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Climate and Urbanization Drive Mosquito Preference for Humans.

ABSTRACT: The majority of mosquito-borne illness is spread by a few mosquito species that have evolved to specialize in biting humans, yet the precise causes of this behavioral shift are poorly understood. We address this gap in the arboviral vector Aedes aegypti. We first collect and characterize the behavior of mosquitoes from 27 sites scattered across the species' ancestral range in sub-Saharan Africa, revealing previously unrecognized variation in preference for human versus animal odor. We then use modeling to show that over 80% of this variation can be predicted by two ecological factors-dry season intensity and human population density. Finally, we integrate this information with whole-genome sequence data from 375 individual mosquitoes to identify a single underlying ancestry component linked to human preference. Genetic changes associated with human specialist ancestry were concentrated in a few chromosomal regions. Our findings suggest that human-biting in this important disease vector originally evolved as a by-product of breeding in human-stored water in areas where doing so provided the only means to survive the long, hot dry season. Our model also predicts that the rapid urbanization currently taking place in Africa will drive further mosquito evolution, causing a shift toward human-biting in many large cities by 2050.

SUBMITTER: Rose NH

PROVIDER: S-EPMC7511451 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:Urban sprawl is one of the most common landscape alterations occurring worldwide, and there is a growing list of species that are recognised to have adapted to urban life. To be successful, processes of urban colonization by wildlife require a broad spectrum of phenotypic (e.g., behavioural or physiological) adjustments, but evidence for genetic adaptations is much scarcer. One hypothesis proposes that different pathogen-driven selective pressures between urban and non-urban landscapes leads to adaptations in host immune genes. Here, we examined urbanization-related differentiation at the key pathogen-recognition genes of vertebrate adaptive immunity-the major histocompatibility complex (MHC)-in a common waterbird, the Eurasian coot (Fulica atra). Samples were collected from an old urban population (established before the 1950s), a new urban population (established in the 2000s), and two rural populations from central Poland. We found strong significant divergence (as measured with Jost's D) at the MHC class II between the old urban population and the remaining (new urban and rural) populations. Also, there was a moderate, but significant divergence at the MHC between the new urban population and two rural populations, while no divergence was found between the two rural populations. The total number of MHC alleles and the number of private (population-specific) MHC alleles was lower in old urban populations, as compared to the rural ones. These patterns of differentiation at the MHC were not consistent with patterns found for neutral genetic markers (microsatellites), which showed few differences between the populations. Our results indicate that MHC allele composition depended on the level of anthropogenic disturbance and the time which passed since urban colonization, possibly due to the processes of genotype sorting and local adaptation. As such, our study contributes to the understanding of genetic mechanisms associated with urbanization processes in wildlife.

Project description:BackgroundDespite long-term research on dirofilariosis in Slovakia, little attention has thus far been paid to Dirofilaria vectors. The particular aim of the present study was molecular screening for filarioid parasites in two different habitats of Bratislava, the capital city of Slovakia. In addition, the effect of urbanisation on mosquito species abundance and composition, associated with the risk of mosquito-borne infections, was studied and discussed.MethodsMosquitoes were identified by morphological features, and molecular methods were also used for determination of selected individuals belonging to cryptic species from the Anopheles maculipennis and Culex pipiens complexes. The presence of filarioid DNA (Dirofilaria repens, Dirofilaria immitis and Setaria spp.) was detected using standard PCR approaches and sequencing.ResultsA total of 6957 female mosquitoes were collected for the study. Overall, the most abundant mosquito species was Aedes vexans, closely followed by unidentified members of the Cx. pipiens complex and the less numerous but still plentiful Ochlerotatus sticticus species. Further investigation of mosquito material revealed 4.26% relative prevalence of Dirofilaria spp., whereby both species, D. repens and D. immitis, were identified. The majority of positive mosquito pools had their origin in a floodplain area on the outskirts of the city, with a relative prevalence of 5.32%; only two mosquito pools (1.26%) were shown to be positive in the residential zone of Bratislava. Setaria spp. DNA was not detected in mosquitoes within this study.ConclusionsThe study presented herein represents initial research focused on molecular mosquito screening for filarioid parasites in urban and urban-fringe habitats of Bratislava, Slovakia. Molecular analyses within the Cx. pipiens complex identified two biotypes: Cx. pipiens biotype pipiens and Cx. pipiens biotype molestus. To our knowledge, Dirofilaria spp. were detected for the first time in Slovakia in mosquitoes other than Ae. vexans, i.e. D. repens in Anopheles messeae and unidentified members of An. maculipennis and Cx. pipiens complexes, and D. immitis in Coquillettidia richiardii and Cx. pipiens biotype pipiens. Both dirofilarial species were found in Och. sticticus. The suitable conditions for the vectors' biology would represent the main risk factor for dirofilariosis transmission.

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Climate and Urbanization Drive Mosquito Preference for Humans.

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