identified in this analysis included insufficient studies of various high burden diseases, asymmetric distribution of studies across LMICs and limited use of some climate parameters as independent variables. Findings from this review could be the basis for future research to help inform climate mitigation and adaptation programmes aimed at safeguarding population health in LMICs.

Phylogenomics revealed migration routes and adaptive radiation timing of Holarctic malaria mosquito species of the Maculipennis Group

BACKGROUND

Phylogenetic analyses of closely related species of mosquitoes are important for better understanding the evolution of traits contributing to transmission of vector-borne diseases. Six out of 41 dominant malaria vectors of the genus Anopheles in the world belong to the Maculipennis Group, which is subdivided into two Nearctic subgroups (Freeborni and Quadrimaculatus) and one Palearctic (Maculipennis) subgroup. Although previous studies considered the Nearctic subgroups as ancestral, details about their relationship with the Palearctic subgroup, and their migration times and routes from North America to Eurasia remain controversial. The Palearctic species An. beklemishevi is currently included in the Nearctic Quadrimaculatus subgroup adding to the uncertainties in mosquito systematics.

RESULTS

To reconstruct historic relationships in the Maculipennis Group, we conducted a phylogenomic analysis of 11 Palearctic and 2 Nearctic species based on sequences of 1271 orthologous genes. The analysis indicated that the Palearctic species An. beklemishevi clusters together with other Eurasian species and represents a basal lineage among them. Also, An. beklemishevi is related more closely to An. freeborni, which inhabits the Western United States, rather than to An. quadrimaculatus, a species from the Eastern United States. The time-calibrated tree suggests a migration of mosquitoes in the Maculipennis Group from North America to Eurasia about 20-25 million years ago through the Bering Land Bridge. A Hybridcheck analysis demonstrated highly significant signatures of introgression events between allopatric species An. labranchiae and An. beklemishevi. The analysis also identified ancestral introgression events between An. sacharovi and its Nearctic relative An. freeborni despite their current geographic isolation. The reconstructed phylogeny suggests that vector competence and the ability to enter complete diapause during winter evolved independently in different lineages of the Maculipennis Group.

CONCLUSIONS

Our phylogenomic analyses reveal migration routes and adaptive radiation timing of Holarctic malaria vectors and strongly support the inclusion of An. beklemishevi into the Maculipennis Subgroup. Detailed knowledge of the evolutionary history of the Maculipennis Subgroup provides a framework for examining the genomic changes related to ecological adaptation and susceptibility to human pathogens. These genomic variations may inform researchers about similar changes in the future providing insights into the patterns of disease transmission in Eurasia.