Résumé La maladie du sommeil, ou trypanosomiase humaine africaine (THA), est due à Trypanosoma brucei transmis par Glossina spp ou mouche tsé-tsé. Après avoir ravagé l'Afrique subsaharienne dans la première moitié du XXe siècle, comme en témoigne l'extraordinaire ouvrage d'Alphonse Laveran et Félix Mesnil en 1912 (Trypanosomes et trypanosomiases), la THA, maladie tropicale négligée mortelle, dite « du bout de la piste » et pour laquelle il n'existe pas de vaccin, semble aujourd'hui à portée de main de l’élimination. Nous passons en revue les stratégies, activités et outils qui ont permis cette forte réduction du fardeau sanitaire pour les populations d'Afrique subsaharienne: environ 300 000 cas estimés dans les années 1990 contre moins de 1000 cas rapportés annuellement depuis 2018. La lutte contre la maladie du sommeil consiste principalement à dépister et traiter les cas ainsi qu’à lutter contre la glossine vectrice pour casser le cycle de transmission. En passant en 30 ans d'un contexte épidémique à un contexte d’élimination, la maladie du sommeil a subi une transition épidémiologique sans précédent à laquelle les stratégies et les outils de lutte ont dû s'adapter. Nous montrons comment la recherche a soutenu ces efforts et examinons certains des défis restants pour rendre effective et durable son élimination.

Tsetse flies (Diptera: Glossinidae) are pupiparous insects that transmit African trypanosomes to humans and animals. Using three species of tsetse flies belonging to two subgenera, Nemorhina and Glossina, our data provide a first answer to the following question: do the juvenile stages of tsetse flies provide metric traits allowing reliable species and/or sex identification? We compared three species using their wings and their pupae: Glossina palpalis gambiensis, Glossina tachinoides and Glossina morsitans submorsitans. To separate size and shape information, 11 landmarks per wing were submitted to the Generalised Procrustes Analysis (GPA). The contour of the pupae was processed by elliptic Fourier analysis (EFA).A validated reclassification method was used to compare the taxonomic power of each organ, as well as its utility for sex recognition. The contour of the pupae did not provide a satisfactory species signal (75 %), relative to the one obtained from wing landmarks (99 %). However, the overall pupae size was much more satisfactory than the wings size (93 % versus 57 %). In spite of a lower taxonomic signal, the morphometric variation observed on pupae was in agreement with known phylogenetic relationships. Contrary to the wings, sexual dimorphism was much reduced in pupae and not strong enough to allow any reliable sex identification.

Nous rapportons l’observation d’une jeune fille, âgée de 11 ans, reçue en consultation de neurologie au centre hospitalier et universitaire (CHU) de Bouaké, pour un trouble de la marche d’installation progressive évoluant depuis environ deux ans, dans un contexte de fièvre. L’anamnèse a révélé un séjour en zone d’endémie trypanosomienne en Côte d’Ivoire. L’examen clinique a noté une dystonie axiale à la marche, des mouvements anormaux des mains, une hypertonie extrapyramidale, des réflexes archaïques, une somnolence diurne et une agitation nocturne. Le scanner cérébral sans et avec injection de produit de contraste a montré des hypodensités de la substance blanche sous-corticale. Trois (3) différents tests de diagnostic rapide (TDR) pour la trypanosomiase ont étés positifs et l’examen parasitologique de la minicolonne (mAECT) a confirmé la présence de trypanosomes dans le sang. La ponction lombaire a ramené un LCR clair avec présence d’une trentaine de trypanosomes. La patiente a reçu un traitement à base de la Combinaison NECT (Nifurtimox-Eflornithine Combination Therapy) pendant 10jours. L’évolution clinique a été favorable avec régression des signes extrapyramidaux. II persiste cependant des troubles comportementaux. Cette observation nous invite à continuer d’évoquer la THA comme étiologie de mouvements anormaux dans notre contexte de travail, même si cette pathologie semble en voie d’éradication.

Dynamics of Settlement and Landscape Modifications in the Southern Rural Area of the Bonon City (Marahoué Region, Côte d'Ivoire). Estimated at 15 million of hectares at the beginning of the 20th century, the surface of ​​dense forests in Ivory Coast was estimated at 2.7 million hectares at the end of the same century. Strong anthropic pressure led to a reduction of forest surface in this country. This is the case in the Bonon area, a sub-prefecture in Marahoué region, where cash crops were developed in the early 1970s. Field data collected in 2000 on settlement and landscape were compared with those from 2015. Changes in population density, spatial organization of the territory and rural communications were described. Within 15 years, the rural population density has increased from 75 inhabitants / km² in 2000 to 134 inhabitants / km² in 2015. This increase in human population densities, despite the socio-political crisis from 2002 to 2011, has profoundly changed the landscape in this area. The analysis of the landscape shows a considerable increase in cultivation surface. Agricultural surface have risen from 3818 hectares in 2000 to 5250 hectares in 2015, so an increase of 31% over 15 years. The original forest has almost disappeared.

