Impact de la dynamique de peuplement sur la distribution des glossines et des trypanosomoses dans la boucle du Mouhoun (Burkina Faso)

In Burkina Faso, the Mouhoun river basin (formerly 'Black Volta") constitutes a historical focus of Human (HAT) and Animal (AAT) African Tryponosomoses, both transmitted by tsetse flies. Nowadays, HAT seems to have disappeared from this area, while AAT still causes severe economic losses. In order to explain these different epidemiological situations, we undertook a geographical study based on the analysis of aerial pictures between 1952 and 2007, and field surveys to collect medical, entomological, and veterinary data on trypanosomoses. Our results suggest that in this area, landscapes have been dramatically modified as a consequence of population growth, and in turn have had an impact on the number and distribution of tsetse flies. Combined with the historical medical action on HAT which probably led to the disappearance of T. b. gambiense, this environmental degradation and the development of hydrological structures provide explanations for the local disappearance of HAT, and for the maintenance of AAT. It appears necessary to extrapolate these studies to other areas in order to identify the factors explaining the presence/absence of trypanosomoses in the context of human population growth and climatic changes, in orde

Influence de l'anthropisation sur la végétation locale et l'abondance des tsé-tsé au sud du Burkina Faso

Entomological and phyto-sociological surveys were undertaken in Folonzo, southern Burkina Faso, along the Comoe river. The purpose of this survey was to compete densities and diversity of tsetse species in a protected versus a non protected area, by the mean of transects going from the river bank to the savannah. A detailed phytological description was made in all the trapping sites. The entomological data were also compared to what was obtained in 1980 in the some trapping sites. The phyto-geographical study showed great vegetation homogeneity between transects, particularly in the forest gallery, while savannah showed more heterogeneity. Four tsetse species were caught in the area, with 74 % G. tachinoides, 20 % G. rn. submorsitans, 4 % G. p. gambiensis and 2 % G. medicorum. There was a significant difference in tsetse densities between the protected and the non-protected area, with in average, four times more tsetse in the protected one. This difference was particularly high for G. m. submorsitans with a ratio of 1/9. This decrease was attributed to the reduction in wildlife density in the non protected area, and can be applied to the situation of the whole country where this tsetse species is of decreasing importance. It is one of the consequences of the increase in human densities, this latter causing much less visible changes in phytological species composition. From the comparison between old (1980) and new data collected on the river bank, we see a general trend of decrease in density, which affects less G. polpolis gambiensis

Introduction

Peu de concepts se révèlent aussi polysémiques que ceux d’environnement et de santé. Quand de plus ils se voient associés, le résultat peut conduire à une multiplicité de sens possibles. Environnement et santé comme apposition de deux champs qui s’expliqueraient mutuellement, environnement ET santé où l’accent est placé sur les interrelations et les liens qui s’inscrivent dans un fonctionnement systémique, santé-environnement comme un raccourci de l’expression précédente servant de cadre à de..

La dynamique spatio-temporelle du virus Ebola dans l’espace CEDEAO

L’espace CEDEAO subit de profondes mutations spatiales liées à une forte croissance démographique, au changement climatique et à une croissance économique exceptionnelle. Entre 1950 et 2015, cet espace a accueilli 280 millions nouveaux habitants, soit une moyenne de 4,3 millions nouveaux arrivants par an, parmi lesquels 2,4 millions nouveaux urbains et 1,9 millions nouveaux ruraux. Les dynamiques de peuplements impulsées par ces forces démographiques, climatiques et économiques, s’effectuent parfois en direction des terres neuves parmi lesquelles les espaces protégés. Ces derniers constituent des réserves de biodiversité qui hébergent des réservoirs de pathogènes et d’insectes vecteurs. L’homme, en exploitant ces nouveaux territoires, s’exposent donc à la piqûre d’insectes vecteurs de maladies ou au contact d’animaux réservoirs de pathogènes, tel que le virus Ebola. Par la densification de sa présence et son extension spatiale généralisée, l’homme créé également de plus en plus de promiscuité avec les animaux sauvages. Dans l’espace CEDEAO, les chimpanzés et quelques espèces de chauve-souris semblent représenter le plus grand danger pour l’homme au regard du risque de transmission du virus Ebola. Cette étude replace l’épidémie d’Ebola survenue en 2013 en Guinée dans son contexte historique et panafricain. Puis, elle présente brièvement le rôle connu de la faune sauvage dans l’épidémiologie d’Ebola et de quelles manières les changements environnementaux opèrent sur les principaux réservoirs connus de ce virus. Ensuite, elle retrace les grandes lignes de l’évolution spatio-temporelle de l’épidémie d’Ebola survenue dans l’espace CEDEAO, en tentant de faire apparaître les tenants et les aboutissants géographiques de cette catastrophe épidémiologique.ECOWAS space undergoes deep modifications related to population growth, climate change and economic development. Between 1950 and 2015, this space accommodated 280 million new inhabitants, i.e. an average of 4.3 million new arrivals a year, among which 2.4 million new urban and 1.9 million new rural. The dynamics of settlements caused by these demographic, climatic and economic phenomena are most of the time carried out towards free lands, among which protected areas. The latter constitutes reserves of biodiversity but also a reservoir of pathogens and of insect vectors. Man, by exploiting these new territories, thus expose himself to the bite of an insect vectors of disease or to a contact with an animal reservoir of a pathogen, such as the Ebola virus. By the thickening of its presence and its generalized space extension, man also created more and more promiscuity with wild animals. In ECOWAS space, chimpanzees and some species of bats seem to represent the greatest danger to man taking into consideration transmission risk of the Ebola virus. This study sets the epidemic of Ebola that occurred in 2013 in Guinea into its historical and Panafrican context. Then, it briefly presents the acknowledged role of wildlife in the epidemiology of Ebola and in which ways the environmental changes operate on the known reservoir of this virus. At last, it reminds of the broad outlines of the space-time evolution of the epidemic of Ebola which occurred in ECOWAS space, while trying to reveal the geographical ins and outs of this epidemiological catastrophe

