Epidemiology of human African trypanosomiasis

Tsetse and African Animal Trypanosomiasis status; prevalence, spatial distribution, and implications to control trypanosomiasis in Uganda

African animal trypanosomiasis (AAT) transmitted by tsetse flies poses a threat to livestock in Uganda. The disease has been present in the country for many years. Mapping of the disease prevalence and vector spatial distribution in the country was undertaken to assess the situation. The disease has been endemic in the northern region of the country. Tsetse entomological surveys, AAT prevalence data together with environmental (climate, vegetation and topographical) explanatory data were used to map the presence and prevalence risk. Tsetse fly surveys were done and the vector was found mostly in areas north of Lake Kyoga and islands in Lake Victoria. Animal trypanosomiasis prevalence data was obtained from published works and samples collected and analysed during COCTU field operations. AAT was mostly prevalent in northern region. Through linear regressions, it was found that AAT prevalence was mainly significantly (P ≤ 0.001) contributed by temperature variance, precipitation of driest month, precipitation of the warmest quarter, precipitation of coldest quarter and recent annual mean precipitation climatic and vegetation cover. Tsetse flies trapped per day (FTD) were significantly (P ≤ 0.05) associated to precipitation of the wettest quarter, precipitation of coldest quarter and annual mean land surface temperature difference climatic factors. Topographical factor (altitude or elevation) did not influence the model outcome for both while vegetation didn't influence the vector model outcome. AAT and tsetse flies were widely prevalent in the northern and northeastern regions of the country (areas north and northeast of L. Kyoga). The risk reduced in areas south of the lake with the exception of areas around big water bodies and some conservation areas. These findings indicate that initiative-taking measures in vector and disease control should be directed towards the northern hemisphere of the country.

Understanding Sex-biases in Kinetoplastid Infections: Leishmaniasis and Trypanosomiasis

BACKGROUND

Leishmaniasis, Chagas disease (CD), and Human African Trypanosomiasis (HAT) are neglected tropical diseases in humans caused by intracellular parasites from the class Kinetoplastida. Leishmaniasis is one infectious disease that exhibits sex-bias not explained solely by behavioral or cultural differences. However, HAT and CD have less well documented and understood sex-related differences, either due to a lack of differences or insufficient research and reporting.

METHODS

This paper reviews the rate of disease and disease severity among male and females infected with CD, HAT, and leishmaniasis. We further review the specific immune response to each pathogen and potential sex-based mechanisms which could impact immune responses and disease outcomes.

RESULTS

These mechanisms include sex hormone modulation of the immune response, sex-related genetic differences, and socio-cultural factors impacting risky behaviors in men and women. The mechanistic differences in immune response among sexes and pathogens provide important insights and identification of areas for further research.

CONCLUSIONS

This information can aid in future development of inclusive, targeted, safe, and effective treatments and control measures for these neglected diseases and other infectious diseases.

A Review on the Epidemiology and Clinical Management of Neglected Tropical Diseases

Infectious disorders known as Neglected Tropical Diseases (NTDs) initially affect the world's underprivileged citizens. They have been disregarded for many years, first as a result of a general indifference to such a developing world and, more recently, as an outcome of the intense attention on AIDS, TB, and malaria. Tropical diseases mostly affect the region where health and hygiene are sacrificed, and most of the population lacks access to sufficient food and living resources. WHO has drafted and released the directions for regulation, prevention, and successful eradication of NTDs as per the revised roadmap of 2021-2030. This shifts from vertical disease programs to integrated cross-cutting methods. In the current work, we have provided comprehensive information on various aspects of neglected tropical diseases, including the clinical management of NTDs. This encompasses the causative agent of the diseases, their symptoms, pathogenesis, diagnosis, treatment, prognosis, and epidemiological perspective of major NTDs. This review will shed light on several perspectives of NTDs having influential roles in proposing strategies to control and treat them around the world.

Carmaphycin B-Based Proteasome Inhibitors to Treat Human African Trypanosomiasis: Structure-Activity Relationship and In Vivo Efficacy

The proteasome is essential for eukaryotic cell proteostasis, and inhibitors of the 20S proteasome are progressing preclinically and clinically as antiparasitics. We screenedTrypanosoma brucei, the causative agent of human and animal African trypanosomiasis, in vitro with a set of 27 carmaphycin B analogs, irreversible epoxyketone inhibitors that were originally developed to inhibit thePlasmodium falciparum20S (Pf20S). The structure-activity relationship was distinct from that of the human c20S antitarget by the acceptance of d-amino acids at the P3 position of the peptidyl backbone to yield compounds with greatly decreased toxicity to human cells. For the three most selective compounds, binding to the Tb20S β5 catalytic subunit was confirmed by competition with a fluorescent activity-based probe. For one compound, J-80, with its P3 d-configuration, the differential binding to the parasite's β5 subunit was supported by both covalent and noncovalent docking analysis. Further, J-80 was equipotent against both Trypanosoma brucei gambiense and Trypanosoma brucei rhodesiense in vitro. In a mouse model of Stage 1 T. brucei infection, a single intraperitoneal (i.p.) dose of 40 mg/kg J-80 halted the growth of the parasite, and when given at 50 mg/kg i.p. twice daily for 5 days, parasitemia was decreased to below the detectable limit, with parasite recrudescence 48 h after the last dose. The in vivo proof of principle demonstrated by a potent, selective, and irreversible inhibitor of Tb20S reveals an alternative path to the development of kinetoplastid proteasome inhibitors that differs from the current focus on allosteric reversible inhibitors.

Dual suppression of Glossina pallidipes using entomopathogenic fungal-based biopesticides and sterile insect technique

Tsetse flies and trypanosomosis significantly impact bovine production and human health in sub-Saharan Africa, exacerbating underdevelopment, malnutrition, and poverty. Despite various control strategies, long-term success has been limited. This study evaluates the combined use of entomopathogenic fungi (EPF) and the sterile insect technique (SIT) to combat tsetse flies. Eleven EPF isolates were tested against teneral males of Glossina pallidipes, focusing on mortality rates, radial growth, and impacts on fly fitness. Temperature effects on conidial growth, sporulation, and spore yield of SIT-compatible/tolerant strains were also assessed. The fungal isolates significantly influenced mortality rates in both unirradiated and irradiated (SIT-treated) males (p < 0.0001). Metarhizium anisopliae strains ICIPE 20, ICIPE 32, ICIPE 41, ICIPE 62, ICIPE 78, and Beauveria bassiana ICIPE 603 showed higher SIT compatibility/tolerance with LT50 values of 11-30 days, compared to other more virulent isolates with LT50 values of 4-9 days. Temperature significantly affected the radial growth of SIT-compatible EPF strains (p < 0.0001), with M. anisopliae ICIPE 78 exhibiting the fastest conidia growth at 25°C. Spore yield varied significantly across temperatures (15-40°C), and the thermal range for conidia germination of SIT-compatible strains was 8.1-45.4°C, with an optimal range of 26.7-31.1°C. Moreover, infected unirradiated females and irradiated males (donors) successfully transmitted conidia to untreated flies (receivers) without significant differences in survival rates (p = 0.6438) and no observed sex dimorphism. Our findings highlight the potential of combining EPF and SIT as a novel dual approach that could effectively and synergistically suppress tsetse fly populations.

Tsetse fly density and trypanosoma infection rate in Bedele and Dabo Hana districts of Buno Bedele Zone, Southwest Ethiopia

BACKGROUND

Trypanosomiasis is an infectious disease caused by parasitic protozoa of the genus Trypanosome and primarily transmitted by tsetse flies. This study aimed to determine the density of tsetse flies and the rate of trypanosome infection in the Bedele and Dabo Hana districts of the Buno Bedele Zone in Ethiopia.

RESULTS

A cross-sectional study was conducted from January to February 2023 to catch tsetse flies, determine tsetse density, and estimate the trypanosome infection rate. We used 100 traps (40 NGU, 30 pyramidal, and 30 biconical) to catch the flies. The following standard procedures were followed to identify the specific trypanosome species in the collected tsetse flies: The flies were dissected, and the salivary glands were removed. We placed the salivary glands in a drop of saline solution on a microscope slide. A coverslip was placed over the salivary glands, the slide was examined under a microscope, and the trypanosomes were identified based on their morphology. A total of 3,740 tsetse flies were captured from 100 traps, resulting in an overall apparent density of 18.7 flies per trap per day. Within the study area, only one species of tsetse fly, Glossina tachinoides, was identified. Of the 1,320 dissected Glossina tachinoides, 1.82% were found to be infected with trypanosome parasites. Among these infections, 58.33% were attributed to Trypanosoma congolense, while the remaining 41.67% were caused by Trypanosoma brucei. The infection rate of trypanosomes was significantly higher in female tsetse flies (87.5%) as compared to male flies (12.5%). Furthermore, a significantly higher infection rate was observed in flies older than 20 days (83.33%) and in hunger stage 1 flies (58.33%) compared to hunger stages 2, 3, and 4.

CONCLUSIONS

This study highlights the necessity of implementing control and suppression measures targeting the vector (tsetse flies) and the parasite (trypanosomes) to effectively manage and prevent pathogenic animal trypanosomiasis.

