Biology subjects

Akorli, J.

Publications and source records attributed to Akorli, J..

13 recordsLinked to original sources

bioRxiv2026

Ambient humidity and temperature influence physicochemical drift during laboratory storage of field-collected mosquito breeding water

The use of field water for laboratory rearing of mosquitoes could offer a better representation of the natural aquatic environment than laboratory tap or deionised water. For logistical reasons, such water may be stored in the laboratory environment for an extended period, but its stability is poorly documented. This study evaluated the influence of laboratory storage conditions on the kinetics of physicochemical parameters of breeding water collected from a field habitat. To capture within-habitat variability, water was collected from multiple spatial points from a breeding site and transferred into plastic containers for storage under laboratory conditions. Water physicochemical parameters were measured in the field to establish baseline readings, while laboratory measurements were done at 2-3-day intervals over 2 months to evaluate temporal changes. A linear mixed-effects model was fitted to evaluate the determinants of changes in physicochemical parameters under laboratory storage. Most parameters exhibited high stability; however, water temperature increased significantly by an average of [~]1.5 (p= 0.046) relative to the field. Water pH demonstrated a long-term rise over the 2-month storage period with a transient, significant dip of 0.71 units after a week of storage (p< 0.001). Overall, LMM analyses revealed that ambient relative humidity was the strongest statistical predictor of change in all water parameters except pH (p< 0.05). Ambient temperature correlated positively with water temperature and ammonium nitrogen (NH4-N) (p<0.002), and negatively with dissolved oxygen (p< 0.002). These results indicate that stored field water is highly sensitive to the laboratory microclimate. Specifically, water temperature, pH, and NH4-N serve as candidate indicators for storage-related physicochemical drift. We recommend the rigorous standardisation of insectary humidity and temperature, and monitoring of water parameters, which are likely relevant for bioassay reproducibility.

ecology↗

bioRxiv2026

Drought tolerance of Aedes aegypti mosquito eggs is influenced by adaptation to local climate conditions and associations with humans

Urbanization is intensifying human interactions with mosquitoes, exacerbating public health challenges. Densely populated areas provide ideal conditions for container-dwelling mosquitoes, with increased host availability and the presence of artificial breeding sites. These anthropophilic mosquitoes often exhibit distinct ecological adaptations compared to their rural counterparts. Since mosquito eggs are immobile and remain at the site of oviposition, they provide a valuable lens for assessing how urbanization, climate-driven shifts in temperature, and drought affect mosquito reproductive success. This study examined Ae. aegypti egg viability under varying temperature and dry conditions over five months, focusing on lineages with distinct ancestries from West African populations. Mosquitoes collected from urban habitats with a high human preference demonstrated higher egg survival under prolonged arid conditions. Analysis of climatic factors revealed that dry season temperature and precipitation during wet periods are significant predictors of egg drought tolerance. Modeling future climate scenarios based on input from our egg viability results suggests a projected shift and expansion in the seasonal survival window for Ae. aegypti by the end of the century. This study highlights the importance of understanding environmental constraints on the drought tolerance of mosquito eggs to predict and mitigate future mosquito outbreaks.

physiology↗

bioRxiv2025

Stage-resolved metabolomics reveals the methionine cycle as a key regulator of Aedes aegypti development and dengue virus susceptibility

Developmental transitions in the mosquito Aedes aegypti are central to vector competence and disease transmission, yet the underlying metabolic programs remain poorly defined. Here, we use untargeted metabolomics, gene expression analysis, and functional assays to delineate stage-specific metabolic fingerprints across the mosquito life cycle, from egg and larva to pupa and adult. Our profiling of the larval diet reveals comprehensive provisioning of essential nutrients, including B vitamins critical for development. Metabolomic analyses uncover distinct, stage-specific signatures, with the larval stage exhibiting a pronounced enrichment of methionine cycle metabolites and maximal methylation capacity. Notably, while S-adenosylmethionine (SAM) and related metabolites peak in larvae, the transcription of the methionine cycle and histone methyltransferase genes is highest in adults. Functional disruption of the methionine cycle in mosquito cells reveals network-level robustness and regulatory crosstalk within the pathway. However, we also identify a specific vulnerability: silencing the gene adenosylhomocysteinase (ahcy) enhances dengue virus 1 replication and infectious particle production. Collectively, our findings identify the methionine cycle as a metabolic-epigenetic hub that integrates nutrition, development, and viral susceptibility, and highlight the larval stage as a strategic target for novel mosquito-control strategies.

