Biology subjects

Diallo, M.

Publications and source records attributed to Diallo, M..

At least 19 recordsLinked to original sources

bioRxiv2026

A chemogenetic CRISPR knockout screen identifies a ubiquitin-mediated calcineurin-BMP pathway relay in T cell activation

T cell activation is dependent on calcineurin signalling, yet how this pathway integrates with other regulatory systems remains incompletely understood. Here, we exploit the dual pharmacology of FK506, which inhibits calcineurin while also releasing FKBP12-mediated repression of BMP receptors, to dissect signalling crosstalk during T cell responses. A comparative genome-wide CRISPR knockout screen using FK506 and Cyclosporin A revealed that FK506 uniquely engages BMP pathway components and ubiquitin regulatory networks. Functional analyses in Jurkat and primary human T cells showed that FK506 induces BMP receptor-dependent activation of SMAD1/5/8 and triggers a rapid remodelling of K48- and K29-linked ubiquitin chains. Proteomics further demonstrated selective ubiquitination of immune signalling proteins and ubiquitin regulators, linking BMP pathway activation to proteasome-dependent turnover and non-proteolytic ubiquitin signalling. In primary T cells, BMP receptor signalling enhance calcineurin-driven activation, while changes in ubiquitin conjugation modulate this response, thereby establishing an integrated calcineurin-BMP-ubiquitin relay. Together, our results uncover a context-dependent signalling axis in which BMP activation and ubiquitin dynamics fine-tune calcineurin-mediated T cell signalling.

cell biology↗

bioRxiv2026

Continuous mark-release recapture to improve estimates of movement and survival of the African malaria mosquitoes

Despite extensive efforts to understand the population biology and ecology of the African malaria mosquitoes questions regarding their movement pattern, survival, and population size persist, reflecting methodological limitations. Site fidelity, in which mosquitoes return to feeding sites, resting sites, or oviposition sites remain debated. Mark release recapture (MRR) studies are vital to address such questions. Using locality- and date-specific DNA tags in fluorescent spray, we carried out a continuous MRR in a Malian village from September to December 2019 with three days interval between capture and release across seven zones. A total of 12,937 Anopheles gambiae s.l. (7,455 females) were captured during 35 indoor collections. Handling related mortality was 3.4%., A. coluzzii predominated (89.7%), followed by A. gambiae (9.4%), and A. arabiensis (0.9%). Overall recapture rate was 1.05% (N=129). Contrary to the site-fidelity hypothesis, the distribution of recaptured mosquitoes across zones (regardless of their zone of release) was similar to the distribution of the captured mosquitoes (r=0.97, P<0.001), with 70% recaptured in a different zone. There was no difference in distance moved between sexes, but males average distance increased over time since release, whereas females distance remained unchanged. Simulated movements (across released points), with equal probability to reach any of the village houses predicted actual distance moved by mosquitoes. The regression of observed distance from each zone over predicted had a slope of 1 (r2=94%, P=0.006), suggesting that the layout of the capture area greatly affected the results. The average days post release (minimum age of wild captured mosquitoes) for recaptures was 6.4 d with the longest being 30 d. No seasonal and sex related difference in minimum age were detected. The corrected probability of daily survival (PDS) was 94% and the daily increase in sporozoite rate was 4.9%. Limiting the recapture duration period showed that PDS increased with recapture duration from 74% to 86% (12 to 30 d, uncorrected). Thus, larger recapture area and longer recapture duration are needed to obtain accurate estimates of movement range and of daily survival.

