Comparison of stochastic and deterministic models for gambiense sleeping sickness at different spatial scales: A health area analysis in the DRC.

The intensification of intervention activities against the fatal vector-borne disease gambiense human African trypanosomiasis (gHAT, sleeping sickness) in the last two decades has led to a large decline in the number of annually reported cases. However, while we move closer to achieving the ambitious target of elimination of transmission (EoT) to humans, pockets of infection remain, and it becomes increasingly important to quantitatively assess if different regions are on track for elimination, and where intervention efforts should be focused. We present a previously developed stochastic mathematical model for gHAT in the Democratic Republic of Congo (DRC) and show that this same formulation is able to capture the dynamics of gHAT observed at the health area level (approximately 10,000 people). This analysis was the first time any stochastic gHAT model has been fitted directly to case data and allows us to better quantify the uncertainty in our results. The analysis focuses on utilising a particle filter Markov chain Monte Carlo (MCMC) methodology to fit the model to the data from 16 health areas of Mosango health zone in Kwilu province as a case study. The spatial heterogeneity in cases is reflected in modelling results, where we predict that under the current intervention strategies, the health area of Kinzamba II, which has approximately one third of the health zone's cases, will have the latest expected year for EoT. We find that fitting the analogous deterministic version of the gHAT model using MCMC has substantially faster computation times than fitting the stochastic model using pMCMC, but produces virtually indistinguishable posterior parameterisation. This suggests that expanding health area fitting, to cover more of the DRC, should be done with deterministic fits for efficiency, but with stochastic projections used to capture both the parameter and stochastic variation in case reporting and elimination year estimations.

Limited impact of vector control on the population genetic structure of Glossina fuscipes fuscipes from the sleeping sickness focus of Maro, Chad.

Tsetse flies (genus Glossina) transmit deadly trypanosomes to human populations and domestic animals in sub-Saharan Africa. Some foci of Human African Trypanosomiasis due to Trypanosoma brucei gambiense (g-HAT) persist in southern Chad, where a program of tsetse control was implemented against the local vector Glossina fuscipes fuscipes in 2018 in Maro. We analyzed the population genetics of G. f. fuscipes from the Maro focus before control (T0), one year (T1), and 18 months (T2) after the beginning of control efforts. Most flies captured displayed a local genetic profile (local survivors), but a few flies displayed outlier genotypes. Moreover, disturbance of isolation by distance signature (increase of genetic distance with geographic distance) and effective population size estimates, absence of any genetic signature of a bottleneck, and an increase of genetic diversity between T0 and T2 strongly suggest gene flows from various origins, and a limited impact of the vector control efforts on this tsetse population. Continuous control and surveillance of g-HAT transmission is thus recommended in Maro. Particular attention will need to be paid to the border with the Central African Republic, a country where the entomological and epidemiological status of g-HAT is unknown.

Title: Impact limité de la lutte antivectorielle sur la structure des populations de Glossina fuscipes fuscipes dans le foyer de la maladie du sommeil de Maro, Tchad. Abstract: Les mouches tsé-tsé (genre Glossina) transmettent des trypanosomes mortels aux populations humaines ainsi qu'aux animaux domestiques en Afrique sub-saharienne. Certains foyers de la trypanosomiase humaine Africaine due à Trypanosoma brucei gambiense (THA-g) persistent au sud du Tchad, où un programme de lutte antivectorielle a été mis en place contre le vecteur local de la maladie, Glossina fuscipes fuscipes, en particulier à Maro en 2018. Nous avons analysé la structure génétique des populations de G. f. fuscipes de ce foyer à T0 (avant lutte), une année après le début de la lutte (T1), et 18 mois après (T2). La plupart des mouches capturées après le début de la lutte ont montré un profil génétique local (survivants locaux), mais quelques-unes d'entre elles présentaient des génotypes d'individus atypiques. Par ailleurs, la présence de perturbations des signatures d'isolement par la distance (augmentation de la distance génétique avec la distance géographique), l'absence de signature génétique d'un goulot d'étranglement, et un accroissement de la diversité génétique entre T0 et T2 sont des arguments forts en faveur de la recolonisation de la zone par des mouches d'origines variées, tout en témoignant des effets limités de la campagne de lutte dans ce foyer. Ces résultats conduisent à recommander une lutte et une surveillance continues dans le foyer de Maro. Une attention particulière devra par ailleurs être prêtée à l'autre côté de la rive, située côté République Centre Africaine, dont le statut épidémiologique reste inconnu concernant les tsé-tsé et la THA-g.

Trypanosoma brucei gambiense group 2 experimental in vivo life cycle: from procyclic to bloodstream form.

Trypanosoma brucei gambiense (Tbg) group 2 is a subgroup of trypanosomes able to infect humans and is found in West and Central Africa. Unlike other agents causing sleeping sickness, such as Tbg group 1 and Trypanosoma brucei rhodesiense, Tbg2 lacks the typical molecular markers associated with resistance to human serum. Only 36 strains of Tbg2 have been documented, and therefore, very limited research has been conducted despite their zoonotic nature. Some of these strains are only available in their procyclic form, which hinders human serum resistance assays and mechanistic studies. Furthermore, the understanding of Tbg2's potential to infect tsetse flies and mammalian hosts is limited. In this study, 165 Glossina palpalis gambiensis flies were experimentally infected with procyclic Tbg2 parasites. It was found that 35 days post-infection, 43 flies out of the 80 still alive were found to be Tbg2 PCR-positive in the saliva. These flies were able to infect 3 out of the 4 mice used for blood-feeding. Dissection revealed that only six flies in fact carried mature infections in their midguts and salivary glands. Importantly, a single fly with a mature infection was sufficient to infect a mammalian host. This Tbg2 transmission success confirms that Tbg2 strains can establish in tsetse flies and infect mammalian hosts. This study describes an effective in vivo protocol for transforming Tbg2 from procyclic to bloodstream form, reproducing the complete Tbg2 cycle from G. p. gambiensis to mice. These findings provide valuable insights into Tbg2's host infectivity, and will facilitate further research on mechanisms of human serum resistance.

