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Towards elimination of human African trypanosomiasis Human African Trypanosomiasis (HAT) is caused by Trypanosoma brucei which is transmitted by the tsetse fly insect vector (Glossina spp). It is one of the 20 Neglected Tropical Diseases (NTD) listed by the WHO. These diseases affect the poorest and most vulnerable communities, for which the WHO has established a dedicated 2021-2030 roadmap. At the time of Alphonse Laveran, HAT devastated the African continent. In the 1960s, the disease was nearly under control, but it strongly re-emerged in the 1990s. A coordinated effort of all stakeholders, with national control programs as the main actors, a strong contribution of research and important donations by the private sector, allowed to decrease the HAT burden significantly. Since 2018, less than 1000 cases are detected annually. We here review new diagnostics, treatments and vector control tools that have been implemented jointly and successfully in several endemic countries. The next key challenge will be to sustain the gains. Newly emerging research questions include long-term carriage of trypanosomes and adaptation of tools to low prevalence contexts. Challenges out of the research area comprise the continued need of funding, maintenance of dedicated human resources, and the key question of access. Sustainable elimination as “interruption of transmission”, which is the 2030 NTD roadmap target, can be reached, if these challenges are solved. We stress the importance of continuing to combine the efforts in the fight against the disease, because sustainable elimination of HAT is the best long-term prevention strategy against re-emergence. As such, HAT elimination can serve as an example for other infectious diseases. Vers l’élimination de la maladie du sommeil La maladie du sommeil, ou trypanosomiase humaine africaine (THA), est due à Trypanosoma brucei transmis par la glossine 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., MTSI, Vol. 3 No 1 (2023): MTSI-Revue

Additional file 1: Table S1. Microscopic observation of the midgut and the salivary glands of 274 G. f. fuscipes (144 from batch 1 and 130 from batch 2) for the presence of T. b. brucei.

Additional file 1. Additional model description, results and PRIME-NTD criteria checklist.

Vector-borne diseases affecting livestock have serious impacts in Africa. Trypanosomosis is caused by parasites transmitted by tsetse flies and other blood-sucking Diptera. The animal form of the disease is a scourge for African livestock keepers, is already present in Latin America and Asia, and has the potential to spread further. A human form of the disease also exists, known as human African trypanosomosis or sleeping sickness. Controlling and progressively minimizing the burden of animal trypanosomosis (COMBAT) is a four-year research and innovation project funded by the European Commission, whose ultimate goal is to reduce the burden of animal trypanosomosis (AT) in Africa. The project builds on the progressive control pathway (PCP), a risk-based, step-wise approach to disease reduction or elimination. COMBAT will strengthen AT control and prevention by improving basic knowledge of AT, developing innovative control tools, reinforcing surveillance, rationalizing control strategies, building capacity, and raising awareness. Knowledge gaps on disease epidemiology, vector ecology and competence, and biological aspects of trypanotolerant livestock will be addressed. Environmentally friendly vector control technologies and more effective and adapted diagnostic tools will be developed. Surveillance will be enhanced by developing information systems, strengthening reporting, and mapping and modelling disease risk in Africa and beyond. The socio-economic burden of AT will be assessed at a range of geographical scales. Guidelines for the PCP and harmonized national control strategies and roadmaps will be developed. Gender equality and ethics will be pivotal in all project activities. The COMBAT project benefits from the expertise of African and European research institutions, national veterinary authorities, and international organizations. The project consortium comprises 21 participants, including a geographically balanced representation from 13 African countries, and it will engage a larger number of AT-affected countries through regional initiatives.

La trypanosomiase humaine africaine ou maladie du sommeil est causée par plusieurs sous-espèces membres de l'espèce Trypanosoma brucei : Trypanosoma brucei rhodesiense (Tbr) et Trypanosoma brucei gambiense groupe 1 (Tbg1). Leur biologie a été étudiée en détail, en particulier en ce qui concerne les protéines impliquées dans les mécanismes de résistance au sérum humain (SH). Il existe un autre groupe également capable d'infecter l'homme nommé Trypanosoma brucei gambiense groupe 2 (Tbg2). Celui-ci se résume à une trentaine de souches répertoriées dans la littérature, ne pose pas de problème de santé publique et par conséquent a été très peu étudié, pour ne pas dire oublié. Après un rappel des mécanismes qui permettent à Tbr et Tbg1 de résister à l'action lytique du SH, nous résumerons les connaissances acquises sur Tbg2. Les phénotypes de résistance au sérum humain sont très variables et seulement une de ces souches a fait l'objet de quelques recherches. La résistance de cette dernière est conditionnelle et implique des mécanismes ayant une action directe sur ApoL-1. Cette revue sera donc l'occasion non seulement de rappeler l'état des connaissances concernant la « course à l'armement » menée entre les trypanosomes et l'homme au cours de l'évolution, mais nous permettra également d'entamer une réflexion sur ce groupe particulier et hétérogène qu'est Tbg2, un trypanosome pathogène pour l'homme mais dont le caractère zoonotique doit être pris en compte dans la perspective du contexte de post-élimination de la maladie du sommeil.