ecology↗

bioRxiv2025

Vector Competence of Temperate and Tropical Mosquito Species for Babanki virus

Babanki virus (BBKV), an alphavirus belonging to the Western Equine encephalitis complex, was isolated from Mansonia africana mosquitoes in 1969 but is not characterized yet. Transmitted to humans and animals through the bite of an infectious female arthropod, it is associated with febrile illness, rash, and arthritis similarly to Sindbis virus to which it is related. No specific treatment or vaccine is available. To investigate any risk of propagation, our study investigated the vector competence of several mosquito species towards BBKV. For this purpose, laboratory mosquito colonies from metropolitan France: Culex pipiens (Paris), Aedes albopictus (Nice) as well as tropical area: Aedes albopictus (Saint-Benoit, La Reunion) and Culex quinquefasciatus (Slab strain), Aedes aegypti (PAEA) were exposed to an artificial blood meal infected with BBKV molecular clone. Midguts, legs, salivary glands and saliva were collected from individual mosquitoes of different strains or species at various time points to assess the infection status, viral replication, and infectiousness. At 7 days post viral exposure, infection rates exceeded 70% in Aedes and 40% in Culex species. They remain above 50% except for Culex quinquefasciatus which decreases to 35% at 14 days post viral exposure. Using genome and protein detection, the dissemination rates are above 50% except for Aedes albopictus (Nice) at 7 days post viral exposure. Infection assays using VeroE6 cells indicated that BBKV replicative viral particles were found in the saliva of the different populations tested. Our data demonstrate that different mosquitoes species from both temperate and tropical areas are competent to transmit BBKV suggesting an emergence risk that could trigger an outbreak in humans. Author SummaryBabanki virus (BBKV) is a non-characterized arbovirus identified in 1969 in Cameroon. BBKV is closely related to Sindbis virus which causes symptoms like febrile illness, rash, and arthritis in humans and animals. Both are alphaviruses within the Western Equine Encephalitis complex. BBKV is identified only in the African continent so far. Despite its potential to cause disease, no effective treatments are available. This study investigates the vector competence of various mosquito species from temperate and tropical regions, to transmit BBKV. After mosquitoes were fed an infectious blood meal, various organs were collected at different time points to assess the infection status, viral replication, and infectiousness. The results showed that BBKV infection occurred in all tested mosquito species and persisted over time, with viral particles detected in mosquito or that can potentially be transmitted to vertebrate hosts via mosquito saliva. These findings highlight the broad vector competence of mosquitoes from diverse climatic regions for BBKV, indicating its potential risk for emergence and outbreaks in different regions of the world. The study emphasizes the need for enhanced surveillance and preventive measures to mitigate the potential threat posed by this emerging virus.

microbiology↗

bioRxiv2025

Discovery of Isobavachin, a natural flavonoid, as an Apolipoprotein E4 (ApoE4) structure corrector for Alzheimer's disease

Alzheimers disease (AD) is a progressive neurodegenerative disease characterized by extensive neurodegeneration and consequent severe memory loss. Apolipoprotein E4 (ApoE4) is the strongest genetic risk factor for AD, with its pathological effects linked to structural instability and altered interactions with lipids and other important disease proteins including amyloid beta (A{beta}) and tau ({tau}). Therefore, correcting and stabilizing the ApoE4 structure has emerged as a promising therapeutic strategy for mitigating its detrimental effects. In this study, we investigated naturally occurring bioavailable flavonoids as ApoE4 stabilizers, focusing on their potential to modulate ApoE4 structure and function. Comprehensive investigation of a focused database using our integrated computational and experimental screening protocol led to the identification of Isobavachin as a potential corrector and stabilizer of ApoE4 structure. In addition, a few other bioavailable flavonoids with similar stabilizing properties were identified, albeit to a much lesser extent as compared to Isobavachin. The findings support the therapeutic potential of flavonoids as ApoE4 modulators and highlight Isobavachin as a lead candidate for further preclinical evaluation. These results provide new insights into the pharmacological targeting of ApoE4 and open avenues for the development of flavonoid-based, ApoE-directed therapies for AD.