Title: Cycle de vie expérimental in vivo de Trypanosoma brucei gambiense groupe 2 : de la forme procyclique à la forme sanguicole. Abstract: Trypanosoma brucei gambiense (Tbg) groupe 2 est un sous-groupe de trypanosomes capables d'infecter l'Homme, présent en Afrique de l'Ouest et en Afrique centrale. Contrairement aux autres agents responsables de la maladie du sommeil, tels que Tbg groupe 1 et Trypanosoma brucei rhodesiense, Tbg2 ne présente pas les marqueurs moléculaires habituellement associés à la résistance au sérum humain. Seules trente-six souches de Tbg2 ont été répertoriées, limitant considérablement les recherches sur ce sous-groupe malgré sa nature zoonotique. Certaines de ces souches ne sont disponibles que sous leur forme procyclique, ce qui freine la réalisation des tests de résistance au sérum humain et les études mécanistiques. De plus, la compréhension du potentiel de Tbg2 à infecter les glossines et les hôtes mammifères est limitée. Dans cette étude, 165 glossines Glossina palpalis gambiensis ont été infectées expérimentalement par des parasites Tbg2 sous leur forme procyclique. Trente-cinq jours après l'infection, 43 des 80 glossines encore en vie se sont révélées positives à Tbg2 en PCR sur leur salive. Ces glossines ont réussi à infecter trois des quatre souris utilisées pour leur repas de sang. La dissection des glossines a révélé que seules six d'entre elles étaient réellement porteuses d'infections matures dans leur intestin et leurs glandes salivaires. Il est important de noter qu'une seule glossine porteuse d'une infection mature a suffi pour infecter un hôte mammifère. Ce succès de transmission de Tbg2 confirme que les souches de Tbg2 peuvent s'établir dans les glossines et infecter des hôtes mammifères. Cette étude décrit un protocole in vivo pour transformer la forme procyclique de Tbg2 en forme sanguicole, en reproduisant le cycle complet de Tbg2 de G. p. gambiensis à la souris. Ces résultats fournissent des informations précieuses sur le potentiel infectieux de Tbg2 et faciliteront la recherche sur les mécanismes de résistance au sérum humain des souches.

Antitrypanosomal Chloronitrobenzamides.

Human African trypanosomiasis (HAT), a neglected tropical disease caused by Trypanosoma brucei gambiense (Tbg) or Trypanosoma brucei rhodesiense (Tbr), remains a significant public health concern with over 55 million people at risk of infection. Current treatments for HAT face the challenges of poor efficacy, drug resistance, and toxicity. This study presents the synthesis and evaluation of chloronitrobenzamides (CNBs) against Trypanosoma species, identifying previously reported compound 52 as a potent and selective orally bioavailable antitrypanosomal agent. 52 was well tolerated in vivo and demonstrated favorable oral pharmacokinetics, maintaining plasma concentrations surpassing the cellular EC50 for over 24 h and achieving peak brain concentrations exceeding 7 µM in rodents after single oral administration (50 mg/kg). Treatment with 52 significantly extended the lifespan of mice infected with Trypanosoma congolense and T. brucei rhodesiense. These results demonstrate that 52 is a strong antitrypanosomal lead with potential for developing treatments for both human and animal African trypanosomiasis.

In vitro anti-trypanosomal activity of synthetic nitrofurantoin-triazole hybrids against Trypanosoma species causing human African trypanosomosis.

Human African trypanosomosis (HAT) which is also known as sleeping sickness is caused by Trypanosoma brucei gambiense that is endemic in western and central Africa and T. b. rhodesiense that is endemic in eastern and southern Africa. Drugs used for treatment against HAT first stage have limited effectiveness, and the second stage drugs have been reported to be toxic, expensive, and have time-consuming administration, and parasitic resistance has developed against these drugs. The aim of this study was to evaluate the anti-trypanosomal activity of nitrofurantoin-triazole hybrids against T. b. gambiense and T. b. rhodesiense parasites in vitro. This study screened 19 synthesized nitrofurantoin-triazole (NFT) hybrids on two strains of human trypanosomes, and cytotoxicity was evaluated on Madin-Darby bovine kidney (MDBK) cells. The findings in this study showed that an increase in the chain length and the number of carbon atoms in some n-alkyl hybrids influenced the increase in anti-trypanosomal activity against T. b. gambiense and T. b. rhodesiense. The short-chain n-alkyl hybrids showed decreased activity compared to the long-chain n-alkyl hybrids, with increased activity against both T. b. gambiense and T. b. rhodesiense. Incorporation of additional electron-donating substituents in some NFT hybrids showed increased anti-trypanosomal activity than to electron-withdrawing substituents in NFT hybrids. All 19 NFT hybrids tested displayed better anti-trypanosomal activity against T. b. gambiense than T. b. rhodesiense. The NFT hybrid no. 16 was among the best performing hybrids against both T. b. gambiense (0.08 ± 0.04 µM) and T. b.rhodesiense (0.11 ± 0.06 µM), and its activity might be influenced by the introduction of fluorine in the para-position on the benzyl ring. Remarkably, the NFT hybrids in this study displayed weak to moderate cytotoxicity on MDBK cells. All of the NFT hybrids in this study had selectivity index values ranging from 18 to greater than 915, meaning that they were up to 10-100 times fold selective in their anti-trypanosomal activity. The synthesized NFT hybrids showed strong selectivity >10 to T. b. gambiense and T. b. rhodesiense, which indicates that they qualify from the initial selection criteria for potential hit drugs.

Discovery of an orally active nitrothiophene-based antitrypanosomal agent.