The comprehensive epidemiological status of human African trypanosomiasis in Nigeria: meta-analysis and systematic review of the full story (1962-2022)

Human African trypanosomiasis (HAT) in Nigeria is caused primarily by Trypanosoma brucei gambiense (gHAT), which has historically been a major human and animal health problem. This study aims to examine the status of gHAT in Nigeria over the past 60 years. The World Health Organization (WHO) set two targets to eliminate HAT as a public health concern by 2020 and terminate its global transmission by 2030. The former target has been achieved, but accurate monitoring and surveillance are important for maintaining this success and delivering the second target. Although recent cases in Nigeria are rare, accurately estimating the national seroprevalence and actual prevalence of gHATs remains challenging. To address this, a meta-analysis reviewed studies on gHATs in Nigeria from databases such as Embase, Global Health, Ovid Medline, Web of Science, and Google Scholar. Ten studies were included, ranging between 1962 and 2016, covering 52 clusters and 5,671,877 individuals, even though databases were scrutinized up to 2022. The seroprevalence ranged from 1.75 to 17.07%, with an overall estimate of 5.01% (95% CI 1.72-9.93). The actual gHAT prevalence detected by parasitological or PCR methods was 0.001 (95% CI 0.000-0.002), indicating a prevalence of 0.1%. Notably, the seroprevalence was greater in southern Nigeria than in northern Nigeria. These findings suggest that the disease might be spreading unnoticed due to the increased movement of people from endemic areas. This study highlights the paucity of studies in Nigeria over the last 60 years and emphasizes the need for further research, systematic surveillance, and proper reporting methods throughout the country.

National capacity strengthening within the context of an international vector control partnership: findings from a qualitative study conducted within the Ugandan 'Tiny Targets' programme

Introduction

The Ugandan Tiny Target programme is an example of an international vector control partnership that held specific capacity strengthening objectives in support of a disease elimination goal. Drawing on this experience, we sought to derive transferable lessons that may inform capacity strengthening approaches within other partnership-based vector control programmes.

Methods

A longitudinal qualitative study encompassing semistructured interviews conducted with Ugandan partners working on the Tiny Target programme. Data analysis was informed by a general inductive approach.

Results

Capacity strengthening priorities evolved over time initially focusing on the immediate capacities needed to perform roles and responsibilities assigned within the partnership and then shifting towards more advanced, transferable knowledge and skills. A distinction between operational and systemic priorities was observed: the former was necessary to support successful programme implementation whereas the latter reflected fundamental limitations or complexities within the Ugandan context that were bypassed by including an international partner. Systemic priorities were fewer in number than their operational counterparts, although substantially harder to resolve. The largest apparent threat to the long-term sustainability of reported capacity gains was their concentration within a small number of individuals.

Conclusion

Our study highlights three key lessons that may inform the design of national capacity strengthening activities conducted within the context of international vector control partnerships, including (1) Multiple approaches to strengthen capacity are needed and that can adapt to changing capacity strengthening priorities over time; (2) Balancing operational and systemic capacity strengthening priorities, the latter becoming increasingly important within longer-term partnerships and (3) Partnership members in focal country/ies should be supported to actively facilitate the transfer of newly acquired knowledge and skills to relevant colleagues/communities outside of the partnership. The generic nature of these recommendations suggests they are likely to be of benefit to many and diverse international partnerships within the wider global health space.

Lysosomal diacylglycerol pyrophosphate phosphatase is not essential in Trypanosoma brucei

Mg2+-independent phosphatidic acid phosphatase (PAP2), diacylglycerol pyrophosphate phosphatase 1 (Dpp1) is a membrane-associated enzyme in Saccharomyces cerevisiae. The enzyme is responsible for inducing the breakdown of β-phosphate from diacylglycerol pyrophosphate (DGPP) into phosphatidate (PA) and then removes the phosphate from PA to give diacylglycerol (DAG). In this study through RNAi suppression, we have demonstrated that Trypanosoma brucei diacylglycerol pyrophosphate phosphatase 1 (TbDpp1) procyclic form production is not required for parasite survival in culture. The steady-state levels of triacylglycerol (TAG), the number of lipid droplets, and the PA content are all maintained constant through the inducible down-regulation of TbDpp1. Furthermore, the localization of C-terminally tagged variants of TbDpp1 in the lysosome was demonstrated by immunofluorescence microscopy.

Targeting Cysteine Proteases and their Inhibitors to Combat Trypanosomiasis

BACKGROUND

Trypanosomiasis, caused by protozoan parasites of the Trypanosoma genus, remains a significant health burden in several regions of the world. Cysteine proteases play a crucial role in the pathogenesis of Trypanosoma parasites and have emerged as potential therapeutic targets for the development of novel antiparasitic drugs.

INTRODUCTION

This review article aims to provide a comprehensive overview of the role of cysteine proteases in trypanosomiasis and their potential as therapeutic targets. We discuss the biological significance of cysteine proteases in Trypanosoma parasites and their involvement in essential processes, such as host immune evasion, cell invasion, and nutrient acquisition.

METHODS

A comprehensive literature search was conducted to identify relevant studies and research articles on the role of cysteine proteases and their inhibitors in trypanosomiasis. The selected studies were critically analyzed to extract key findings and provide a comprehensive overview of the topic.

RESULTS

Cysteine proteases, such as cruzipain, TbCatB and TbCatL, have been identified as promising therapeutic targets due to their essential roles in Trypanosoma pathogenesis. Several small molecule inhibitors and peptidomimetics have been developed to target these proteases and have shown promising activity in preclinical studies.

CONCLUSION

Targeting cysteine proteases and their inhibitors holds great potential for the development of novel antiparasitic drugs against trypanosomiasis. The identification of potent and selective cysteine protease inhibitors could significantly contribute to the combat against trypanosomiasis and improve the prospects for the treatment of this neglected tropical disease.

Human African Trypanosomiasis (Sleeping Sickness)-Epidemiology, Clinical Manifestations, Diagnosis, Treatment, and Prevention

Purpose of Review

Human African Trypanosomiasis (HAT), also known as sleeping sickness, is a vector-borne parasitic neglected tropical disease (NTD) endemic in sub-Saharan Africa. This review aims to enhance our understanding of HAT and provide valuable insights to combat this significant public health issue by synthesizing the latest research and evidence.

Recent Findings

HAT has reached a historical < 1000 cases in 2018. In patients without neurologic symptoms and signs, the likelihood of a severe meningoencephalitic stage is deemed low, obviating the need for a lumbar puncture to guide treatment decisions using fexinidazole.

Summary

Both forms of the disease, gambiense HAT (gHAT) and rhodesiense HAT (rHAT), have specific epidemiology, risk factors, diagnosis, and treatment. Disease management still requires a high index of suspicion, infectious disease expertise, and specialized medical care. Essential stakeholders in health policy are critical to accomplishing the elimination goals of the NTD roadmap for 2021-2030.

The pathogenicity of blood stream and central nervous system forms of Trypanosoma brucei rhodesiense trypanosomes in laboratory mice: a comparative study

Background: Human African trypanosomiasis (HAT) develops in two stages namely early stage when trypanosomes are found in the blood and late stage when trypanosomes are found in the central nervous system (CNS). The two environments are different with CNS environment reported as being hostile to the trypanosomes than the blood environment. The clinical symptoms manifested by the disease in the two environments are different. Information on whether blood stream are pathologically different from CNS trypanosomes is lacking. This study undertook to compare the inter-isolate pathological differences caused by bloodstream forms (BSF) and central nervous system (CNS) of five Trypanosoma brucei rhodesiense ( Tbr) isolates in Swiss white mice. Methods: Donor mice infected with each of the five isolates were euthanized at 21 days post infection (DPI) for recovery of BSF trypanosomes in heart blood and CNS trypanosomes in brain supernatants. Groups of Swiss white mice (n = 10) were then infected with BSF or CNS forms of each isolate and monitored for parasitaemia, packed cell volume (PCV), body weight, survivorship, trypanosome length, gross and histopathology characteristics. Results: Amplification of SRA gene prior to trypanosome morphology and pathogenicity studies confirmed all isolates as T. b. rhodesiense. At 21 DPI, CNS trypanosomes were predominantly long slender (LS) while BSF were a mixture of short stumpy and intermediate forms. The density of BSF trypanosomes was on average 2-3 log-scales greater than that of CNS trypanosomes with isolate KETRI 2656 having the highest CNS trypanosome density. Conclusions: The pathogenicity study revealed clear differences in the virulence/pathogenicity of the five (5) isolates but no distinct and consistent differences between CNS and BSF forms of the same isolate. We also identified KETRI 2656 as a suitable isolate for acute menigo- encephalitic studies.

Adipocyte lipolysis protects mice against Trypanosoma brucei infection

Trypanosoma brucei causes African trypanosomiasis, colonizing adipose tissue and inducing weight loss. Here we investigated the molecular mechanisms responsible for adipose mass loss and its impact on disease pathology. We found that lipolysis is activated early in infection. Mice lacking B and T lymphocytes fail to upregulate adipocyte lipolysis, resulting in higher fat mass retention. Genetic ablation of the rate-limiting adipose triglyceride lipase specifically from adipocytes (AdipoqCre/+-Atglfl/fl) prevented the stimulation of adipocyte lipolysis during infection, reducing fat mass loss. Surprisingly, these mice succumbed earlier and presented a higher parasite burden in the gonadal adipose tissue, indicating that host lipolysis limits parasite growth. Consistently, free fatty acids comparable with those of adipose interstitial fluid induced loss of parasite viability. Adipocyte lipolysis emerges as a mechanism controlling local parasite burden and affecting the loss of fat mass in African trypanosomiasis.

Tackling Sleeping Sickness: Current and Promising Therapeutics and Treatment Strategies

Human African trypanosomiasis is a neglected tropical disease caused by the extracellular protozoan parasite Trypanosoma brucei, and targeted for eradication by 2030. The COVID-19 pandemic contributed to the lengthening of the proposed time frame for eliminating human African trypanosomiasis as control programs were interrupted. Armed with extensive antigenic variation and the depletion of the B cell population during an infectious cycle, attempts to develop a vaccine have remained unachievable. With the absence of a vaccine, control of the disease has relied heavily on intensive screening measures and the use of drugs. The chemotherapeutics previously available for disease management were plagued by issues such as toxicity, resistance, and difficulty in administration. The approval of the latest and first oral drug, fexinidazole, is a major chemotherapeutic achievement for the treatment of human African trypanosomiasis in the past few decades. Timely and accurate diagnosis is essential for effective treatment, while poor compliance and resistance remain outstanding challenges. Drug discovery is on-going, and herein we review the recent advances in anti-trypanosomal drug discovery, including novel potential drug targets. The numerous challenges associated with disease eradication will also be addressed.