neuroscience↗

bioRxiv2024

Pathogens spread by high-altitude windborne mosquitoes

Recent studies have revealed that many mosquito species regularly engage in high-altitude windborne migration, but its epidemiological significance was debated. The hypothesis that high-altitude mosquitoes spread pathogens over large distances has not been directly tested. Here, we report for the first time that high-altitude windborne mosquitoes are commonly infected with arboviruses, protozoans, and helminths affecting vertebrates and humans, and provide the first description of this pathogen-vector aerial network. A total of 1,017 female mosquitoes (81.4%, N=1,249) intercepted on nets suspended from helium balloons at altitudes of 120-290 m above ground over Mali and Ghana were screened for infection with arboviruses, plasmodia, and filariae, using pan-genus qPCR analyses followed by sequencing of positive samples. The mosquito fauna collected at altitude comprised 61 species, across 9 genera, dominated by Culex, Aedes, and Anopheles. Infection and infectiousness rates of high-altitude migrant mosquitoes were 7.2% and 4.4% with plasmodia, 1.6% and 0.6% with filariae, 3.5% and 1.1% with flaviviruses, respectively. Nineteen mosquito-borne pathogens were identified, including three arboviruses: dengue, West Nile and MPoko viruses, 13 putative plasmodia species including Plasmodium matutinum and P. relictum, three filariids, including Pelecitus spp., 27 insect-specific viruses and 5 non-mosquito-borne pathogens (e.g., Trypanosoma theileri). Confirmed head-thorax (disseminated) infections of multiple pathogens in multiple mosquito species, eg., Culex perexiguus, Coquilletidia metallica, Mansonia uniformis, and Anopheles squamosus provides evidence that pathogens carried by high-altitude windborne mosquitoes are infectious and likely capable of infecting naive hosts far from their starting location. This traffic of sylvatic pathogens may be key to their maintenance among foci as well as initiating outbreaks away from them.

microbiology↗

bioRxiv2024

Invasion and spread of the neotropical leafhopper Curtara insularis (Hemiptera: Cicadellidae) in Africa and North America and the role of high-altitude windborne migration in invasive insects

Invasive insects threaten ecosystem stability, public health, and food security. Documenting newly invasive species and understanding how they reach into new territories, establish populations, and interact with other species remain vitally important. Here, we report on the invasion of the South American leafhopper, Curtara insularis into Africa, where it has established populations in Ghana, encroaching inland at least 350 km off the coast. Importantly, 80% of the specimens collected were intercepted between 160 and 190 m above ground. Further, the fraction of this species among all insects collected was also higher at altitude, demonstrating its propensity to engage in high-altitude windborne dispersal. Its aerial densities at altitude translate into millions of migrants/km over a year, representing massive propagule pressure. Given the predominant south-westerly winds, these sightings suggest an introduction of C. insularis into at least one of the Gulf of Guinea ports. To assess the contribution of windborne dispersal to its spread in a new territory, we examine records of C. insularis range-expansion in the USA. Reported first in 2004 from central Florida, it reached north Florida (Panhandle) by 2008-2011 and subsequently spread across the southeastern and south-central US. Its expansion fits a "diffusion-like" process with 200--300 km long "annual displacement steps"--a pattern consistent with autonomous dispersal rather than vehicular transport. Most "steps" are consistent with common wind trajectories from the nearest documented population, assuming 2--8 hours of wind-assisted flight at altitude. Curtara insularis has been intercepted at US ports and on trucks. Thus, it uses multiple dispersal modalities, yet its rapid overland spread is better explained by its massive propagule pressure linked with its high-altitude windborne dispersal. We propose that high-altitude windborne dispersal is common yet under-appreciated in invasive insect species.

ecology↗

bioRxiv2024

Detection of clade 2.3.4.4b highly pathogenic H5N1 influenza virus in New York City

Highly pathogenic avian influenza viruses of the H5N1 clade 2.3.4.4b arrived in North America in the winter of 2021/2022. These viruses have spread across the Americas causing morbidity and mortality in both wild and domestic birds as well as some mammalian species, including cattle. Many surveillance programs in wildlife as well as commercial poultry operations have detected these viruses. Here we conducted surveillance of avian species in the urban environment in New York City. We detected highly pathogenic H5N1 viruses in six samples from four different bird species and performed full genome sequencing. Sequence analysis showed the presence of multiple different genotypes. Our work highlights that the interface between animals and humans that may give rise to zoonotic infections or even pandemics is not limited to rural environments and commercial poultry operations but extends into the heart of our urban centers. ImportanceWhile surveillance for avian influenza viruses is often focused on migratory routes and their associated stop-over locations, or commercial poultry operations, many bird species - including migratory birds - frequent or live in urban green spaces and wetlands. This brings them into contact with a highly dense population of humans and pets providing an extensive urban animal-human interface in which the general public may have little awareness of circulating infectious diseases. This study focuses on virus surveillance at this interface, combined with culturally responsive science education and community outreach.

