Biology subjects

Seck, M. T.

Publications and source records attributed to Seck, M. T..

6 recordsLinked to original sources

bioRxiv2026

Population genetic structure and connectivity of Glossina palpalis gambiensis and G. morsitans submorsitans in Southwestern Senegal

In sub-Saharan Africa, human and animal health is threatened by African trypanosomoses. These diseases are caused by trypanosomes that are transmitted primarily by tsetse flies. Vector control remains one of the most effective strategies for reducing disease transmission, but requires a minimum level of knowledge of the population biology, ecology and dispersal patterns of the targeted vectors. In this respect, population genetic approaches using appropriate polymorphic genetic markers can provide valuable tools to inform and optimize control strategies. Senegal is currently engaged in a national tsetse control programme and has been identified as a study country within a European Union-funded research initiative, COMBAT (controlling and progressively minimizing the burden of animal trypanosomosis). Baseline entomological studies are currently underway in the Sine Saloum (Southern Senegal). This preliminary study aimed to characterize the population genetic structure and connectivity of tsetse fly species present in Southern Senegal, Glossina palpalis gambiensis and G. morsitans submorsitans, in order to assess their population sizes (geographically and demographically), population densities and dispersal capacities. The two species exhibited markedly contrasting population structures. The first, G. p. gambiensis, displayed an isolation by distance with rather dense subpopulations exchanging immigrants at short distances (1.6 km/generation) and continuously from Sine-Saloum to Casamance, in line with the apparent continuity of the mangrove network found along this coast. In contrast, G. m. submorsitans presented a relatively dense population over a 75 km wide area, fragmented into sparsely distributed, very dense and interconnected pockets. These findings indicate that G. p. gambiensis likely constitutes a large metapopulation comprising 3266 effective individuals on average (and up to 7765), whereas G. m. submorsitans appeared as a single and large population, scattered in small pockets that could be readily replenished by immigrants from distant areas in case of control. These results suggest that elimination is not a realistic option for any of these two populations. Alternatively, localized integrated pest management is likely to be the most effective approach for controlling the negative effects of these biting flies on domestic animals, by reducing trypanosome transmission. However, further entomological investigations and the use of more informative genetic markers are needed to obtain a more precise understanding of the epidemiological processes involved.

ecology↗

bioRxiv2023

Host influence on the eukaryotic virome of sympatric mosquitoes and abundance of diverse viruses with a broad host range.

Mosquitoes harbor a large diversity of eukaryotic viruses. Those viromes probably influence mosquito physiology and the transmission of human pathogens. Nevertheless, their ecology remains largely unstudied. Here, we address two key questions in virome ecology. First, we assessed the influence of mosquito species on virome taxonomic diversity and relative abundance. Contrary to most previous studies, the potential effect of the habitat was explicitly included. Thousands of individuals of Culex poicilipes and Culex tritaeniorhynchus, two vectors of viral diseases, were concomitantly sampled in three habitats over two years. A total of 95 viral taxa from 25 families were identified with meta-transcriptomics, with 75% of taxa shared by both mosquitoes. Viromes significantly differed by mosquito species but not by habitat. Differences were largely due to changes in relative abundance of shared taxa. Then, we studied the diversity of viruses with a broad host range. We searched for viral taxa shared by the two Culex species and Aedes vexans, another disease vector, present in one of the habitats. Twenty-six out of the 163 viral taxa were found in the three mosquitoes. These taxa encompassed 14 families. A database analysis supported broad host ranges for many of those viruses, as well as a widespread geographical distribution. Thus, the viromes of mosquitoes from the same genera mainly differed in the relative abundance of shared taxa, whereas differences in viral diversity dominated between mosquito genera. Whether this new model of virome diversity and structure applies to other mosquito communities remains to be determined.

ecology↗

bioRxiv2020

A new automated chilled adult release system for the aerial distribution of sterile male tsetse flies

BackgroundTsetse flies transmit trypanosomes that cause the debilitating diseases human African trypanosomosis (HAT) or sleeping sickness in humans and animal African trypanosomosis (AAT) or nagana in livestock. The riverine tsetse species Glossina palpalis gambiensis Vanderplank (Diptera: Glossinidae) inhabits riparian forests along river systems in West Africa. The Government of Senegal has embarked on a project to eliminate a population of this tsetse species from the Niayes area with the objective to manage AAT in this area. The project is implemented following an area-wide integrated pest management approach with an SIT component. The SIT can only be successful when the sterile males that are released in the field are of high biological quality, i.e. have the same dispersal capacity, survival and competitiveness as their wild counterparts. To date, sterile tsetse males have been released by air using biodegradable cardboard cartons that were manually dropped from a fixed-wing aircraft or gyrocopter. The cardboard boxes are however expensive, and the system is rather cumbersome to implement. MethodsA new prototype of an automated chilled adult release system (Bruno Spreader Innovation, (BSI)) for tsetse flies was tested for its accuracy (in counting numbers of sterile males as loaded into the machine), release rate consistency and impact on quality of the released males. The impact of the release process was evaluated on several performance indicators of the irradiated male flies such as flight propensity, survival, mating competitiveness, premating and mating duration, and insemination rate of mated females. ResultsThe BSI release system counted with a consistent accuracy and released homogenously tsetse flies at the lowest motor speed (0.6 rpm). In addition, the chilling conditions (6 {+/-} 1 {degrees}C) and the release process (passing of flies through the machine) had no significant negative impact on the males flight propensity. No significant differences were observed between the control males (no irradiation and no exposure to the release process), irradiated males (no exposure to the release process) and irradiated males exposed to the release process with respect to mating competitiveness, premating period and mating duration. Only survival of irradiated males that were exposed to the release process was reduced ([~]2 folds), irrespective of whether the males were held with or without feeding. ConclusionAlthough the release process had a negative effect on survival of the flies, the data of the experiments indicate that the BSI machine holds promise for use in tsetse SIT programmes. The results of this study will now need to be confirmed under operational field conditions in West Africa.

