52 research outputs found
African horse sickness virus: history, transmission, and current status
No full textAfrican horse sickness virus (AHSV) is a lethal arbovirus of equids that is transmitted between hosts primarily by biting midges of the genus Culicoides (Diptera: Ceratopogonidae). AHSV affects draft, thoroughbred, and companion horses and donkeys in Africa, Asia, and Europe. In this review, we examine the impact of AHSV critically and discuss entomological studies that have been conducted to improve understanding of its epidemiology and control. The transmission of AHSV remains a major research focus and we critically review studies that have implicated both Culicoides and other blood-feeding arthropods in this process. We explore AHSV both as an epidemic pathogen and within its endemic range as a barrier to development, an area of interest that has been underrepresented in studies of the virus to date. By discussing AHSV transmission in the African republics of South Africa and Senegal, we provide a more balanced view of the virus as a threat to equids in a diverse range of settings, thus leading to a discussion of key areas in which our knowledge of transmission could be improved. The use of entomological data to detect, predict and control AHSV is also examined, including reference to existing studies carried out during unprecedented outbreaks of bluetongue virus in Europe, an arbovirus of wild and domestic ruminants also transmitted by Culicoides
Seasonal dynamics of Culicoides (Diptera: Ceratopogonidae) biting midges, potential vectors of African horse sickness and bluetongue viruses in the Niayes area of Senegal
Get PDFBackground The African horse sickness epizootic in Senegal in 2007 caused considerable mortality in the equine population and hence major economic losses. The vectors involved in the transmission of this arbovirus have never been studied specifically in Senegal. This first study of the spatial and temporal dynamics of the Culicoides (Diptera: Ceratopogonidae) species, potential vectors of African horse sickness in Senegal, was conducted at five sites (Mbao, Parc Hann, Niague, Pout and Thies) in the Niayes area, which was affected by the outbreak. Methods Two Onderstepoort light traps were used at each site for three nights of consecutive collection per month over one year to measure the apparent abundance of the Culicoides midges. Results In total, 224,665 specimens belonging to at least 24 different species (distributed among 11 groups of species) of the Culicoides genus were captured in 354 individual collections. Culicoides oxystoma, Culicoides kingi, Culicoides imicola, Culicoides enderleini and Culicoides nivosus were the most abundant and most frequent species at the collection sites. Peaks of abundance coincide with the rainy season in September and October. Conclusions In addition to C. imicola, considered a major vector for the African horse sickness virus, C. oxystoma may also be involved in the transmission of this virus in Senegal given its abundance in the vicinity of horses and its suspected competence for other arboviruses including bluetongue virus. This study depicted a site-dependent spatial variability in the dynamics of the populations of the five major species in relation to the eco-climatic conditions at each site
Environmental impact of tsetse eradication in Senegal
Get PDFThe sterile insect technique is an environment friendly control tactic and is very species specific. It is not a stand-alone technique and has been used mostly in combination with other control tactics within an area-wide integrated pest management strategy. For a period of eight years, the direct impact of a campaign to eradicate a population of the tsetse fly Glossina palpalis gambiensis in Senegal was monitored using a set of fruit-feeding insect species (Cetoniinae and Nymphalidae) that served as ecological indicators of the health of the ecosystem. Here we show that the eradication campaign had very limited impacts on the apparent densities of the most frequent species as well as three diversity indexes during the reduction phase involving insecticides but reverted to pre-intervention levels as soon as the release of the sterile male insects started. These results greatly expand our understanding of the impact of vector eradication campaigns on non-target species
Host preferences and circadian rhythm of Culicoides (Diptera: Ceratopogonidae), vectors of African horse sickness and bluetongue viruses in Senegal
No full textAfrican horse sickness- and bluetongue virus are orbiviruses transmitted by Culicoides biting midges (Diptera: Ceratopogonidae) to horses and to ruminants, respectively. Since the last epizootic outbreak of African horse sickness in 2007 in Senegal, extensive investigations have been undertaken to improve our knowledge on Culicoides species involved locally in the transmission of the virus. The purpose of this study was to compare and quantify the host preferences of potential vectors of these orbiviruses on horse and sheep and to study their circadian rhythm. We found that Culicoides oxystoma and species of the sub-genus Avaritia (Culicoides imicola, Culicoides bolitinos and Culicoides pseudopallidipennis) had a preference for horse when compared to sheep (the predicted ratio between horse and sheep was 80 for C. oxystoma and 26 for C. imicola), and were mostly crepuscular: C. oxystoma had continuous activity throughout the diel with peaks in numbers collected after sunrise and sunset, while C. imicola was mostly nocturnal with peak after sunset. Unexpectedly, species of the subgenus Lasiohelea was also collected during this study. This diurnal biting species was a nuisance pest for both animal species used as bait
Quality of hydro-alcoholic products used in Senegal: pilot study