microbiology↗

bioRxiv2024

Nationwide surveillance identifies yellow fever and chikungunya viruses transmitted by various species of Aedes mosquitoes in Nigeria

BackgroundSince its reemergence in 2017, yellow fever (YF) has been active in Nigeria. The Nigeria Centre for Disease Control (NCDC) has coordinated responses to the outbreaks with the support of the World Health Organization (WHO). The National Arbovirus and Vectors Research Centre (NAVRC) handles the vector component of these responses. This study sought to identify the vectors driving YF transmission and any of the targeted arboviruses and their distribution across states. MethodsEggs, larvae and pupae as well as adult mosquitoes were collected in observational, analytical, and cross-sectional surveys conducted in sixteen YF outbreak states between 2017 and 2020. Adult mosquitoes (field-collected or reared from immature stages) were morphologically identified, and arboviruses were detected using RT-qPCR at the African Centre of Excellence for Genomics of Infectious Diseases (ACEGID). ResultsAedes mosquitoes were collected in eleven of the sixteen states surveyed and the mosquitoes in nine states were found infected with arboviruses. A total of seven Aedes species were collected from different parts of the country. Aedes aegypti was the most dominant (51%) species, whereas Aedes africanus was the least (0.2%). Yellow fever virus (YFV) was discovered in 33 ([~]26%) out of the 127 Aedes mosquito pools. In addition to YFV, the Chikungunya virus (CHIKV) was found in nine pools. Except for Ae. africanus, all the Aedes species tested positive for at least one arbovirus. YFV-positive pools were found in six (6) Aedes species while CHIKV-positive pools were only recorded in two Aedes species. Edo State had the most positive pools (16), while Nasarawa, Imo, and Anambra states had the least (1 positive pool). Breteau and house indices were higher than normal transmission thresholds in all but one state. ConclusionIn Nigeria, there is a substantial risk of arbovirus transmission by Aedes mosquitoes, with YFV posing the largest threat at the moment. This risk is heightened by the fact that YFV and CHIKV have been detected in vectors across outbreak locations. Hence, there is an urgent need to step up arbovirus surveillance and control activities in the country. Author summaryEpidemics of arboviral infections are fast becoming the norm across Africa, especially in Nigeria, where sporadic epidemics of Aedes-borne Yellow Fever (YF) have been on the rise since 2017. A nationwide surveillance was conducted to detect the arboviruses and the vectors transmitting them during large YF outbreaks across Nigeria. Aedes mosquitoes collected from 57 local government areas/outbreak locations, covering 16 out of the 36 states in Nigeria, were reared to adulthood, morphologically identified to species level and assayed using qRT-PCR to detect six epidemiologically important arboviruses (Dengue, Chikungunya (CHIKV), Zika, YF, West Nile and Onyong nyong). Seven Aedes species (including Ae. aegypti, Ae. albopictus, Ae. circumluteolus, Ae. vittatus, Ae. simpsoni complex, Ae. luteocephalus, and Ae. africanus), were caught, with Ae. aegypti and Ae. albopictus the most widespread and predominant. Only YF and CHKV were found in mosquito pools from 9 states, with only Ae. aegypti pools positive for CHKV, while YF virus was found predominantly in this species and Ae. albopictus. This study provides a baseline for widespread distribution of the major Aedes vectors, and their arboviral transmission profiles, which can enhance evidence-based control measures, and strengthen nationwide surveillance systems to forestall future outbreaks of public health magnitude.

zoology↗

bioRxiv2023

Integrin-like adhesin CglD confers traction and stabilizes bacterial focal adhesions involved in myxobacterial gliding motility