Human African Trypanosomiasis (HAT), caused by Trypanosoma brucei gambiense and rhodesiense, is a parasitic disease endemic to sub-Saharan Africa. Untreated cases of HAT can be severely debilitating and fatal. Although the number of reported cases has decreased progressively over the last decade, the number of effective and easily administered medications is very limited. In this work, we report the antitrypanosomal activity of a series of potent compounds. A subset of molecules in the series are highly selective for trypanosomes and are metabolically stable. One of the compounds, (E)-N-(4-(methylamino)-4-oxobut-2-en-1-yl)-5-nitrothiophene-2-carboxamide (10), selectively inhibited the growth of T. b. brucei, T. b. gambiense and T. b. rhodesiense, have excellent oral bioavailability and was effective in treating acute infection of HAT in mouse models. Based on its excellent bioavailability, compound 10 and its analogs are candidates for lead optimization and pre-clinical investigations.

Modelling host- Trypanosoma brucei gambiense interactions in vitro using human induced pluripotent stem cell-derived cortical brain organoids.

Background: Sleeping sickness is caused by the extracellular parasite Trypanosoma brucei and is associated with neuroinflammation and neuropsychiatric disorders, including disruption of sleep/wake patterns, and is now recognised as a circadian disorder. Sleeping sickness is traditionally studied using murine models of infection due to the lack of alternative in vitro systems that fully recapitulate the cellular diversity and functionality of the human brain. The aim of this study is to develop a much-needed in vitro system that reduces and replaces live animals for the study of infections in the central nervous system, using sleeping sickness as a model infection. Methods: We developed a co-culture system using induced pluripotent stem cell (iPSC)-derived cortical human brain organoids and the human pathogen T. b. gambiense to model host-pathogen interactions in vitro. Upon co-culture, we analysed the transcriptional responses of the brain organoids to T. b. gambiense over two time points. Results: We detected broad transcriptional changes in brain organoids exposed to T. b. gambiense, mainly associated with innate immune responses, chemotaxis, and blood vessel differentiation compared to untreated organoids. Conclusions: Our co-culture system provides novel, more ethical avenues to study host-pathogen interactions in the brain as alternative models to experimental infections in mice. Although our data support the use of brain organoids to model host-pathogen interactions during T. brucei infection as an alternative to in vivo models, future work is required to increase the complexity of the organoids ( e.g., addition of microglia and vasculature). We envision that the adoption of organoid systems is beneficial to researchers studying mechanisms of brain infection by protozoan parasites. Furthermore, organoid systems have the potential to be used to study other parasites that affect the brain significantly reducing the number of animals undergoing moderate and/or severe protocols associated with the study of neuroinflammation and brain infections.

Target product profile: Trypanosoma brucei gambiense test to verify elimination.

Human African trypanosomiasis is a life-threatening parasitic infection transmitted by the tsetse fly in sub-Saharan Africa. The most common form is caused by Trypanosoma brucei gambiense, with humans as the main reservoir. Diagnosis in the field requires microscopic examination performed by specifically trained personnel. After over two decades of sustained efforts, the incidence of the disease is strongly declining, and some historically endemic countries are no longer detecting cases. The World Health Organization (WHO) has targeted the elimination of transmission of gambiense human African trypanosomiasis by 2030, defined as zero autochthonous cases for at least five consecutive years. Endemic countries reaching this goal must maintain dedicated surveillance to detect re-emergence or re-introduction. With this new agenda, new tools are needed for verification of the absence of transmission. WHO has therefore developed a target product profile calling for development of a method for population-level cross-cutting surveillance of T. b. gambiense transmission. The method needs to be performed in national or sub-national reference laboratories, and to test in parallel numerous samples shipped from remote rural areas. Among other characteristics the product profile specifies: (i) a simple specimen collection procedure; (ii) no cold-chain requirement to transfer specimens to reference laboratories; (iii) high sensitivity and specificity; (iv) high-throughput, substantially automatized; (v) low cost per specimen, when analysed in large batches; and (vi) applicable also in animals.

La trypanosomiase humaine africaine est une infection parasitaire potentiellement mortelle transmise par la mouche tsé-tsé en Afrique subsaharienne. La forme la plus répandue est causée par Trypanosoma brucei gambiense, les humains constituant son principal réservoir. Établir un diagnostic sur le terrain nécessite un examen microscopique réalisé par du personnel formé à cet effet. Après plus de deux décennies d'efforts soutenus, l'incidence de la maladie diminue fortement et quelques pays historiquement endémiques ne découvrent plus aucun cas. L'objectif de l'Organisation mondiale de la Santé (OMS) est d'éliminer la transmission de la trypanosomiase humaine africaine à T. b. gambiense d'ici 2030, ce qui correspond à zéro cas autochtone pendant au moins cinq années consécutives. Les pays endémiques qui atteignent cet objectif doivent maintenir une surveillance spécifique afin de détecter toute réémergence ou réintroduction. Ce nouveau programme doit s'accompagner de nouveaux outils servant à vérifier l'absence de transmission. L'OMS a donc élaboré un profil de produit cible pour le développement d'un procédé de surveillance transversale de la transmission de T. b. gambiense à l'échelle de la population. Ce procédé doit être effectué dans des laboratoires de référence nationaux ou infranationaux et tester simultanément de nombreux échantillons envoyés depuis des régions rurales isolées. Ce profil de produit comporte notamment les caractéristiques suivantes: (i) une procédure simple de collecte d'échantillons; (ii) aucune exigence concernant le respect de la chaîne du froid lors du transfert des échantillons vers les laboratoires de référence; (iii) un niveau élevé de sensibilité et de spécificité; (iv) un haut débit, en grande partie automatisé; (v) de faibles coûts par échantillon lors d'analyses en masse; et enfin, (vi) applicable aux animaux également.