Anthropogenic Pressure and Landscape Dynamics in the Ivoirian Forest Area in the Meagui Region. In Ivory Coast, population density increased from 8 inhabitants/km² in 1950 to 71 inhabitants/km² in 2014. The population growth impulse strong dynamics of settlement and generated an increase of the cultivated surfaces. To visualize these dynamics in the area of Meagui, a diachronic study was realized on settlement and landscape on a transect from Meagui town (East) to National Park of Taï (West), covering a surface of 233 km². The combination of field information and analysis of LANDSAT satellite imagery taken at different dates (1986, 2002 and 2014) allowed to discriminate settlement dynamics and land-use patterns. From 6 units of settlements, identified in the eastern part of the zone in the early 1975s, the number was increased to 489 in 2016. In the same time, the forest, which occupied 40% of the area studied in 1986, had almost disappeared in 2014, in favor of perennial crops (more than 90%). The total population density is estimated at 416 inhabitants/km², i.e 6 times most important than the national density. These results show how important the population/resource problem is in Ivory Coast.

Dynamics of Settlement and Landscaped Modification in the National Park of Marahoue (Côte d'Ivoire). In Ivory Coast, the population grew from 8.3 inh;/km² in 1950 to 71.4 inh;/km² in 2015. This increase of density of population, especially in forest area, caused land saturation that has oriented the last pioneering fronts of coffee-cocoa to the protected areas, as is the case of the National Park of Marahoué (NPM). In this park, an questionnaire survey and a mapping of the territory with the Global Positioning System were realized in order to count the population, to locate the settlements and to trace tracks. At the same time, a diachronic analysis of the land use inside the NPM was made. The results show that the dynamics of populating in the NPM was characterized since 1955 by a progressive but slow settlement of localities, which abruptly accelerated from 2000 onwards. In 2015, 53651 persons (52,15 inh./km ²) lived in this park, dispatched in 174 localities. Due to this pressure of population on the natural space, the forest disappeared for the benefit of cultures. Their area increased from 82281 hectares in 1974 to 00 hectares in 2015.

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Tsetse flies Glossina palpalis gambiensis and G. tachinoides are among the major vectors of sleeping sickness (Human African Trypanosomiasis‐HAT) and nagana (African Animal Trypanosomiasis – AAT) in West Africa. Both riparian species occur sympatrically in gallery forests of south west Burkina Faso, but little is known of their interspecies relationships although different authors think there may be some competition between them. The aim of this study was to check if sympatric species have different strategies when approaching a host. A man placed in a sticky cube (1 m × 1 m × 1 m) and a sticky black‐blue‐black target (1 m × 1 m) were used to capture tsetse along the Comoe river banks in a Latin Square design. The number and the height at which tsetse were caught by each capture method were recorded according to species and sex. Glossina p. gambiensis was more attracted to human bait than to the target, but both species were captured at a significantly higher height on the target compared with the human bait (P < 0.05). No significant difference in heights was found between G. tachinoides and G. p. gambiensis captured on targets (33 and 35 cm, respectively, P > 0.05). However, catches on human bait showed a significant difference in height between G. tachinoides and G. p. gambiensis (22.5 and 30.6 cm, respectively, P < 0.001). This study showed that these sympatric species had different attack behaviours to humans, which is not the case with the target. The implications of these findings are discussed.

This is the first study to explore the potential of various geometric morphometrics methods to help the morphological diagnostic of tsetse species, vectors of human and animal trypanosomiases in sub-Saharan Africa. We compared landmarks, semilandmarks and outlines techniques on male and female samples of species, and suggested adapted strategies according to the countries and their own Glossina fauna. We could compare up to 7 taxa belonging to the three main subgenera of the Glossina genus: Nemorhina (5 species), Glossina (1 species) and Austenina (1 species). Our sample included the major vectors of sleeping sickness: G. palpalis palpalis, G. p. gambiensis, G. fuscipes fuscipes and G. f. quanzensis, as well as two important vectors of African animal trypanosomoses: G. tachinoides and Glossina morsitans submorsitans. The average level of correct species recognition by the wing shape was satisfactory, and slightly higher for females than for males. The best scores of correct assignment, in both sexes, were obtained by the contour technique (96% of correct attribution in females, 92% in males), slightly higher than for semilandmarks (95% and 91%) or landmarks (94% and 89%) techniques. We made our images of wings freely available to be used as reference images (http://mome-clic.com), and we describe the conditions and the analytical steps to be followed to identify unknown specimens using external reference images. Under adequate conditions, such use of reference images obtained from a free access server could help species identification of new samples anywhere in Africa.