AO_SCPLOWBSTRACTC_SCPLOWIntegrins are crucial for eukaryotic cell attachment and motility within the extracellular matrix (ECM) via focal-adhesion formation, with their evolutionary emergence important for the development of multicellularity. Intriguingly, single gliding cells of the predatory deltaproteobacterium Myxococcus xanthus form bacterial focal-adhesion (bFA) sites; therein, helically-trafficked motors become immobilized at anchored locations through Glt apparatus association with cell-surface integrin I-domain-like adhesin CglB. Using traction-force, bead-force, and total internal reflection-fluorescence microscopies combined with biochemical approaches, we herein identify the von Willebrand A domain-containing cell-surface lipoprotein CglD to be a {beta}-integrin-like outer-membrane lipoprotein that functionally associates with and anchors the trans-envelope Glt-CglB gliding apparatus, stabilizing and efficiently anchoring this assembly at bFAs. Calcium dependence governs CglD importance, consistent with its integrated ECM eukaryotic cartilage oligomeric matrix protein domains. CglD thus confers mechanosensory and mechanotransductory capabilities to the gliding apparatus, helping explain bFA-mediated trans-envelope force transduction, from inner-membrane-embedded motors to the cell surface.

microbiology↗

bioRxiv2023

Larval thermosensitivity shapes adult population dynamics in Anopheles mosquitoes

Mosquitoes are vectors of human life-threatening pathogens, posing a significant global health threat. While the influence of temperature on mosquito life-history traits has been extensively studied in laboratory settings, the ecological factors shaping mosquito development and population dynamics in natural environments remain poorly understood. Here, we used a multi-disciplinary approach, integrating field data from Mali, laboratory experiments, and mathematical modeling, to investigate the causal relationships between climate variables and the abundance of Anopheles gambiae s.l. mosquitoes. Using convergent-cross mapping analyses an adult abundance in the Nanguilabou village, we observed that the dynamics of adult mosquito populations was driven by larval thermosensitivity. To elucidate the underlying mechanisms, we conducted experimental studies that revealed a density-dependent larval thermal response. Through mathematical modeling, we quantified the complex interplay between temperature and larval density, demonstrating that temperature and density have independent, non-synergistic effects on larval developmental speed, mortality, and pupation rates. Our findings provide a mechanistic understanding of how larval development shapes adult mosquito populations, highlighting the significance of multidisciplinary approaches in studying climate-driven mosquito population dynamics.

ecology↗

bioRxiv2023

Proteome-scale characterisation of protein motif interactome rewiring by disease mutations

Whole genome and exome sequencing are reporting on hundreds of thousands of missense mutations. Taking a pan-disease approach, we explored how mutations in the intrinsically disordered regions (IDRs) break or generate protein interactions mediated by short linear motifs. We created a peptide-phage display library tiling [~]57,000 peptides from the IDRs of the human proteome overlapping 12,301 single nucleotide variant associated with diverse phenotypes including cancer, metabolic diseases and neurological diseases. By screening 80 human proteins, we identified 366 mutation-modulated interactions, with half of the mutations diminishing binding, and half enhancing binding or creating novel interaction interfaces. The effects of the mutations were confirmed by affinity measurements. In cellular assays, the effects of motif-disruptive mutations were validated, including loss of a nuclear localisation signal in the cell division control protein CDC45 by a mutation associated with Meier-Gorlin syndrome. The study provides insights into how disease-associated mutations may perturb and rewire the motif-based interactome.

biochemistry↗

bioRxiv2023

The influence of the larval microbiome on susceptibility to Zika virus is mosquito genotype dependent

