Performance of diagnostic tests for Trypanosoma brucei brucei in experimentally infected pigs.

Animal African trypanosomosis is an important vector-borne disease of livestock in sub-Saharan Africa. Pigs seem relatively tolerant to trypanosome infection and could act as a reservoir of trypanosomes affecting animals and humans. Our ability to reliably detect trypanosome infection in pigs depends on the performance of diagnostic tools, which is not well known. In pigs experimentally infected with Trypanosoma brucei brucei, we evaluated the performance of parasitological Buffy Coat Technique (BCT), two molecular (TBR and 5.8S PCR) and four serological tests (CATT, HAT Sero-K-Set rapid diagnostic test-RDT, indirect ELISA, immune trypanolysis). Most diagnostic tests showed high specificity, estimated at 100% (95% CI = 74-100%) with the exception of CATT and RDT whose specificity varied between 100% (95% CI = 74-100%) to 50% (95% CI = 7-93%) during the experiment. The sensitivity of each test fluctuated over the course of the infection. The percentage of positive BCT over the infection (30%) was lower than of positive PCR (56% and 62%, depending on primers). Among the serological tests, the percentage of positive tests was 97%, 96%, 86% and 84% for RDT, ELISA, immune trypanolysis and CATT, respectively. Fair agreement was observed between both molecular tests (κ = 0.36). Among the serological tests, the agreement between the ELISA and the RDT was substantial (κ = 0.65). Our results on the T.b. brucei infection model suggest that serological techniques are efficient in detecting the chronic phase of infection, PCR is able to detect positive samples several months after parasites inoculation while BCT becomes negative. BCT examination and RDT are useful to get a quick information in the field, and BCT can be used for treatment decision. ELISA appears most suited for epidemiological studies. The selection of diagnostic tests for trypanosomosis in pigs depends on the context, the objectives and the available resources.

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: diagnostic test for Trypanosoma brucei rhodesiense.

Rhodesiense human African trypanosomiasis is a lethal parasitic infection caused by Trypanosoma brucei rhodesiense and transmitted by tsetse flies in eastern and southern Africa. It accounts for around 5% of all cases of human African trypanosomiasis. Currently, there is no simple serological test for rhodesiense human African trypanosomiasis and diagnosis relies on microscopic confirmation of trypanosomes in samples of blood or other tissues. The availability of a simple and accurate diagnostic test would aid the control, surveillance and treatment of the disease. 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. rhodesiense infection. The optimum tool would have a sensitivity and specificity above 99% for detecting T. b. rhodesiense, but be simple enough for use by minimally trained health-care workers in unsophisticated peripheral health facilities or mobile teams in villages. The test should yield a qualitative result that can be easily observed and can be used to determine treatment. An antigen test would be preferable, with blood collected by finger-prick. Ideally, there should be no need for a cold chain, instrumentation or precision liquid handling. The test should be usable between 10 °C and 40 °C and between 10% and 88% relative humidity. Basic training should take under 2 hours and the test should involve fewer than five steps. The unit cost should be less than 1 United States dollar.

La trypanosomiase humaine africaine à T. b. rhodesiense est une infection parasitaire mortelle causée par Trypanosoma brucei rhodesiense et transmise par les mouches tsé-tsé en Afrique orientale et australe. Elle représente environ 5% de l'ensemble des cas de trypanosomiase humaine africaine. À l'heure actuelle, il n'existe aucun test sérologique simple pour l'infection à T. b. rhodesiense et le diagnostic repose sur la confirmation microscopique de la présence de trypanosomes dans des échantillons de sang ou d'autres tissus. Fournir un test de diagnostic simple et précis favoriserait la lutte, la surveillance et la prise en charge 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 donc élaboré un profil de produit cible pour un outil visant à détecter une infection par T. b. rhodesiense. L'outil le plus adapté présenterait un niveau de sensibilité et de spécificité supérieur à 99% pour la détection de T. b. rhodesiense, tout en étant à la portée de professionnels de la santé ayant reçu une formation sommaire, tant dans des structures de santé périphériques basiques qu'au sein d'équipes mobiles dans les villages. Cet outil doit fournir un résultat fiable, facile à interpréter, qui peut servir à établir un traitement. Un test antigénique serait préférable, avec prélèvement de l'échantillon sanguin par le biais d'une piqûre au bout du doigt. Idéalement, l'outil ne doit pas être thermosensible, ni nécessiter un équipement spécifique ou une manipulation de liquides délicate. Le test doit pouvoir être utilisé à une température comprise entre 10 °C et 40 °C, ainsi que dans une humidité relative de 10% à 88%. La formation requise pour son utilisation doit durer moins de deux heures et le test doit être effectué en moins de cinq étapes, Enfin, son coût unitaire doit être inférieur à un dollar américain.

