RESUMO
Spatio-temporally heterogeneous environments may lead to unexpected population dynamics. Knowledge is needed on local properties favouring population resilience at large scale. For pathogen vectors, such as tsetse flies transmitting human and animal African trypanosomosis, this is crucial to target management strategies. We developed a mechanistic spatio-temporal model of the age-structured population dynamics of tsetse flies, parametrized with field and laboratory data. It accounts for density- and temperature-dependence. The studied environment is heterogeneous, fragmented and dispersal is suitability-driven. We confirmed that temperature and adult mortality have a strong impact on tsetse populations. When homogeneously increasing adult mortality, control was less effective and induced faster population recovery in the coldest and temperature-stable locations, creating refuges. To optimally select locations to control, we assessed the potential impact of treating them and their contribution to the whole population. This heterogeneous control induced a similar population decrease, with more dispersed individuals. Control efficacy was no longer related to temperature. Dispersal was responsible for refuges at the interface between controlled and uncontrolled zones, where resurgence after control was very high. The early identification of refuges, which could jeopardize control efforts, is crucial. We recommend baseline data collection to characterize the ecosystem before implementing any measures.
Assuntos
Tripanossomíase Africana , Moscas Tsé-Tsé , Animais , Ecossistema , Humanos , Insetos Vetores , Dinâmica PopulacionalRESUMO
African animal trypanosomosis (AAT) was one of the main disease-related constraints to the development of intensive livestock production systems in the Niayes region of Senegal, a 30 km wide strip of land along the coast between Dakar and Saint-Louis. To overcome this constraint, the Government of Senegal initiated an area-wide integrated pest management programme combining chemical control tactics with the sterile insect technique to eradicate a population of the tsetse fly Glossina palpalis gambiensis Vanderplank, 1949 (Diptera, Glossinidae) in this area. The project was implemented following a phased conditional approach, and the target area was divided into three blocks treated sequentially. This study aims to assess the temporal dynamics of the prevalence of Trypanosoma spp. during the implementation of this programme. Between 2009 and 2022, 4,359 blood samples were collected from cattle and screened for trypanosomes using both the buffy coat and ELISA techniques, and PCR tests since 2020. The seroprevalence decreased from 18.9% (95%CI: 11.2-26.5) in 2009 to 0% in 2017-2022 in block 1, and from 92.9% (95%CI: 88.2-97) in 2010 to 0% in 2021 in block 2. The parasitological and serological data confirm the entomological monitoring results, i.e., that there is a high probability that the population of G. p. gambiensis has been eradicated from the Niayes and that the transmission of AAT has been interrupted in the treated area. These results indicate the effectiveness of the adopted approach and show that AAT can be sustainably removed through the creation of a zone free of G. p. gambiensis.
Title: Trypanosomose animale éliminée dans une importante région de production d'élevage au Sénégal suite à l'éradication d'une population de glossines. Abstract: La trypanosomose animale africaine (TAA) était l'une des principales contraintes pathologiques au développement de systèmes de production animale intensifs dans les Niayes du Sénégal, une bande de terre large de 30 km longeant la côte entre Dakar et Saint-Louis. Pour surmonter cette contrainte, le Gouvernement du Sénégal a lancé un programme de lutte intégrée à l'échelle de la zone combinant lutte chimique et technique de l'insecte stérile pour éradiquer une population de Glossina palpalis gambiensis Vanderplank, 1949 (Diptera, Glossinidae). Le projet a été mis en Åuvre selon une approche conditionnelle progressive, et la zone cible a été divisée en trois blocs, traités de manière séquentielle. L'objectif de cette étude était d'évaluer la dynamique temporelle de la prévalence de Trypanosoma spp. au cours de la mise en Åuvre du programme. Entre 2009 et 2022, 4 359 échantillons de sang ont été prélevés sur des bovins et ont fait l'objet d'un dépistage des trypanosomes à l'aide des techniques du buffy-coat et ELISA, ainsi que de test PCR depuis 2020. Dans le bloc 1, la séroprévalence est passée de 18,9 % (IC 95 % : 11,226,5) en 2009 à 0 % entre 20172022 et de 92,9 % (IC 95 % : 88,2-97) en 2010 à 0 % en 2021 pour le block 2. Les données parasitologiques et sérologiques confirment les résultats du suivi entomologique selon lesquels il est très probable que la population de Glossina palpalis gambiensis soit éradiquée des Niayes, et que la transmission de la TAA a été interrompue dans la zone traitée. Elles indiquent l'efficacité de l'approche adoptée, et montrent que la TAA peut être durablement éliminée grâce à la création d'une zone exempte de G. p. gambiensis.