Peuplements, mobilités et paysages en zone de mangrove guinéenne : le cas de la baie de Sangaréah (Guinée)

L’Afrique de l’Ouest connaît depuis le début du XXe siècle des évolutions démographiques considérables qui s’effectuent dans un contexte de forte variabilité climatique. Ces changements ont des conséquences sur le peuplement et le paysage. La Guinée, notamment maritime, n’échappe pas à ces évolutions. Ce travail décrit le peuplement, la mobilité humaine et le paysage dans la Baie de Sangaréah en Guinée Maritime. Son but est d’élaborer un état des lieux de la géographie de cette baie, et de mettre en évidence les dynamiques qui s’inscrivent dans ce territoire. Un recensement de la population et des enquêtes géographiques ont été organisés afin de définir le peuplement et la mobilité. Le paysage a été caractérisé à partir d’observations de terrain et du traitement d’une image satellite Landsat de 2006. Les résultats montrent une présence humaine importante en mangrove, pas seulement en terme de fréquentation, mais aussi en terme d’implantation. Les nombreux villages, hameaux et campements recensés sur ces îles en attestent. Le paysage végétal de la mangrove s’en trouve directement modifié. Nos résultats doivent pouvoir servir de base pour des études diachroniques sur le peuplement, la mobilité et le paysage en mangrove. Ces éléments géographiques évolueront rapidement dans les années à venir, au vu des orientations démographiques et climatiques annoncées.Settlement, human mobility and landscapes in the Sangaréah mangrove swamp (Guinea) Western Africa knows since the beginning of the XXth century considerable demographic evolutions which happened in a context of strong climatic variability. These changes have consequences on the populating and the landscapes. Guinea, in particular Guinea Maritime, does not escape to these evolutions. This work describes the landscape, the populating and the human mobility in the region of the Bay of Sangaréah. The objective is to make an inventory of fixtures of the populating and the spatial practices, and to replace them in their environmental context. A census and geographical inquiries were organized to define the populating and the human mobility. The landscape was characterized from observations of ground and the treatment of a satellite picture Landsat of 2006. The results show an important human presence in mangrove swamp, not only in term of attendance, but also in term of settlement. The numerous villages, the hamlets and encampments identified on these islands give evidence of it. The landscape of the mangrove is directly modified there. Our results allow understanding better the dynamics of populating in the Bay of Sangaréah. They must be able to serve as base for diachronic studies on the landscape and the populating in mangrove swamp

: The impact of war on the evolution of sleeping sickness in west-central Cote d'Ivoire

