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International audience; In the context of food self-sufficiency, the River Senegal Valley has been undergoing profound environmental changes for several decades. Rice production has increased due to the development of vast irrigated perimeters, which has been accompanied by recurrent proliferations of rodent populations that are crop pests and reservoirs of zoonoses. The aim of our study was to determine the factors underlying these phases of increased rodent abundance over a ten-year (2008 to 2019) sampling period during the hot dry season (February-May). A total of 1,867 rodents of four species were captured, among which Arvicanthis niloticus and Mastomys huberti dominated. Our results showed that, during this season, rodent abundance (i) increases significantly with rainfall from the previous year, (ii) is higher in cultivated than in uncultivated plots, (iii) increases with plant cover, (iv) increases, for M. huberti, with the presence of open water. We showed that in an area that was first sparsely cultivated and then impacted by hydro-agricultural rehabilitation of irrigation and drainage infrastructure, the abundance of A. niloticus changed following this program, reaching the level of a nearby area that has been intensively cultivated for decades. Moreover, we showed that the proportion of adults among the captured individuals was lower in rice plots than in vegetable gardening fields and uncultivated plots. The breeding pattern of adult individuals was also affected by land use. Results suggest that uncultivated areas and vegetable gardening fields constitute refuge and breeding ground hotspots and would thus form a starting point for the invasion of rice fields. Following these results, we advocate for regular monitoring of rodent breeding and abundance patterns, with a special focus on these refuge areas, particularly during the hot dry season. We recommend implementing effective and sustainable science-based control strategies at national and community levels to keep rodent populations within tolerable limits.; Dans un contexte de recherche d'autosuffisance alimentaire, la vallée du fleuve Sénégal subit depuis plusieurs décennies de profondes modifications environnementales. La production rizicole a augmenté grâce au développement de vastes périmètres irrigués. Cette évolution s'est accompagnée de proliférations récurrentes de populations de rongeurs ravageurs des cultures et réservoirs de zoonoses. L'objectif de notre étude était de déterminer les facteurs sous-jacents à ces phases d'augmentation de l'abondance des rongeurs sur une période d'échantillonnage de dix ans (2008 à 2019) pendant la saison sèche chaude (février-mai). Au total, 1867 rongeurs de quatre espèces ont été capturés, parmi lesquels les espèces Arvicanthis niloticus et Mastomys huberti dominaient. Nos résultats ont montré que, pendant cette saison, l'abondance des rongeurs (i) augmente significativement avec les précipitations de l'année précédente, (ii) est plus élevée dans les parcelles cultivées que dans les parcelles non cultivées, (iii) augmente avec le couvert végétal, (iv) augmente, pour M. huberti, avec la présence d'eau libre. Nous avons montré que dans une zone d'abord faiblement cultivée puis impactée par une réhabilitation hydro-agricole des infrastructures d'irrigation et de drainage, l'abondance d'A. niloticus a changé suite à ce programme, atteignant le niveau d'une zone voisine intensivement cultivée depuis des décennies. De plus, nous avons montré que la proportion d'adultes parmi les individus capturés était plus faible dans les parcelles de riz que dans les cultures maraîchères et les parcelles non cultivées. L’état reproducteur des individus adultes était également affecté par l'usage des terres. Les résultats suggèrent que les zones non cultivées et les champs de cultures maraîchères constituent des points chauds de refuge et de reproduction et formeraient ainsi un point de départ pour l'invasion des rizières. Suite à ces résultats, nous préconisons un suivi régulier de l’activité de reproduction et de l'abondance des rongeurs, avec une attention particulière sur ces zones de refuge, notamment pendant la saison sèche chaude. Nous recommandons la mise en oeuvre de stratégies de contrôle efficaces et durables, basées sur des données scientifiques, aux niveaux national et communautaire, afin de maintenir les populations de rongeurs dans des limites tolérables.

