Biology subjects

Da, D. F.

Publications and source records attributed to Da, D. F..

7 recordsLinked to original sources

bioRxiv2025

Anopheles mosquitoes exposed to long-acting antimalarials via drug-spiked bloodmeal absorb drug but do not suffer fitness costs

The World Health Organizations recommendations regarding the use of antimalarials for the prevention of malaria in endemic areas have greatly expanded, allowing more flexibility in the demographic groups and regions where chemoprevention and mass treatment are acceptable. An overlooked aspect of expanding human population-level drug exposure is the downstream impact of ingested drug on the mosquito vector. Data suggest both infected and uninfected Anopheles mosquitoes re-feed often with [≥]4 blood meals during their lifespan. This provides repeated opportunities for mosquitoes to ingest drug via bloodmeals taken from people with antimalarials in the bloodstream and raises questions as to whether exposure may impact the mosquito itself, and/or parasites developing within the infected mosquito. We investigated the impact of exposure to physiologic levels of commonly used long-acting human antimalarials in the Anopheles mosquito via drug-spiked blood feeds. We did not observe any significant differences in mosquito feeding, behavior, fertility, or viability after ingestion of amodiaquine, desethylamodiaquine, piperaquine, and sulfadoxine-pyrimethamine in either lab-reared An. gambiae or field-derived An. coluzzii mosquitoes. Interrogating drug distribution within mosquitoes utilizing LC-MS/MS, desethylamodiaquine, the longer-acting active metabolite of amodiaquine, was fed at 2 concentrations (1/2X and 2X Cmax) with drug subsequently detected in a dose-dependent manner in pooled whole mosquitoes, midguts and hemolymph. This was significant for whole mosquitoes harvested at 24hrs and 120hrs, and midguts harvested at 24hrs. Between 24 to 120 hrs, drug decreased in midguts but increased in hemolymph. Our results show biochemical evidence of antimalarial absorption into Anopheles hemolymph following bloodmeal ingestion. These studies lay the foundation for future work to assess the impact of vector-stage antimalarial drug exposure on parasite progression throughout development in the mosquito, which could in turn have important implications for transmission dynamics and drug resistance spread. Author summaryDrug resistance to first-line antimalarials has emerged in multiple African countries. A better understanding of antimalarial drug resistance emergence and spread is critical in preventing further morbidity and mortality. Millions regularly receive antimalarials for prophylaxis and mass treatment that are purposefully long-acting. Anopheles mosquitoes re-feed frequently, and these malaria vectors (both infected and uninfected) routinely feed on people whose blood contains these long-acting antimalarials. Parasites take approximately 10 days to develop within the mosquito. There is published precedent that several antimalarials can act upon vector-stage parasites, yet any potential impact of antimalarials on mosquitoes and/or parasites developing within has been largely overlooked. We questioned whether antimalarials ingested in mosquito bloodmeals could influence parasite development and drug resistance selection. As initial investigations, we exposed uninfected Anopheles mosquitoes to commonly used long-acting antimalarials via drug-spiked bloodmeals, mimicking predicted physiologic drug exposure. Investigated drugs did not impact mosquito viability. However, mass spectrometry confirmed drug absorption in whole mosquitoes, as well as within midguts and circulatory fluid, several days after feeding, demonstrating that mosquitoes can ingest key drugs without suffering fitness costs, and these drugs can persist in mosquitoes. This highlights the potential for antimalarials to impact parasite development and drug resistance selection within the mosquito.

microbiology↗

bioRxiv2024

Near-infrared spectroscopy discriminates mass-reared sterile and wild tsetse flies

In the frame of the Pan African Tsetse and Trypanosomosis Eradication Campaign, an integrated pest management approach has been adopted to manage tsetse fly populations using a sterile insect technique (SIT).. Monitoring the efficacy of the SIT programs requires the discrimination between wild and sterile males collected in monitoring traps. The discrimination between sterile and wild males relies mainly on marking of sterile males with a fluorescent dye powder (before the releases) and their identification using a fluorescence camera and /or a fluorescence microscope. However, the accuracy of this method remains limited with defective marking and wild flies contaminated with a few dye particles in the monitoring traps. The molecular techniques developed to discriminate doubtful flies are costly for endemic countries. Here, we investigate the ability of a new generation monitoring tool, the near-infrared spectroscopy (NIRS) to discriminate between lab-reared Glossina palpalis gambiensis and their counterparts in the field. NIRS technique discriminates wild flies males with 86% accuracy to Glossina palpalis gambiensis males reared in an insectarium. Interestingly, the prediction accuracy between wild and laboratory-reared flies improved to 88% when the Glossina lab colony flies were irradiated. In light of these results, NIRS can discriminate tsetse flies even when identification with the UV camera is doubtful. However, more investigations integrating some natural variables are required before the validation of the technical as a complementary method for potential future tsetse eradication programs.