microbiology↗

bioRxiv2024

Single-cell transcriptional landscapes of Aedes aegypti midgut and fat body after a bloodmeal

Aedes aegypti mosquitoes are vectors for numerous arboviruses that have an increasingly substantial global health burden. Following a bloodmeal, mosquitoes experience significant physiological changes, primarily orchestrated by the midgut and fat body tissues. These changes begin with digestion and culminate in egg production. However, our understanding of those key processes at the cellular and molecular level remains limited. We have created a comprehensive cell atlas of the mosquito midgut and fat body by employing single-cell RNA sequencing and metabolomics techniques. This atlas unveils the dynamic cellular composition and metabolic adaptations that occur following a bloodmeal. Our analyses reveal highly diverse cell populations, specialized in digestion, metabolism, immunity, and reproduction. While the midgut primarily comprises enterocytes, enteroendocrine and intestinal stem cells, the fat body consists not only of trophocytes and oenocytes, but also harbors a substantial hemocyte population and a newly found fat body-yolk cell population. The fat body exhibits a complex cellular and metabolomic profile and exerts a central role in coordinating immune and metabolic processes. Additionally, an insect-specific virus, PCLV (Phasi Charoen-Like Virus) was detected in single cells, mainly in the midgut a week after the bloodmeal. These findings highlight the complexity of the mosquitos abdominal tissues, and pave the way towards the development of exquisitely refined vector control strategies consisting of genetically targeting specific cell populations and metabolic pathways necessary for egg development after a bloodmeal.

cell biology↗

bioRxiv2024

Trophic Interactions of Anopheles Gambiae Mosquito Larvae in Aquatic Ecosystem: A Metagenomics Approach

BackgroundUnderstanding the trophic interactions of Anopheles gambiae mosquito larvae in aquatic environments is essential for malaria prevention efforts such as in gene drive application. In this study, metagenomics method was employed to explore the feeding behavior and ecological associations of An. gambiae larvae within their aquatic ecosystems. MethodsAnopheles gambiae larvae and their co-existing fauna species were collected from December 2022 to June 2023. DNA from dissected midguts of the co-existing fauna was sequenced using Illumina NovaSeq for diet analysis through a shotgun sequencing approach. ResultsThe study revealed a complex network of trophic interactions in the freshwater habitat, with significant resource sharing between A. gambiae larvae and other filter-feeding species, including various Diptera and non-Dipteran feeders. Contrary to assumptions, predator species did not exhibit exclusive predation on Anopheles larvae, preferring other fauna instead. ConclusionThis study has demonstrated complex trophic interactions among Anopheles gambiae larvae and other organisms in freshwater ecosystems. It has offered essential insights for optimizing vector control strategies, such as in gene drive applications. Additionally, the study has provided valuable information on the aquatic fauna of the study area, which can serve as a baseline for developing a macroinvertebrate identification database for freshwater systems in Ghana. A complementary study that further explores the ecological role of An. gambiae larvae in these freshwater habitats is presented in a subsequent publication.

ecology↗

bioRxiv2024

Global genomics of Aedes aegypti unveils widespread and novel persistent infectious viruses capable of triggering a small RNA response

The mosquito Aedes aegypti is a prominent vector for arboviruses, but the breadth of mosquito viruses that infects this specie is not fully understood. In the broadest global survey to date of over 200 Ae. aegypti small RNA samples, we detected viral small interfering RNAs (siRNAs) and Piwi interacting RNAs (piRNAs) arising from mosquito viruses. We confirmed that most academic laboratory colonies of Ae. aegypti lack persisting viruses, yet two commercial strains were infected by a novel tombus-like virus. Ae. aegypti from North to South American locations were also teeming with multiple insect viruses, with Anphevirus and a bunyavirus displaying geographical boundaries from the viral small RNA patterns. Asian Ae. aegypti small RNA patterns indicate infections by similar mosquito viruses from the Americas and reveal the first wild example of dengue virus infection generating viral small RNAs. African Ae. aegypti also contained various viral small RNAs including novel viruses only found in these African substrains. Intriguingly, viral long RNA patterns can differ from small RNA patterns, indicative of viral transcripts evading the mosquitoes RNA interference (RNAi) machinery. To determine whether the viruses we discovered via small RNA sequencing were replicating and transmissible, we infected C6/36 and Aag2 cells with Ae. aegypti homogenates. Through blind passaging, we generated cell lines stably infected by these mosquito viruses which then generated abundant viral siRNAs and piRNAs that resemble the native mosquito viral small RNA patterns. This mosquito small RNA genomics approach augments surveillance approaches for emerging infectious diseases.