Assuntos
Doenças dos Bovinos , Tripanossomíase Africana , Tripanossomíase , Animais , Bovinos , Gado , Senegal/epidemiologia , Estudos Soroepidemiológicos , Tripanossomíase Africana/epidemiologia , Tripanossomíase Africana/prevenção & controle , Tripanossomíase Africana/veterináriaRESUMO
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.
Assuntos
Culex , Especificidade de Hospedeiro , Mosquitos Vetores , Viroma , Animais , Viroma/genética , Culex/virologia , Mosquitos Vetores/virologia , Aedes/virologia , Culicidae/virologia , Ecossistema , Simpatria , Vírus/classificação , Vírus/genética , Vírus/isolamento & purificaçãoRESUMO
Tsetse flies are the cyclical vectors of trypanosomes, the causative agents of 'sleeping sickness' or human African trypanosomosis (HAT) in humans and 'nagana' or African animal trypanosomosis (AAT) in livestock in Sub-saharan Africa. Many consider HAT as one of the major neglected tropical diseases and AAT as the single greatest health constraint to increased livestock production. This review provides some background information on the taxonomy of tsetse flies, their unique way of reproduction (adenotrophic viviparity) making the adult stage the only one easily accessible for control, and how their ecological affinities, their distribution and population dynamics influence and dictate control efforts. The paper likewise reviews four control tactics (sequential aerosol technique, stationary attractive devices, live bait technique and the sterile insect technique) that are currently accepted as friendly to the environment, and describes their limitations and advantages and how they can best be put to practise in an IPM context. The paper discusses the different strategies for tsetse control i.e. localised versus area-wide and focusses thereafter on the principles of area-wide integrated pest management (AW-IPM) and the phased-conditional approach with the tsetse project in Senegal as a recent example. We argue that sustainable tsetse-free zones can be created on Africa mainland provided certain managerial and technical prerequisites are in place.
Assuntos
Controle de Insetos/métodos , Tripanossomíase Africana/prevenção & controle , Moscas Tsé-Tsé , Animais , Bovinos , HumanosRESUMO
PURPOSE: The authors studied the role of bacteria belonging to Anaplasmataceae family as the causes of acute illnesses of sheep in West Africa. METHODS: We examined and sampled 120 febrile sheep in two regions of Senegal for this study. The DNA extracted from these blood samples was tested by PCR using two pairs of primers (groEL-based and 16S rRNA gene-based). RESULTS: In 52/120 samples, the microscopic examination revealed intraerythrocytic and/or intraphagocytic spherical inclusions. In 48/52 cases, we succeeded in identifying the bacterial agent: in 38 cases, it was Anaplasma ovis; in six cases, it was Ehrlichia ruminantium; in two cases, Anaplasma phagocytophilum; in one case, Anaplasma platys; and in one case, a yet uncultured Anaplasma sp. closely related to A. phagocytophilum. CONCLUSIONS: Our studies demonstrated the great variety of pathogenic bacteria from the Anaplasmataceae family in the blood of clinically ill sheep. A. ovis was identified unexpectedly often. For the first time, A. phagocytophilum was found in sub-Saharan Africa, and its further epidemiology may be now reconsidered. The roles of canine pathogen, A. platys, and yet undescribed Anaplasma sp. "Badiouré" in ovine pathology should be more closely studied.