The microbiome of the mosquito Aedes aegypti is largely determined by the environment and influences mosquito susceptibility for arthropod-borne viruses (arboviruses). Larval interactions with different bacteria can influence adult Ae. aegypti replication of arboviruses, but little is known about the role that mosquito host genetics play in determining how larval-bacterial interactions shape Ae aegypti susceptibility to arboviruses. To address this question, we isolated single bacterial isolates and complex microbiomes from Ae. aegypti larvae from various field sites in Senegal. Either single bacterial isolates or complex microbiomes were added to two different genetic backgrounds of Ae. aegypti in a gnotobiotic larval system. Using 16S amplicon sequencing we show that similarities in bacterial community structures when given identical microbiomes between different genetic backgrounds of Ae. aegypti was dependent on the source microbiome, and the abundance of single bacterial taxa differed between Ae. aegypti genotypes. Using single bacterial isolates or the entire preserved complex microbiome, we tested the ability of specific microbiomes to drive differences in infection rates for Zika virus in different genetic backgrounds of Ae. aegypti. We observed that the proportion of Zika virus-infected adults was dependent on the interaction between the larval microbiome and Ae. aegypti host genetics. By using the larval microbiome as a component of the environment, these results demonstrate that interactions between the Ae. aegypti genotype and its environment can influence Zika virus infection. As Ae. aegypti expands and adapts to new environments under climate change, an understanding of how different genotypes interact with the same environment will be crucial for implementing arbovirus transmission control strategies.

microbiology↗

bioRxiv2022

Multiplex genome engineering in Clostridium beijerinckii NCIMB 8052 using CRISPR-Cas12a

Clostridium species are re-emerging as biotechnological workhorses for industrial acetone-butanol-ethanol production. This re-emergence is largely due to advances in fermentation technologies but also due to advances in genome engineering and re-programming of the native metabolism. Several genome engineering techniques have been developed including the development of several CRISPR-Cas tools. Here, we expanded the CRISPR-Cas toolbox and developed a CRISPR-Cas12a genome engineering tool in Clostridium beijerinckii NCIMB 8052. By controlling the expression of FnCas12a with the strict xylose-inducible promoter, we achieved efficient (25-100%) single-gene knockout of five C. beijerinckii NCIMB 8052 genes (Spo0A, Upp, Cbei_1291, Cbei_3238, Cbei_3832). Moreover, we achieved multiplex genome engineering by simultaneously knocking out the Spo0A and Upp genes in a single step with an efficiency of 18%. Finally, we showed that the spacer sequence and position in the CRISPR array can affect the editing efficiency outcome.

microbiology↗

bioRxiv2022

Diversity, composition, altitude, and seasonality of high-altitude windborne migrating mosquitoes in the Sahel: Implications for disease transmission

Recent studies have reported Anopheles mosquitoes captured at high-altitude (40-290 m above ground) in the Sahel. Here, we describe this migration modality across genera and species of African Culicidae and examine its implications for disease transmission and control. As well as Anopheles, six other genera--Culex, Aedes, Mansonia, Mimomyia, Lutzia, and Eretmapodites comprised 90% of the 2,340 mosquitoes captured at altitude. Of the 50 molecularly confirmed species (N=2,107), 33 species represented by multiple specimens were conservatively considered high-altitude windborne migrants, suggesting it is a common migration modality in mosquitoes (31-47% of the known species in Mali), and especially in Culex (45-59%). Overall species abundance varied between 2 and 710 specimens/species (in Ae. vittatus and Cx. perexiguus, respectively). At altitude, females outnumbered males 6:1, and 93% of the females have taken at least one blood meal on a vertebrate host prior to their departure. Most taxa were more common at higher sampling altitudes, indicating that total abundance and diversity are underestimated. High-altitude flight activity was concentrated between June and November coinciding with availability of surface waters and peak disease transmission by mosquitoes. These hallmarks of windborne mosquito migration bolster their role as carriers of mosquito-borne pathogens (MBPs). Screening 921 mosquitoes using pan-Plasmodium assays revealed that thoracic infection rate in these high-altitude migrants was 2.4%, providing a proof of concept that vertebrate pathogens are transported by windborne mosquitoes at altitude. Fourteen of the 33 windborne mosquito species had been reported as vectors to 25 MBPs in West Africa, which represent 32% of the MBPs known in that region and include those that inflict the heaviest burden on human and animal health, such as malaria, yellow fever, dengue, and Rift Valley fever. We highlight five arboviruses that are most likely affected by windborne mosquitoes in West Africa: Rift Valley fever, Onyongnyong, Ngari, Pangola, and Ndumu. We conclude that the study of windborne spread of diseases by migrating insects and the development of surveillance to map the sources, routes, and destinations of vectors and pathogens is key to understand, predict, and mitigate existing and new threats of public health.