genomics↗

bioRxiv2024

Thermal tolerance of mosquito eggs is associated with urban adaptation and human interactions

Climate change is expected to profoundly affect mosquito distributions and their ability to serve as vectors for disease, specifically with the anticipated increase in heat waves. The rising temperature and frequent heat waves can accelerate mosquito life cycles, facilitating higher disease transmission. Conversely, higher temperatures could increase mosquito mortality as a negative consequence. Warmer temperatures are associated with increased human density, suggesting a need for anthropophilic mosquitoes to adapt to be more hardy to heat stress. Mosquito eggs provide an opportunity to study the biological impact of climate warming as this stage is stationary and must tolerate temperatures at the site of female oviposition. As such, egg thermotolerance is critical for survival in a specific habitat. In nature, Aedes mosquitoes exhibit different behavioral phenotypes, where specific populations prefer depositing eggs in tree holes and prefer feeding non-human vertebrates. In contrast, others, particularly human-biting specialists, favor laying eggs in artificial containers near human dwellings. This study examined the thermotolerance of eggs, along with adult stages, for Aedes aegypti and Ae. albopictus lineages associated with known ancestry and shifts in their relationship with humans. Mosquitoes collected from areas with higher human population density, displaying increased human preference, and having a human-associated ancestry profile have increased egg viability following high-temperature stress. Unlike eggs, thermal tolerance among adults showed no significant correlation based on the area of collection or human-associated ancestry. This study highlights that the egg stage is likely critical to mosquito survival when associated with humans and needs to be accounted when predicting future mosquito distribution.

ecology↗

bioRxiv2024

Intra-species quantification reveals differences in activity and sleep levels in the yellow fever mosquito, Aedes aegypti

Aedes aegypti is an important mosquito vector of human disease with a wide distribution across the globe. Climatic conditions and ecological pressure drive differences in the biology of several populations of this mosquito, including blood-feeding behavior and vector competence. However, no study has compared activity and/or sleep among different populations/lineages of Ae. aegypti. Having recently established sleep-like states in three mosquito species with observable differences in timing and amount of sleep among species, we investigated differences in activity and sleep levels among 17 Ae. aegypti lines drawn from both its native range in Africa and its invasive range across the global tropics. Activity monitoring indicates that all the lines show consistent diurnal activity, but significant differences in activity level, sleep amount, number of sleep bouts, and bout duration were observed among the lines. Variations in specific activity and sleep parameters were explained by differences in host preference, ancestry, and human population density for the lineages collected in Africa. This study provides evidence that the diurnal sleep and activity profiles for Ae. aegypti are consistent, but there are significant population differences for Ae. aegypti sleep and activity levels and interactions with humans may significantly impact mosquito activity and sleep.

physiology↗

bioRxiv2023

Extensive variation and strain-specificity in dengue virus susceptibility among African Aedes aegypti populations