La tripanosomiasis humana africana rhodesiense es una infección letal parasitaria causada por el Trypanosoma brucei rhodesiense, y es transmitida por la mosca tse-tsé en África oriental y meridional. Representa aproximadamente el 5% de todos los casos de tripanosomiasis humana africana. Actualmente, no existe ninguna prueba serológica simple para la tripanosomiasis humana africana rhodesiense, y el diagnóstico se basa en la confirmación microscópica de tripanosomas existentes en muestras de sangre u otros tejidos. Una prueba diagnóstica sencilla y precisa ayudaría a controlar, vigilar y tratar la enfermedad. Un subcomité del Grupo Asesor Técnico de Diagnóstico de Enfermedades Tropicales Desatendidas de la Organización Mundial de la Salud ha creado un perfil de producto objetivo para una herramienta de diagnóstico que permita identificar la infección T. b. rhodesiense. La herramienta óptima tendría una sensibilidad y una especificidad superiores al 99% para detectar la T. b. rhodesiense y, al ser lo suficientemente sencilla, podrían utilizarla trabajadores sanitarios mínimamente formados, en centros sanitarios periféricos no sofisticados, o bien equipos móviles. La prueba debe arrojar un resultado cualitativo de fácil lectura y que pueda utilizarse para determinar el tratamiento. Sería preferible una prueba de antígenos, con sangre extraída mediante punción digital. Idealmente, no debería ser necesaria la cadena de frío, la instrumentación ni la manipulación de líquidos de precisión. La prueba debe poder utilizarse entre 10 °C y 40 °C, con una humedad relativa de entre el 10% y el 88%. La instrucción básica debe llevar menos de 2 horas y la prueba debe incluir menos de cinco pasos. El coste de la unidad debe ser inferior a 1 dólar estadounidense.

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.

Performance of clinical signs and symptoms, rapid and reference laboratory diagnostic tests for diagnosis of human African trypanosomiasis by passive screening in Guinea: a prospective diagnostic accuracy study.