evolutionary biology↗

bioRxiv2022

Intervention reducing malaria parasite load in vector mosquitoes: no impact on Plasmodium falciparum extrinsic incubation period and the survival of Anopheles gambiae

In the fight against malaria, transmission blocking interventions (TBIs) are promising approaches to complement conventional tools. They aim to prevent the infection of the vectors and thereby reduce the subsequent exposure of a human population to infectious mosquitoes. The effectiveness of these approaches has been shown to depend on the initial intensity of infection in mosquitoes, often measured as the mean number of oocysts resulting from an infectious blood meal prior to intervention. In mosquitoes exposed to a high infection load, current TBI candidates are expected to be ineffective at completely blocking infection but will decrease parasite load and therefore, potentially also affect key parameters of vector transmission. The present study aims to investigate the consequences of changes in oocyst intensity on downstream parasite development and mosquito survival. To address this, we experimentally produced different infection intensities in Anopheles gambiae females by diluting gametocytes from natural Plasmodium falciparum isolates and used a newly developed non-destructive method based on the exploitation of mosquito sugar feeding to track parasite and mosquito life history traits throughout sporogonic development. Our results indicate that P. falciparum extrinsic incubation period (EIP) and mosquito survival did not vary with parasite density but differed significantly between parasite isolates. Our results do not identify here unintended consequences of the decrease of parasite loads in mosquitoes on the parasite incubation period or on mosquito survival, two key parameters of vectorial capacity, and hence support the transmission blocking strategies to control malaria. Author summaryIn the fight against malaria, it is recognized that the use of several complementary strategies is necessary to significantly reduce transmission and improve human health. Among these, transmission blocking strategies aim at blocking the development of the parasites within the mosquito vectors. This approach should prevent infection in most of mosquitoes feeding on infectious hosts and thus block the transmission. However, in some cases it may only reduce parasite load without fully clearing the infection. Here we identified potential risks: if reducing parasite load would reduce the incubation period of the parasite in the mosquitoes or increase the longevity of the mosquitoes, undesirable consequences may occur with an increased efficiency of these mosquitoes to transmit parasites to human. We therefore tested these hypotheses and experimentally produced different infection loads in vector mosquitoes Anopheles gambiae by using dilutions of Plasmodium falciparum isolates from naturally infected human donors. We observed that the longevity of the mosquitoes and the incubation period of the parasites were not affected by the parasite load. This is not consistent with the unintended risks that we investigated and thus strengthens the potential of transmission blocking interventions in the toolbox to combat malaria.

evolutionary biology↗

bioRxiv2020

Using a non-destructive sugar-feeding assay for sporozoite detection and estimating the extrinsic incubation period of Plasmodium falciparum in mosquito vectors

Despite its epidemiological importance, the time Plasmodium parasites take to achieve development in the vector mosquito (the extrinsic incubation period, EIP) remains poorly characterized. A novel non-destructive assay designed to estimate EIP in single mosquitoes, and more broadly to study Plasmodium - Anopheles vectors interactions, is presented. The assay uses small pieces of cotton wool soaked in sugar solution to collect malaria sporozoites from individual mosquitoes during sugar feeding to monitor infection status over time. This technique has been tested across four natural malaria mosquito species of Africa and Asia, six parasite isolates of Plasmodium falciparum, and across a range of temperatures relevant to malaria transmission in field conditions. We find that monitoring individual infectious mosquitoes is feasible, although due to the frequency of mosquito sugar feeding and inter-individual variation in infection intensity, there is inherent risk that this technique will result in some false negatives. The sensitivity rate ranged from 0.27 to 0.81 depending on mosquito species and on infection intensity in mosquitoes used to collect saliva. Using this non-destructive technique, the estimated median extrinsic incubation period of P. falciparum at 27{degrees}C was 11 to 14 days depending on mosquito species and parasite isolate. Long-term individual tracking also revealed that sporozoite transfer onto cotton wool can occur at least until day 40 post-infection. In addition to contributing to a better understanding of EIP and mosquito to human transmission with implications for improving epidemiological models, this technique also allows to link different transmission traits at the mosquito individual level. As one example, we found a significant relationship between EIP and mosquito lifespan, with short individual EIP associated with short mosquito lifespan. Correlations between mosquito/parasite traits often reveal trade-offs and constraints and have important implications for understanding the evolution of parasite transmission strategies.