La tripanosomiasis humana africana es una infección parasitaria potencialmente mortal transmitida por la mosca tsetsé en el África Subsahariana. El principal reservorio es el ser humano, y la forma más común está causada por Trypanosoma brucei gambiense. El diagnóstico práctico requiere un examen microscópico a cargo de personal con formación específica. Tras más de dos décadas de esfuerzos sostenidos, la incidencia de la enfermedad está disminuyendo considerablemente, y en algunos países históricamente endémicos ya no se detectan casos. La Organización Mundial de la Salud (OMS) se ha fijado como objetivo la eliminación de la transmisión de la tripanosomiasis africana humana gambiense para 2030, es decir, cero casos autóctonos durante al menos cinco años consecutivos. Los países endémicos que alcancen este objetivo deben mantener una vigilancia permanente para detectar la reaparición o reintroducción de la enfermedad. Con esta agenda nueva, se necesitan herramientas nuevas para verificar la ausencia de transmisión. Por consiguiente, la OMS ha elaborado un perfil de producto objetivo en el que se pide el desarrollo de un método para la vigilancia transversal a nivel de población sobre la transmisión de T. b. gambiense. El método debe realizarse en laboratorios de referencia nacionales o subnacionales y analizar en paralelo numerosas muestras enviadas desde regiones rurales remotas. Entre otras características, el perfil del producto detalla: (i) un procedimiento sencillo de recogida de muestras; (ii) ningún requisito de cadena de frío para transferir las muestras a los laboratorios de referencia; (iii) alta sensibilidad y especificidad; (iv) alto rendimiento, sustancialmente automatizado; (v) bajo coste por muestra, cuando se analizan en grandes lotes; y (vi) aplicable también en animales.

Target product profile: Trypanosoma brucei gambiense test for low-prevalence settings.

Having caused devastating epidemics during the 20th century, the incidence of life-threatening human African trypanosomiasis has fallen to historically low levels as a result of sustained and coordinated efforts over the past 20 years. Humans are the main reservoir of one of the two pathogenic trypanosome subspecies, Trypanosoma brucei gambiense, found in western and central Africa. The expected advent of a safe and easy-to-use treatment to be given to seropositive but microscopically unconfirmed individuals would lead to further depletion; in the meantime, the presence of T. b. gambiense infection in the community must be monitored to allow the control strategy to be adapted and the elimination status to be assessed. The World Health Organization has therefore developed a target product profile that describes the optimal and minimal characteristics of an individual laboratory-based test to assess T. b. gambiense infection in low-prevalence settings. Development of the target product profile involved the formation of a Neglected Tropical Diseases Diagnostics Technical Advisory Group and a subgroup on human African trypanosomiasis diagnostic innovation needs, and an analysis of the available products and development pipeline. According to the product profile, the test should ideally: (i) require a minimally invasive or non-invasive specimen, collectable at peripheral facilities by minimally trained health workers; (ii) demonstrate good sensitivity and high specificity; (iii) have a stability of samples allowing transfer to reference laboratories preferably without cold chain; (iv) be stable over a wide range of environmental conditions for more than 2 years; and (v) after marketing, be available at low cost for at least 7 years.

Après avoir causé des épidémies dévastatrices au cours du 20e siècle, la trypanosomiase humaine africaine, potentiellement mortelle, a vu son incidence chuter à un niveau historiquement bas grâce aux efforts conjoints et soutenus déployés ces deux dernières décennies. Les humains constituent le principal réservoir de l'une des deux sous-espèces pathogéniques de trypanosome, Trypanosoma brucei gambiense, que l'on retrouve en Afrique occidentale et centrale. L'arrivée d'un traitement sûr et simple d'utilisation, qui serait administré aux individus séropositifs mais sans confirmation microscopique, devrait entraîner une nouvelle diminution; dans l'intervalle, la présence d'une infection à T. b. gambiense au sein de la communauté doit être surveillée afin de pouvoir adapter la stratégie de lutte et évaluer le statut d'élimination. Par conséquent, l'Organisation mondiale de la Santé a élaboré un profil de produit cible qui détaille les caractéristiques minimales et optimales d'un test individuel en laboratoire visant à confirmer l'infection à T. b. gambiense dans les régions à faible prévalence. La mise au point de ce profil a entraîné la formation d'un Groupe consultatif technique sur le diagnostic des maladies tropicales négligées et d'un sous-groupe consacré aux besoins en matière d'innovation diagnostique pour la trypanosomiase humaine africaine, qui a conduit une analyse des produits existants et des projets de développement. Selon le profil de produit, le test devrait idéalement: (i) nécessiter un prélèvement d'échantillon peu ou non invasif, pouvant être effectué dans des structures périphériques par des professionnels de la santé ayant reçu une formation sommaire; (ii) faire preuve d'un bon niveau de sensibilité et d'un niveau élevé de spécificité; (iii) avoir une stabilité des échantillons permettant le transfert vers des laboratoires de référence, de préférence sans chaîne de froid; (iv) rester stable dans un large éventail de conditions environnementales pendant plus de deux ans; et enfin, (v) après commercialisation, être disponible à bas coût pendant au moins sept ans.