International audienceTo evaluate the situation of sleeping sickness in west-central Cote d'Ivoire from 2000 to 2003, in view of the war which broke out in September 2002. Active surveys by medical teams and passive case detection. Between 2000 and 2003, 250 patients were diagnosed with sleeping sickness. At first it appeared that sleeping sickness prevalence had fallen since the beginning of political troubles. But this apparent drop was due to poor population coverage. Participation in medical surveys differed according to ethnic group, reflecting land use conflicts between ethnic communities. Such conflicts are common in this area, but have been exacerbated by the war. In war, assessing the importance of sleeping sickness by medical surveys only is very difficult. But detection of sleeping sickness cases by passive surveillance increased.Evaluer la situation de la maladie du sommeil dans le centre-ouest de la Cote d'Ivoire de 2000 a 2003, en tenant compte des evenements survenus depuis en septembre 2002. Enquete active realisee par des equipes medicales et detection passive des cas. Entre 2000 et 2003, 250 patients ont ete diagnostiques pour la maladie du sommeil. De prime abord la prevalence de la maladie du sommeil semblait avoir baisse depuis le debut de la guerre. Mais cette baisse apparente etait due a une faible couverture de la population. La participation dans l'enquete medicale etait differente selon le groupe ethnique, refletant les conflits entre les differentes communautes pour les terres. De tels conflits sont courants dans la zone mais ont ete exacerbes par la guerre. L'evaluation de l'importance de la maladie du sommeil durant la guerre par enquete medicale seule est tres difficile. Mais la detection de la maladie du sommeil par surveillance passive a augmente

Progress towards the eradication of Tsetse from the Loos islands, Guinea

Background: The tsetse fly Glossina palpalis gambiensis is the main vector of sleeping sickness (Human African Trypanosomiasis - HAT) in West Africa, in particular in littoral Guinea where this disease is currently very active. The Loos islands constitute a small archipelago some 5 km from mainland Guinea, where G. p. gambiensis is well known as a nuisance and potential disease vector by inhabitants of the three main islands, Fotoba, Room, and Kassa. The National Control Program against HAT of Guinea has decided to eradicate tsetse in Loos islands in order to sustainably protect humans and economic activities. After baseline data collection, tsetse control began on the islands in 2006. On each of the three islands a specific combination of control methods was implemented according to the entomological situation found. Results: Starting densities before control operations were 10, 3 and 1 tsetse/trap/day in Kassa, Room and Fotoba respectively, but by July 2010, tsetse were no longer caught in any of the sentinel traps used for monitoring. The reduction rate was faster where several control methods were implemented as a combination (impregnated traps and targets ITT, selective groundspraying, epicutaneous insecticide treatment of pigs, and impregnated fences around pig pens), whereas it was slower when ITT were used as the only control method. Conclusions: This 100% suppression is a promising step in the eradication process, but G. p. gambiensis may still occur at very low, undetectable, densities on the archipelago. Next step will consist in assessing a 0.05 probability of tsetse absence to ascertain a provisional eradication status. Throughout these operations, a key factor has been the involvement of local teams and local communities without whom such results would be impossible to obtain. Work will continue thanks to the partners involved until total eradication of the tsetse on Loos islands can be declared

Towards understanding the presence/absence of Human African Trypanosomosis in a focus of Côte d'Ivoire: a spatial analysis of the pathogenic system

BACKGROUND: This study aimed at identifying factors influencing the development of Human African Trypanosomosis (HAT, or sleeping sickness) in the focus of Bonon, located in the mesophile forest of Côte d'Ivoire. A previous study mapping the main daytime activity sites of 96 patients revealed an important disparity between the area south of the town- where all the patients lived- and the area north of the town, apparently free of disease. In order to explain this disparity, we carried out a spatial analysis of the key components of the pathogenic system, i.e. the human host, the tsetse vector and the trypanosomes in their environment using a geographic information system (GIS). RESULTS: This approach at the scale of a HAT focus enabled us to identify spatial patterns which linked to the transmission and the dissemination of this disease. The history of human settlement (with the rural northern area exploited much earlier than the southern one) appears to be a major factor which determines the land use pattern, which itself may account for differences found in vector densities (tsetse were found six times more abundant in the southern rural area than in the northern). Vector density, according to the human and environmental context in which it is found (here an intense mobility between the town of Bonon and the rural areas), may explain the observed spatial differences in HAT prevalence. CONCLUSION: This work demonstrates the role of GIS analyses of key components of the pathogenic system in providing a better understanding of transmission and dissemination of HAT. Moreover, following the identification of the most active transmission areas, and of an area unfavourable to HAT transmission, this study more precisely delineates the boundaries of the Bonon focus. As a follow-up, targeted tsetse control activities starting north of Bonon (with few chances of reinvasion due to very low densities) going south, and additional medical surveys in the south will be proposed to the Ivoirian HAT control program to enhance the control of the disease in this focus. This work also shows the evolution of HAT regarding time and environment, and the methodology used may be able to predict possible sleeping sickness development/extinction in areas with similar history and space organization