BACKGROUND: Passive diagnosis of human African trypanosomiasis (HAT) at the health facility level is a major component of HAT control in Guinea. We examined which clinical signs and symptoms are associated with HAT, and assessed the performance of selected clinical presentations, of rapid diagnostic tests (RDT), and of reference laboratory tests on dried blood spots (DBS) for diagnosing HAT in Guinea. METHOD: The study took place in 14 health facilities in Guinea, where 2345 clinical suspects were tested with RDTs (HAT Sero-K-Set, rHAT Sero-Strip, and SD Bioline HAT). Seropositives underwent parasitological examination (reference test) to confirm HAT and their DBS were tested in indirect enzyme-linked immunoassay (ELISA)/Trypanosoma brucei gambiense, trypanolysis, Loopamp Trypanosoma brucei Detection kit (LAMP) and m18S quantitative PCR (qPCR). Multivariable regression analysis assessed association of clinical presentation with HAT. Sensitivity, specificity, positive and negative predictive values of key clinical presentations, of the RDTs and of the DBS tests for HAT diagnosis were determined. RESULTS: The HAT prevalence, as confirmed parasitologically, was 2.0% (48/2345, 95% CI: 1.5-2.7%). Odds ratios (OR) for HAT were increased for participants with swollen lymph nodes (OR = 96.7, 95% CI: 20.7-452.0), important weight loss (OR = 20.4, 95% CI: 7.05-58.9), severe itching (OR = 45.9, 95% CI: 7.3-288.7) or motor disorders (OR = 4.5, 95% CI: 0.89-22.5). Presence of at least one of these clinical presentations was 75.6% (95% CI: 73.8-77.4%) specific and 97.9% (95% CI: 88.9-99.9%) sensitive for HAT. HAT Sero-K-Set, rHAT Sero-Strip, and SD Bioline HAT were respectively 97.5% (95% CI: 96.8-98.1%), 99.4% (95% CI: 99.0-99.7%) and 97.9% (95% CI: 97.2-98.4%) specific, and 100% (95% CI: 92.5-100.0%), 59.6% (95% CI: 44.3-73.3%) and 93.8% (95% CI: 82.8-98.7%) sensitive for HAT. The RDT's positive and negative predictive values ranged from 45.2-66.7% and 99.2-100% respectively. All DBS tests had specificities ≥ 92.9%. While LAMP and m18S qPCR sensitivities were below 50%, trypanolysis and ELISA/T.b. gambiense had sensitivities of 85.3% (95% CI: 68.9-95.0%) and 67.6% (95% CI: 49.5-82.6%). CONCLUSIONS: Presence of swollen lymph nodes, important weight loss, severe itching or motor disorders are simple but accurate clinical criteria for HAT referral in HAT endemic areas in Guinea. Diagnostic performances of HAT Sero-K-Set and SD Bioline HAT are sufficient for referring positives to microscopy. Trypanolysis on DBS may discriminate HAT patients from false RDT positives. Trial registration The trial was registered under NCT03356665 in clinicaltrials.gov (November 29, 2017, retrospectively registered https://clinicaltrials.gov/ct2/show/NCT03356665 ).

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.

Trypanosome spliced leader RNA for diagnosis of acoziborole treatment outcome in gambiense human African trypanosomiasis: A longitudinal follow-up study.

BACKGROUND: Detection of spliced leader (SL)-RNA allows sensitive diagnosis of gambiense human African trypanosomiasis (HAT). We investigated its diagnostic performance for treatment outcome assessment. METHODS: Blood and cerebrospinal fluid (CSF) from a consecutive series of 97 HAT patients, originating from the Democratic Republic of the Congo, were prospectively collected before treatment with acoziborole, and during 18 months of longitudinal follow-up after treatment. For treatment outcome assessment, SL-RNA detection was compared with microscopic trypanosome detection and CSF white blood cell count. The trial was registered under NCT03112655 in clinicaltrials.gov. FINDINGS: Before treatment, respectively 94.9% (92/97; CI 88.5-97.8%) and 67.7% (65/96; CI 57.8-76.2%) HAT patients were SL-RNA positive in blood or CSF. During follow-up, one patient relapsed with trypanosomes observed at 18 months, and was SL-RNA positive in blood and CSF at 12 months, and CSF positive at 18 months. Among cured patients, one individual tested SL-RNA positive in blood at month 12 (Specificity 98.9%; 90/91; CI 94.0-99.8%) and 18 (Specificity 98.9%; 88/89; CI 93.9-99.8%). INTERPRETATION: SL-RNA detection for HAT treatment outcome assessment shows ≥98.9% specificity in blood and 100% in CSF, and may detect relapses without lumbar puncture. FUNDING: The DiTECT-HAT project is part of the EDCTP2 programme, supported by Horizon 2020, the European Union Funding for Research and Innovation (grant number DRIA-2014-306-DiTECT-HAT).

VSGs Expressed during Natural T. b. gambiense Infection Exhibit Extensive Sequence Divergence and a Subspecies-Specific Bias towards Type B N-Terminal Domains.