Assuntos
Infecções por Anaplasmataceae/veterinária , Anaplasmataceae/genética , Doenças dos Ovinos/epidemiologia , Anaplasmataceae/isolamento & purificação , Anaplasmataceae/metabolismo , Infecções por Anaplasmataceae/epidemiologia , Infecções por Anaplasmataceae/microbiologia , Animais , DNA Bacteriano/análise , Feminino , Masculino , Dados de Sequência Molecular , Filogenia , Reação em Cadeia da Polimerase/veterinária , Prevalência , RNA Ribossômico 16S/análise , Senegal/epidemiologia , Análise de Sequência de DNA/veterinária , Ovinos , Doenças dos Ovinos/microbiologiaRESUMO
In the implementation of mosquito control strategy programs using Sterile Insect Technique and other rear and release strategies, knowledge on the dispersion, competitiveness and survival of mosquitos is considered essential. To assess these parameters, marking techniques are generally used to differentiate colony mosquitoes from wild ones. Most of the existing mosquito marking methods require numerous manipulations that can impact their quality. In this study, we have developed a self-marking technique that can reduce the damage associated with mosquito handling. The marking technique consisted of adding fluorescent powder (DayGlo: A-17-N Saturn yellow) directly to the surface water of the receptacle containing Aedes aegypti male pupae. Different quantities of powder were used, and marking efficacy, powder persistence and mosquito survival were assessed. The results show a mean marking rate of 98 ± 1.61%, and the probability of marking increased significantly (p < 0.001) with increasing concentrations of fluorescent powder. Fluorescent powder persisted up to 20 days and did not induce a negative effect on mosquito survival (χ2 = 5.3, df = 7, p = 0.63). In addition, powder transfer did not occur between marked and unmarked populations. This marking method significantly reduces human intervention and mosquito handling during the marking process, improving the quality of marked mosquitoes used to assess SIT programs.
RESUMO
Bluetongue (BT) is an infectious, arthropod-borne viral disease of domestic and wild ruminants. The disease causes animal mortality, production decrease and commercial limits for herds. Despite the active circulation of the disease in the world, few studies have been carried out in Senegal. The objective of this study was to assess the current prevalence of BT in small ruminants and the serotypes circulating in Senegal. A cross-sectional study was conducted in the fourteen regions of Senegal. After the sampling campaign, sera collected in sheep and goats herds were screened for the presence of Bluetongue virus (BTV) specific antibodies using c-Elisa. The whole blood of seropositive animals was further analyzed by RT-qPCR and positive samples were typed to identify BTV serotypes. Analysis of several risk factors such as age, sex and species of animals was performed using logistic regression. The overall seroprevalence of BTV in Senegal was 72.6% (95% CI: 70.3-74.9%) with 75.9% (95% CI: 72.2-79.5%) in goat and 70.6% (95% CI: 67.5-73.6%) in sheep. Female (prevalence=77.1%) and adult (prevalence=80%) animals showed the highest seropositivity to BTV compared respectively to male (55.7%, p=6.133e-09) and young (49.4%, p < 2.2e-16). The RT-qPCR results showed the presence of BT viral genome in 359 small ruminants. The results obtained from serological and genotyping studies showed an active spread of the Bluetongue virus in domestic ruminants and phylogenetic analysis showed that the BTV-2 is one of the circulating serotypes in Senegal. This study allows having baseline information for controlling Bluetongue in Senegal.
Assuntos
Vírus Bluetongue , Bluetongue , Doenças das Cabras , Animais , Anticorpos Antivirais , Bluetongue/epidemiologia , Estudos Transversais , Feminino , Doenças das Cabras/epidemiologia , Cabras , Masculino , Filogenia , Ruminantes , Senegal/epidemiologia , Estudos Soroepidemiológicos , OvinosRESUMO
The use of efficient mosquito sampling methods in vector surveillance programs is crucial to inform control actions and prevent outbreaks. amongst existing trapping methods, the BG sentinel trap is widely used for collecting mosquitoes from the subgenus Stegomyia. However, studies state that the BG-sentinel trap underestimates the relative abundance of mosquito vectors. In this study, we used mice to enhance the effectiveness of the BG-sentinel trap to collect Aedes aegypti (Linnaeus) and follow the species' daily abundance under local conditions. The Latin square method was used to compare different combinations in three different seasons. Of the 35,107 mosquitoes collected, Ae. aegypti (53.82%) and Culex quinquefasciatus (46.07%) were dominant. The combination of BG-Lure + 3 mice captured more Ae. aegypti individuals (apparent density per trap/day (ADT = 187.65 ± 133.53; p < 0.001) followed by the 3 mice-baited BG-sentinel trap (ADT = 163.47 ± 117.32), the BG-sentinel trap without attractant (ADT = 74.15 ± 117.07) and the BG-sentinel trap + BG-Lure (ADT = 47.1 ± 115.91). Aedes aegypti showed two peaks of activity in the day, one following the sunrise and one before the sunset, influenced by temperature and relative humidity. Our study suggests the use of mice to enhance the efficiency of the BG-Sentinel trap to catch Ae. aegypti. However, its application in large scale entomological monitoring programs should be difficult because of ethical and operational constraints.
