Trypanosomiasis prevalence in the cotton basin in the Sudanese zone of Côte d'Ivoire

La prévalence trypanosomienne a été évaluée dans les cheptels du bassin cotonnier en zone soudanaise de Côte d’Ivoire. Les prélèvements de sang ont été effectués du 22 avril au 21 mai 2016, sur 582 bovins dont 374 mâles et 195 femelles, appartenant aux phénotypes Méré, Zébu et Ndama. Les espèces de trypanosomes ont été d’abord identifiées sur le terrain à partir de frottis sanguins, puis caractérisées au laboratoire au moyen de la PCR (Polymerase Chain Reaction). Les trois espèces diagnostiquées sont, dans l’ordre décroissant de leur taux de prévalence, Trypanosoma congolense groupe savane, Trypanosoma vivax et Trypanosoma brucei brucei. Le plus grand nombre de bovins infectés provient de Korhogo, suivi de M’Bengué, puis de Ferkessédougou. Le taux d’infection est plus faible et du même ordre à Katiola, Koumbala, Diawara et Niellé. Les Méré sont les plus infectés par rapport aux Zébu et aux Ndama. Ces derniers sont les plus faiblement infectés. Chez les Ndama, la trypanotolérance apparaît encore plus efficiente chez les animaux de moins de 8 ans. Les Méré montrent une forte parasitémie due à Trypanosoma congolense ou à Trypanosoma vivax, sans toutefois faire la maladie. Mots clés : TAA, Prévalence, Zone soudanaise, Côte d’IvoireTrypanosomiais prevalence was evaluated in the flocks of the cotton basin in the Sudanese zone of Côte d'Ivoire. The blood samples were taken from April 22 to May 21, 2016, on 582 cattle including 374 males and 195 females, belonging to the phenotypes Méré, Zébu and Ndama. Trypanosome species were first identified in the field from blood smears and then characterized in the laboratory using PCR (Polymerase Chain Reaction). The three species diagnosed are, in decreasing order of their prevalence rate, Trypanosoma congolense savannah group, Trypanosoma vivax and Trypanosoma brucei brucei. Most of the infected cattle come from Korhogo, followed by M'Bengué and then Ferkessédougou. The infection rate is lower and of the same order in Katiola, Koumbala, Diawara and Niellé. Méré are the most infected compared to Zebu and Ndama. The latter are the most weakly infected. For the Ndama, trypanotolerance appears to be even more efficient in animals less than 8 years old. The Méré show a strong parasitaemia due to Trypanosoma congolense or Trypanosoma vivax, without however being sick. Keywords : AAT, Prevalence, Sudanese zone, Côte d’Ivoir

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

Use of vector control to protect people from sleeping sickness in the focus of Bonon (Côte d’Ivoire)

Background Gambian human African trypanosomiasis (gHAT) is a neglected tropical disease caused by Trypanosoma brucei gambiense transmitted by tsetse flies (Glossina). In Côte d’Ivoire, Bonon is the most important focus of gHAT, with 325 cases diagnosed from 2000 to 2015 and efforts against gHAT have relied largely on mass screening and treatment of human cases. We assessed whether the addition of tsetse control by deploying Tiny Targets offers benefit to sole reliance on the screen-and-treat strategy. Methodology and principal findings In 2015, we performed a census of the human population of the Bonon focus, followed by an exhaustive entomological survey at 278 sites. After a public sensitization campaign, ~2000 Tiny Targets were deployed across an area of 130 km2 in February of 2016, deployment was repeated annually in the same month of 2017 and 2018. The intervention’s impact on tsetse was evaluated using a network of 30 traps which were operated for 48 hours at three-month intervals from March 2016 to December 2018. A second comprehensive entomological survey was performed in December 2018 with traps deployed at 274 of the sites used in 2015. Sub-samples of tsetse were dissected and examined microscopically for presence of trypanosomes. The census recorded 26,697 inhabitants residing in 331 settlements. Prior to the deployment of targets, the mean catch of tsetse from the 30 monitoring traps was 12.75 tsetse/trap (5.047–32.203, 95%CI), i.e. 6.4 tsetse/trap/day. Following the deployment of Tiny Targets, mean catches ranged between 0.06 (0.016–0.260, 95%CI) and 0.55 (0.166–1.794, 95%CI) tsetse/trap, i.e. 0.03–0.28 tsetse/trap/day. During the final extensive survey performed in December 2018, 52 tsetse were caught compared to 1,909 in 2015, with 11.6% (5/43) and 23.1% (101/437) infected with Trypanosoma respectively. Conclusions The annual deployment of Tiny Targets in the gHAT focus of Bonon reduced the density of Glossina palpalis palpalis by >95%. Tiny Targets offer a powerful addition to current strategies towards eliminating gHAT from Côte d’Ivoire

Tsetse fly ecology and risk of transmission of African trypanosomes related to a protected forest area at a military base in the city of Abidjan, Côte d’Ivoire