ecology↗

bioRxiv2021

The African mosquito-borne diseasosome: Geographical patterns and range expansion

Mosquito-borne diseases (MBDs) such as malaria, dengue, and Rift Valley fever threaten public health and food security globally. Despite their cohesive nature, they are typically treated as distinct entities. Applying biological system analysis to the African MBDs from a One Health perspective, we provide the first biogeographic description of the African mosquito fauna corresponding with the pathogens they transmit. After compiling records accumulated over a century, we find that there are 677 mosquito species in Africa, representing 16 genera, and 151 mosquito-borne pathogens (MBPs) circulating primarily among wild tetrapods, dominated by viruses (95) and protozoans (47). We estimate that reported MBPs represent [~]1% of the actual number. Unlike mosquitoes, African arboviruses and mammalian plasmodia represent a higher share of the Worlds total based on the area - species richness relationship (P<0.0001), explaining the disproportional large share of global MBPs that originated from Africa. Species richness of African mosquitoes and MBPs are similarly concentrated along the equator, peaking in central Africa, with a secondary "ridge" along eastern Africa. Moderate diversity and low endemicity in mosquitoes across the Sahel reveals a fauna with high propensity for long-range migration. Regional differences in species richness, endemicity, and composition agreed with country-based results. The composition of mosquitoes and MBPs separates sub-Saharan Africa from north Africa, in accordance with the Palearctic and Afrotropical faunal realms, and west and central Africa are clustered together distinctly from the cluster of eastern and southern Africa. With [~]25% of the species occupying a single country, [~]50% in 1-3 countries and <5% found in >25 countries, the typical ranges of both mosquitoes and MBPs are surprisingly small. The striking similarity in diversity and especially in range distributions of mosquitoes and MBPs suggest that most MBPs are transmitted by one or few narrow-range mosquito vectors. Exceptionally widespread mosquito species (e.g., Ae. aegypti, Cx. quinquefasciatus, and 10 Anopheles species) feed preferentially on people and domestic animals, and nearly half are windborne migrants. Likewise, exceptionally widespread MBPs are transmitted between people or domestic animals and are vectored by one or more of the aforementioned widespread mosquitoes. Our results suggest that few MBPs have undergone a dramatic range expansion, after adapting to people or domestic animals as well as to exceptionally-widespread mosquitoes. During the intermediate phase of range expansion, MBPs extend their vector and vertebrate host ranges with a concomitant gradual increase in geographical range. Because range size may serve as a marker of the phase of range expansion, ranking the African MBPs according to range, we identified several MBPs that pose elevated risk for disease emergence (e.g., Wesselsbron virus). Taken together, our database, approach, and results can help improve MBD surveillance and lead to a better understanding of disease emergence. This knowledge has the potential to improve capacity to prevent and mitigate new and emerging MBD threats.

zoology↗

bioRxiv2021

Evaluating the contribution of aestivation to the persistence of malaria mosquitoes through the Sahelian dry season using stable isotopes