Tras haber causado epidemias devastadoras durante el siglo XX, la incidencia de la tripanosomiasis humana africana potencialmente mortal ha descendido a niveles históricamente bajos gracias a los esfuerzos sostenidos y coordinados de los últimos 20 años. El ser humano es el principal reservorio de una de las dos subespecies patógenas del tripanosoma, Trypanosoma brucei gambiense, presente en África Occidental y Central. La prevista disponibilidad de un tratamiento seguro y fácil de administrar a personas seropositivas, pero no confirmadas al microscopio, permitiría una mayor eliminación; mientras tanto, se debe vigilar la presencia de la infección por T. b. gambiense en la comunidad para poder adaptar la estrategia de control y evaluar el estado de eliminación. Por consiguiente, la Organización Mundial de la Salud ha elaborado un perfil de producto objetivo que describe las características óptimas y mínimas de una prueba de laboratorio individual para evaluar la infección por T. b. gambiense en regiones de baja prevalencia. El desarrollo del perfil de producto objetivo implicó la formación de un Grupo de Asesoramiento Técnico sobre Diagnóstico de Enfermedades Tropicales Desatendidas y un subgrupo sobre las necesidades de innovación en el diagnóstico de la tripanosomiasis humana africana, así como un análisis de los productos disponibles y en desarrollo. Según el perfil objetivo, lo ideal sería que la prueba: (i) requiriera una muestra mínimamente invasiva o no invasiva, que pudiera ser recogida en centros periféricos por personal sanitario con una capacitación mínima; (ii) demostrara una buena sensibilidad y alta especificidad; (iii) tuviera una estabilidad de las muestras que permita su transferencia a laboratorios de referencia, preferiblemente sin cadena de frío; (iv) fuera estable en un amplio rango de condiciones ambientales durante más de 2 años; y (v) tras su comercialización, estuviera disponible a bajo coste durante al menos 7 años.

Target product profile: diagnostic test for Trypanosoma brucei gambiense.

Human African trypanosomiasis is a life-threatening parasitic infection endemic to sub-Saharan Africa. Around 95% of cases are due to Trypanosoma brucei gambiense, found in western and central Africa. Clinical signs and symptoms are nonspecific, current diagnostic tests are not sufficiently accurate, and parasitological confirmation of infection requires microscopic examination of body fluids and specialized techniques for concentrating parasites. Moreover, current treatment is not recommended on the basis of suspicion alone because it is not sufficiently safe. The availability of a simple and accurate diagnostic test to identify individuals harbouring parasites would widen treatment and help decrease disease prevalence. A subcommittee of the World Health Organization's Neglected Tropical Diseases Diagnostics Technical Advisory Group has developed a target product profile for a diagnostic tool to identify T. b. gambiense infection. This tool should have a high sensitivity for detecting T. b. gambiense but be simple enough to use in rural Africa. Ideally, the tool could be applied by any minimally trained individual in an unsophisticated peripheral health facility, or a mobile team in a village with little infrastructure. The test should be able to function under hot and humid conditions. Basic training should take under 2 hours and the test should involve fewer than five steps. There should be no need for instrumentation or precision liquid handling. The test should yield a qualitative result in under 20 minutes that can be easily observed, and one test should be sufficient for determining treatment. A unit cost below 1 United States dollar (US$) would enable mass screening.

La trypanosomiase humaine africaine est une infection parasitaire potentiellement mortelle endémique en Afrique subsaharienne. Dans près de 95% des cas, elle est causée par Trypanosoma brucei gambiense, que l'on trouve en Afrique occidentale et centrale. Les symptômes et signes cliniques sont aspécifiques, les tests de diagnostic existants ne sont pas assez précis et la confirmation parasitologique de l'infection nécessite un examen microscopique des liquides corporels ainsi que des techniques spécialisées pour concentrer les parasites. En outre, il n'est pas recommandé d'entamer le traitement actuel sur la base d'une simple suspicion car celui-ci n'est pas suffisamment sûr. Fournir un test de diagnostic simple et précis permettant d'identifier les individus porteurs de parasites contribuerait à élargir le traitement et à une diminution de la prévalence de la maladie. Un sous-comité du Groupe consultatif technique sur les produits de diagnostic des maladies tropicales négligées de l'Organisation mondiale de la Santé a élaboré un profil de produit cible pour un outil visant à détecter une infection par T. b. gambiense. Cet outil doit être suffisamment sensible pour déceler la présence de T. b. gambiense mais suffisamment simple pour être utilisé dans les régions rurales du continent. Idéalement, il doit pouvoir être employé par toute personne ayant reçu une formation sommaire, tant dans des structures de santé périphériques basiques qu'au sein d'une équipe mobile dans un village doté d'infrastructures restreintes. Par ailleurs, il doit fonctionner dans une atmosphère chaude et humide. La formation requise pour son utilisation doit durer moins de deux heures et le test doit être effectué en moins de cinq étapes, sans exiger d'équipement spécifique ni de manipulation délicate. Cet outil doit fournir un résultat fiable en moins de 20 minutes, facile à interpréter, et un seul test doit suffire à établir un traitement. Enfin, afin d'organiser un dépistage de masse, son coût unitaire ne doit pas dépasser un dollar américain.

La tripanosomiasis humana africana es una infección parasitaria potencialmente mortal endémica del África Subsahariana. Alrededor del 95% de los casos se deben al Trypanosoma brucei gambiense, presente en África Occidental y Central. Los signos y síntomas clínicos no son específicos, las pruebas diagnósticas actuales no son suficientemente precisas y la confirmación parasitológica de la infección requiere el examen microscópico de los fluidos corporales y técnicas especializadas de concentración de parásitos. Además, el tratamiento actual no se recomienda a partir de la sola sospecha porque no es suficientemente seguro. La disponibilidad de una prueba diagnóstica sencilla y precisa para identificar a las personas con parásitos ampliaría el tratamiento y ayudaría a disminuir la prevalencia de la enfermedad. Un subcomité del Grupo de Asesoramiento Técnico sobre Diagnóstico de Enfermedades Tropicales Desatendidas de la Organización Mundial de la Salud ha desarrollado un perfil de producto objetivo para una herramienta de diagnóstico destinada a identificar la infección por T. b. gambiense. Esta herramienta debe tener una alta sensibilidad para detectar T. b. gambiense, pero ser lo suficientemente sencilla para su uso en las regiones rurales de África. Lo ideal sería que la herramienta pudiera ser aplicada por cualquier persona mínimamente capacitada en un centro sanitario periférico poco sofisticado o por un equipo móvil en un pueblo con poca infraestructura. La prueba debería funcionar en condiciones de calor y humedad. La formación básica debe durar menos de 2 horas y la prueba debe constar de menos de cinco pasos. No debe necesitarse instrumentación ni manipulación precisa de líquidos. La prueba debe dar un resultado cualitativo en menos de 20 minutos que pueda observarse fácilmente y debe bastar una prueba para determinar el tratamiento. Su coste unitario, inferior a un dólar estadounidense, permitiría un cribado masivo.