Targeting Metalloenzymes: The "Achilles' Heel" of Viruses and Parasites

Metalloenzymes are central to the regulation of a wide range of essential viral and parasitic functions, including protein degradation, nucleic acid modification, and many others. Given the impact of infectious diseases on human health, inhibiting metalloenzymes offers an attractive approach to disease therapy. Metal-chelating agents have been expansively studied as antivirals and antiparasitics, resulting in important classes of metal-dependent enzyme inhibitors. This review provides the recent advances in targeting the metalloenzymes of viruses and parasites that impose a significant burden on global public health, including influenza A and B, hepatitis B and C, and human immunodeficiency viruses as well as Trypanosoma brucei and Trypanosoma cruzi.

Anti-trypanosomatid drug discovery: progress and challenges

Leishmaniasis (visceral and cutaneous), Chagas disease and human African trypanosomiasis cause substantial death and morbidity, particularly in low- and middle-income countries. Although the situation has improved for human African trypanosomiasis, there remains an urgent need for new medicines to treat leishmaniasis and Chagas disease; the clinical development pipeline is particularly sparse for Chagas disease. In this Review, we describe recent advances in our understanding of the biology of the causative pathogens, particularly from the drug discovery perspective, and we explore the progress that has been made in the development of new drug candidates and the identification of promising molecular targets. We also explore the challenges in developing new clinical candidates and discuss potential solutions to overcome such hurdles.

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).

Fexinidazole for Human African Trypanosomiasis, the Fruit of a Successful Public-Private Partnership

After 100 years of chemotherapy with impractical and toxic drugs, an oral cure for human African trypanosomiasis (HAT) is available: Fexinidazole. In this case, we review the history of drug discovery for HAT with special emphasis on the discovery, pre-clinical development, and operational challenges of the clinical trials of fexinidazole. The screening of the Drugs for Neglected Diseases initiative (DNDi) HAT-library by the Swiss TPH had singled out fexinidazole, originally developed by Hoechst (now Sanofi), as the most promising of a series of over 800 nitroimidazoles and related molecules. In cell culture, fexinidazole has an IC50 of around 1 µM against Trypanosoma brucei and is more than 100-fold less toxic to mammalian cells. In the mouse model, fexinidazole cures both the first, haemolymphatic, and the second, meningoencephalitic stage of the infection, the latter at 100 mg/kg twice daily for 5 days. In patients, the clinical trials managed by DNDi and supported by Swiss TPH mainly conducted in the Democratic Republic of the Congo demonstrated that oral fexinidazole is safe and effective for use against first- and early second-stage sleeping sickness. Based on the positive opinion issued by the European Medicines Agency in 2018, the WHO has released new interim guidelines for the treatment of HAT including fexinidazole as the new therapy for first-stage and non-severe second-stage sleeping sickness caused by Trypanosoma brucei gambiense (gHAT). This greatly facilitates the diagnosis and treatment algorithm for gHAT, increasing the attainable coverage and paving the way towards the envisaged goal of zero transmission by 2030.

Anti-trypanosomatid structure-based drug design - lessons learned from targeting the folate pathway

INTRODUCTION

Trypanosomatidic parasitic infections of humans and animals caused by Trypanosoma brucei, Trypanosoma cruzi, and Leishmania species pose a significant health and economic burden in developing countries. There are few effective and accessible treatments for these diseases, and the existing therapies suffer from problems such as parasite resistance and side effects. Structure-based drug design (SBDD) is one of the strategies that has been applied to discover new compounds targeting trypanosomatid-borne diseases.

AREAS COVERED

We review the current literature (mostly over the last 5 years, searched in PubMed database on Nov 11^th 2021) on the application of structure-based drug design approaches to identify new anti-trypanosomatidic compounds that interfere with a validated target biochemical pathway, the trypanosomatid folate pathway.

EXPERT OPINION

The application of structure-based drug design approaches to perturb the trypanosomatid folate pathway has successfully provided many new inhibitors with good selectivity profiles, most of which are natural products or their derivatives or have scaffolds of known drugs. However, the inhibitory effect against the target protein(s) often does not translate to anti-parasitic activity. Further progress is hampered by our incomplete understanding of parasite biology and biochemistry, which is necessary to complement SBDD in a multiparameter optimization approach to discovering selective anti-parasitic drugs.

Performance of the SD Bioline rapid diagnostic test as a good alternative to the detection of human African trypanosomiasis in Cameroon

BACKGROUND

Case detection is essential for the management of human African trypanosomiasis (HAT), which is caused by Trypanosoma brucei gambiense. Prior to parasitological confirmation, routine screening using the card agglutination test for trypanosomiasis (CATT) is essential. Recently, individual rapid diagnostic tests (RDTs) for the serodiagnosis of HAT have been developed.

OBJECTIVE

The purpose of this study was to evaluate the contribution of SD Bioline HAT to the serological screening of human African trypanosomiasis in Cameroonian foci.Methods. Between June 2014 and January 2015, blood samples were collected during surveys in the foci of Campo, Yokadouma, and Fontem. The sensitivity (Se) and specificity (Sp) of SD Bioline HAT were determined using the CATT as the gold standard for the detection of specific antibodies against Trypanosoma brucei gambiense.

RESULTS

A total of 88 samples were tested: 59.1% (n=52) in Campo, 31.8% (n=28) in Yokadouma, and 9.1% (n=8) in Fontem. There were 61.4% (n=54) males and 38.4% (n=34) females, and the average age was 35.4 19.0 years. In probed foci, the overall seroprevalence was 11.4% (95% confidence interval: 6.3-19.7) with the CATT method and 18.2% (95% confidence interval: 11.5-27.2%) with the SD Bioline HAT RDT method. The SD Bioline HAT's Se and Sp were 80.0% and 89.7%, respectively.

CONCLUSIONS

This study demonstrated that the overall performance of the SD Bioline HAT was comparable to that of the CATT, with high specificity in the serological detection of HAT.

Molecular Detection and Characterization of Trypanosomes Infecting Traditionally Managed Cattle in the Tropic Warm Sub-Humid Zone of Nigeria

Traditionally managed cattle constitutes the main source of animal protein to humans in Nigeria. However, seasonal migration in search of pasture exposes them to several vector-borne infections such as the African Animal Trypanosomosis (AAT), which limits their productivity. In this study, blood samples from 130 cattle in Plateau and Nasarawa states collected from May to June, 2021 were examined by the Polymerase Chain Reaction (PCR) and sequencing methods to determine the prevalence of pathogenic trypanosomes. Overall, the DNA of T. vivax was detected in 19 out of the 130 (14.6 %) samples examined by the PCR. However, using the micro-hematocrit centrifugation technique, motile haemoparasites were detected in only six (4.6 %, confidence interval [CI] 0.5—6.9 %) of the samples. The higher prevalence of T. vivax was recorded in samples sourced from the abattoir than in samples submitted from the field in Plateau state (16.7 % versus 11.5 %). However, the reverse was the case in Nasarawa state (2.9 % versus 37.5 %). The difference in prevalence of T. vivax between the abattoir and field samples was significant (P = 0.009) in Nasarawa state, but not in Plateau state (P = 0.55). The mean PCV (Packed Cell Volume) of the trypanosome infected animals was lower than that of the non-infected animals, but the difference was not significant (P = 0.29). The internal transcribe spacer region (ITS) nucleotide sequences of T. vivax generated in this study were 100 % identical to each other and formed a monophyletic cluster with the sequences of T. vivax from different countries in the GenBank. AAT remains a major constraint to profitable cattle production and food security in Nigeria and deserves more attention.

The History of the ABC Proteins in Human Trypanosomiasis Pathogens

Human trypanosomiasis affects nearly eight million people worldwide, causing great economic and social impact, mainly in endemic areas. T. cruzi and T. brucei are protozoan parasites that present efficient mechanisms of immune system evasion, leading to disease chronification. Currently, there is no vaccine, and chemotherapy is effective only in the absence of severe clinical manifestations. Nevertheless, resistant phenotypes to chemotherapy have been described in protozoan parasites, associated with cross-resistance to other chemically unrelated drugs. Multidrug resistance is multifactorial, involving: (i) drug entry, (ii) activation, (iii) metabolism and (iv) efflux pathways. In this context, ABC transporters, initially discovered in resistant tumor cells, have drawn attention in protozoan parasites, owing to their ability to decrease drug accumulation, thus mitigating their toxic effects. The discovery of these transporters in the Trypanosomatidae family started in the 1990s; however, few members were described and functionally characterized. This review contains a brief history of the main ABC transporters involved in resistance that propelled their investigation in Trypanosoma species, the main efflux modulators, as well as ABC genes described in T. cruzi and T. brucei according to the nomenclature HUGO. We hope to convey the importance that ABC transporters play in parasite physiology and chemotherapy resistance.

Persistently High Incidences of Trypanosoma brucei rhodesiense Sleeping Sickness With Contrasting Focus-Dependent Clinical Phenotypes in Malawi

Background

Human African trypanosomiasis (HAT) has caused social–economic burden in remote rural communities mostly in sub-Saharan Africa for over a century. The World Health Organization had targeted the year 2020 for the elimination of HAT caused by Trypanosoma brucei rhodesiense, which is mainly endemic in Malawi, Uganda, Tanzania, and Zambia. Significant progress has been made in reducing reported HAT cases in some countries. Area-specific updated epidemiological and clinical data may facilitate in understanding the progress of such efforts as well as the development of new intervention strategies.