African populations of the mosquito Aedes aegypti are usually considered less susceptible to infection by human-pathogenic flaviviruses than globally invasive populations found outside Africa. Although this contrast has been well documented for Zika virus (ZIKV), it is unclear to what extent it is true for dengue virus (DENV), the most prevalent flavivirus of humans. Addressing this question is complicated by substantial genetic diversity among DENV strains, most notably in the form of four genetic types (DENV1 to DENV4), that can lead to genetically specific interactions with mosquito populations. Here, we carried out a continent-wide survey of DENV susceptibility using a panel of field-derived Ae. aegypti colonies from across the African range of the species and a colony from Guadeloupe, French West Indies as non-African reference. We found considerable variation in the ability of African Ae. aegypti populations to acquire and replicate a panel of six DENV strains spanning the four DENV types. Although African Ae. aegypti populations were generally less susceptible than the reference non-African population from Guadeloupe, in several instances some African populations were equally or more susceptible than the Guadeloupe population. Moreover, the relative level of susceptibility between African mosquito populations depended on the DENV strain, indicating genetically specific interactions. We conclude that unlike ZIKV susceptibility, there is no clear-cut dichotomy in DENV susceptibility between African and non-African Ae. aegypti. DENV susceptibility of African Ae. aegypti populations is highly heterogeneous and largely governed by the specific pairing of mosquito population and DENV strain. Author summaryAfrican populations of the mosquito Aedes aegypti are usually thought to be less likely to get infected by flaviviruses compared to Ae. aegypti mosquitoes found outside Africa. While this has been well-demonstrated for Zika virus, it is not clear if the same is true for dengue virus, which is the most common flavivirus in humans. Studying this is complicated by the strain diversity of dengue virus, including four main genetic types, potentially causing different interactions. In this study, we compared several mosquito populations and found that, in general, African mosquitoes were less likely to get infected by dengue virus compared to mosquitoes from outside Africa. However, in some cases, African mosquitoes were just as or even more likely to get infected. The specific strain of dengue virus also influenced how likely African mosquitoes were to get infected, showing that the relationship between African mosquitoes and dengue virus is complex.

microbiology↗

bioRxiv2022

Dating the origin and spread of specialization on human hosts in Aedes aegypti mosquitoes

The globally invasive mosquito subspecies Aedes aegypti aegypti is a highly effective vector of human arboviruses because it specializes in biting humans and breeding in human habitats. Recent work suggests that specialization first arose as an adaptation to long, hot dry seasons in the West African Sahel, where Ae. aegypti is forced to rely on human-stored water for breeding. However, rainfall patterns in this region have changed dramatically over the past 10-20 thousand years, and we do not yet know exactly when specialization occurred. Here we use whole-genome cross-coalescent analysis to date the emergence of human specialist populations in the Sahel and thus further probe the climate hypothesis. Importantly, we take advantage of the known migration of human-specialist populations out of Africa during the Atlantic Slave Trade to calibrate the coalescent clock and thus obtain a more precise estimate of the older evolutionary event than would otherwise be possible. We find that human-specialist mosquitoes diverged rapidly from ecological generalists approximately 5,000 years ago, which corresponds to the end of the African Humid Period--a time when the Sahara dried and water stored by humans became a uniquely stable, aquatic niche in the Sahel. We also use population genomic analyses to date a previously observed influx of human-specialist alleles into major West African cities, where mosquitoes tend to be more attracted to humans than in nearby rural populations regardless of climate. In this case, the characteristic length of tracts of human-specialist ancestry present on a generalist genetic background in Kumasi, Ghana and Ouagadougou, Burkina Faso suggests the change in behavior occurred during rapid urbanization over the last 20-40 years. Taken together, we show that the timing and ecological context of two previously observed shifts towards human biting in Ae. aegypti differ; climate was likely the original driver, but urbanization has become increasingly important in recent decades. Understanding the changing relationship between mosquitoes and humans over time is critical for predicting and managing burdens of mosquito-borne disease.