Get PDFAntisepsis and disinfection have always played an important role in the fight against infectious diseases. The use of these products has been effective in breaking the chain of transmission of microorganisms. Today, with the advent of COVID-19, the main recommendations are, among other things, physical distance and the use of antiseptic products, including hydro-alcoholic products. In Senegal, with poor regulations on the acquisition and distribution of antiseptics and disinfectants, this situation has led to a proliferation of antiseptics and disinfectants on the national market. this work aimed to study the quality of hydroalcoholic products found in the trade. We evaluated ten samples of hydro-alcohol products collected during the month of March 2020. Physical and microbiological controls were performed at the National Drug Control Laboratory. The alcohol content of the samples ranged from 63 to 85% and were consistent with WHO recommendations except for samples E3 and E5. The pH values varied between 4.02 and 6.64 and the densities of the hydro-alcoholic gel samples ranged from 0.84 to 0.92 g/cm3; E2, E4, E5, E6 samples had densities greater than 0.89 g/cm3. The samples of hydro-alcoholic products all conformed to the sterility test and no microbiological contamination was observed. Antimicrobial activities of the hydro-alcoholic samples tested ranged from 58.3 to 100% with two samples showing no activity (E2 and E5). In view of the results of this study, it would be relevant to expand and deepen investigations by a significant increase in the number of samples and by carrying out as complete an analysis as possible
Ecological distribution and population dynamics of Rift Valley fever virus mosquito vectors (Diptera, Culicidae) in Senegal
Get PDFBackground: Many zoonotic infectious diseases have emerged and re-emerged over the last two decades. There has been a significant increase in vector-borne diseases due to climate variations that lead to environmental changes favoring the development and adaptation of vectors. This study was carried out to improve knowledge of the ecology of mosquito vectors involved in the transmission of Rift Valley fever virus (RVFV) in Senegal. Methods: An entomological survey was conducted in three Senegalese agro-systems, Senegal River Delta (SRD), Senegal River Valley (SRV) and Ferlo, during the rainy season (July to November) of 2014 and 2015. Mosquitoes were trapped using CDC light traps set at ten sites for two consecutive nights during each month of the rainy season, for a total of 200 night-traps. Ecological indices were calculated to characterize the different populations of RVFV mosquito vectors. Generalized linear models with mixed effects were used to assess the influence of climatic conditions on the abundance of RVFV mosquito vectors. Results: A total of 355,408 mosquitoes belonging to 7 genera and 35 species were captured in 200 night-traps. RVFV vectors represented 89.02% of the total, broken down as follows: Ae. vexans arabiensis (31.29%), Cx. poicilipes (0.6%), Cx. tritaeniorhynchus (33.09%) and Ma. uniformis (24.04%). Comparison of meteorological indices (rainfall, temperature, relative humidity), abundances and species diversity indicated that there were no significant differences between SRD and SRV (P = 0.36) while Ferlo showed significant differences with both (P < 0.001). Mosquito collection increased significantly with temperature for Ae. vexans arabiensis (P < 0.001), Cx. tritaeniorhynchus (P = 0.04) and Ma. uniformis (P = 0.01), while Cx. poicilipes decreased (P = 0.003). Relative humidity was positively and significantly associated with the abundances of Ae. vexans arabiensis (P < 0.001), Cx. poicilipes (P = 0.01) and Cx. tritaeniorhynchus (P = 0.007). Rainfall had a positive and significant effect on the abundances of Ae. vexans arabiensis (P = 0.005). The type of biotope (temporary ponds, river or lake) around the trap points had a significant effect on the mosquito abundances (P < 0.001). Conclusions: In terms of species diversity, the SRD and SRV ecosystems are similar to each other and different from that of Ferlo. Meteorological indices and the type of biotope (river, lake or temporary pond) have significant effects on the abundance of RVFV mosquito vectors
Insight on the larval habitat of Afrotropical Culicoides Latreille (Diptera: Ceratopogonidae) in the Niayes area of Senegal, West Africa
Get PDFBackground: Certain biting midges species of the genus Culicoides (Diptera: Ceratopogonidae) are vectors of virus to livestock worldwide. Culicoides larval ecology has remained overlooked because of difficulties to identify breeding sites, methodological constraints to collect samples and lack of morphological tools to identify field-collected individuals to the species level. After the 2007 unforeseen outbreaks of African horse sickness virus (AHSV) in Senegal (West Africa), there is a need to identify suitable and productive larval habitats in horse farms for the main Culicoides species to evaluate the implementation of vector control measures or preventive actions. Methods : We investigate twelve putative larval habitats (habitat types) of Culicoides inside and outside of three horse farms in the Niayes area of Senegal using a combination of flotation and emergence methods during four collection sessions. Results: Among the three studied horse farms, three habitat types were found positive for Culicoides larvae: pond edge, lake edge and puddle edge. A total of 1420 Culicoides individuals (519♂/901♀) belonging to ten species emerged from the substrate samples. Culicoides oxystoma (40 %), C. similis (25 %) and C. nivosus (24 %) were the most abundant species and emerged from the three habitat types while C. kingi (5 %) was only retrieved from lake edges and one male emerged from puddle edge. Culicoides imicola (1.7 %) was found in low numbers and retrieved only from pond and puddle edges. Conclusions: Larval habitats identified were not species-specific. All positive larval habitats were found outside the horse farms. This study provides original baseline information on larval habitats of Culicoides species in Senegal in an area endemic for AHSV, in particular for species of interest in animal health. These data will serve as a point of reference for future investigations on larval ecology and larval control measures