Methods

We analyzed HAT prevalence and demographics from epidemiological surveys carried out from 2012 to 2020 obtained from the Ministry of Health, Malawi. In addition, we analyzed blood samples and clinical profiles of HAT patients surveyed between 2016 and 2020 from Rumphi and Nkhotakota districts. From the blood samples, parasite observations and speciation were carried out, whereas disease staging and severity were ascertained from the clinical profiles.

Results

Malawi reported 315 HAT cases from 2012 to 2020. The majority of HAT cases were men (70.2%), and the mean age was 29.9 ± 15.3 with all HAT fatalities resulting from stage 2 disease. Clinical symptoms were not significantly associated with disease outcome; however, swollen lymph nodes (p = 0.004), weight loss (p = 0.010), headache (p = 0.019), and sleep disturbance (p = 0.032) were significantly associated with the HAT stage of patients. About 50% of all HAT patients were reported within 2 years from 2019 to 2020, suggesting a HAT outbreak in Malawi.

Conclusion

This study has highlighted the current epidemiological insights of the rHAT trend in Malawi. We have shown that rHAT clinical phenotypes in Malawi are focus-dependent and that there has been a steady increase in rHAT cases compared to all countries with incidences of rHAT. We have also highlighted an outbreak of rHAT that occurred in Malawi from 2019 to 2020 with almost 50% of the total rHAT cases that we have presented in this study reported within 2 years of the outbreak. These should call for a review of Malawi’s rHAT control and elimination strategies. A One-Health approach with the inclusion of key stakeholders such as the department of parks and wildlife may also be considered.

Current Treatments to Control African Trypanosomiasis and One Health Perspective

Human African Trypanosomiasis (HAT, sleeping sickness) and Animal African Trypanosomiasis (AAT) are neglected tropical diseases generally caused by the same etiological agent, Trypanosoma brucei. Despite important advances in the reduction or disappearance of HAT cases, AAT represents a risky reservoir of the infections. There is a strong need to control AAT, as is claimed by the European Commission in a recent document on the reservation of antimicrobials for human use. Control of AAT is considered part of the One Health approach established by the FAO program against African Trypanosomiasis. Under the umbrella of the One Health concepts, in this work, by analyzing the pharmacological properties of the therapeutic options against Trypanosoma brucei spp., we underline the need for clearer and more defined guidelines in the employment of drugs designed for HAT and AAT. Essential requirements are addressed to meet the challenge of drug use and drug resistance development. This approach shall avoid inter-species cross-resistance phenomena and retain drugs therapeutic activity.

Stage-Specific COPII-Mediated Cargo Selectivity in African Trypanosomes

A hallmark of eukaryotic cells is the ability to form a secretory pathway connecting many intracellular compartments. In the early secretory pathway, coated protein complex II (COPII)-coated vesicles mediate the anterograde transport of newly synthesized secretory cargo from the endoplasmic reticulum to the Golgi apparatus. The COPII coat complex is comprised of an inner layer of Sec23/Sec24 heterodimers and an outer layer of Sec13/Sec31 heterotetramers. In African trypanosomes, there are two paralogues each of Sec23 and Sec24, that form obligate heterodimers (TbSec23.2/TbSec24.1, TbSec23.1/TbSec24.2). It is not known if these form distinct homotypic classes of vesicles or one heterotypic class, but it is known that TbSec23.2/TbSec24.1 specifically mediate forward trafficking of GPI-anchored proteins (GPI-APs) in bloodstream-form trypanosomes (BSF). Here, we showed that this selectivity was lost in insect procyclic stage parasites (PCF). All isoforms of TbSec23 and TbSec24 are essential in PCF parasites as judged by RNAi knockdowns. RNAi silencing of each subunit had equivalent effects on the trafficking of GPI-APs and p67, a transmembrane lysosomal protein. However, silencing of the TbSec23.2/TbSec24.1 had heterodimer had a significant impact on COPII mediated trafficking of soluble TbCatL from the ER to the lysosome. This finding suggests a model in which selectivity of COPII transport was altered between the BSF and PCF trypanosomes, possibly as an adaptation to a digenetic life cycle.

IMPORTANCE African trypanosomes synthesize dense surface coats composed of stage-specific glycosylphosphatidylinositol lipid anchored proteins. We previously defined specific machinery in bloodstream stage parasites that mediate the exit of these proteins from the endoplasmic reticulum. Here, we performed similar analyses in the procyclic insect stage and found significant differences in this process. These findings contribute to our understanding of secretory processes in this unusual eukaryotic model system.

Neuroimmunology of Common Parasitic Infections in Africa

Parasitic infections of the central nervous system are an important cause of morbidity and mortality in Africa. The neurological, cognitive, and psychiatric sequelae of these infections result from a complex interplay between the parasites and the host inflammatory response. Here we review some of the diseases caused by selected parasitic organisms known to infect the nervous system including Plasmodium falciparum, Toxoplasma gondii, Trypanosoma brucei spp., and Taenia solium species. For each parasite, we describe the geographical distribution, prevalence, life cycle, and typical clinical symptoms of infection and pathogenesis. We pay particular attention to how the parasites infect the brain and the interaction between each organism and the host immune system. We describe how an understanding of these processes may guide optimal diagnostic and therapeutic strategies to treat these disorders. Finally, we highlight current gaps in our understanding of disease pathophysiology and call for increased interrogation of these often-neglected disorders of the nervous system.

An Update on African Trypanocide Pharmaceutics and Resistance

African trypanosomiasis is associated with Trypanosoma evansi, T. vivax, T. congolense, and T. brucei pathogens in African animal trypanosomiasis (AAT) while T. b gambiense and T. b rhodesiense are responsible for chronic and acute human African trypanosomiasis (HAT), respectively. Suramin sodium suppresses ATP generation during the glycolytic pathway and is ineffective against T. vivax and T. congolense infections. Resistance to suramin is associated with pathogen altered transport proteins. Melarsoprol binds irreversibly with pyruvate kinase protein sulfhydryl groups and neutralizes enzymes which interrupts the trypanosome ATP generation. Melarsoprol resistance is associated with the adenine-adenosine transporter, P2, due to point mutations within this transporter. Eflornithine is used in combination with nifurtimox. Resistance to eflornithine is caused by the deletion or mutation of TbAAT6 gene which encodes the transmembrane amino acid transporter that delivers eflornithine into the cell, thus loss of transporter protein results in eflornithine resistance. Nifurtimox alone is regarded as a poor trypanocide, however, it is effective in melarsoprol-resistant gHAT patients. Resistance is associated with loss of a single copy of the genes encoding for nitroreductase enzymes. Fexinidazole is recommended for first-stage and non-severe second-stage illnesses in gHAT and resistance is associated with trypanosome bacterial nitroreductases which reduce fexinidazole. In AAT, quinapyramine sulfate interferes with DNA synthesis and suppression of cytoplasmic ribosomal activity in the mitochondria. Quinapyramine sulfate resistance is due to variations in the potential of the parasite's mitochondrial membrane. Pentamidines create cross-links between two adenines at 4–5 pairs apart in adenine-thymine-rich portions of Trypanosoma DNA. It also suppresses type II topoisomerase in the mitochondria of Trypanosoma parasites. Pentamidine resistance is due to loss of mitochondria transport proteins P2 and HAPT1. Diamidines are most effective against Trypanosome brucei group and act via the P2/TbAT1 transporters. Diminazene aceturate resistance is due to mutations that alter the activity of P2, TeDR40 (T. b. evansi). Isometamidium chloride is primarily employed in the early stages of trypanosomiasis and resistance is associated with diminazene resistance. Phenanthridine (homidium bromide, also known as ethidium bromide) acts by a breakdown of the kinetoplast network and homidium resistance is comparable to isometamidium. In humans, the development of resistance and adverse side effects against monotherapies has led to the adoption of nifurtimox-eflornithine combination therapy. Current efforts to develop new prodrug combinations of nifurtimox and eflornithine and nitroimidazole fexinidazole as well as benzoxaborole SCYX-7158 (AN5568) for HAT are in progress while little comparable progress has been done for the development of novel therapies to address trypanocide resistance in AAT.

A review on the diagnosis of animal trypanosomoses

This review focuses on the most reliable and up-to-date methods for diagnosing trypanosomoses, a group of diseases of wild and domestic mammals, caused by trypanosomes, parasitic zooflagellate protozoans mainly transmitted by insects. In Africa, the Americas and Asia, these diseases, which in some cases affect humans, result in significant illness in animals and cause major economic losses in livestock. A number of pathogens are described in this review, including several Salivarian trypanosomes, such as Trypanosoma brucei sspp. (among which are the agents of sleeping sickness, the human African trypanosomiasis [HAT]), Trypanosoma congolense and Trypanosoma vivax (causing “Nagana” or animal African trypanosomosis [AAT]), Trypanosoma evansi (“Surra”) and Trypanosoma equiperdum (“Dourine”), and Trypanosoma cruzi, a Stercorarian trypanosome, etiological agent of the American trypanosomiasis (Chagas disease). Diagnostic methods for detecting zoonotic trypanosomes causing Chagas disease and HAT in animals, as well as a diagnostic method for detecting animal trypanosomes in humans (the so-called “atypical human infections by animal trypanosomes” [a-HT]), including T. evansi and Trypanosoma lewisi (a rat parasite), are also reviewed. Our goal is to present an integrated view of the various diagnostic methods and techniques, including those for: (i) parasite detection; (ii) DNA detection; and (iii) antibody detection. The discussion covers various other factors that need to be considered, such as the sensitivity and specificity of the various diagnostic methods, critical cross-reactions that may be expected among Trypanosomatidae, additional complementary information, such as clinical observations and epizootiological context, scale of study and logistic and cost constraints. The suitability of examining multiple specimens and samples using several techniques is discussed, as well as risks to technicians, in the context of specific geographical regions and settings. This overview also addresses the challenge of diagnosing mixed infections with different Trypanosoma species and/or kinetoplastid parasites. Improving and strengthening procedures for diagnosing animal trypanosomoses throughout the world will result in a better control of infections and will significantly impact on “One Health,” by advancing and preserving animal, human and environmental health.