[Towards elimination of human African trypanosomiasis]. / Vers l'élimination de la maladie du sommeil.

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.

Towards the sustainable elimination of gambiense human African trypanosomiasis in Côte d'Ivoire using an integrated approach.

BACKGROUND: Human African trypanosomiasis is a parasitic disease caused by trypanosomes among which Trypanosoma brucei gambiense is responsible for a chronic form (gHAT) in West and Central Africa. Its elimination as a public health problem (EPHP) was targeted for 2020. Côte d'Ivoire was one of the first countries to be validated by WHO in 2020 and this was particularly challenging as the country still reported around a hundred cases a year in the early 2000s. This article describes the strategies implemented including a mathematical model to evaluate the reporting results and infer progress towards sustainable elimination. METHODS: The control methods used combined both exhaustive and targeted medical screening strategies including the follow-up of seropositive subjects- considered as potential asymptomatic carriers to diagnose and treat cases- as well as vector control to reduce the risk of transmission in the most at-risk areas. A mechanistic model was used to estimate the number of underlying infections and the probability of elimination of transmission (EoT) was met between 2000-2021 in two endemic and two hypo-endemic health districts. RESULTS: Between 2015 and 2019, nine gHAT cases were detected in the two endemic health districts of Bouaflé and Sinfra in which the number of cases/10,000 inhabitants was far below 1, a necessary condition for validating EPHP. Modelling estimated a slow but steady decline in transmission across the health districts, bolstered in the two endemic health districts by the introduction of vector control. The decrease in underlying transmission in all health districts corresponds to a high probability that EoT has already occurred in Côte d'Ivoire. CONCLUSION: This success was achieved through a multi-stakeholder and multidisciplinary one health approach where research has played a major role in adapting tools and strategies to this large epidemiological transition to a very low prevalence. This integrated approach will need to continue to reach the verification of EoT in Côte d'Ivoire targeted by 2025.

Health economic evaluation of strategies to eliminate gambiense human African trypanosomiasis in the Mandoul disease focus of Chad.

Human African trypanosomiasis, caused by the gambiense subspecies of Trypanosoma brucei (gHAT), is a deadly parasitic disease transmitted by tsetse. Partners worldwide have stepped up efforts to eliminate the disease, and the Chadian government has focused on the previously high-prevalence setting of Mandoul. In this study, we evaluate the economic efficiency of the intensified strategy that was put in place in 2014 aimed at interrupting the transmission of gHAT, and we make recommendations on the best way forward based on both epidemiological projections and cost-effectiveness. In our analysis, we use a dynamic transmission model fit to epidemiological data from Mandoul to evaluate the cost-effectiveness of combinations of active screening, improved passive screening (defined as an expansion of the number of health posts capable of screening for gHAT), and vector control activities (the deployment of Tiny Targets to control the tsetse vector). For cost-effectiveness analyses, our primary outcome is disease burden, denominated in disability-adjusted life-years (DALYs), and costs, denominated in 2020 US$. Although active and passive screening have enabled more rapid diagnosis and accessible treatment in Mandoul, the addition of vector control provided good value-for-money (at less than $750/DALY averted) which substantially increased the probability of reaching the 2030 elimination target for gHAT as set by the World Health Organization. Our transmission modelling and economic evaluation suggest that the gains that have been made could be maintained by passive screening. Our analysis speaks to comparative efficiency, and it does not take into account all possible considerations; for instance, any cessation of ongoing active screening should first consider that substantial surveillance activities will be critical to verify the elimination of transmission and to protect against the possible importation of infection from neighbouring endemic foci.

Prevalence of blood and skin trypanosomes in domestic and wild fauna from two sleeping sickness foci in Southern Cameroon.

Although studies on African Trypanosomiases revealed a variety of trypanosome species in the blood of various animal taxa, animal reservoirs of Trypanosoma brucei gambiense and anatomical niches such as skin have been overlooked in most epidemiological settings. This study aims to update epidemiological data on trypanosome infections in animals from human African trypanosomiasis (HAT) foci of Cameroon. Blood and skin snips were collected from 291 domestic and wild animals. DNA was extracted from blood and skin snips and molecular approaches were used to identify different trypanosomes species. Immunohistochemical analyses were used to confirm trypanosome infections in skin snips. PCR revealed 137 animals (47.1%) with at least one trypanosome species in the blood and/or in the skin. Of these 137 animals, 90 (65.7%) and 32 (23.4%) had trypanosome infections respectively in the blood and skin. Fifteen (10.9%) animals had trypanosome infections in both blood and skin snip. Animals from the Campo HAT focus (55.0%) were significantly (X2 = 17.6; P< 0.0001) more infected than those (29.7%) from Bipindi. Trypanosomes of the subgenus Trypanozoon were present in 27.8% of animals while T. vivax, T. congolense forest type and savannah type were detected in 16.5%, 10.3% and 1.4% of animals respectively. Trypanosoma b. gambiense infections were detected in the blood of 7.6% (22/291) of animals. No T. b. gambiense infection was detected in skin. This study highlights the presence of several trypanosome species in the blood and skin of various wild and domestic animals. Skin appeared as an anatomical reservoir for trypanosomes in animals. Despite methodological limitations, pigs, sheep, goats and wild animals were confirmed as potential reservoirs of T. b. gambiense. These animal reservoirs must be considered for the designing of control strategies that will lead to sustainable elimination of HAT.