evolutionary biology↗

bioRxiv2022

Transmission risk assessment of Aedes-borne arboviral diseases in Accra, Ghana

BackgroundDengue, Zika and Chikungunya are Aedes-borne viral diseases that have risen to become great global health concerns in the past years. Several countries in Africa have reported outbreaks of these diseases and despite Ghana sharing borders with some of such countries, it remains free of these outbreaks. Recent studies in Ghana have revealed that there are antibodies and viral RNA of the Dengue virus serotype-2 among individuals in some localities in the Greater Accra Region. This is an indication of a possible silent transmission ongoing in the population, hence the need to assess the risk of transmission of these viruses within the country. This cross-sectional study, therefore, assessed the risk of transmission of Dengue, Zika and Chikungunya viruses in a domestic/peri-domestic (Madina) and a forest (Achimota Forest) population in the Greater Accra Region, Ghana. Methodology/FindingsAll stages of the Aedes mosquito (egg, larvae, pupae and adults) were collected around homes and in the forest area for estimation of risk indices. All eggs and immature stages were reared to adults and morphologically identified. The predominant species of Aedes mosquitoes identified from both sites were Aedes aegypti (98 % in Madina and 98.1% in Achimota forest). Aedes albopictus, an important arbovirus vector, was identified only in Madina at a prevalence of 1.5% but Achimota forest had the higher species diversity. Both study sites recorded high risk indices; Madina: Positive Ovitrap Index = 26.6%, Container Index = 36.8%, House Index = 19.8%, Breteau Index = 70.4%; Achimota: Positive Ovitrap Index = 34.2% and Container Index = 67.9%. RT-PCR to detect the presence of Dengue, Chikungunya and Zika viruses was negative for all pools tested. ConclusionAll entomological risk indicators estimated showed that both sites had a high potential of an outbreak of arboviral diseases following the introduction of these viruses. Author SummaryThe detection of antibodies and viral RNA of the dengue virus serotype 2 in some communities in the urban city of Accra, suggested the possibility of silent transmission of arboviral disease within the city. We assessed the risk of arboviral disease transmission using entomological risk indices. The study was a cross-sectional study conducted in a forest and peri domestic setting located in the southern urban city of Accra. The different stages of the Aedes mosquito were collected and, houses and containers positive for Aedes mosquitoes were also noted. The Breteau (BI), House (HI), Container (CI) and Positive ovitrap (POI) indices were determined. Real Time-PCR was conducted to determine the presence of Dengue, Zika and Chikungunya viruses in the larvae and adults collected. Aedes aegypti was the most common species identified from both sites. Aedes albopictus another competent arbovirus vector was identified in the peri-domestic site. Almost all risk indices recorded for both sites were higher than the WHO thresholds allowed for these indices. However, real time-PCR to detect the presence of Dengue, Chikungunya and Zika viruses was negative. The high entomological risk indicators estimated showed that both sites had a great potential of an outbreak following the introduction of these viruses, and a well-structured surveillance for these vectors is highly recommended. The detection of the presence of Ae. albopictus, an invasive species is also of great concern.

ecology↗

bioRxiv2020

Climate and urbanization drive mosquito preference for humans

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 characterize the behaviour of mosquitoes from 27 sites scattered across the species ancestral range in sub-Saharan Africa, revealing previously unrecognized diversity in female preference for human versus animal odor. We then use modelling to show that this diversity can be almost fully predicted by two ecological factors - dry season intensity and human population density. Finally we integrate this information with whole genome sequence data from 345 individual mosquitoes to identify a single underlying ancestry component linked to human preference, with genetic changes concentrated in a few key chromosomal regions. Our findings strongly 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 changes in human population density are likely to drive future mosquito evolution. Rapid urbanization may drive a shift to human-biting in many cities across Africa by 2050.

evolutionary biology↗

bioRxiv2019

Evaluation of DNA extracted from blood filter spots and eluates processed for enzyme linked immunosorbent assay (ELISA)

Dried filter blood spots have become a significant blood collection method for screening individuals for clinical purposes. When used for ELISAs, they are normally discarded after the blood has been eluted. However, they may still be useful for extraction of DNA for molecular-based assays. The aim of this work was to determine the integrity of DNA extracted from filter paper spots from which blood has initially been eluted for ELISA with sample dilution buffer (SDB) and phosphate buffered saline (PBS). DNA was extracted from the eluted filter spots, the eluate, and dried blood filter spots (controls) using spin column extraction. The quality and quantity of the extracted DNA was assessed and used for PCR to further evaluate their usefulness in molecular assays. Concentration of DNA obtained was dependent on the buffer used for processing the filter blood blots. Accounting for the DNA concentration obtained from dried blood spots, which were used as controls, DNA extracted from the already eluted blood spots were 32 times higher in PBS than SDB processed filter paper. The ratio was even higher for the eluates, which were 57 times higher in PBS than SDS eluates. SDB eluates had significantly higher average DNA concentration than their eluted filter paper, but their purity ratios were similar. 85% PCR success rate was achieved with the DNA samples. Useful DNA can be extracted from blood spots after it has been eluted with SDB. Although the DNA concentration and purity may be low, the DNA could be useful for rather simple PCR assays. Author SummaryCollection of blood onto filter paper has become an accepted method for screening individuals for clinical and public health purposes since the 1960s. This method of blood collection has become increasingly popular due to its ease and convenience in collection and transportation. The use of dried blood spots for clinical evaluations and research has become very significant. For research purposes, DBS when used for ELISAs are discarded after single use. DNA may however be extracted from the used filter blots and used for molecular assays. The concentration of DNA obtained may be low but simple assays like PCR could be done using the DNA extracted from the eluted filter spot.

molecular biology↗