Assuntos
Aedes , Controle de Mosquitos , Animais , Culex , Camundongos , Mosquitos Vetores , SenegalRESUMO
Since November 2018, several countries in West and Central Africa have reported mortalities in donkeys and horses. Specifically, more than 66,000 horses and donkeys have succumbed to disease in Burkina Faso, Chad, Cameroon, The Gambia, Ghana, Mali, Niger, Nigeria, and Senegal. Strangles caused by Streptococcus equi subsp equi, African Horse Sickness (AHS) virus, and Equine influenza virus (EIV) were all suspected as potential causative agents. This study reports the identification of EIV in field samples collected in Niger and Senegal. Phylogenetic analysis of the hemagglutinin and neuraminidase genes revealed that the identified viruses belonged to clade 1 of the Florida sublineage and were very similar to viruses identified in Nigeria in 2019. Interestingly, they were also more similar to EIVs from recent outbreaks in South America than to those in Europe and the USA. This is one of the first reports providing detailed description and characterization of EIVs in West and Central Africa region.
Assuntos
Surtos de Doenças/veterinária , Doenças dos Cavalos/epidemiologia , Vírus da Influenza A Subtipo H3N8/genética , Infecções por Orthomyxoviridae/veterinária , Animais , Genes Virais , Glicoproteínas de Hemaglutininação de Vírus da Influenza/genética , Doenças dos Cavalos/transmissão , Doenças dos Cavalos/virologia , Cavalos , Vírus da Influenza A Subtipo H3N8/classificação , Neuraminidase/genética , Níger/epidemiologia , Infecções por Orthomyxoviridae/epidemiologia , Infecções por Orthomyxoviridae/transmissão , Infecções por Orthomyxoviridae/virologia , Filogenia , Senegal/epidemiologiaRESUMO
The riverine tsetse species Glossina palpalis gambiensis Vanderplank 1949 (Diptera: Glossinidae) inhabits riparian forests along river systems in West Africa. The government of Senegal has embarked on a project to eliminate this tsetse species, and African animal trypanosomoses, from the Niayes area using an area-wide integrated pest management approach. A stratified entomological sampling strategy was therefore developed using spatial analytical tools and mathematical modeling. A preliminary phytosociological census identified eight types of suitable habitat, which could be discriminated from LandSat 7 ETM+ satellite images and denominated wet areas. At the end of March 2009, 683 unbaited Vavoua traps had been deployed, and the observed infested area in the Niayes was 525 km2. In the remaining area, a mathematical model was used to assess the risk that flies were present despite a sequence of zero catches. The analysis showed that this risk was above 0.05 in 19% of this area that will be considered as infested during the control operations. The remote sensing analysis that identified the wet areas allowed a restriction of the area to be surveyed to 4% of the total surface area (7,150 km2), whereas the mathematical model provided an efficient method to improve the accuracy and the robustness of the sampling protocol. The final size of the control area will be decided based on the entomological collection data. This entomological sampling procedure might be used for other vector or pest control scenarios.
Assuntos
Controle de Insetos/métodos , Moscas Tsé-Tsé/fisiologia , Animais , Demografia , Ecossistema , SenegalRESUMO
Tsetse eradication continues to be a top priority for African governments including that of Senegal, which embarked on a project to eliminate Glossina palpalis gambiensis from the Niayes area, following an area-wide integrated pest management approach with an SIT component. A successful SIT programme requires competitive sterile males of high biological quality. This may be hampered by handling processes including irradiation and the release mechanisms, necessitating continued improvement of these processes, to maintain the quality of flies. A new prototype of an automated chilled adult release system (Bruno Spreader Innovation, (BSI™)) for tsetse flies was tested for its accuracy (in counting) and release rate consistency. Also, its impact on the quality of the released sterile males was evaluated on performance indicators, including flight propensity, mating competitiveness, premating and mating duration, insemination rate of mated females and survival of male flies. The BSITM release system accurately counted and homogenously released flies at the lowest motor speed set (0.6 rpm), at a consistent rate of 60±9.58 males/min. Also, the release process, chilling (6 ± 1°C) and passing of flies through the machine) had no significant negative impact on the male flight propensity, mating competitiveness, premating and mating durations and the insemination rates. Only the survival of flies was negatively affected whether under feeding or starvation. The positive results of this study show that the BSI™ release system is promising for use in future tsetse SIT programmes. However, the negative impact of the release process on survival of flies needs to be addressed in future studies and results of this study confirmed under operational field conditions in West Africa.