Data suggests the malaria vector Anopheles coluzzii persists in the Sahel by dry-season aestivation though evidence is scant. We have marked Anopheles mosquitoes using deuterium (2H) to assess the contribution of aestivation to persistence of mosquitoes through the seven-month dry season. If local aestivation is the only way A. coluzzii persists, the frequency of marked mosquitoes should remain stable throughout, whereas finding no marked mosquitoes would be evidence against aestivation. Larval sites were spiked with 2H at the end of the 2017 wet season in two Sahelian villages in Mali. We monitored 2H-enriched populations until the onset of rains. By the end of the enrichment period, 33% of A. coluzzii mosquitoes were clearly marked. Expectedly, 2H levels in marked mosquitoes degraded over time, resulting in a partial overlap of the marked and non-marked 2H distributions. We utilized three methods to estimate the fraction of marked mosquitoes in the population. Seven months after enrichment, 7% of the population had 2H values above the highest pre-enrichment value. An excess of 21% exceeded the 3rd quartile of the pre-enrichment population. A finite mixed population model showed 2.5% represented a subpopulation of marked mosquitoes with elevated 2H, compatible with our predictions. We provide evidence that aestivation is a major persistence mechanism of A. coluzzii in the Sahel, contributing at least 20% of the adults at the onset of rains, suggesting A. coluzzii utilizes multiple persistence strategies enabling its populations rapid buildup, facilitating subsequent malaria resurgence. These may complicate vector control and malaria elimination campaigns. Significance statementHere we estimated the contribution of aestivation to the persistence of mosquitoes through the seven-month long dry season, by marking a known fraction of the adult population through larval site 2H-spiking by the end of the wet season and assessing the change in this fraction through the dry season, until after the onset of the first rain of the subsequent wet season. In a mark-release-recapture study using stable isotopes, we provide compelling evidence that the primary Sahelian malaria vector Anopheles coluzzii aestivates on a population-scale, contributing at least 20% of the adults which reestablish the population of the subsequent wet season. The capacity to use multiple strategies of persistence in time and space might complicate vector control and elimination campaigns.

ecology↗

bioRxiv2021

Insect-specific viruses regulate vector competence in Aedes aegypti mosquitoes via expression of histone H4

Aedes aegypti and Aedes albopictus are major mosquito vectors for arthropod-borne viruses (arboviruses) such as dengue (DENV) and Zika (ZIKV) viruses. Mosquitoes also carry insect-specific viruses (ISVs) that may affect the transmission of arboviruses. Here, we analyzed the global virome in urban Aedes mosquitoes and observed that two insect-specific viruses, Phasi Charoen-like virus (PCLV) and Humaita Tubiacanga virus (HTV), were the most prevalent in A. aegypti worldwide except for African cities, where transmission of arboviruses is low. Spatiotemporal analysis revealed that presence of HTV and PCLV led to a 200% increase in the chances of having DENV in wild mosquitoes. In the laboratory, we showed that HTV and PCLV prevented downregulation of histone H4, a previously unrecognized proviral host factor, and rendered mosquitoes more susceptible to DENV and ZIKV. Altogether, our data reveals a molecular basis for the regulation of A. aegypti vector competence by highly prevalent ISVs that may impact how we analyze the risk of arbovirus outbreaks.

microbiology↗

bioRxiv2020

A novel fluorescence and DNA combination for complex, long-term marking of mosquitoes

BackgroundCurrent mark release recapture methodologies are limited in their ability to address complex problems in vector biology, such as studying multiple groups overlapping in space and time. Additionally, limited mark retention, reduced post-marking survival, and the large effort in marking, collection and recapture, all complicate effective insect tracking. MethodWe have developed and evaluated a marking method using a fluorescent dye (Smartwater(R)) combined with synthetic DNA tags to informatively and efficiently mark adult mosquitoes using an airbrush pump and nebulizer. Using handheld UV flashlights, the fluorescent marking enabled quick and simple initial detection of recaptures in a simple, field-ready, and non-destructive approach that when combined with a simple, extraction-free PCR on individual mosquito legs provides potentially unlimited marking information. ResultsThis marking, first tested in the laboratory with Anopheles gambiae s.l. mosquitoes, did not affect survival (median ages 24-28 days, p-adj > 0.25), oviposition (median eggs/female of 28.8, 32.5, 33.3 for water, green, red dyes, respectively, p-adj > 0.44), or Plasmodium competence (mean oocysts 5.56 to 10.6, p-adj > 0.95). DNA and fluorescence had 100% retention up to 3 weeks (longest time point tested) with high intensity, indicating marks would persist longer. ConclusionsWe describe a novel, simple, no/low-impact, and long-lasting marking method that allows separation of multiple insect subpopulations by combining unlimited length and sequence variation in the synthetic DNA tags. This method can be readily deployed in the field for marking multiple groups of mosquitoes or other insects.

ecology↗