Human African trypanosomiasis (HAT) (or sleeping sickness) due to Trypanosoma brucei gambiense ) occurs in Western and Central Africa. T. brucei s.l. displays a huge diversity of adaptations and host specificities, and questions about its reproductive mode, dispersal abilities, and effective size remain under debate. We have investigated genetic variation at eight microsatellite loci of T. b. gambiense strains isolated from HAT patients in Côte d’Ivoire and Guinea, with the aim of knowing how genetic information was partitioned within and between individuals, between foci and between temporally spaced samples. The results indicate that (i) migration of T. b. gambiense group 1 strains does not occur at the scale of West Africa, and that even at a finer scale (e.g. within Guinea) migration is restricted; (ii) effective population sizes of trypanosomes as reflected by infected hosts are probably higher than what the epidemiological surveys suggest; and (iii) T. b. gambiense group 1 is most likely a strictly clonally reproducing organism.

The increase of human population, combined with climatic changes, contributed to the modification of spatial distribution of tsetse flies, main vector of trypanosomiasis. In order to establish and compare tsetse presence and their relationship with vegetation, entomological survey was performed using biconical traps deployed in transects, simultaneously with phyto-sociological study, on the Comoe river at its source in the village of Moussodougou, and in the semi-protected area of Folonzo, both localities in Southern Burkina Faso. In Folonzo, the survey revealed a diversity of tsetse with 4 species occurring with apparent densities as follows: Glossina tachinoides (8.9 tsetse/trap/day); G. morsitans submorsitans (1.8 tsetse/trap/day); G. palpalis gambiensis (0.6/trap/day) and G. medicorum (0.15 tsetse/trap/day). In Moussodougou, a highly anthropized area, mainly G. p. gambiensis was caught (2.06 tsetse/trap/day), and rarely G. tachinoides. The phyto-sociological study allowed discrimination of 6 types of vegetation in both localities, with 3 concordances that are riparian forest, shrubby and woody savannah. In Moussodougou, all tsetse were caught in the riparian forest. That was also the case in Folonzo where a great proportion (95 to 99 % following the season) of G. p. gambiensis and G. tachinoides were caught in the gallery, while G. m. submorsitans was occurring as well in the gallery as in the savannah, and G. medicorum in the forest gallery. This study showed that although G. tachinoides and G.p. gambiensis are both riparian, they do not have the same preference in terms of biotope.

To investigate the spatial and temporal diversity of tsetse flies, vectors of trypanosomosis, in Ivory Coast, surveys were conducted on the Comoe River in three sites located in different ecoclimatic zones: north, center and south. They were carried out during the dry and rainy seasons. For each site and season, the flies were captured during five consecutive days in biconical traps arranged in transects perpendicular to the Comoe River. In Kafolo in savanna, three species and subspecies were captured regardless of the season: Glossina palpalis gambiensis, G. tachinoides and G. medicorum. In Aboisso-Comoe and Groumania, in forest and forest-savanna transition areas, respectively, only G. palpalis palpalis was captured. The apparent density per trap, all species combined, was higher in Kafolo than in Groumania and Aboisso-Comoe. It was 9.48 tsetse flies (tf)/trap/day (standard deviation [SD] = 26.30) in Kafolo, 0.79 tf/trap/day (SD = 2.65) in Groumania, and 0.18 tf/trap/day (SD = 0.58) in Aboisso Comoe in the dry season. In the rainy season, it was 3.64 tf/trap/day (SD = 9.76) in Kafolo and 1.42 tf/trap/day (SD = 2.35) in Groumania. These results show that the diversity of tsetse species along the Comoe River depends on the biotope conservation, as illustrated by the gradual disappearance of species such as G. morsitans submorsitans which was not captured during the study. We also confirm that only the major vector of human African trypano-somiasis, G. palpalis s.l., can adapt to humans.