Trypanosoma brucei gambiense is the primary causative agent of human African trypanosomiasis (HAT), a vector-borne disease endemic to West and Central Africa. The extracellular parasite evades antibody recognition within the host bloodstream by altering its variant surface glycoprotein (VSG) coat through a process of antigenic variation. The serological tests that are widely used to screen for HAT use VSG as one of the target antigens. However, the VSGs expressed during human infection have not been characterized. Here, we use VSG sequencing (VSG-seq) to analyze the VSGs expressed in the blood of patients infected with T. b. gambiense and compared them to VSG expression in Trypanosoma brucei rhodesiense infections in humans as well as Trypanosoma brucei brucei infections in mice. The 44 VSGs expressed during T. b. gambiense infection revealed a striking bias toward expression of type B N termini (82% of detected VSGs). This bias is specific to T. b. gambiense, which is unique among T. brucei subspecies in its chronic clinical presentation and anthroponotic nature. The expressed T. b. gambiense VSGs also share very little similarity to sequences from 36 T. b. gambiense whole-genome sequencing data sets, particularly in areas of the VSG protein exposed to host antibodies, suggesting the antigen repertoire is under strong selective pressure to diversify. Overall, this work demonstrates new features of antigenic variation in T. brucei gambiense and highlights the importance of understanding VSG repertoires in nature. IMPORTANCE Human African trypanosomiasis is a neglected tropical disease primarily caused by the extracellular parasite Trypanosoma brucei gambiense. To avoid elimination by the host, these parasites repeatedly replace their variant surface glycoprotein (VSG) coat. Despite the important role of VSGs in prolonging infection, VSG expression during human infections is poorly understood. A better understanding of natural VSG gene expression dynamics can clarify the mechanisms that T. brucei uses to alter its VSG coat. We analyzed the expressed VSGs detected in the blood of patients with trypanosomiasis. Our findings indicate that there are features of antigenic variation unique to human-infective T. brucei subspecies and that natural VSG repertoires may vary more than previously expected.

Monitoring the elimination of gambiense human African trypanosomiasis in the historical focus of Batié, South-West Burkina Faso.

The World Health Organisation has targeted the elimination of human African trypanosomiasis (HAT) as zero transmission by 2030. Continued surveillance needs to be in place for early detection of re-emergent cases. In this context, the performance of diagnostic tests and testing algorithms for detection of the re-emergence of Trypanosoma brucei gambiense HAT remains to be assessed. We carried out a door-to-door active medical survey for HAT in the historical focus of Batié, South-West Burkina Faso. Screening was done using three rapid diagnostic tests (RDTs). Two laboratory tests (ELISA/T. b. gambiense and immune trypanolysis) and parasitological examination were performed on RDT positives only. In total, 5883 participants were screened, among which 842 (14%) tested positive in at least one RDT. Blood from 519 RDT positives was examined microscopically but no trypanosomes were observed. The HAT Sero-K-Set test showed the lowest specificity of 89%, while the specificities of SD Bioline HAT and rHAT Sero-Strip were 92% and 99%, respectively. The specificity of ELISA/T. b. gambiense and trypanolysis was 99% (98-99%) and 100% (99-100%), respectively. Our results suggest that T. b. gambiense is no longer circulating in the study area and that zero transmission has probably been attained. While a least cost analysis is still required, our study showed that RDT preselection followed by trypanolysis may be a useful strategy for post-elimination surveillance in Burkina Faso.