pathology↗

bioRxiv2019

Feeding behavior of Aedes (Aedimorphus) vexans arabiensis, a Rift valley fever virus vector in the Ferlo pastoral ecosystem of Senegal.

Host-vector contact is a key factor in vectorial capacity assessment and thus the transmission of mosquito-borne viruses such as Rift Valley Fever (RVF), an emerging zoonotic disease of interest in West Africa. The knowledge of the host-feeding patterns of vector species constitutes a key element in the assessment of their epidemiological importance in a given environment. The aim of this work was to identify the blood meal origins of Aedes vexans arabiensis Patton (Diptera: Culicidae), the main vector of RVF virus in the Ferlo pastoral ecosystem of Senegal. Engorged female mosquitoes were collected in Younoufere in the pastoral ecosystem in the Ferlo region during the 2014 rainy season. CDC light CO2-baited traps were set at six sites for two consecutive nights every month from July to November. Domestic animals present around traps were identified and counted for each trapping session. Blood meal sources of engorged mosquitoes were identified using a vertebrate-specific multiplexed primer set based on cytochrome b. Blood meal sources were successfully identified for 319 out of 416 blood-fed females (76.68%), of which 163 (51.1%) were single meals, 146 (45.77%) mixed meals from two different hosts and 10 (3.13%) mixed meals from three different hosts. Aedes vexans arabiensis fed preferentially on mammals especially on horse compared to other hosts (P < 0.001). Proportions of single and mixed meals showed significant temporal (P < 0.001) and spatial variations (P < 0.001) according to hosts availability. Aedes vexans arabiensis shows an opportunistic feeding behavior depending on the host availability. Results were discussed in relation with the Rift valley fever virus transmission and vector involvement as well as its primary hosts.

epidemiology↗

bioRxiv2018

Chilling, irradiation and transport of male Glossina palpalis gambiensis pupae: effect on the emergence, flight ability and survival.

BackgroundThe sterile insect technique (SIT) requires mass-rearing of the target species, irradiation to induce sexual sterility and transportation from the mass-rearing facility to the target site. Those treatments require several steps that may affect the biological quality of sterile males. This study has been carried out to evaluate the relative impact of the chilling, irradiation and transport on emergence rate, flight ability and survival of sterile male tsetse flies Glossina palpalis gambiensis.\n\nResultsChilling, irradiation and transport all affected the quality control parameters studied. The emergence rate was significantly reduced by long chilling periods and transport, i.e. from 92% at the source insectary to 78% upon arrival in Dakar. Flight ability was affected by all three parameters with 31% operational flies lossed between the source and arrival insectaries. Only survival under stress was not affected by any of the treatments.\n\nConclusionThe chilling period and transport were the main treatments which impacted significantly the quality of sterile male pupae. Therefore, the delivery of sterile males was divided over two shipments per week in order to reduce the chilling time and improve the quality of the sterile males. Quality of the male pupae may further be improved by reducing the transport time and vibration during transport.\n\nAuthor summaryTsetse fly and the disease it transmits, trypanosomosis, remain an enormous challenge in several countries in sub-Saharan Africa. The use of the Sterile Insect Technique (SIT) has become one of the components of the eradication of tsetse fly in Africa. The sterile insect technique (SIT) requires mass-rearing of the target species, irradiation to induce sexual sterility and transportation from the mass-rearing facility to the target site. In this study, we demonstrate the relative impact of the chilling, irradiation and transport on the emergence rate, the flight ability and the survival of sterile male tsetse flies Glossina palpalis gambiensis. We found that the chilling, irradiation and transport affected the emergence rate and flight ability. But the survival of the sterile male under stress was not affected by any of the treatments. Hence, the quality of the male pupae may further be improved by reducing the transport time and vibration during transport.

physiology↗

bioRxiv2018

Environmental heterogeneity drives tsetse fly population dynamics

A spatially and temporally heterogeneous environment may lead to unexpected population dynamics, and knowledge still is needed on which of the local environment properties favour population maintenance at larger scale. As regards pathogen vectors, such as tsetse flies transmitting human and animal African trypanosomosis, such a knowledge is crucial for proposing relevant management strategy. We developed an original mechanistic spatio-temporal model of tsetse fly population dynamics, accounting for combined effects of spatial complexity, density-dependence, and temperature on the age-structured population, and parametrized with field and laboratory data. We confirmed the strong impact of temperature and adult mortality on tsetse populations. We showed that patches with the lowest mean temperatures and lowest variations act as refuges when adult mortality is homogeneously increased. Our results highlighted the importance of baseline data collection to characterize the targeted ecosystem before any control measure is implemented to maximize its efficiency.

ecology↗