Modern methods allow a geometric representation of forms, separating size and shape. In entomology, as well as in many other fields involving arthropod studies, shape variation has proved useful for species identification and population characterization. In medical entomology, it has been applied to very specific questions such as population structure, reinfestation of insecticide-treated areas and cryptic species recognition. For shape comparisons, great importance is given to the quality of landmarks in terms of comparability. Two conceptually and statistically separate approaches are: (i) landmark-based morphometrics, based on the relative position of a few anatomical “true” or “traditional” landmarks, and (ii) outline-based morphometrics, which captures the contour of forms through a sequence of close “pseudo-landmarks”.Most of the studies on insects of medical, veterinary or economic importance make use of the landmark approach. The present survey makes a case for the outline method, here based on elliptic Fourier analysis. The collection of pseudo-landmarks may require the manual digitization of many points and, for this reason, might appear less attractive. It, however, has the ability to compare homologous organs or structures having no landmarks at all. This strength offers the possibility to study a wider range of anatomical structures and thus, a larger range of arthropods.We present a few examples highlighting its interest for separating close or cryptic species, or characterizing conspecific geographic populations, in a series of different vector organisms. In this simple application, i.e. the recognition of close or cryptic forms, the outline approach provided similar scores as those obtained by the landmark-based approach.

The objective of this paper was to describe recent data from Burkina Faso and Côte d'Ivoire on Human African Trypanosomosis medical monitoring in order to (i) update the disease situation in these two countries that have been sharing important migratory, economic and epidemiological links for more than a century and (ii) to define the future strategic plans to achieve the goal of a sustainable control/elimination process. Results of active and passive surveillance indicate that all sleeping sickness patients diagnosed these last years in Burkina Faso were imported cases from Côte d'Ivoire. Nevertheless the re-introduction of the parasite is effective and the risk of a resumption of transmission exists. In Côte d'Ivoire, few cases are still diagnosed in several historical foci and the fear exists that the disease could reemerge in these foci or spread to other areas. In order to achieve a sustainable elimination of sleeping sickness in these two countries, control entities have to adapt their strategy to the different epidemiological contexts. At the exception of specific cases, the current disease prevalence no longer justifies the use of expensive medical surveys by exhaustive screening of the population. New disease control strategies, based on the exchange of epidemiological information between the two countries and integrated to the regular national health systems are required to target priority intervention areas. Follow-up in time of both treated patients and serological suspects that are potential asymptomatic carriers of parasite is also important. In parallel, researchers need to better characterize the respective roles of the human and animal reservoir in the maintenance of transmission and evaluate the different control strategies taken by National Control Programs in term of cost/effectiveness to help optimize them.

L'objectif de cet article est de décrire les récentes données de surveillance médicale de la Trypanosomose Humaine Africaine (THA) au Burkina Faso et en Côte d'Ivoire afin (i) de dresser un bilan de la situation actuelle de la maladie dans ces deux pays qui entretiennent depuis plus d'un siècle des liens migratoires, économiques et épidémiologiques intimes et (ii) de définir les stratégies à mettre en place dans l'objectif d'une élimination durable. Les résultats de la surveillance active et passive ont montré que les trypanosomés dépistés au Burkina-Faso ces dernières années sont tous des cas importés provenant de Côte d'Ivoire. Cependant, la réintroduction du parasite est effective et le risque d'une reprise de la transmission existe. En Côte d'Ivoire, plusieurs foyers "historiques" toujours endémiques font craindre des phénomènes de réémergence et de propagation. Dans l'objectif d'une élimination durable de la THA dans ces deux pays, les acteurs de la lutte doivent adapter leur système de surveillance en fonction des différents contextes épidémiologiques. Les prévalences actuelles ne justifient plus, excepté des cas particuliers, l'usage systématique et très onéreux du dépistage actif par prospections médicales exhaustives. Elles tendent plutôt à privilégier des systèmes intégrés aux systèmes de santé nationaux et utiliser des méthodes permettant de cibler les zones prioritaires d'intervention à partir notamment d'un échange d'informations épidémiologiques entre les deux pays. Pour accompagner le processus d'élimination durable, les acteurs de la recherche doivent étudier le rôle respectif des réservoirs humain et animal dans le maintien de la transmission, participer au suivi sur le long terme des cas traités et des suspects sérologiques, et évaluer en termes de coût/efficacité les stratégies mises en place par les Programmes Nationaux afin de les optimiser.