Background Significant efforts to control human African trypanosomiasis (HAT) over the two past decades have resulted in drastic decrease of its prevalence in Côte d’Ivoire. In this context, passive surveillance, integrated in the national health system and based on clinical suspicion, was reinforced. We describe here the health-seeking pathway of a girl who was the first HAT patient diagnosed through this strategy in August 2017. Methods After definitive diagnosis of this patient, epidemiological investigations were carried out into the clinical evolution and the health and therapeutic itinerary of the patient before diagnosis. Results At the time of diagnosis, the patient was positive in both serological and molecular tests and trypanosomes were detected in blood and cerebrospinal fluid. She suffered from important neurological disorders. The first disease symptoms had appeared three years earlier, and the patient had visited several public and private peripheral health care centres and hospitals in different cities. The failure to diagnose HAT for such a long time caused significant health deterioration and was an important financial burden for the family. Conclusion This description illustrates the complexity of detecting the last HAT cases due to complex diagnosis and the progressive disinterest and unawareness by both health professionals and the population. It confirms the need of implementing passive surveillance in combination with continued sensitization and health staff training., Author summary Human African trypanosomiasis (HAT) or sleeping sickness is a parasitic disease caused by Trypanosoma brucei that is transmitted by tsetse flies. In 2012, HAT was included in the World Health Organization roadmap for the control of neglected tropical diseases with the objective of elimination as a public health problem by 2020. In Côte d’Ivoire, HAT prevalence has dropped sharply the last decade. A passive HAT surveillance was therefore integrated in the national health system, which allowed to detect a first patient in 2017. This article describes the complex health seeking pathway and suffering before diagnosis of this patient, an 11 years old girl, and illustrates the challenge when health agents and population no longer consider HAT as a threat in an elimination context. Our results show the need to install a solid surveillance system, in combination with continued sensitization and repeated health staff training.

Background: Since 2012, the World Health Organisation and the countries affected by the Gambian form of human African trypanosomiasis (HAT) have been committed to eliminating the disease, primarily through active case-finding and treatment. To interrupt transmission of Trypanosoma brucei gambiense and move more rapidly towards elimination, it was decided to add vector control using 'tiny targets'. Chad's Mandoul HAT focus extends over 840 km(2), with a human population of 39,000 as well as 14,000 cattle and 3000 pigs. Some 2700 tiny targets were deployed annually from 2014 onwards. Methods: A protocol was developed for the routine collection of tsetse control costs during all field missions. This was implemented throughout 2015 and 2016, and combined with the recorded costs of the preliminary survey and sensitisation activities. The objective was to calculate the full costs at local prices in Chad. Costs were adjusted to remove research components and to ensure that items outside the project budget lines were included, such as administrative overheads and a share of staff salaries. Results: Targets were deployed at about 60 per linear km of riverine tsetse habitat. The average annual cost of the operation was USD 56,113, working out at USD 66.8 per km(2) protected and USD 1.4 per person protected. Of this, 12.8% was an annual share of the initial tsetse survey, 40.6% for regular tsetse monitoring undertaken three times a year, 36.8% for target deployment and checking and 9.8% for sensitisation of local populations. Targets accounted for 8.3% of the cost, and the cost of delivering a target was USD 19.0 per target deployed. Conclusions: This study has confirmed that tiny targets provide a consistently low cost option for controlling tsetse in gambiense HAT foci. Although the study area is remote with a tsetse habitat characterised by wide river marshes, the costs were similar to those of tiny target work in Uganda, with some differences, in particular a higher cost per target delivered. As was the case in Uganda, the cost was between a quarter and a third that of historical target operations using full size targets or traps.

Additional file 2: Text S2. Cost data collection protocol (in French).

Additional file 1: Text S1. Cost data collection protocol.

Les trypanosomiases humaines et animales, maladies mortelles affectant les plus pauvres, sont dues à des trypanosomes transmis de manière cyclique par la mouche tsé-tsé, et mécaniquement par d'autres insectes hématophages. Toute action visant à éliminer le vecteur aura donc un impact sur la transmission de ces parasites. Nous revoyons ici les différents contextes, stratégies, et méthodes de lutte existantes appliquées en Afrique, ainsi que quelques perspectives de recherche prometteuses