Biology subjects

Sedda, L.

Publications and source records attributed to Sedda, L..

7 recordsLinked to original sources

bioRxiv2025

Spatially-explicit genomics of An. gambiae s.l uncovers fine-scale population structure and mechanisms of insecticide resistance

Progress in malaria control in sub-Saharan Africa is stalling, partly due to the spread of insecticide resistance in Anopheles vectors. Monitoring the evolution of insecticide resistance alleles and their spatial heterogeneity is important for malaria control programmes, and genomic surveillance has emerged as a pivotal tool for this purpose. Earlier genomics research has typically employed convenience-based sampling, and research has yet to be performed to optimise sampling regimens for malaria vector genomics. In an earlier study, we developed a spatially explicit sampling framework that considers the underlying ecology to enable sampling mosquitoes with reduced bias. We applied this framework to sample and perform whole-genome sequencing on 485 individual specimens of An. gambiae s.l mosquitoes from Obuasi, central Ghana, an area with extensive gold mining activities. In this region, An. gambiae s.l have been documented as highly resistant to multiple insecticides, including pyrethroids used for the treatment of bed-nets. High resolution of fine-scale population structure enabled the detection of isolation-by-distance in An. coluzzii in Obuasi, whilst finding that at this scale, geographic distance, rather than the underlying habitat, drives population structure. We examine methods to estimate mosquito kinship, demonstrating that polymorphic chromosomal inversions significantly confound established analytical tools, while revealing how the mosquitos chromosome architecture generates high variance in genetic relatedness among kin. Using genome-wide selection scans and clustering, we discover the novel mutations Gste2-F120L and Cyp9K1-N224I in detoxification enzymes that are driving selective sweeps, likely in response to insecticidal pressure. We find that the frequencies of some resistance variants are associated with artisanal-gold mines, and elucidate the continued evolution of the Voltage-gated sodium channel, the target of pyrethroid insecticides. Overall, we show that sampling vectors strategically may enhance our ability to perform effective genomic surveillance.

genomics↗

bioRxiv2023

Spatially explicit sampling frameworks to identify regions of increased mosquito abundance

Vector control interventions often lack comprehensive information on vector population distribution and dynamics. This knowledge gap poses challenges in targeting interventions effectively, especially in areas with heterogeneous transmission and where complementary vector control tools may be required to achieve sustained impact on disease transmission. In this study, we implemented a spatially explicit sampling framework for improved vector surveillance in coastal Kenya. Our stratified lattice with close pair sampling design aimed to characterise the vector dynamics of the primary malaria-transmitting species in the area and assess the ecotype classifications effectiveness at identifying clear population patterns. The study collected 3,621 mosquitoes, with An. funestus s.l. being the most abundant malaria vector. The inclusion of the ecotype classification significantly improved spatial abundance model estimates for An. gambiae and Culex spp. Wetlands, topographic wetness index, and proximity to rivers were associated with increased mosquito abundance. Spatial modelling revealed high abundance regions near the Galana-Sabaki River. Our study demonstrates the applicability of a reproducible spatial sampling approach to identify areas with high vector abundance and inform targeted vector control strategies. The study highlights the importance of ecological stratification and a spatial explicit sampling approach for predicting mosquito presence when prior data is limited and underscores the potential for refining future sampling for control efforts.

ecology↗

bioRxiv2023

Development and deployment of improved Anopheles gambiae s.l. field surveillance by adaptive spatial sampling design

Accurate assessments of vector occurrence and abundance, particularly in widespread vector-borne diseases such as malaria, is essential for efficient deployment of disease surveillance and control interventions. This study emphasizes the need for flexible spatial sampling designs that can capture the dynamic relationships between disease vector species and the environment. Although previous studies have examined the benefits of adaptive sampling for disease hotspot identification (mostly by simulations), limited research has been conducted on field surveillance of malaria vectors. Here, an adaptive spatial sampling design targeting potential and uncertain An. gambiae hotspots, a major malaria vector in sub-Saharan Africa, is presented. The first phase of the proposed design involved ecological zone delineation and a proportional lattice with close pairs sampling design to maximise spatial coverage, representativeness of ecological zones and vector spatial autocorrelation (by the employment of close pairs). In the second phase, a spatial adaptive sampling design targeted high-risk areas with the largest uncertainty. For the second phase, the sample size was reduced compared to the first phase, but predictions improved for out-of-sample and training data. However, the overall model uncertainty increased, highlighting the trade-off in multi-criteria adaptive sampling designs. It is important that future research focuses on these trade-offs to reduce the timescale for effective malaria control and elimination efforts.