molecular biology↗

bioRxiv2020

Functional data analysis techniques to improve the generalizability of near-infrared spectral data for monitoring mosquito populations

Near infrared spectroscopy is increasingly being used as an economical method to monitor mosquito vector populations in support of disease control. Despite this rise in popularity, strong geographical variation in spectra has proven an issue for generalising predictions from one location to another. Here, we use a functional data analysis approach--which models spectra as smooth curves rather than as a discrete set of points--to develop a method that is robust to geographic heterogeneity. Specifically, we use a penalised generalised linear modelling framework which includes efficient functional representation of spectra, spectral smoothing and regularisation. To ensure better generalisation of model predictions from one training set to another, we use cross-validation procedures favouring smoother representation of spectra. To illustrate the performance of our approach, we collected spectra for field-caught specimens of Anopheles gambiae complex mosquitoes - the most epidemiologically important vector species on the planet - in two sites in Burkina Faso. Using these spectra, we show how models trained on data from one site can successfully classify morphologically identical sibling species in another site, over 250km away. Whilst we apply our framework to species prediction, our unified statistical framework can, alternatively, handle regression analysis (for example, to determine mosquito age) and other types of multinomial classification (for example, to determine infection status). To make our methods readily available for field entomologists, we have created an open-source R package mlevcm. All data used is publicly also available.

bioinformatics↗

bioRxiv2019

High Plasmodium infection intensity in naturally infected malaria vectors in Africa

The population dynamics of human-to-mosquito malaria transmission in the field has important implications for the genetics, epidemiology and control of malaria. The number of oocysts in oocysts positive mosquitoes developing from a single, naturally acquired infectious blood meal (herein referred to as parasite exposure) greatly influence the effectiveness of transmission blocking interventions but still remains poorly documented. During a year-long analysis of malaria parasite transmission in Burkina Faso we caught and dissected wild malaria vectors to assess Plasmodium oocysts prevalence and load (the number of oocysts counted in mosquitoes with detectable oocysts) and the prevalence of salivary gland sporozoites. This was compared to malaria endemicity in the human population assessed in cross-sectional surveys. Data was analyzed using a novel transmission mathematical model to estimate the per-bite transmission probability and the average parasite exposure of mosquitoes for each location. Observed oocysts load and estimated parasite exposure in naturally infected mosquitoes is substantially higher than previous estimates (ranging from 3.2 to 24.5 according to seasons and locations) and indicates a strong positive association between parasite exposure of mosquitoes and parasite prevalence in human. This work suggests that highly infected mosquitoes may have a greater influence on the epidemiology and genetics of the parasite and that novel partially effective transmission blocking interventions may become more effective at halting transmission as parasite exposure is diminished.

ecology↗

bioRxiv2018

Detection of Plasmodium berghei infected Anopheles stephensi using near-infrared spectroscopy

BackgroundThe proportion of mosquitoes infected with malaria is an important entomological metric used to assess the intensity of transmission and the impact of vector control interventions. Currently the prevalence of mosquitoes with salivary gland sporozoites is estimated by dissecting mosquitoes under a microscope or using molecular methods. These techniques are laborious, subjective, and require either expensive equipment or training. This study evaluates the potential of near infra-red spectroscopy (NIRS) to identify laboratory reared mosquitoes infected with rodent malaria.\n\nMethodsAnopheles stephensi mosquitoes were reared in the laboratory and fed on Plasmodium berghei infected blood. After 12 and 21 days post-feeding mosquitoes were killed, scanned and analysed using NIRS and immediately dissected by microscopy to determine the number of oocysts on the midgut wall or sporozoites in the salivary glands. A predictive classification model was used to determine parasite prevalence and intensity status from spectra.\n\nResultsThe predictive model correctly classifies infectious and uninfectious mosquitoes with an overall accuracy of 72%. The false negative and false positive rates are, respectively, 30% and 26%. While NIRS was able to differentiate between uninfectious and highly infectious mosquitoes, differentiating between mid-range infectious groups was less accurate. Multiple scans of the same specimen, with repositioning the mosquito between scans, is shown to improve accuracy. On a smaller dataset NIRS was unable to predict whether mosquitoes harboured oocysts.\n\nConclusionsWe provide the first evidence that NIRS can differentiate between infectious and uninfectious mosquitoes. Currently the method has moderate accuracy and distinguishing between different intensities of infection is challenging. The classification model provides a flexible framework and allows for different error rates to be optimised, enabling the sensitivity and specificity of the technique to be varied according to requirements.

epidemiology↗