African trypanosomoses, whose pathogens are transmitted by tsetse flies, are a threat to animal and human health. Tsetse flies observed at the military base of the French Forces in Côte d’Ivoire (FFCI base) were probably involved in the infection and death of military working dogs. Entomological and parasitological surveys were carried out during the rainy and dry seasons using “Vavoua” traps to identify tsetse fly species, their distribution, favorable biotopes and food sources, as well as the trypanosomes they harbor. A total of 1185 Glossina palpalis palpalis tsetse flies were caught, corresponding to a high average apparent density of 2.26 tsetse/trap/day. The results showed a heterogeneous distribution of tsetse at the FFCI base, linked to more or less favorable biotopes. No significant variation in tsetse densities was observed according to the season. The overall trypanosomes infection rate according to microscopic observation was 13.5%. Polymerase chain reaction (PCR) analyses confirmed the presence of Trypanosoma vivax and T. congolense forest type, responsible for African animal trypanosomosis. Our findings suggest that there is a risk of introduction and transmission of T. brucei gambiense, responsible for human African trypanosomiasis, on the study site. This risk of transmission of African trypanosomes concerns not only the FFCI base, but also inhabited peripheral areas. Our study confirmed the need for vector control adapted to the eco-epidemiological context of the FFCI base

Active Dépistage actif vers dépistage passif de la Trypanosomiase Humaine Africaine en Côte d’Ivoire: impact sur l’efficacité de la lutte médicale

Human African Trypanosomiasis is a threat in Côte d'Ivoire, despite the declaration of its elimination in 2021. The medical fight against this disease was first based on active screening in the localities and then on reactive and passive screening in health centers. Through a sociological approach, the objective of this paper is to understand the impact of the shift from active to passive screening on the efficacity of medical control, particularly in Bonon and Sinfra in the central-western region. The analysis is based on both qualitative and quantitative data collected from actors involved in the fight against this disease and from a sample of 398 peoples. The results show that in a context of declining prevalence, the shift from active to passive screening was based on a cost-effective economy of scale. However, this change in approach had a negative impact on the efficacity of medical control insofar as it increased the population's disinterest in control activities. This lack of interest can be explained by the lack of communication about the change of approach, the perception that the disease does not exist because of the rarity of cases, and the cost-benefit calculations between passive screening and screening. La Trypanosomiase Humaine Africaine, constitue une menace en Côte d’Ivoire, malgré la déclaration de son élimination en 2021. La lutte médicale contre cette maladie a reposé d’abord sur le dépistage actif gratuit dans les localités puis sur le dépistage réactif et passif gratuit dans des structures sanitaires. A travers une posture sociologique, l’objectif de cette communication est de comprendre l’incidence du passage du dépistage actif au dépistage passif sur l’efficacité de la lutte médicale, notamment à Bonon et Sinfra dans le Centre-Ouest. L’analyse, s’appuie sur des données à la fois qualitative et quantitative collectées auprès d’acteurs intervenant dans la lutte contre cette maladie d’une part et d’un échantillon de 398 personnes. Les résultats révèlent que dans un contexte de baisse de la prévalence le passage du dépistage actif au dépistage passif s’est inscrit dans une logique d’économie d’échelle coût-efficacité. Cependant, ce changement d’approche a impacté négativement l’efficacité de la lutte médicale. Il a accentué le désintérêt des populations des activités de lutte. Ce désintérêt s’explique par le manque de communication autour du changement d’approche, la perception de l’inexistence de la maladie du fait de la rareté des cas, et les calculs coût-bénéfices entre le dépistage passif et le dépistage actif

Active Dépistage actif vers dépistage passif de la Trypanosomiase Humaine Africaine en Côte d’Ivoire: impact sur l’efficacité de la lutte médicale

Human African Trypanosomiasis is a threat in Côte d'Ivoire, despite the declaration of its elimination in 2021. The medical fight against this disease was first based on active screening in the localities and then on reactive and passive screening in health centers. Through a sociological approach, the objective of this paper is to understand the impact of the shift from active to passive screening on the efficacity of medical control, particularly in Bonon and Sinfra in the central-western region. The analysis is based on both qualitative and quantitative data collected from actors involved in the fight against this disease and from a sample of 398 peoples. The results show that in a context of declining prevalence, the shift from active to passive screening was based on a cost-effective economy of scale. However, this change in approach had a negative impact on the efficacity of medical control insofar as it increased the population's disinterest in control activities. This lack of interest can be explained by the lack of communication about the change of approach, the perception that the disease does not exist because of the rarity of cases, and the cost-benefit calculations between passive screening and screening. La Trypanosomiase Humaine Africaine, constitue une menace en Côte d’Ivoire, malgré la déclaration de son élimination en 2021. La lutte médicale contre cette maladie a reposé d’abord sur le dépistage actif gratuit dans les localités puis sur le dépistage réactif et passif gratuit dans des structures sanitaires. A travers une posture sociologique, l’objectif de cette communication est de comprendre l’incidence du passage du dépistage actif au dépistage passif sur l’efficacité de la lutte médicale, notamment à Bonon et Sinfra dans le Centre-Ouest. L’analyse, s’appuie sur des données à la fois qualitative et quantitative collectées auprès d’acteurs intervenant dans la lutte contre cette maladie d’une part et d’un échantillon de 398 personnes. Les résultats révèlent que dans un contexte de baisse de la prévalence le passage du dépistage actif au dépistage passif s’est inscrit dans une logique d’économie d’échelle coût-efficacité. Cependant, ce changement d’approche a impacté négativement l’efficacité de la lutte médicale. Il a accentué le désintérêt des populations des activités de lutte. Ce désintérêt s’explique par le manque de communication autour du changement d’approche, la perception de l’inexistence de la maladie du fait de la rareté des cas, et les calculs coût-bénéfices entre le dépistage passif et le dépistage actif