Title: Suivi de l'élimination de la Trypanosomiase Humaine Africaine dans le foyer historique de Batié au sud-ouest du Burkina Faso. Abstract: L'Organisation mondiale de la santé a ciblé l'élimination de la trypanosomiase humaine africaine (THA) comme transmission zéro d'ici 2030. Une surveillance continue doit être mise en place pour la détection précoce des cas réémergents. Dans ce contexte, la performance des tests de diagnostic et des algorithmes de test pour la détection de la réémergence de la THA de Trypanosoma brucei gambiense reste à évaluer. Nous avons réalisé une enquête médicale en porte-à-porte pour la THA dans le foyer historique de Batié, au sud-ouest du Burkina Faso. Le dépistage a été effectué à l'aide de trois tests de diagnostic rapide (TDR). Deux tests de laboratoire (ELISA/T. b. gambiense et trypanolyse immunitaire) et un examen parasitologique ont été effectués uniquement sur les TDR positifs. Au total, 5883 participants ont été dépistés, parmi lesquels 842 (14 %) ont été testés positifs dans au moins un TDR. Le sang de 519 TDR positifs a été examiné au microscope mais aucun trypanosome n'a été observé. Le test HAT Sero-K-Set a montré la spécificité la plus faible de 89 %, tandis que les spécificités de SD Bioline HAT et rHAT Sero-Strip étaient de 92 % et 99 %, respectivement. La spécificité d'ELISA/T. b. gambiense et de la trypanolyse étaient respectivement de 99 % (98­99 %) et 100 % (99­100 %). Nos résultats suggèrent que T. b. gambiense ne circule plus dans la zone d'étude et que la transmission zéro a probablement été atteinte. Bien qu'une analyse de moindre coût soit toujours nécessaire, notre étude a montré qu'une présélection par TDR suivie d'une trypanolyse peut être une stratégie utile pour la surveillance post-élimination au Burkina Faso.

The COMBAT project: controlling and progressively minimizing the burden of vector-borne animal trypanosomosis in Africa.

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.

Trypanosome SL-RNA detection in blood and cerebrospinal fluid to demonstrate active gambiense human African trypanosomiasis infection.

BACKGROUND: Spliced Leader (SL) trypanosome RNA is detectable only in the presence of live trypanosomes, is abundant and the Trypanozoon subgenus has a unique sequence. As previously shown in blood from Guinean human African trypanosomiasis (HAT) patients, SL-RNA is an accurate target for diagnosis. Detection of SL-RNA in the cerebrospinal fluid (CSF) has never been attempted. In a large group of Congolese gambiense HAT patients, the present study aims i) to confirm the sensitivity of SL-RNA detection in the blood and; ii) to assess the diagnostic performance of SL-RNA compared to trypanosome detection in CSF. METHODOLOGY/PRINCIPAL FINDINGS: Blood and CSF from 97 confirmed gambiense HAT patients from the Democratic Republic of Congo were collected using PAXgene blood RNA Tubes. Before RNA extraction, specimens were supplemented with internal extraction control RNA to monitor the extraction, which was performed with a PAXgene Blood RNA Kit. SL-RNA qPCR was carried out with and without reverse transcriptase to monitor DNA contamination. In blood, 92/97 (94.8%) HAT patients tested SL-RNA positive, which was significantly more than combined trypanosome detection in lymph and blood (78/97 positive, 80.4%, p = 0.001). Of 96 CSF RNA specimens, 65 (67.7%) were SL-RNA positive, but there was no significant difference between sensitivity of SL-RNA and trypanosome detection in CSF. The contribution of DNA to the Cq values was negligible. In CSF with normal cell counts, a fraction of SL-RNA might have been lost during extraction as indicated by higher internal extraction control Cq values. CONCLUSIONS/SIGNIFICANCE: Detection of SL-RNA in blood and CSF allows sensitive demonstration of active gambiense HAT infection, even if trypanosomes remain undetectable in blood or lymph. As this condition often occurs in treatment failures, SL-RNA detection in blood and CSF for early detection of relapses after treatment deserves further investigation. TRIAL REGISTRATION: This study was an integral part of the diagnostic trial "New Diagnostic Tools for Elimination of Sleeping Sickness and Clinical Trials: Early tests of Cure" (DiTECT-HAT-WP4, ClinicalTrials.gov Identifier: NCT03112655).

Passive surveillance of human African trypanosomiasis in Côte d'Ivoire: Understanding prevalence, clinical symptoms and signs, and diagnostic test characteristics.