A modelling assessment of short- and medium-term risks of programme interruptions for gambiense human African trypanosomiasis in the DRC.

Gambiense human African trypanosomiasis (gHAT) is a deadly vector-borne, neglected tropical disease found in West and Central Africa targeted for elimination of transmission (EoT) by 2030. The recent pandemic has illustrated how it can be important to quantify the impact that unplanned disruption to programme activities may have in achieving EoT. We used a previously developed model of gHAT fitted to data from the Democratic Republic of the Congo, the country with the highest global case burden, to explore how interruptions to intervention activities, due to e.g. COVID-19, Ebola or political instability, could impact progress towards EoT and gHAT burden. We simulated transmission and reporting dynamics in 38 regions within Kwilu, Mai Ndombe and Kwango provinces under six interruption scenarios lasting for nine or twenty-one months. Included in the interruption scenarios are the cessation of active screening in all scenarios and a reduction in passive detection rates and a delay or suspension of vector control deployments in some scenarios. Our results indicate that, even under the most extreme 21-month interruption scenario, EoT is not predicted to be delayed by more than one additional year compared to the length of the interruption. If existing vector control deployments continue, we predict no delay in achieving EoT even when both active and passive screening activities are interrupted. If passive screening remains as functional as in 2019, we expect a marginal negative impact on transmission, however this depends on the strength of passive screening in each health zone. We predict a pronounced increase in additional gHAT disease burden (morbidity and mortality) in many health zones if both active and passive screening were interrupted compared to the interruption of active screening alone. The ability to continue existing vector control during medical activity interruption is also predicted to avert a moderate proportion of disease burden.

Cryo-EM structures of Trypanosoma brucei gambiense ISG65 with human complement C3 and C3b and their roles in alternative pathway restriction.

African Trypanosomes have developed elaborate mechanisms to escape the adaptive immune response, but little is known about complement evasion particularly at the early stage of infection. Here we show that ISG65 of the human-infective parasite Trypanosoma brucei gambiense is a receptor for human complement factor C3 and its activation fragments and that it takes over a role in selective inhibition of the alternative pathway C5 convertase and thus abrogation of the terminal pathway. No deposition of C4b, as part of the classical and lectin pathway convertases, was detected on trypanosomes. We present the cryo-electron microscopy (EM) structures of native C3 and C3b in complex with ISG65 which reveal a set of modes of complement interaction. Based on these findings, we propose a model for receptor-ligand interactions as they occur at the plasma membrane of blood-stage trypanosomes and may facilitate innate immune escape of the parasite.

Efficacy and safety of acoziborole in patients with human African trypanosomiasis caused by Trypanosoma brucei gambiense: a multicentre, open-label, single-arm, phase 2/3 trial.

BACKGROUND: Human African trypanosomiasis caused by Trypanosoma brucei gambiense (gambiense HAT) in patients with late-stage disease requires hospital admission to receive nifurtimox-eflornithine combination therapy (NECT). Fexinidazole, the latest treatment that has been recommended by WHO, also requires systematic admission to hospital, which is problematic in areas with few health-care resources. We aim to assess the safety and efficacy of acoziborole in adult and adolescent patients with gambiense HAT. METHODS: This multicentre, prospective, open-label, single-arm, phase 2/3 study recruited patients aged 15 years or older with confirmed gambiense HAT infection from ten hospitals in the Democratic Republic of the Congo and Guinea. Inclusion criteria included a Karnofsky score greater than 50, ability to swallow tablets, a permanent address or traceability, ability to comply with follow-up visits and study requirements, and agreement to hospital admission during treatment. Oral acoziborole was administered as a single 960 mg dose (3 × 320 mg tablets) to fasted patients. Patients were observed in hospital until day 15 after treatment administration then for 18 months as outpatients with visits at 3, 6, 12, and 18 months. The primary efficacy endpoint was the success rate of acoziborole treatment at 18 months in patients with late-stage gambiense HAT (modified intention-to-treat [mITT] population), based on modified WHO criteria. A complementary post-hoc analysis comparing the 18-month success rates for acoziborole and NECT (using historical data) was performed. This study is registered at ClinicalTrials.gov, NCT03087955. FINDINGS: Between Oct 11, 2016, and March 25, 2019, 260 patients were screened, of whom 52 were ineligible and 208 were enrolled (167 with late-stage and 41 with early-stage or intermediate-stage gambiense HAT; primary efficacy analysis set). All 41 (100%) patients with early-stage or intermediate-stage and 160 (96%) of 167 with late-stage disease completed the last 18-month follow-up visit. The mean age of participants was 34·0 years (SD 12·4), including 117 (56%) men and 91 (44%) women. Treatment success rate at 18 months was 95·2% (95% CI 91·2-97·7) reached in 159 of 167 patients with late-stage gambiense HAT (mITT population) and 98·1% (95·1-99·5) reached in 159 of 162 patients (evaluable population). Overall, 155 (75%) of 208 patients had 600 treatment-emergent adverse events. A total of 38 drug-related treatment-emergent adverse events occurred in 29 (14%) patients; all were mild or moderate and most common were pyrexia and asthenia. Four deaths occurred during the study; none were considered treatment related. The post-hoc analysis showed similar results to the estimated historical success rate for NECT of 94%. INTERPRETATION: Given the high efficacy and favourable safety profile, acoziborole holds promise in the efforts to reach the WHO goal of interrupting HAT transmission by 2030. FUNDING: Bill & Melinda Gates Foundation, UK Aid, Federal Ministry of Education and Research, Swiss Agency for Development and Cooperation, Médecins Sans Frontières, Dutch Ministry of Foreign Affairs, Norwegian Agency for Development Cooperation, Norwegian Ministry of Foreign Affairs, the Stavros Niarchos Foundation, Spanish Agency for International Development Cooperation, and the Banco Bilbao Vizcaya Argentaria Foundation. TRANSLATION: For the French translation of the abstract see Supplementary Materials section.