Assuntos
Temperatura Baixa/efeitos adversos , Infertilidade Masculina/veterinária , Controle Biológico de Vetores/métodos , Tripanossomíase Africana/prevenção & controle , Moscas Tsé-Tsé/fisiologia , Animais , Vetores de Doenças , Feminino , Voo Animal/fisiologia , Humanos , Infertilidade Masculina/etiologia , Gado/parasitologia , Masculino , Controle Biológico de Vetores/instrumentação , Senegal , Comportamento Sexual Animal/fisiologia , Trypanosoma/patogenicidade , Tripanossomíase Africana/parasitologia , Tripanossomíase Africana/veterinária , Moscas Tsé-Tsé/parasitologiaRESUMO
Bluetongue is a non-contagious viral disease affecting small ruminants and cattle that can cause severe economic losses in the livestock sector. The virus is transmitted by certain species of the genus Culicoides and consequently, understanding their distribution is essential to enable the identification of high-risk transmission areas. In this work we use bioclimatic and environmental variables to predict vector abundance, and estimate spatial variations in the basic reproductive ratio R0. The resulting estimates were combined with livestock mobility and serological data to assess the risk of Bluetongue outbreaks in Senegal. The results show an increasing abundance of C. imicola, C. oxystoma, C. enderleini, and C. miombo from north to south. R0 < 1 for most areas of Senegal, whilst southern (Casamance) and southeastern (Kedougou and part of Tambacounda) agro-pastoral areas have the highest risk of outbreak (R0 = 2.7 and 2.9, respectively). The next higher risk areas are in the Senegal River Valley (R0 = 1.07), and the Atlantic coast zones. Seroprevalence rates, shown by cELISA, weren't positively correlated with outbreak probability. Future works should include follow-up studies of competent vector abundancies and serological surveys based on the results of the risk analysis conducted here to optimize the national epidemiological surveillance system.
RESUMO
BACKGROUND: 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 the mosquito Aedes vexans arabiensis, the main vector of RVF virus in the Ferlo pastoral ecosystem of Senegal. METHODOLOGY/PRINCIPAL FINDINGS: Engorged female mosquitoes were collected in Younouféré in the pastoral ecosystem in the Ferlo region during the 2014 rainy season. CO2-baited CDC light traps were set at six points 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 (FR = 46.83). Proportions of single and mixed meals showed significant temporal and spatial variations according to the availability of the hosts. CONCLUSION: Aedes vexans arabiensis shows an opportunistic feeding behavior depending on the host availability. This species fed preferentially on mammals especially on horses (primary hosts) and ruminants (secondary hosts).
Assuntos
Aedes/fisiologia , Ecossistema , Comportamento Alimentar/fisiologia , Mosquitos Vetores/fisiologia , Febre do Vale de Rift/transmissão , Zoonoses/transmissão , Animais , Feminino , Humanos , Febre do Vale de Rift/epidemiologia , Senegal , Zoonoses/epidemiologiaRESUMO
BACKGROUND: 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. 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 chilling, irradiation and transport on emergence rate, flight ability and survival of sterile male Glossina palpalis gambiensis. RESULTS: Chilling, 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 in Burkina Faso to 78% upon arrival in Senegal. Flight ability was affected by all three parameters with 31% operational flies lost between the production facility and the destination site. Only survival under stress was not affected by any of the treatments. CONCLUSION: The chilling period and transport were the main factors that impacted significantly the quality of sterile male pupae. Therefore, in the operational programme, the delivery of sterile male pupae was divided over two shipments per week 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 vibrations during transport.