The situation of human African trypanosomiasis (sleeping sickness) is poorly known in Gabon. Most of the historical foci have not been investigated for more than 15 years. Few cases are passively recorded from the historical focus of Bendjé; they involved mainly fishermen but determining their contamination site is difficult because of their mobility due to their activity. The presence of these cases in that focus could favour its reactivation if the vector is still there. In order to assess a potential transmission risk in that area, an entomological survey has been carried out in it. Traps were set up during four days in different habitats used by humans during their daily activities. Three species of tsetse flies (Glossina palpalis palpalis, G. pallicera newsteadi and G. caliginea) were caught and two species of trypanosomes (Trypanosoma vivax and T. brucei s.l.) were identified by PCR. These results suggest the presence of an animal transmission cycle. Human-flies contact was confirmed in all type of habitats but no transmission was quantified in the mangrove.

ENTOMOLOGICAL SURVEY IN THE HISTORICAL SLEEPING SICKNESS FOCUS OF BENDJE (GABON)The situation of human African trypanosomiasis (sleeping sickness) is poorly known in Gabon. Most of the historical foci have not been investigated for more than 15 years. Few cases are passively recorded from the historical focus of Bendje; they involved mainly fishermen but determining their contamination site is difficult because of their mobility due to their activity. The presence of these cases in that focus could favour its reactivation if the vector is still there. In order to assess a potential transmission risk in that area, an entomological survey has been carried out in it. Traps were set up during four days in different habitats used by humans during their daily activities. Three species of tsetse flies (Glossina palpalis palpalis, G. pallicera newsteadi and G. caliginea) were caught and two species of trypanosomes (Trypanosoma vivax and I brucei s.I.) were identified by PCR. These results suggest the presence of an animal transmission cycle. Human-flies contact was confirmed in all type of habitats but no transmission was quantified in the mangrove.

Field studies were done of the responses of Glossina palpalis palpalis in Côte d'Ivoire, and G. p. gambiensis and G. tachinoides in Burkina Faso, to odours from humans, cattle and pigs. Responses were measured either by baiting (1.) biconical traps or (2.) electrocuting black targets with natural host odours. The catch of G. tachinoides from traps was significantly enhanced ( approximately 5x) by odour from cattle but not humans. In contrast, catches from electric targets showed inconsistent results. For G. p. gambiensis both human and cattle odour increased (>2x) the trap catch significantly but not the catch from electric targets. For G. p. palpalis, odours from pigs and humans increased (approximately 5x) the numbers of tsetse attracted to the vicinity of the odour source but had little effect on landing or trap-entry. For G. tachinoides a blend of POCA (P = 3-n-propylphenol; O = 1-octen-3-ol; C = 4-methylphenol; A = acetone) alone or synthetic cattle odour (acetone, 1-octen-3-ol, 4-methylphenol and 3-n-propylphenol with carbon dioxide) consistently caught more tsetse than natural cattle odour. For G. p. gambiensis, POCA consistently increased catches from both traps and targets. For G. p. palpalis, doses of carbon dioxide similar to those produced by a host resulted in similar increases in attraction. Baiting traps with super-normal (approximately 500 mg/h) doses of acetone also consistently produced significant but slight (approximately 1.6x) increases in catches of male flies. The results suggest that odour-baited traps and insecticide-treated targets could assist the AU-Pan African Tsetse and Trypanosomiasis Eradication Campaign (PATTEC) in its current efforts to monitor and control Palpalis group tsetse in West Africa. For all three species, only approximately 50% of the flies attracted to the vicinity of the trap were actually caught by it, suggesting that better traps might be developed by an analysis of the visual responses and identification of any semiochemicals involved in short-range interaction.

In order to implement or) anti-vector programme in the suburb of Abidjan (Cote d'Ivoire), investigations were conducted to assess the tsetse fly densities as well as infection with trypanosomes. Catches were carried out during the rainy season and dry season with Vavoua traps laid during four consecutive days in different sites (Banco forest, Abidjan zoological park, area of the University of Abobo-Adjame). One species of tsetse fly (Glossina palpalis palpalis) and two species of tryponosomes (Trypanosoma congolense, T. vivax) have been revealed. The apparent density per trap per day (DAP) is very high in the zoological park, 54.8 tsetse fly/trap/day during the dry season and 28.1 during the rainy season. At the University of Abobo-Adjame, the DAP is respectively 13.5 and 8.1 tsetse fly/trap/day during the rainy season, and in the dry season it is only 0.9 and 0.8 in the Banco Forest. The physiological age on all sites is as follows: 57.5% of old porous, 39% of young porous and 3.6% of nulliparous in the rainy season. These proportions vary to 51.9% of young porous, 47.1% of old porous and 1% of nulliporous in the dry season. The overall infection fate is estimated at 20.7% in the rainy season and 20% in the cry season. Statistical analysis have showed a significant difference in the distribution of infection rates.