Perspectives on Odor-Based Control of Tsetse Flies in Africa

Tsetse-transmitted trypanosomiases are among the most neglected tropical diseases in sub-Sahara Africa. Although all tsetse species are susceptible to trypanosome infections, their differential attraction/feeding preferences for different wildlife, domestic animals, and/or humans constitute critical determinants of trypanosomes species they predominantly transmit. Artificial bait technologies, based on long-range tsetse olfactory responses to natural cues emitted by preferred hosts and blends of synthetic versions that mimic these cues, have successfully been applied in attractant-odor-based (“pull” tactic) reduction of field populations of some tsetse species. Olfactory attribute associated with active avoidance of tsetse-refractory non-hosts has similarly been exploited in design of repellent-odor-based (“push” tactic) protection of livestock. These tactics have opened possibility of spatially strategic deployment of the two sets of odor baits in “push-pull” tactics. Possibility of developing blends with enhanced attraction and repellence compared with those associated with savannah tsetse fly hosts and non-hosts, respectively, have been explored, where structure activity and blends of different components generated two novel blends. The studies evaluated structure activity and blends of different components. One based on attractive constituents associated with buffalo (Syncerus caffer) comprised of ε-nonalactone, nonanoic acid, 2-nonanone (in 1:3:2 proportion) delivered together with acetone, which showed significantly better attractancy on savannah tsetse fly than the standard blend comprised of 3-propylphenol, octenol, p-cresol, and acetone (POCA). The other blend comprised of δ-nonalactone, heptanoic acid, 4-methylguaiacol and geranylacetone (in 6:4:2:1 proportion) was significantly more repellent than previously characterized blend based on tsetse fly refractory waterbuck (Kobus defassa) constituents (δ-octalactone, pentanoic acid, guaiacol and geranylacetone). So far, no effective attractants or repellents of riverine tsetse fly species have been characterized. Optimized attractant and repellent blends for savannah tsetse flies lay down useful groundwork for future development of the “push-pull” deployment tactic for area-wide control of tsetse flies. Better understanding of the physiological, cellular, and molecular basis of response in the tsetse fly to odors can potentially augment the current tsetse fly-control interventions.

Chemical Cartography Approaches to Study Trypanosomatid Infection

Pathogen tropism and disease tropism refer to the tissue locations selectively colonized or damaged by pathogens, leading to localized disease symptoms. Human-infective trypanosomatid parasites include Trypanosoma cruzi, the causative agent of Chagas disease; Trypanosoma brucei, the causative agent of sleeping sickness; and Leishmania species, causative agents of leishmaniasis. Jointly, they affect 20 million people across the globe. These parasites show specific tropism: heart, esophagus, colon for T. cruzi, adipose tissue, pancreas, skin, circulatory system and central nervous system for T. brucei, skin for dermotropic Leishmania strains, and liver, spleen, and bone marrow for viscerotropic Leishmania strains. A spatial perspective is therefore essential to understand trypanosomatid disease pathogenesis. Chemical cartography generates 3D visualizations of small molecule abundance generated via liquid chromatography-mass spectrometry, in comparison to microbiological and immunological parameters. This protocol demonstrates how chemical cartography can be applied to study pathogenic processes during trypanosomatid infection, beginning from systematic tissue sampling and metabolite extraction, followed by liquid chromatography-tandem mass spectrometry data acquisition, and concluding with the generation of 3D maps of metabolite distribution. This method can be used for multiple research questions, such as nutrient requirements for tissue colonization by T. cruzi, T. brucei, or Leishmania, immunometabolism at sites of infection, and the relationship between local tissue metabolic perturbation and clinical disease symptoms, leading to comprehensive insight into trypanosomatid disease pathogenesis.

Community Perception on Trypanosomosis, Parasitological, and Entomological Studies in Two Selected Districts of South Omo Zone, Ethiopia

Participatory investigation and trypanosomosis prevalence studied during April 2019 and March 2020 in two selected districts of South Omo, Ethiopia. The study site is located in the gridline of 04.90 to 5.60^oN and 35.80 to 36.90⁰ E. Twelve community groups are employed. A cross-sectional study design and 288 animals bled and examined a wet film prepared from the buffy coat. Sixty NGU traps baited with acetone and cow urine were deployed for 48 hrs to estimate the apparent density. Data generated from focus group discussion and trypanosomosis prevalence analyzed using an appropriate statistical package. Proportional piling showed that cattle, goats, and sheep were proportionally dominant with a high median score of 32(14–40), 26(12–33), and 21(5–23), respectively; trypanosomosis ranked first with a proportional median score of 24(13–26) followed by contagious bovine/caprine pleuropneumonia with a proportional median score of 23(19–26) among others. Community unanimously agreed that (W = 0.9) trypanosomosis affects their socioeconomic status and was able to describe clinical signs with significant (p < 0.05) agreement. Tsetse fly (Echut and Kusubo) is the main vector with the agreement of W = 0.9(p < 0.05). Perception on human trypanosomosis varies between Benna Tsemay and Gnagatom districts. Therefore, further study supported by laboratory like molecular test is very important to conclude the presence of human trypanosomosis in the suggested area. The overall prevalence of cattle trypanosomosis was 10.1%. The prevalence of trypanosomosis was significantly higher in poor body condition (OR = 2.1, P < 0.05) and in black coat color (OR = 13.5, P < 0.05) animals. T. congolense and T. vivax were circulating in the area. A total of 455 Glossina (385 G. pallidipes, 17 G. tachinoides, and 53 G. fuscipes) were trapped. The overall apparent density of Glossina was 3.79 Flies/Trap/Day. Three species of Glossina, namely G. pallidipes, G. tachinoides, and G. fuscipes, were distributed in the study areas. Therefore, the finding suggests that the problem is significant and the human trypanosomosis is doubtful. Hence regular control measures and molecular diagnosis need to be conducted.

The elimination of human African trypanosomiasis: Achievements in relation to WHO road map targets for 2020

Background

In the 20th century, epidemics of human African trypanosomiasis (HAT) ravaged communities in a number of African countries. The latest surge in disease transmission was recorded in the late 1990s, with more than 35,000 cases reported annually in 1997 and 1998. In 2013, after more than a decade of sustained control efforts and steady progress, the World Health Assembly resolved to target the elimination of HAT as a public health problem by 2020. We report here on recent progress towards this goal.

Methodology/principal findings

With 992 and 663 cases reported in 2019 and 2020 respectively, the first global target was amply achieved (i.e. fewer than 2,000 HAT cases/year). Areas at moderate or higher risk of HAT, where more than 1 case/10,000 people/year are reported, shrunk to 120,000 km² for the five-year period 2016–2020. This reduction of 83% from the 2000–2004 baseline (i.e. 709,000 km²) is slightly below the target (i.e. 90% reduction). As a result, the second global target for HAT elimination as a public health problem cannot be considered fully achieved yet. The number of health facilities able to diagnose and treat HAT expanded (+9.6% compared to a 2019 survey), thus reinforcing the capacity for passive detection and improving epidemiological knowledge of the disease. Active surveillance for gambiense HAT was sustained. In particular, 2.8 million people were actively screened in 2019 and 1.6 million in 2020, the decrease in 2020 being mainly caused by COVID-19-related restrictions. Togo and Côte d’Ivoire were the first countries to be validated for achieving elimination of HAT as a public health problem at the national level; applications from three additional countries are under review by the World Health Organization (WHO).

Conclusions/significance

The steady progress towards the elimination of HAT is a testament to the power of multi-stakeholder commitment and coordination. At the end of 2020, the World Health Assembly endorsed a new road map for 2021–2030 that set new bold targets for neglected tropical diseases. While rhodesiense HAT remains among the diseases targeted for elimination as a public health problem, gambiense HAT is targeted for elimination of transmission. The goal for gambiense HAT is expected to be particularly arduous, as it might be hindered by cryptic reservoirs and a number of other challenges (e.g. further integration of HAT surveillance and control into national health systems, availability of skilled health care workers, development of more effective and adapted tools, and funding for and coordination of elimination efforts).

Human African trypanosomiasis (HAT) is a lethal neglected tropical disease (NTD) transmitted by the bite of infected tsetse flies. The disease is also known as “sleeping sickness”. During the 20^th century it caused enormous suffering in the endemic areas in sub-Saharan Africa. HAT transmission last soared in the late 1990s, triggering a renewed, coordinated and very successful control effort. In this paper, we present achievements towards HAT elimination, with a focus on the WHO road map targets for 2020. In particular, reported cases continue to decline, from over 30,000 cases per year at the turn of the century to 663 cases in 2020. Despite the impact of the COVID-19 pandemic, HAT surveillance was largely sustained, and the network of health facilities able to diagnose and treat the disease further expanded. Looking to the future, the World Health Organization (WHO) set bold new targets for HAT in its 2021–2030 road map for NTDs, namely: the elimination of transmission of gambiense HAT, which occurs in western and central Africa, and the elimination as a public health problem of rhodesiense HAT, which is found in eastern and southern Africa. The strong commitment of national health authorities and the international community will be essential if these goals are to be achieved.

The Trypanosomatids Cell Cycle: A Brief Report

Trypanosomatids are protozoan parasites among which are the etiologic agents of various infectious diseases in humans, such as Trypanosoma cruzi (causative agent of Chagas disease), Trypanosoma brucei (causative agent of sleeping sickness), and species of the genus Leishmania (causative agents of leishmaniases). The cell cycle in these organisms presents a sequence of events conserved throughout evolution. However, these parasites also have unique characteristics that confer some peculiarities related to the cell cycle phases. This review compares general and peculiar aspects of the cell cycle in the replicative forms of trypanosomatids. Moreover, a brief discussion about the possible cross-talk between telomeres and the cell cycle is presented. Finally, we intend to open a discussion on how a profound understanding of the cell cycle would facilitate the search for potential targets for developing antiparasitic therapies that could help millions of people worldwide.