BACKGROUND: Little is known about the diagnostic performance of rapid diagnostic tests (RDTs) for passive screening of human African trypanosomiasis (HAT) in Côte d'Ivoire. We determined HAT prevalence among clinical suspects, identified clinical symptoms and signs associated with HAT RDT positivity, and assessed the diagnostic tests' specificity, positive predictive value and agreement. METHODS: Clinical suspects were screened with SD Bioline HAT, HAT Sero-K-Set and rHAT Sero-Strip. Seropositives were parasitologically examined, and their dried blood spots tested in trypanolysis, ELISA/Tbg, m18S-qPCR and LAMP. The HAT prevalence in the study population was calculated based on RDT positivity followed by parasitological confirmation. The association between clinical symptoms and signs and RDT positivity was determined using multivariable logistic regression. The tests' Positive Predictive Value (PPV), specificity and agreement were determined. RESULTS: Over 29 months, 3433 clinical suspects were tested. The RDT positivity rate was 2.83%, HAT prevalence 0.06%. Individuals with sleep disturbances (p<0.001), motor disorders (p = 0.002), convulsions (p = 0.02), severe weight loss (p = 0.02) or psychiatric problems (p = 0.04) had an increased odds (odds ratios 1.7-4.6) of being HAT RDT seropositive. Specificities ranged between 97.8%-99.6% for individual RDTs, and 93.3-98.9% for subsequent tests on dried blood spots. The PPV of the individual RDTs was below 14.3% (CI 2-43), increased to 33.3% (CI 4-78) for serial RDT combinations, and reached 67% for LAMP and ELISA/Tbg on RDT positives. Agreement between diagnostic tests was poor to moderate (Kappa ≤ 0.60), except for LAMP and ELISA/Tbg (Kappa = 0.66). CONCLUSION: Identification of five key clinical symptoms and signs may simplify referral for HAT RDT screening. The results confirm the appropriateness of the diagnostic algorithm presently applied, with screening by SD Bioline HAT or HAT Sero-K-Set, supplemented with trypanolysis. ELISA/Tbg could replace trypanolysis and is simpler to perform. TRIAL REGISTRATION: ClinicalTrials.gov NCT03356665.

Diagnostics and the neglected tropical diseases roadmap: setting the agenda for 2030.

Accurate and reliable diagnostic tools are an essential requirement for neglected tropical diseases (NTDs) programmes. However, the NTD community has historically underinvested in the development and improvement of diagnostic tools, potentially undermining the successes achieved over the last 2 decades. Recognizing this, the WHO, in its newly released draft roadmap for NTD 2021-2030, has identified diagnostics as one of four priority areas requiring concerted action to reach the 2030 targets. As a result, WHO established a Diagnostics Technical Advisory Group (DTAG) to serve as the collaborative mechanism to drive progress in this area. Here, the purpose and role of the DTAG are described in the context of the challenges facing NTD programmes.

Analytical sensitivity of loopamp and quantitative real-time PCR on dried blood spots and their potential role in monitoring human African trypanosomiasis elimination.

The objective set by WHO to reach elimination of human African trypanosomiasis (HAT) as a public health problem by 2020 is being achieved. The next target is the interruption of gambiense-HAT transmission in humans by 2030. To monitor progress towards this target, in areas where specialized local HAT control capacities will disappear, is a major challenge. Test specimens should be easily collectable and safely transportable such as dried blood spots (DBS). Monitoring tests performed in regional reference centres should be reliable, cheap and allow analysis of large numbers of specimens in a high-throughput format. The aim of this study was to assess the analytical sensitivity of Loopamp, M18S quantitative real-time PCR (M18S qPCR) and TgsGP qPCR as molecular diagnostic tests for the presence of Trypanosoma brucei gambiense in DBS. The sensitivity of the Loopamp test, with a detection limit of 100 trypanosomes/mL, was in the range of parasitaemias commonly observed in HAT patients, while detection limits for M18S and TgsGP qPCR were respectively 1000 and 10,000 trypanosomes/mL. None of the tests was entirely suitable for high-throughput use and further development and implementation of sensitive high-throughput molecular tools for monitoring HAT elimination are needed.

The complex health seeking pathway of a human African trypanosomiasis patient in Côte d'Ivoire underlines the need of setting up passive surveillance systems.

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.