ecology↗

bioRxiv2023

Newly born mesenchymal cells disperse through a rapid mechanosensitive migration

Embryonic mesenchymal cells are dispersed within an extracellular matrix but can coalesce to form condensates with key developmental roles. Cells within condensates undergo fate and morphological changes, and induce cell fate changes in nearby epithelia to produce structures including hair follicles, feathers or intestinal villi. Here, by imaging of mouse and chicken embryonic skin, we find that mesenchymal cells undergo much of their dispersal in early interphase, in a stereotyped process of displacement driven by three hours of rapid and persistent migration, followed by a long period of low motility. The cell division plane and the elevated migration speed and persistence of newly born mesenchymal cells are mechanosensitive, aligning with tension in the tissue. This early G1 migratory behaviour disperses mesenchymal cells and allows the daughters of recent divisions to travel long distances to enter dermal condensates, demonstrating an unanticipated effect of a cell cycle sub-phase on core mesenchymal behaviour. HighlightsO_LIAfter mesenchymal cell division the speed and persistence of daughter cell migration is elevated for 180 minutes C_LIO_LIMesenchymal cell division and migration are directed by tissue tension C_LIO_LINewly born mesenchymal cells are uniquely responsive to tissue strain C_LIO_LINewly born mesenchymal cells are preferentially recruited to dermal condensates C_LIO_LIIncreased dispersal of newly born cells enables long distance travel to dermal condensates C_LI Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=200 SRC="FIGDIR/small/525849v1_ufig1.gif" ALT="Figure 1"> View larger version (46K): org.highwire.dtl.DTLVardef@c69b4dorg.highwire.dtl.DTLVardef@fe0295org.highwire.dtl.DTLVardef@5b9f61org.highwire.dtl.DTLVardef@13ca1aa_HPS_FORMAT_FIGEXP M_FIG C_FIG

cell biology↗

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↗

bioRxiv2019

Volatile organic chemical analyser (eNose) diagnosis of dogs naturally infected with visceral leishmaniasis in Brazil

Visceral leishmaniasis (VL) in Brazil is a neglected vector-borne tropical parasitic disease that is responsible for several thousand human deaths every year. The numbers of cases more than doubled between 1990 and 2016. Transmission occurs when sand flies become infected after feeding on infected dogs (the reservoir host) and then subsequently on humans. A major component of the VL control effort is the identification and euthanasia of infected dogs to remove them as a source of infection. Rapid, accurate identification of infected dogs would be key to this strategy. Here we demonstrate the potential of a volatile organic chemical analyser (eNose) to rapidly and accurately identify dogs infected with Leishmania infantum parasites. The eNose could discriminate between the odours present in the hair of infected and uninfected dogs with greater than 95% sensitivity and 95% specificity. The device was sufficiently sensitive to be able to identify infected dogs even when parasite loads in the circulating blood were very low. Future improvements to VOC analyser technology, portability and ease of use suggest that this methodology could significantly improve the diagnosis of VL infected dogs in Brazil and elsewhere and with other parasitic diseases such as Malaria, Chagas Disease and Leishmania in humans.

zoology↗

bioRxiv2018

Improved spatial ecological sampling using open data and standardization: an example from malaria mosquito surveillance

Vector-borne disease control relies on efficient vector surveillance, mostly carried out using traps whose number and locations are often determined by expert opinion rather than a rigorous quantitative sampling design. In this work we first propose a framework for ecological sampling design which in its preliminary stages can take into account environmental conditions obtained from open data (i.e. remote sensing and meteorological stations). These environmental data are used to delimit the area into ecologically homogenous strata. By employing a model-based sampling design, the traps are deployed among the strata using a mixture of random and grid locations which allows balancing predictions and fitting accuracies. Sample sizes and the effect of ecological strata on sample sizes are estimated from previous sampling campaigns. Notably, we found that a configuration of 30 locations with 4 households each (120 traps) will have a similar accuracy in the estimates of mosquito abundance as 300 random samples. In addition, we show that random sampling independently from ecological strata, produces biased estimates of the mosquito abundance. Finally, we propose standardizing reporting of sampling designs to allow transparency and repetition / re-use in subsequent sampling campaigns.

ecology↗