Bioinvasion is a major public health issue because it can lead to the introduction of pathogens in new areas and favours the emergence of zoonotic diseases. Rodents are prominent invasive species, and act as reservoirs in many zoonotic infectious diseases. The aim of this study was to determine the link between the distribution and spread of two parasite taxa (Leishmania spp. and Trypanosoma lewisi) and the progressive invasion of Senegal by two commensal rodent species (the house mouse Mus musculus domesticus and the black rat Rattus rattus). M. m. domesticus and R. rattus have invaded the northern part and the central/southern part of the country, respectively. Native and invasive rodents were caught in villages and cities along the invasion gradients of both invaders, from coastal localities towards the interior of the land. Molecular diagnosis of the two trypanosomatid infections was performed using spleen specimens. In the north, neither M. m. domesticus nor the native species were carriers of these parasites. Conversely, in the south, 17.5% of R. rattus were infected by L. major and 27.8% by T. lewisi, while very few commensal native rodents were carriers. Prevalence pattern along invasion gradients, together with the knowledge on the geographical distribution of the parasites, suggested that the presence of the two parasites in R. rattus in Senegal is of different origins. Indeed, the invader R. rattus could have been locally infected by the native parasite L. major. Conversely, it could have introduced the exotic parasite T. lewisi in Senegal, the latter appearing to be poorly transmitted to native rodents. Altogether, these data show that R. rattus is a carrier of both parasites and could be responsible for the emergence of new foci of cutaneous leishmaniasis, or for the transmission of atypical human trypanosomiasis in Senegal., Author summary Biological invasions (the introduction and adaptation of living organisms to a new environment) are increasingly frequent due to worldwide intensification of human-associated exchanges. They can lead to the introduction of pathogens in new areas and favour the emergence of diseases. Rodents are prominent invasive species, and act as reservoirs in many infectious diseases. The aim of our study was to determine the link between the distribution and spread of two parasites, Leishmania spp. and Trypanosoma lewisi, and the progressive invasion of Senegal by two commensal rodent species, the house mouse Mus musculus domesticus, and the black rat Rattus rattus. We identified R. rattus as a potential reservoir for Leishmania major and T. lewisi in the southern part of Senegal. The presence of these two pathogens in R. rattus may be of different origins. The invader R. rattus could have been locally contaminated with L. major. Conversely, T. lewisi infection could have been introduced in Senegal by R. rattus, and seems to be poorly transmitted to native rodents. Altogether, these data show that R. rattus is a carrier of both parasites, and could be responsible for the emergence of new foci of cutaneous leishmaniasis or for the transmission of atypical human trypanosomiasis in Senegal.

Changes in host-parasite ecological interactions during biological invasion events may affect both the outcome of invasions and the dynamics of exotic and/or endemic infections. We tested these hypotheses, by investigating ongoing house mouse (Mus musculus domesticus) and black rat (Rattus rattus) invasions in Senegal (West Africa). We used a 16S gene rRNA amplicon sequencing approach to study potentially zoonotic bacterial communities in invasive and native rodents sampled along two well-defined independent invasion routes. We found that individual host factors (body mass and sex) were important drivers of these bacterial infections in rodents. We observed that the bacterial communities varied along invasion routes and differed between invasive and native rodents, with native rodents displaying higher overall bacterial diversity than invasive rodents. Differences in prevalence levels for some bacterial Operational Taxonomic Units (OTUs) provided support for ecological processes connecting parasitism and invasion success. Finally, our results indicated that rodent invasions may lead to the introduction of exotic bacterial genera and/or to changes in the prevalence of endemic ones. This study illustrates the difficulty of predicting the relationship between biodiversity and disease risks, and advocate for public health prevention strategies based on global pathogen surveillance followed by accurate characterization of potential zoonotic agents.

In 1989 a conflict arose on the Senegal-Mauritania border, resulting in violence by populations on either side against those suspected of “foreign” origins. This situation entailed mass slaughters of people of Senegalese descent in Mauritania and expulsion for the luckier ones. Their assimilation in the Senegalese part of the borderland has been made partly easier by the language they share with the host communities, which enabled them, on arrival, to undertake activities that would also ensure their integration. Mauritanian refugees now have the possibility to move freely between their former sites and their new environment. Yet this process of losing and regaining their status is paralleled by a more complex process of identity seeking or recovery. This paper examines these identity issues by focusing on the experience of the Djolly Senegal refugee community, and also on the cultural bridging strategies that they have developed, with a particular interest in representations and discourse.

This publication is one of the results of a conference organised in Lisbon in 2011 on the theme of African borders and their relationships with migration and mobility. The selected papers are a sample of the diverse perspectives on the general theme presented at the meeting. The African Borderlands Research Network (ABORNE) promoted this event, allowing a substantial number of its members to exchange results of ongoing and long-term research. The Fundação para a Ciência e a Tecnologia (Portugal) funded the research project Borders and Identity in Africa (PTDC/AFR/098339/2008) which prepared this publication.

International audience; The worldwide intensification of human-associated exchanges favours the multiplication of biological invasions. Among mammals, rodent species, including the house mouse Mus musculus, are identified as major invaders with profound impacts on native biodiversity, human health and activities. Though contemporary rodent invasions are described on several islands, there are few data describing ongoing house mouse invasions in continental areas. We first outline the known picture of the distribution of the house mouse in Africa. We then describe the ongoing range expansion of the house mouse in Senegal, in order to update its distribution area, assess the location of the invasion front, describe the spatio-temporal dynamics of the invasion at the country scale and evaluate its impact on native small mammal communities. We briefly review the worldwide status of the house mouse, with special focus on its situation in Africa. Focusing on Senegal, we then use historical records and a large body of spatio-temporal indoor trapping data obtained from small mammal communities over the last 30 years to analyse the invasion dynamics of the subspecies at the scale of the country.The geographic range of the invasive house mouse is surprisingly poorly known in Africa. In Senegal, we document a large range expansion of the subspecies in human settlements over the whole country within the last 30 years. The invasion is still ongoing further east and south within the country, and has major consequences for small mammal communities and thus probably for risks associated with zoonotic diseases.