Sesquiterpene Lactones with Dual Inhibitory Activity against the Trypanosoma brucei Pteridine Reductase 1 and Dihydrofolate Reductase

The parasite Trypanosoma brucei (T. brucei) is responsible for human African trypanosomiasis (HAT) and the cattle disease "Nagana" which to this day cause severe medical and socio-economic issues for the affected areas in Africa. So far, most of the available treatment options are accompanied by harmful side effects and are constantly challenged by newly emerging drug resistances. Since trypanosomatids are auxotrophic for folate, their pteridine metabolism provides a promising target for an innovative chemotherapeutic treatment. They are equipped with a unique corresponding enzyme system consisting of the bifunctional dihydrofolate reductase-thymidylate synthase (TbDHFR-TS) and the pteridine reductase 1 (TbPTR1). Previously, gene knockout experiments with PTR1 null mutants have underlined the importance of these enzymes for parasite survival. In a search for new chemical entities with a dual inhibitory activity against the TbPTR1 and TbDHFR, a multi-step in silico procedure was employed to pre-select promising candidates against the targeted enzymes from a natural product database. Among others, the sesquiterpene lactones (STLs) cynaropicrin and cnicin were identified as in silico hits. Consequently, an in-house database of 118 STLs was submitted to an in silico screening yielding 29 further virtual hits. Ten STLs were subsequently tested against the target enzymes in vitro in a spectrophotometric inhibition assay. Five compounds displayed an inhibition over 50% against TbPTR1 as well as three compounds against TbDHFR. Cynaropicrin turned out to be the most interesting hit since it inhibited both TbPTR1 and TbDHFR, reaching IC50 values of 12.4 µM and 7.1 µM, respectively.

Spatial analysis of G.f.fuscipes abundance in Uganda using Poisson and Zero-Inflated Poisson regression models

BACKGROUND

Tsetse flies are the major vectors of human trypanosomiasis of the form Trypanosoma brucei rhodesiense and T.b.gambiense. They are widely spread across the sub-Saharan Africa and rendering a lot of challenges to both human and animal health. This stresses effective agricultural production and productivity in Africa. Delimiting the extent and magnitude of tsetse coverage has been a challenge over decades due to limited resources and unsatisfactory technology. In a bid to overcome these limitations, this study attempted to explore modelling skills that can be applied to spatially estimate tsetse abundance in the country using limited tsetse data and a set of remote-sensed environmental variables.

METHODOLOGY

Entomological data for the period 2008-2018 as used in the model were obtained from various sources and systematically assembled using a structured protocol. Data harmonisation for the purposes of responsiveness and matching was carried out. The key tool for tsetse trapping was itemized as pyramidal trap in many instances and biconical trap in others. Based on the spatially explicit assembled data, we ran two regression models; standard Poisson and Zero-Inflated Poisson (ZIP), to explore the associations between tsetse abundance in Uganda and several environmental and climatic covariates. The covariate data were constituted largely by satellite sensor data in form of meteorological and vegetation surrogates in association with elevation and land cover data. We finally used the Zero-Inflated Poisson (ZIP) regression model to predict tsetse abundance due to its superiority over the standard Poisson after model fitting and testing using the Vuong Non-Nested statistic.

RESULTS

A total of 1,187 tsetse sampling points were identified and considered as representative for the country. The model results indicated the significance and level of responsiveness of each covariate in influencing tsetse abundance across the study area. Woodland vegetation, elevation, temperature, rainfall, and dry season normalised difference vegetation index (NDVI) were important in determining tsetse abundance and spatial distribution at varied scales. The resultant prediction map shows scaled tsetse abundance with estimated fitted numbers ranging from 0 to 59 flies per trap per day (FTD). Tsetse abundance was found to be largest at low elevations, in areas of high vegetative activity, in game parks, forests and shrubs during the dry season. There was very limited responsiveness of selected predictors to tsetse abundance during the wet season, matching the known fact that tsetse disperse most significantly during wet season.

CONCLUSIONS

A methodology was advanced to enable compilation of entomological data for 10 years, which supported the generation of tsetse abundance maps for Uganda through modelling. Our findings indicate the spatial distribution of the G. f. fuscipes as; low 0-5 FTD (48%), medium 5.1-35 FTD (18%) and high 35.1-60 FTD (34%) grounded on seasonality. This approach, amidst entomological data shortages due to limited resources and absence of expertise, can be adopted to enable mapping of the vector to provide better decision support towards designing and implementing targeted tsetse and tsetse-transmitted African trypanosomiasis control strategies.

Cnidarians as a potential source of antiparasitic drugs

New antiparasitic drugs are urgently required for treating parasitic infections. The marine environment has proven to be a valuable source of compounds with therapeutic properties against many diseases, including parasitic diseases. Cnidarian venoms are known for their toxicological properties and are candidates for developing medications. In this review, the antiparasitic properties of cnidarian toxins, discovered over the last two decades, were examined. A total of 61 cnidarian compounds from 18 different genera of cnidaria were studied for their antiparasitic activities. The assessed genera belonged mainly to three geographical areas: South America, North America, and Southeast Asia. The in vitro activities of crude extracts and compounds against a range of parasites including Plasmodium falciparum, Trypanosoma brucei gambiense, T. cruzi, T. congolense, Leishmania donovani, L. chagasi, L. braziliensis, and Giardia duodenalis are reviewed. The challenges involved in developing these compounds into effective drugs are discussed.

Antitrypanosomal activity of hydromethanol extract of leaves of Cymbopogon citratus and seeds of Lepidium sativum: in-vivo mice model

Background

Trypanosomiasis is one of the neglected tropical diseases of both humans and animals which decreases their productivity and causes death in the worst scenario. Unavailability of vaccines, the low therapeutic index of trypanocidal drugs, and the development of resistance lead to the need for research focused on developing alternative treatment options especially from medicinal plants. The present study was aimed to investigate antitrypanosomal activities of leaves of Cymbopogon citratus and seeds of Lepidium sativum in in-vivo mice model.

Methods

The plant extracts were prepared by maceration using 80% methanol and reconstituted with 10% dimethyl sulfoxide (DMSO) to have the desired concentration. The test doses were adjusted to 100, 200 and 400 mg/kg based on the toxicity profile. The plants extracts were administered to the respective groups of mice after the 12^th day of field isolate T. congolense inoculation for seven consecutive days. The level of parasitemia, bodyweight, packed cell volume (PCV), and differential white blood cell counts were measured.

Results

The in -vivo test results revealed that both plant extracts had dose-dependent antitrypanosomal activity. Both crude extracts showed a significant reduction in parasite load (P < 0.05), increased or prevent the fall of PCV value (P < 0.05), decreased lymphocytosis and increased neutrophil counts (p < 0.05) and improved bodyweight but significant bodyweight increment (P < 0.05) was observed only in C. citratus treated mice compared to the negative and positive controls.

Conclusion

The present study concluded that the crude extracts of leaves of C. citratus and seeds of L. sativum had antitrypanosomal effects. Both plants extracts reduced parasitemia level, prevented anemia and improved bodyweight of treated mice. Comparative results from all tested parameters showed that the best activities were observed with C. citratus treated groups of mice.

Effectiveness of Nifurtimox Eflornithine Combination Therapy (NECT) in T. b. gambiense second stage sleeping sickness patients in the Democratic Republic of Congo: Report from a field study

Background

Nifurtimox-eflornithine combination therapy (NECT) for the treatment of second stage gambiense human African trypanosomiasis (HAT) was added to the World Health Organization’s Essential Medicines List in 2009 after demonstration of its non-inferior efficacy compared to eflornithine therapy. A study of NECT use in the field showed acceptable safety and high efficacy until hospital discharge in a wide population, including children, pregnant and breastfeeding women, and patients with a HAT treatment history. We present here the effectiveness results after the 24-month follow-up visit.

Methodology/Principal findings

In a multicenter, open label, single arm phase IIIb study, second stage gambiense HAT patients were treated with NECT in the Democratic Republic of Congo. Clinical cure was defined 24 months after treatment as survival without clinical and/or parasitological signs of HAT. Of the 629 included patients, 619 (98.4%) were discharged alive after treatment and were examined for the presence of trypanosomes, white blood cell count in cerebro-spinal fluid, and disease symptoms. The clinical cure rate of 94.1% was comparable for all subpopulations analyzed at the 24-month follow-up visit. Self-reported adverse events during follow-up were few and concerned mainly nervous system disorders, infections, and gastro-intestinal disorders. Overall, 28 patients (4.3%) died during the course of the trial. The death of 16 of the 18 patients who died during the follow-up period was assessed as unlikely or not related to NECT. Within 24 months, eight patients (1.3%) relapsed and received rescue treatment. Sixteen patients were completely lost to follow-up.

Conclusions/Significance

NECT treatment administered under field conditions was effective and sufficiently well tolerated, no major concern arose for children or pregnant or breastfeeding women. Patients with a previous HAT treatment history had the same response as those who were naïve. In conclusion, NECT was confirmed as effective and appropriate for use in a broad population, including vulnerable subpopulations.

Trial registration

The trial is registered at ClinicalTrials.gov, number NCT00906880.

The advanced stage of the neglected tropical disease human African trypanosomiasis was, until relatively recently, treated with an old toxic arsenical drug and there was little investment in an improved treatment option. Eflornithine alone was efficacious, but difficult to administer as it required four two-hour infusions a day for 14 days. Nifurtimox-eflornithine combination therapy (NECT) was developed as a simplified and easier to use treatment and was shown to be effective and sufficiently well tolerated in a randomized clinical trial. The present study was conducted to assess the overall effectiveness, including the feasibility of implementation of NECT under field conditions in a wider population than in the randomized clinical trial. We found that NECT can be implemented under field conditions and in remote areas, with the necessary logistical support and staff training for treatment administration. Adverse events, although very frequent, were considered acceptable given the severity of the disease. Less than 10% of patients showed severe adverse events. Over 24 months, the case fatality rate was 4.5% and relapses were rare (1.3%). The effectiveness of NECT was confirmed in a broad spectrum of second stage gambiense HAT patients, including children, pregnant and breastfeeding women, and patients who had been previously treated for HAT.