Dynamiques territoriales en périphérie des Parcs Nationaux de Taï et de la Comoé (Côte d’Ivoire)

En Afrique subsaharienne, la croissance démographique et la variabilité climatique génèrent d’importants mouvements de population en direction des espaces protégés. Ces changements n’épargnent pas la Côte d’Ivoire où la population est passée de 2,6 millions d’habitants (8 hab./km2) en 1950 à 23,1 millions d’habitants (soit 71,6 hab./km2) en 2015 (UN, 2017). Les dynamiques de peuplements impulsées par cette croissance démographique ont abouti à une saturation foncière, ce qui a orienté les populations agricoles en direction des espaces protégés générant ainsi des fronts pionniers agricoles à l’intérieur et en périphérie de ces territoires. Aujourd’hui, la raréfaction des ressources foncières en périphérie des espaces protégés ivoiriens témoigne de l’ampleur de la saturation foncière, et suscite une convoitise accrue des ressources de ces espaces (agriculture, chasse, pêche, cueillette, orpaillage), mettant ainsi en péril leur biodiversité. L’objectif de cette étude est de rendre compte des processus d’exploitation de deux territoires situés en marge d’espaces protégés, afin d’entrevoir l’évolution de la pression anthropique. Il s’agit de caractériser les dynamiques de peuplements (création, extension et multiplication des peuplements, augmentation des densités de populations humaines) et les évolutions de l’emprise rurale (superficies cultivées et types de cultures) en périphérie du Parc National de Taï (forêt) et du Parc National de la Comoé (savane). En raison de la pression anthropique actuelle et des projections démographiques annoncées dans un contexte de variabilité climatique, il est nécessaire de s’interroger sur le devenir à plus ou moins long terme des aires protégées ivoiriennes.In Sub-Saharan Africa, population growth and climatic variability generated significant population movements towards protected areas. These changes do not spared Côte d’Ivoire where the population has increased from 2.6 million (8 inh/km2) in 1950 to 23.1 million in 2015 (71,6 inh/km2) (UN, 2017). The population dynamics driven by this demographic growth have led to land saturation, which has directed agricultural populations towards protected areas, thus generating pioneer agricultural front at the periphery of these territories. Today, the disappearance of land resources on the periphery of Ivorian protected areas testifies to the extreme greed of these areas (agriculture, hunting, fishing, gathering, gold panning), with a risk for biodiversity in National Parks and classified forests. The objective of this study is to report the dynamics of territories situated in margins of two main protected areas of Côte d’Ivoire. It is a question of characterizing the dynamics of stands (creation, extension and multiplication of settlements, increase of densities of human populations) and evolutions of the rural hold (cultivated areas and types of crops) on the outskirts of the Tai National Park (forest) and the Comoé National Park (savannah). Given the current human pressure and demographic projections, it is necessary to consider the future of Ivorian protected areas in longer or shorter term

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

International audienceBackground 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

A targeted door-to-door strategy for sleeping sickness detection in low-prevalence settings in Côte d’Ivoire

Significant efforts to control human African trypanosomiasis (HAT) over the three past decades have resulted in drastic reductions of disease prevalence in Côte d’Ivoire. In this context, the costly and labor-intensive active mass screening strategy is no longer efficient. In addition to a more cost-effective passive surveillance system being implemented in this low-prevalence context, our aim was to develop an alternative targeted active screening strategy. In 2012, we carried out a targeted door-to-door (TDD) survey focused on the immediate vicinities of former HAT patients detected in the HAT focus of Bonon and compared the results to those obtained during classical active mass screening (AMS) surveys conducted from 2000 to 2012 in the same area. The TDD that provides a friendlier environment, inviting inhabitants to participate and gain awareness of the disease, detected significantly more HAT cases than the AMS. These results suggest that the TDD is an efficient and useful strategy in low-prevalence settings where very localized transmission cycles may persist and, in combination with passive surveillance, could help in eliminating HAT