Assuntos
Controle Biológico de Vetores/métodos , Moscas Tsé-Tsé/fisiologia , Animais , Burkina Faso , Temperatura Baixa , Infertilidade Masculina/etiologia , Infertilidade Masculina/veterinária , Masculino , Pupa/fisiologia , Pupa/efeitos da radiação , Reprodução , Senegal , Meios de Transporte , Moscas Tsé-Tsé/efeitos da radiaçãoRESUMO
BACKGROUND: In Senegal, the last epidemic of African horse sickness (AHS) occurred in 2007. The western part of the country (the Niayes area) concentrates modern farms with exotic horses of high value and was highly affected during the 2007 outbreak that has started in the area. Several studies were initiated in the Niayes area in order to better characterize Culicoides diversity, ecology and the impact of environmental and climatic data on dynamics of proven and suspected vectors. The aims of this study are to better understand the spatial distribution and diversity of Culicoides in Senegal and to map their abundance throughout the country. METHODS: Culicoides data were obtained through a nationwide trapping campaign organized in 2012. Two successive collection nights were carried out in 96 sites in 12 (of 14) regions of Senegal at the end of the rainy season (between September and October) using OVI (Onderstepoort Veterinary Institute) light traps. Three different modeling approaches were compared: the first consists in a spatial interpolation by ordinary kriging of Culicoides abundance data. The two others consist in analyzing the relation between Culicoides abundance and environmental and climatic data to model abundance and investigate the environmental suitability; and were carried out by implementing generalized linear models and random forest models. RESULTS: A total of 1,373,929 specimens of the genus Culicoides belonging to at least 32 different species were collected in 96 sites during the survey. According to the RF (random forest) models which provided better estimates of abundances than Generalized Linear Models (GLM) models, environmental and climatic variables that influence species abundance were identified. Culicoides imicola, C. enderleini and C. miombo were mostly driven by average rainfall and minimum and maximum normalized difference vegetation index. Abundance of C. oxystoma was mostly determined by average rainfall and day temperature. Culicoides bolitinos had a particular trend; the environmental and climatic variables above had a lesser impact on its abundance. RF model prediction maps for the first four species showed high abundance in southern Senegal and in the groundnut basin area, whereas C. bolitinos was present in southern Senegal, but in much lower abundance. CONCLUSIONS: Environmental and climatic variables of importance that influence the spatial distribution of species abundance were identified. It is now crucial to evaluate the vector competence of major species and then combine the vector densities with densities of horses to quantify the risk of transmission of AHS virus across the country.
Assuntos
Doença Equina Africana/transmissão , Bluetongue/transmissão , Ceratopogonidae/fisiologia , Doenças dos Cavalos/transmissão , Insetos Vetores/fisiologia , Doença Equina Africana/epidemiologia , Doença Equina Africana/virologia , Vírus da Doença Equina Africana/genética , Vírus da Doença Equina Africana/isolamento & purificação , Vírus da Doença Equina Africana/fisiologia , Distribuição Animal , Animais , Bluetongue/epidemiologia , Bluetongue/virologia , Vírus Bluetongue/genética , Vírus Bluetongue/isolamento & purificação , Vírus Bluetongue/fisiologia , Ceratopogonidae/virologia , Ecossistema , Cavalos , Insetos Vetores/virologia , Modelos Estatísticos , Estações do Ano , Senegal/epidemiologiaRESUMO
BACKGROUND: Biting midge species of the genus Culicoides Latreille (Diptera: Ceratopogonidae) comprise more than 1300 species distributed worldwide. Several species of Culicoides are vectors of various viruses that can affect animals, like the African horse sickness virus (AHSV), known to be endemic in sub-Saharan Africa. The ecological and veterinary interest of Culicoides emphasizes the need for rapid and reliable identification of vector species. However, morphology-based identification has limitations and warrants integration of molecular data. DNA barcoding based on the mitochondrial gene cytochrome c oxidase subunit 1 (cox1) is used as a rapid and authentic tool for species identification in a wide variety of animal taxa across the globe. In this study, our objectives were as follows: (i) establish a reference DNA barcode for Afrotropical Culicoides species; (ii) assess the accuracy of cox1 in identifying Afrotropical Culicoides species; and (iii) test the applicability of DNA barcoding for species identification on a large number of samples of Culicoides larvae from the Niayes area of Senegal, West Africa. RESULTS: A database of 230 cox1 sequences belonging to 42 Afrotropical Culicoides species was found to be reliable for species-level assignments, which enabled us to identify cox1 sequences of Culicoides larvae from the Niayes area of Senegal. Of the 933 cox1 sequences of Culicoides larvae analyzed, 906 were correctly identified by their barcode sequences corresponding to eight species of Culicoides. A total of 1131 cox1 sequences of adult and larval Culicoides were analyzed, and a hierarchical increase in mean divergence was observed according to two taxonomic levels: within species (mean = 1.92%, SE = 0.00), and within genus (mean = 17.82%, SE = 0.00). CONCLUSIONS: Our study proves the efficiency of DNA barcoding for studying Culicoides larval diversity in field samples. Such a diagnostic tool offers great opportunities for investigating Culicoides immature stages ecology and biology, a prerequisite for the implementation of eco-epidemiological studies to better control AHSV in the Niayes region of Senegal, and more generally in sub-Saharan Africa.