El dispositivo pedagogía de proyectos: intervención/inserción y grupos grandes
Get PDFThis article describes the experience of students from a Senegalese elementary school within the framework of a research study on learning tools adapted to large groups. To this effect, project-based learning tools, launched and implemented for over 30 years by Annie Couëdel at Paris University 8, was transposed in this institution to address major academic concerns in sub-Saharan African countries in general and Senegal in particular. This entails addressing the constantly growing effects of the difficulties of learning French as a second language and adapting teaching content to the realities of everyday life. For this purpose, the relevance of our tool as the solution to this difficult issue among large groups has been proposed and shown, as its efficiency has been proven by proposing not only an active learning method but also a process that adds value to national languages. Finally, this study has provided answers for the interaction between the inside and the outside, as our tool incorporates learning as well as social, cultural, political and economic needs. This has been implemented for six months with students in accordance with the tool’s principles and achieved the implementation of projects that have led to an actual transformation of attitudes from students, teachers and their environment to a certain extent at many levels.En este artículo se describe una experiencia con estudiantes de una escuela primaria en Senegal, en el marco de una investigación sobre los dispositivos pedagógicos adaptados a grupos grandes. Para ello hicimos allí la transposición del dispositivo de pedagogía de proyectos, iniciado e implementado por más de treinta años por Annie Coüedel en la Universidad Paris 8, con el fin de responder a las grandes preocupaciones de la escuela en los países de África subsahariana, en general, y de Senegal, en particular. Se trata de asumir los efectos, que no cesan de aumentar, de la problemática del aprendizaje del francés como segunda lengua y de la adaptación de los contenidos de la enseñanza a las realidades de la vida cotidiana. Para tal efecto, hemos propuesto y demostrado la pertinencia de nuestro dispositivo como solución a este difícil asunto de los grupos grandes, por cuanto ha demostrado ser eficaz al proponer no solamente una pedagogía activa, sino también un proceso que le confiere valor a las lenguas nacionales. Finalmente, hemos aportado respuestas a la articulación entre el interior y el exterior, dado que nuestro dispositivo integra aprendizaje y necesidades sociales, culturales, políticas y económicas. Alineados con los principios del dispositivo, conjuntamente con los estudiantes, lo implementamos durante seis meses y logramos poner en funcionamiento proyectos que, en cierta media, han impulsado la transformación real de las actitudes de los estudiantes, de los docentes y de su entorno en muchos niveles
Circadian activity of Culicoides oxystoma (Diptera: Ceratopogonidae), potential vector of bluetongue and African horse sickness viruses in the Niayes area, Senegal
Get PDFCulicoides biting midges (Diptera: Ceratopogonidae) are important vectors of arboviruses in Africa. Culicoides oxystoma has been recently recorded in the Niayes region of Senegal (West Africa) and its high abundance on horses suggests a potential implication in the transmission of the African horse sickness virus in this region. This species is also suspected to transmit bluetongue virus to imported breeds of sheep. Little information is available on the biology and ecology of Culicoides in Africa. Therefore, understanding the circadian host-seeking activity of this putative vector is of primary importance to assess the risk of the transmission of Culicoides-borne pathogens. To achieve this objective, midges were collected using a sheep-baited trap over two consecutive 24-h periods during four seasons in 2012. A total of 441 Culicoides, belonging to nine species including 418 (94.8 %) specimens of C. oxystoma, were collected. C. oxystoma presented a bimodal circadian host-seeking activity at sunrise and sunset in July and was active 3 h after sunrise in April. Daily activity appeared mainly related to time periods. Morning activity increased with the increasing temperature up to about 27 °C and then decreased with the decreasing humidity, suggesting thermal limits for C. oxystoma activity. Evening activity increased with the increasing humidity and the decreasing temperature, comprised between 20 and 27 °C according to seasons. Interestingly, males were more abundant in our sampling sessions, with similar activity periods than females, suggesting potential animal host implication in the facilitation of reproduction. Finally, the low number of C. oxystoma collected render practical vector-control recommendations difficult to provide and highlight the lack of knowledge on the bio-ecology of this species of veterinary interest
Feeding behaviour of potential vectors of West Nile virus in Senegal
Get PDFWest Nile virus (WNV) is a widespread pathogen maintained in an enzootic cycle between mosquitoes and birds with occasional spill-over into dead-end hosts such as horses and humans. Migratory birds are believed to play an important role in its dissemination from and to the Palaearctic area, as well as its local dispersion between wintering sites. The Djoudj Park, located in Senegal, is a major wintering site for birds migrating from Europe during the study period (Sept. 2008- Jan. 2009). In this work, we studied the seasonal feeding behaviour dynamics of the potential WNV mosquito vectors at the border of the Djoudj Park, using a reference trapping method (CDC light CO2-baited traps) and two host-specific methods (horse- and pigeon-baited traps). Blood meals of engorged females were analysed to determine their origin
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