International audience; Maize is attacked by many post-harvest pests including Sitophilus spp and Prostephanus spp, which causes remarkable loss during storage. Approximately 30 to 40 % loss in the absence of treatment has been reported worldwide. This study compare genetically Central African and Senegalese populations of Sitophilus zeamais from various agroecological zones using 3 markers namely cytochrome b, cytochrome oxidase and nuclear 28S gene. S. zeamais samples were analyzed on both of two other sites 34 for the 28S gene; 68 for cytochrome b and 36 for the cytochrome oxydase. Results analyzed by AMOVA have shown high genetic variation outside population of each country (6.17 % with Cyt b; 21.45 % with 49.83 % and COI in the case of 28S) and low within subpopulations (-10.06 % for Cyt b, 9.36 % for the COI and-15.23 % for 28S). Majority haplotype is shared between the two populations for 28S and cytochrome b genes and there is a very high haplotype diversity in populations of Senegal considering the Cytochrome b gene (0.781 + /-0.00364) while with COI and 28S, high values of diversity are observed in Central African sequences, respectively 1.000 + /-0.00274 and 0.867 + /-0.011. Genetic differentiation obtained according to the geographical origin is significant between the two populations; however, it is not at the level of subpopulations. Developed by the three approaches (parsimony, likelihood and Bayesian) phylogenetic trees are resolved and show a speciation of the two populations according to the geographical origin.

Carnivore are undoubtedly among the most threatened of the mammal species in Africa because of the low density at which they occur and their large home range requirements that do not match with human propensity to develop and alter wildlife habitat. However, the degree of threat is unevenly distributed within the continent, with western and central African carnivores being the most threatened and the least studied. I estimated population size, density, and proportion of area occupied in relation to environmental factors of one medium-size (serval – Leptailurus serval) and two large carnivores (lion – Panthera leo and leopard – P. pardus) in the Niokolo Koba National Park, Senegal, West Africa, using remote camera surveys and both traditional (CR), spatially explicit capture-recapture (SECR) techniques for servals and leopards, and non-spatial (MR) and spatial mark resight (SMR) methods for lions. Lions selected optimal sites with both high tree density and prey activity; leopards occupied areas with high tree density but with less prey activity; and servals selected habitats with more dense canopy cover where leopards were absent. The presence of lions was favorable to serval presence, as we presume leopards avoid lions, although we did not have strong evidence to support it. Moreover, the half mean maximum distance moved (½ MMDM) method under CR methods appeared to overestimate leopard and serval density while full MMDM estimates were close to SECR methods density estimates. For lions, both ½ MMDM and full MMDM methods in MR framework overestimated density whereas the SMR method resulted in more reasonable estimates, especially in light of previous assessments of lion densities in West Africa.. These results are of high importance for conservation and management purposes of the imperiled Niokolo Koba carnivore community. Master of Science

In 1989 a conflict arose on the Senegal-Mauritania border, resulting in violence by populations on either side against those suspected of “foreign” origins. This situation entailed mass slaughters of people of Senegalese descent in Mauritania and expulsion for the luckier ones. Their assimilation in the Senegalese part of the borderland has been made partly easier by the language they share with the host communities, which enabled them, on arrival, to undertake activities that would also ensure their integration. Mauritanian refugees now have the possibility to move freely between their former sites and their new environment. Yet this process of losing and regaining their status is paralleled by a more complex process of identity seeking or recovery. This paper examines these identity issues by focusing on the experience of the Djolly Senegal refugee community, and also on the cultural bridging strategies that they have developed, with a particular interest in representations and discourse.

Using the same set of microsatellite markers, we compared the population genetic structure of two Mastomys species, one being exclusively commensal in southeastern Senegal, and the other being continuously distributed outside villages in this region. Both species were sampled in the same landscape context and at the same spatial scale. According to the expectations based on the degree of habitat patchiness (which is higher for commensal populations in this rural area), genetic diversity was lower and genetic differentiation was higher in commensal populations of Mastomys natalensis than in wild populations of Mastomys erythroleucus. Contrasting estimates of effective dispersal and current migration rates corroborates previous data on differences in social structure between the two species. Isolation-by-distance analyses showed that human-mediated dispersal is not a major factor explaining the pattern of genetic differentiation for M. natalensis, and that gene flow is high and random between M. erythroleucus populations at the spatial scale considered.