Assuntos
Ceratopogonidae/classificação , Código de Barras de DNA Taxonômico , Insetos Vetores/classificação , Larva/classificação , Animais , Biodiversidade , Ceratopogonidae/genética , Ciclo-Oxigenase 1/genética , Proteínas de Insetos/genética , Insetos Vetores/genética , Larva/genética , SenegalRESUMO
BACKGROUND: In the Niayes area, located in the west of Senegal, only one tsetse species, Glossina palpalis gambiensis Vanderplank (Diptera: Glossinidae) was present. The Government of Senegal initiated and implemented an elimination programme in this area that included a sterile insect technique (SIT) component. The G. p. gambiensis strain (BKF) mass-reared at the Centre International de Recherche-Développement sur l'Elevage en zone Subhumide (CIRDES) in Burkina Faso was used for the SIT component. METHODOLOGY/PRINCIPAL FINDINGS: Studies conducted in 2011 in four localities in the Niayes area (Pout, Sébikotane, Diacksao Peul and the Parc de Hann) showed that the BKF strain demonstrated inferior survival in the ecosystem of the Parc de Hann, a forested area in the city centre of the capital Dakar. Therefore, G. p. gambiensis flies from the Niayes area (SEN strain) were colonized. Here we compared the competitiveness and survival of the two strains (BKF and SEN) in the Parc de Hann. Released sterile males of the SEN colony showed a daily mortality rate of 0.08 (SD 0.08) as compared with 0.14 (SD 0.08) for the BKF flies but the difference was not significant (p-value = 0.14). However, the competitiveness of the SEN males was lower (0.14 (SD 0.10)) as compared with that of the BKF males (0.76 (SD 0.11)) (p-value < 10-3). CONCLUSIONS/SIGNIFICANCE: Based on the results of this study, it can be concluded that the BKF strain will remain the main strain to be used in the elimination programme. Despite the slightly longer survival of the SEN males in the Parc de Hann, the superior competitiveness of the BKF males is deemed more important for the SIT component, as their shorter survival rates can be easily compensated for by more frequent fly releases.
Assuntos
Agentes de Controle Biológico , Infertilidade Masculina/genética , Controle de Insetos/métodos , Moscas Tsé-Tsé/crescimento & desenvolvimento , Animais , Feminino , Insetos Vetores/crescimento & desenvolvimento , Insetos Vetores/virologia , Masculino , Senegal , Moscas Tsé-Tsé/genéticaRESUMO
BACKGROUND: The Government of Senegal has embarked several years ago on a project that aims to eradicate Glossina palpalis gambiensis from the Niayes area. The removal of the animal trypanosomosis would allow the development more efficient livestock production systems. The project was implemented using an area-wide integrated pest management strategy including a sterile insect technique (SIT) component. The released sterile male flies originated from a colony from Burkina Faso. METHODOLOGY/PRINCIPAL FINDINGS: Monitoring the efficacy of the sterile male releases requires the discrimination between wild and sterile male G. p. gambiensis that are sampled in monitoring traps. Before being released, sterile male flies were marked with a fluorescent dye powder. The marking was however not infallible with some sterile flies only slightly marked or some wild flies contaminated with a few dye particles in the monitoring traps. Trapped flies can also be damaged due to predation by ants, making it difficult to discriminate between wild and sterile males using a fluorescence camera and / or a fluorescence microscope. We developed a molecular technique based on the determination of cytochrome oxidase haplotypes of G. p. gambiensis to discriminate between wild and sterile males. DNA was isolated from the head of flies and a portion of the 5' end of the mitochondrial gene cytochrome oxidase I was amplified to be finally sequenced. Our results indicated that all the sterile males from the Burkina Faso colony displayed the same haplotype and systematically differed from wild male flies trapped in Senegal and Burkina Faso. This allowed 100% discrimination between sterile and wild male G. p. gambiensis. CONCLUSIONS/SIGNIFICANCE: This tool might be useful for other tsetse control campaigns with a SIT component in the framework of the Pan-African Tsetse and Trypanosomosis Eradication Campaign (PATTEC) and, more generally, for other vector or insect pest control programs.