An annotated checklist of the eukaryotic parasites of humans, exclusive of fungi and algae

The classification of "parasites" in the medical field is a challenging notion, a group which historically has included all eukaryotes exclusive of fungi that invade and derive resources from the human host. Since antiquity, humans have been identifying and documenting parasitic infections, and this collective catalog of parasitic agents has expanded considerably with technology. As our understanding of species boundaries and the use of molecular tools has evolved, so has our concept of the taxonomy of human parasites. Consequently, new species have been recognized while others have been relegated to synonyms. On the other hand, the decline of expertise in classical parasitology and limited curricula have led to a loss of awareness of many rarely encountered species. Here, we provide a comprehensive checklist of all reported eukaryotic organisms (excluding fungi and allied taxa) parasitizing humans resulting in 274 genus-group taxa and 848 species-group taxa. For each species, or genus where indicated, a concise summary of geographic distribution, natural hosts, route of transmission and site within human host, and vectored pathogens are presented. Ubiquitous, human-adapted species as well as very rare, incidental zoonotic organisms are discussed in this annotated checklist. We also provide a list of 79 excluded genera and species that have been previously reported as human parasites but are not believed to be true human parasites or represent misidentifications or taxonomic changes.

Single-cell transcriptome profiling and the use of AID deficient mice reveal that B cell activation combined with antibody class switch recombination and somatic hypermutation do not benefit the control of experimental trypanosomosis

Salivarian trypanosomes are extracellular protozoan parasites causing infections in a wide range of mammalian hosts, with Trypanosoma evansi having the widest geographic distribution, reaching territories far outside Africa and occasionally even Europe. Besides causing the animal diseases, T. evansi can cause atypical Human Trypanosomosis. The success of this parasite is attributed to its capacity to evade and disable the mammalian defense response. To unravel the latter, we applied here for the first time a scRNA-seq analysis on splenocytes from trypanosome infected mice, at two time points during infection, i.e. just after control of the first parasitemia peak (day 14) and a late chronic time point during infection (day 42). This analysis was combined with flow cytometry and ELISA, revealing that T. evansi induces prompt activation of splenic IgM+CD1d+ Marginal Zone and IgMIntIgD+ Follicular B cells, coinciding with an increase in plasma IgG2c Ab levels. Despite the absence of follicles, a rapid accumulation of Aicda+ GC-like B cells followed first parasitemia peak clearance, accompanied by the occurrence of Xbp1+ expressing CD138+ plasma B cells and Tbx21+ atypical CD11c+ memory B cells. Ablation of immature CD93+ bone marrow and Vpreb3+Ly6d+Ighm+ expressing transitional spleen B cells prevented mature peripheral B cell replenishment. Interestingly, AID-/- mice that lack the capacity to mount anti-parasite IgG responses, exhibited a superior defense level against T. evansi infections. Here, elevated natural IgMs were able to exert in vivo and in vitro trypanocidal activity. Hence, we conclude that in immune competent mice, trypanosomosis associated B cell activation and switched IgG production is rapidly induced by T. evansi, facilitating an escape from the detrimental natural IgM killing activity, and resulting in increased host susceptibility. This unique role of IgM and its anti-trypanosome activity are discussed in the context of the dilemma this causes for the future development of anti-trypanosome vaccines.

Thinking outside the blood: Perspectives on tissue-resident Trypanosoma brucei

Trypanosoma brucei is a protozoan parasite that causes human and animal African trypanosomiases (HAT and AAT). In the mammalian host, the parasite lives entirely extracellularly, in both the blood and interstitial spaces in tissues. Although most T. brucei research has focused on the biology of blood- and central nervous system (CNS)-resident parasites, a number of recent studies have highlighted parasite reservoirs in the dermis and adipose tissue, leading to a renewed interest in tissue-resident parasite populations. In light of this renewed interest, work describing tissue-resident parasites can serve as a valuable resource to inform future investigations of tissue-resident T. brucei. Here, we review this body of literature, which describes infections in humans, natural hosts, and experimental animal models, providing a wealth of information on the distribution and biology of extravascular parasites, the corresponding immune response in each tissue, and resulting host pathology. We discuss the implications of these studies and future questions in the study of extravascular T. brucei.

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.

As human African trypanosomiasis (HAT) or sleeping sickness is approaching elimination, case management is progressively transferred from specialized teams to front line health care centres. This approach raises practical questions. What clinical symptoms and signs should trigger HAT testing? What rapid diagnostic tests (RDT) are suitable for screening? Which unconfirmed serological suspects should be examined further? During this study conducted in Côte d’Ivoire, individuals with sleep disturbances, motor disorders, convulsions, severe weight loss, or psychiatric problems were more often positive in RDTs. These symptoms and signs should trigger referral for HAT screening. Our results confirm appropriateness of the existing HAT screening strategy with SD Bioline HAT or HAT Sero-K-Set having specificities of 97.8% and 98.9%. Subsequent tests on dried blood spots from RDT positives were 93.3% to 98.9% specific, and increased the positive predictive value from below 15% up to 67%. For selection of RDT seropositives for additional parasitological examinations, trypanolysis on dried blood spots is suitable, but could be replaced by ELISA, which can be performed locally. The optimal diagnostic test algorithm for Côte d’Ivoire, in terms of cost-effectiveness, remains to be determined.

The History of Anti-Trypanosome Vaccine Development Shows That Highly Immunogenic and Exposed Pathogen-Derived Antigens Are Not Necessarily Good Target Candidates: Enolase and ISG75 as Examples

Salivarian trypanosomes comprise a group of extracellular anthroponotic and zoonotic parasites. The only sustainable method for global control of these infection is through vaccination of livestock animals. Despite multiple reports describing promising laboratory results, no single field-applicable solution has been successful so far. Conventionally, vaccine research focusses mostly on exposed immunogenic antigens, or the structural molecular knowledge of surface exposed invariant immunogens. Unfortunately, extracellular parasites (or parasites with extracellular life stages) have devised efficient defense systems against host antibody attacks, so they can deal with the mammalian humoral immune response. In the case of trypanosomes, it appears that these mechanisms have been perfected, leading to vaccine failure in natural hosts. Here, we provide two examples of potential vaccine candidates that, despite being immunogenic and accessible to the immune system, failed to induce a functionally protective memory response. First, trypanosomal enolase was tested as a vaccine candidate, as it was recently characterized as a highly conserved enzyme that is readily recognized during infection by the host antibody response. Secondly, we re-addressed a vaccine approach towards the Invariant Surface Glycoprotein ISG75, and showed that despite being highly immunogenic, trypanosomes can avoid anti-ISG75 mediated parasitemia control.

Nanotechnological interventions for treatment of trypanosomiasis in humans and animals

Trypanosomiasis is a parasitic infection caused by Trypanosoma. It is one of the major causes of deaths in underprivileged, rural areas of Africa, America and Asia. Depending on the parasite species responsible for the disease, it can take two forms namely African trypanosomiasis (sleeping sickness) and American trypanosomiasis (Chagas disease). The complete life-cycle stages of trypanosomes span between insect vector (tsetse fly, triatomine bug) and mammalian host (humans, animals). Only few drugs have been approved for the treatment of trypanosomiasis. Moreover, current trypanocidal therapy has major limitations of poor efficacy, serious side effects and drug resistance. Due to the lack of economic gains from tropical parasitic infection, it has always been neglected by the researchers and drug manufacturers. There is an immense need of more effective innovative strategies to decrease the deaths associated with this diseases. Nanotechnological approaches for delivery of existing drugs have shown significant improvement in efficacy with many-fold decrease in their dose. The review emphasizes on nanotechnological interventions in the treatment of trypanosomiasis in both humans and animals. Current trypanocidal therapy and their limitations have also been discussed briefly. Graphical abstract.

Costs and Outcomes of Integrated Human African Trypanosomiasis Surveillance System Using Rapid Diagnostic Tests, Democratic Republic of the Congo

We integrated sleeping sickness case detection into the primary healthcare system in 2 health districts in the Democratic Republic of the Congo. We replaced a less field-friendly serologic test with a rapid diagnostic test, which was followed up by human African trypanosomiasis microscopic testing, and used a mixed costing methodology to estimate costs from a healthcare provider perspective. We screened a total of 18,225 persons and identified 27 new cases. Average financial cost (i.e., actual expenditures) was US $6.70/person screened and $4,464/case diagnosed and treated. Average economic cost (i.e., value of resources foregone that could have been used for other purposes) was $9.40/person screened and $6,138/case diagnosed and treated. Our study shows that integrating sleeping sickness surveillance into the primary healthcare system is feasible and highlights challenges in completing the diagnostic referral process and developing a context-adapted diagnostic algorithm for the large-scale implementation of this strategy in a sustainable and low-cost manner.