Risk factors and prevalence of human African trypanosomiasis in individuals living in remote areas of the republic of Congo.

BACKGROUND: Human African trypanosomiasis (HAT) is one of the world's classical neglected tropical diseases representing a major public health threat in sub-Saharan Africa. Although the parasitic disease is in decline in the Republic of Congo, the better understanding of the epidemiological situation of active foci is required to reduce the risk of disease resurgence which could impede progress registered so far. The aim of this study was to determine the prevalence of HAT and the associated risk factors in individuals living in remote areas of the Republic of Congo. METHODS: A cross-sectional survey was carried out in volunteers living in rural settings from June 2020 to January 2021. Socio-demographic and Clinical parameters of the participants were recorded. The presence of HAT-specific antibodies was assessed in whole blood, and then confirmed in serial diluted plasma samples using Card-Agglutination Trypanosomiasis Test (CATT)/T.b. gambiense CATT. The Capillary Tube Centrifugation (CTC) and Lymph nodes (LN) examination were done for detecting trypanosome parasites in CATT-serum positive cases. The staging of positive participants was determined by cerebrospinal fluid (CSF) examination. RESULTS: Out of 8556 enrolled participants, 48.5% were more than 15 years old, 57.7% were unschooled and 67.2% practiced peasant activities. The prevalence of HAT infection was 0.3% with the predominance of patients at stage 1 of the disease (84.0%). The districts of Mindouli (OR: 25.9 (5.2-468); p = 0.0016) and Mpouya (OR: 13.3 (2.5-246); p = 0.0140) was revealed as the foci of high risk of HAT infection. Several factors were associated with an increased risk of HAT infection mainly including the non-schooling (OR: 5.1 (1.2-21.9); p = 0.0268), the life in couple or married (OR: 3.3 (1.0-11.3); p = 0.0545) and the practice of peasant activities (OR: 6.9 (2.4-29.3); p = 0.0017). CONCLUSION: This study highlights the need of revising and strengthening the strategies of HAT control in Republic of Congo, using an approach which will take into account the education level, the marital status and the occupation of the population at risk.

Experimental evidence that immune trypanolysis using the LiTat 1.3 and LiTat 1.5 variant antigen types is not specific to Trypanosoma brucei gambiense in pigs.

In the context of the human African trypanosomiasis elimination process, reliable and accurate diagnostic tools are crucial for exploring the role of a potential animal reservoir of Trypanosoma brucei gambiense. The immune trypanolysis test (TL) using the variant antigen types (VAT) LiTat 1.3 and LiTat 1.5, described as a specific serological method to detect people infected by T. b. gambiense, seems to be a promising tool. However, its specificity was recently questioned during field animal surveys. The present study evaluates the performance of TL during experimental T. b. brucei infection in pigs. Eight infected pigs and four uninfected pigs were followed up with blood and plasma collection. Blood was used for parasitological investigation. TL was performed on the plasma with the LiTat 1.3, LiTat 1.5 and LiTat 1.6 VATs. All control pigs remained negative to parasitological investigation and TL. Trypanosomes were detected in all the infected pigs and the first detection was between 10 and 14 days post infection (dpi). TL results showed that infected pigs developed antibodies against the three VATs. The first antibody detections by TL occurred between 14 and 21 dpi for antibodies directed against LiTat 1.6, 21 and 168 dpi for antibodies directed against LiTat 1.5 and 70, and 182 dpi for antibodies directed against LiTat 1.3. This study highlights for the first time that TL using LiTat 1.3 and LiTat 1.5 VATs is not specific to T. b. gambiense. Development of specific diagnostic tools for the detection of T. b. gambiense infections in animals, especially in pigs, is still needed.

Title: Évidence expérimentale que la trypanolyse basée sur les types d'antigène variable LiTat 1.3 et LiTat 1.5 n'est pas spécifique de Trypanosoma brucei gambiense. Abstract: Dans le contexte d'élimination de la trypanosomiase humaine Africaine, des outils de diagnostic fiables et précis sont essentiels afin d'explorer le rôle d'un potentiel réservoir animal de Trypanosoma brucei gambiense. La trypanolyse (TL) qui utilise les types d'antigène variable (TAV) LiTat 1.3 et LiTat 1.5, et qui est décrite comme une méthode sérologique spécifique pour détecter les personnes infectées par T. b. gambiense, semble être un outil prometteur. Cependant, sa spécificité a été récemment remise en question lors d'enquêtes sur les animaux. La présente étude évalue la performance de ce test lors d'une infection expérimentale à T. b. brucei chez le porc. Huit porcs infectés et quatre porcs témoins non infectés ont été suivis avec des prélèvements de sang et de plasma. Le sang a été utilisé pour l'examen parasitologique. La TL a été réalisée sur les échantillons de plasma avec les TAV LiTat 1.3, LiTat 1.5 et LiTat 1.6. Tous les porcs témoins ont été négatifs en parasitologie et à la TL. Les trypanosomes ont été détectés sur tous les porcs infectés avec les premières détections entre 10 et 14 jours post-infection (jpi). Les résultats de la TL ont montré que les porcs infectés ont développé des anticorps contre les trois TAV. Les premiers anticorps détectés par la TL étaient dirigés contre le LiTat 1.6 entre 14 et 21 jpi, puis le LiTat 1.5 entre 21 et 168 jpi et enfin le LiTat 1.3 entre 70 et 182 jpi. Cette étude démontre pour la première fois que la TL basée sur les TAV LiTat 1.3 et LiTat 1.5 n'est pas spécifique de T. b. gambiense. Il est donc toujours nécessaire et urgent de développer un outil de diagnostic spécifique pour la détection des infections à T. b. gambiense chez les animaux, notamment chez les porcs.