Assuntos
Tripanossomíase Africana/transmissão , Moscas Tsé-Tsé/fisiologia , Animais , Análise Discriminante , Complexo IV da Cadeia de Transporte de Elétrons/genética , Complexo IV da Cadeia de Transporte de Elétrons/metabolismo , Feminino , Controle de Insetos , Proteínas de Insetos/genética , Proteínas de Insetos/metabolismo , Masculino , Reprodução , Moscas Tsé-Tsé/genéticaRESUMO
BACKGROUND: The application of the sterile insect technique (SIT) requires mass-production of sterile males of good biological quality. The size of the project area will in most cases determine whether it is more cost effective to produce the sterile flies locally (and invest in a mass-rearing facility) or import the sterile flies from a mass-rearing facility that is located in another country. This study aimed at assessing the effect of long distance transport of sterile male Glossina palpalis gambiensis pupae on adult male fly yield. METHODS: The male pupae were produced at the Centre International de Recherche-Développement sur l'Elevage en zone Subhumide (CIRDES), Bobo-Dioulasso, Burkina Faso, and shipped with a commercial courier service in insulated transport boxes at a temperature of ±10°C to Senegal (±36 h of transport). Upon arrival in the insectary in Dakar, the pupae were transferred to an emergence room and the flies monitored for 3-6 days. RESULTS: The results showed that the used system of isothermal boxes that contained phase change material packs (S8) managed to keep the temperature at around 10°C which prevented male fly emergence during transport. The emergence rate was significantly higher for pupae from batch 2 (chilled at 4°C for one day in the source insectary before transport) than those from batch 1 (chilled at 4°C for two days in the source insectary before transport) i.e. an average (±sd) of 76.1 ± 13.2% and 72.2 ± 14.3%, respectively with a small proportion emerging during transport (0.7 ± 1.7% and 0.9 ± 2.9%, respectively). Among the emerged flies, the percentage with deformed (not fully expanded) wings was significantly higher for flies from batch 1 (12.0 ± 6.3%) than from batch 2 (10.7 ± 7.5%). The amount of sterile males available for release as a proportion of the total pupae shipped was 65.8 ± 13.3% and 61.7 ± 14.7% for batch 1 and 2 pupae, respectively. CONCLUSIONS: The results also showed that the temperature inside the parcel must be controlled around 10°C with a maximal deviation of 3°C to maximize the male yield.
Assuntos
Moscas Tsé-Tsé/fisiologia , Animais , Burkina Faso , Temperatura Baixa , Infertilidade Masculina , Masculino , Controle Biológico de Vetores , Pupa , Reprodução , Senegal , Fatores de TempoRESUMO
In Senegal, considerable mortality in the equine population and hence major economic losses were caused by the African horse sickness (AHS) epizootic in 2007. Culicoides oxystoma and Culicoides imicola, known or suspected of being vectors of bluetongue and AHS viruses are two predominant species in the vicinity of horses and are present all year-round in Niayes area, Senegal. The aim of this study was to better understand the environmental and climatic drivers of the dynamics of these two species. Culicoides collections were obtained using OVI (Onderstepoort Veterinary Institute) light traps at each of the 5 sites for three nights of consecutive collection per month over one year. Cross Correlation Map analysis was performed to determine the time-lags for which environmental variables and abundance data were the most correlated. C. oxystoma and C. imicola count data were highly variable and overdispersed. Despite modelling large Culicoides counts (over 220,000 Culicoides captured in 354 night-traps), using on-site climate measures, overdispersion persisted in Poisson, negative binomial, Poisson regression mixed-effect with random effect at the site of capture models. The only model able to take into account overdispersion was the Poisson regression mixed-effect model with nested random effects at the site and date of capture levels. According to this model, meteorological variables that contribute to explaining the dynamics of C. oxystoma and C. imicola abundances were: mean temperature and relative humidity of the capture day, mean humidity between 21 and 19 days prior a capture event, density of ruminants, percentage cover of water bodies within a 2 km radius and interaction between temperature and humidity for C. oxystoma; mean rainfall and NDVI of the capture day and percentage cover of water bodies for C. imicola. Other variables such as soil moisture, wind speed, degree days, land cover or landscape metrics could be tested to improve the models. Further work should also assess whether other trapping methods such as host-baited traps help reduce overdispersion.