Critical Linkages Between Livestock Production, Livestock Trade and Potential Spread of Human African Trypanosomiasis in Uganda: Bioeconomic Herd Modeling and Livestock Trade Analysis

Background: Tsetse-transmitted human African trypanosomiasis (HAT) remains endemic in Uganda. The chronic form caused by Trypanosoma brucei gambiense (gHAT) is found in north-western Uganda, whereas the acute zoonotic form of the disease, caused by T. b. brucei rhodesiense (rHAT), occurs in the eastern region. Cattle is the major reservoir of rHAT in Uganda. These two forms of HAT are likely to converge resulting in a public health disaster. This study examines the intricate and intrinsic links between cattle herd dynamics, livestock trade and potential risk of spread of rHAT northwards. Methods: A bio-economic cattle herd model was developed to simulate herd dynamics at the farm level. Semi-structured interviews (n = 310), focus group discussions (n = 9) and key informant interviews (n = 9) were used to evaluate livestock markets (n = 9) as part of the cattle supply chain analysis. The cattle market data was used for stochastic risk analysis. Results: Cattle trade in eastern and northern Uganda is dominated by sale of draft and adult male cattle as well as exportation of young male cattle. The study found that the need to import draft cattle at the farm level was to cover deficits because of the herd structure, which is mostly geared towards animal traction. The importation and exportation of draft cattle and disposal of old adult male cattle formed the major basis of livestock movement and could result in the spread of rHAT northwards. The risk of rHAT infected cattle being introduced to northern Uganda from the eastern region via cattle trade was found to be high (i.e. probability of 1). Conclusion: Through deterministic and stochastic modelling of cattle herd and cattle trade dynamics, this study identifies critical links between livestock production and trade as well as potential risk of rHAT spread in eastern and northern Uganda. The findings highlight the need for targeted and routine surveillance and control of zoonotic diseases such as rHAT.

Oral fexinidazole for stage 1 or early stage 2 African Trypanosoma brucei gambiense trypanosomiasis: a prospective, multicentre, open-label, cohort study

BACKGROUND

Staging and treatment of human African trypanosomiasis caused by Trypanosoma brucei gambiense (g-HAT) required lumbar puncture to assess cerebrospinal fluid (CSF) and intravenous drugs that cross the blood-brain barrier for late-stage infection. These procedures are inconvenient in rural health systems of disease-endemic countries. A pivotal study established fexinidazole as the first oral monotherapy to be effective against non-severe stage 2 g-HAT. We aimed to assess the safety and efficacy of fexinidazole in early g-HAT.

METHODS

In this prospective, multicentre, open-label, single-arm cohort study, patients with stage 1 or early stage 2 g-HAT were recruited from eight treatment centres in the Democratic Republic of the Congo. Primary inclusion criteria included being older than 15 years, being able to ingest at least one complete meal per day (or at least one sachet of Plumpy'Nut®), a Karnofsky score higher than 50, evidence of trypanosomes in the blood or lymph but no evidence of trypanosomes in the CSF, willingness to be admitted to hospital to receive treatment, having a permanent address, and being able to comply with the follow-up visit schedule. Exclusion criteria included severe malnutrition, inability to take medication orally, pregnant or breastfeeding women, any clinically important medical condition that could jeopardise patient safety or participation in the study, severely deteriorated general status, any contraindication to imidazole drugs, HAT treatment in the past 2 years, previous enrolment in the study or previous intake of fexinidazole, abnormalities on electrocardiogram that did not return to normal in pretreatment repeated assessments or were considered clinically important, QT interval corrected using Fridericia's formula of at least 450 ms, and patients not tested for malaria or not having received appropriate treatment for malaria or for soil-transmitted helminthiasis. Patients were classified into stage 1 or early stage 2 g-HAT groups following evidence of trypanosomes in the blood, lymph, and absence in CSF, and using white-blood-cell count in CSF. Patients received 1800 mg fexinidazole once per day on days 1-4 then 1200 mg fexinidazole on days 5-10. Patients were observed for approximately 19 months in total. Study participants were followed up on day 5 and day 8 during treatment, at end of treatment on day 11, at end of hospitalisation on days 11-18, at week 9 for a subset of patients, and after 6 months, 12 months, and 18 months. The primary endpoint was treatment success at 12 months. Safety was assessed through routine monitoring. Analyses were done in the intention-to-treat population. The acceptable success rate was defined as treatment efficacy in more than 80% of patients. This study is completed and registered with ClinicalTrials.gov (NCT02169557).

FINDINGS

Patients were enrolled between April 30, 2014, and April 25, 2017. 238 patients were recruited: 195 (82%) patients with stage 1 g-HAT and 43 (18%) with early stage 2 g-HAT. 189 (97%) of 195 patients with stage 1 g-HAT and 41 (95%) of 43 patients with early stage 2 g-HAT were finally included and completed the 10 day treatment period. Three patients with stage 1 g-HAT died after the 10 day treatment period and before the 12 month primary follow-up visit, considered as treatment failure and were withdrawn from the study. Treatment was effective at 12 months for 227 (99%) of 230 patients (95% CI 96·2-99·7): 186 (98%) of 189 patients (95·4-99·7) with stage 1 and 41 (100%) of 41 patients (91·4-100·0) with early stage 2, indicating that the primary study endpoint was met. No new safety issues were observed. The most frequent adverse events were headache and vomiting. In total, 214 (93%) of 230 patients had treatment-emergent adverse events, mainly common-terminology criteria for adverse events grades 1 to 3. None led to treatment discontinuation.

INTERPRETATION

Fexinidazole is a valuable first-line treatment option in the early stages of g-HAT.

FUNDING

Through the Drugs for Neglected Diseases initiative: the Bill & Melinda Gates Foundation, the Republic and Canton of Geneva (Switzerland), the Dutch Ministry of Foreign Affairs (also known as DGIS; Netherlands), the Norwegian Agency for Development Cooperation (also known as Norad; Norway), the Federal Ministry of Education and Research (also known as BMBF) through KfW (Germany), the Brian Mercer Charitable Trust (UK), and other private foundations and individuals from the HAT campaign.

TRANSLATION

For the French translation of the abstract see Supplementary Materials section.

A machine learning approach to integrating genetic and ecological data in tsetse flies (Glossina pallidipes) for spatially explicit vector control planning

Vector control is an effective strategy for reducing vector-borne disease transmission, but requires knowledge of vector habitat use and dispersal patterns. Our goal was to improve this knowledge for the tsetse species Glossina pallidipes, a vector of human and animal African trypanosomiasis, which are diseases that pose serious health and socioeconomic burdens across sub-Saharan Africa. We used random forest regression to (i) build and integrate models of G. pallidipes habitat suitability and genetic connectivity across Kenya and northern Tanzania and (ii) provide novel vector control recommendations. Inputs for the models included field survey records from 349 trap locations, genetic data from 11 microsatellite loci from 659 flies and 29 sampling sites, and remotely sensed environmental data. The suitability and connectivity models explained approximately 80% and 67% of the variance in the occurrence and genetic data and exhibited high accuracy based on cross-validation. The bivariate map showed that suitability and connectivity vary independently across the landscape and was used to inform our vector control recommendations. Post hoc analyses show spatial variation in the correlations between the most important environmental predictors from our models and each response variable (e.g., suitability and connectivity) as well as heterogeneity in expected future climatic change of these predictors. The bivariate map suggests that vector control is most likely to be successful in the Lake Victoria Basin and supports the previous recommendation that G. pallidipes from most of eastern Kenya should be managed as a single unit. We further recommend that future monitoring efforts should focus on tracking potential changes in vector presence and dispersal around the Serengeti and the Lake Victoria Basin based on projected local climatic shifts. The strong performance of the spatial models suggests potential for our integrative methodology to be used to understand future impacts of climate change in this and other vector systems.

Feasibility of a dried blood spot strategy for serological screening and surveillance to monitor elimination of Human African Trypanosomiasis in the Democratic Republic of the Congo

In recent years, the number of reported Human African Trypanosomiasis (HAT) cases caused by Trypanosoma brucei (T.b.) gambiense has been markedly declining, and the goal of ‘elimination as a public health problem’ is within reach. For the next stage, i.e. interruption of HAT transmission by 2030, intensive screening and surveillance will need to be maintained, but with tools and strategies more efficiently tailored to the very low prevalence. We assessed the sequential use of ELISA and Immune Trypanolysis (ITL) on dried blood spot (DBS) samples as an alternative to the traditional HAT field testing and confirmation approach. A cross-sectional study was conducted in HAT endemic and previously endemic zones in Kongo Central province, and a non-endemic zone in Haut Katanga province in the Democratic Republic of the Congo (DRC). Door-to-door visits were performed to collect dried blood spot (DBS) samples on filter paper. ELISA/T.b. gambiense was conducted followed by ITL for those testing positive by ELISA and in a subset of ELISA negatives. In total, 11,642 participants were enrolled. Of these, 11,535 DBS were collected and stored in appropriate condition for ELISA testing. Ninety-seven DBS samples tested positive on ELISA. In the endemic zone, ELISA positivity was 1.34% (95%CI: 1.04–1.64). In the previously endemic zone and non-endemic zone, ELISA positivity was 0.34% (95% CI: 0.13–0.55) and 0.37% (95% CI: 0.15–0.60) respectively. Among the ELISA positives, only two samples had a positive ITL result, both from the endemic zone. One of those was from a former HAT patient treated in 2008 and the other from an individual who unfortunately had deceased prior to the follow-up visit. Our study showed that a surveillance strategy, based on DBS samples and centralized testing with retracing of patients if needed, is feasible in DRC. ELISA seems well suited as initial test with a similar positivity rate as traditional screening tests, but ITL remains complex. Alternatives for the latter, also analyzable on DBS, should be further explored.

Human African Trypanosomiasis (HAT), also known as sleeping sickness is a parasitic disease, transmitted by tsetse flies, that is usually fatal if untreated. The number of cases have been rapidly declining over the past years indicating that elimination of the disease as a public health problem is within reach. To achieve the next stage, i.e. interruption of HAT transmission by 2030, intensive screening and surveillance will need to be maintained, but with tools and strategies more efficiently tailored to the very low prevalence. In contrast to the traditional approach of sending laboratory expertise to the field, we assessed an alternative approach based on the collection of dried blood samples on filter paper that were tested in a regional laboratory. Samples were taken in endemic, previously endemic and non-endemic villages and tested by ELISA and Immune Trypanolysis. The ELISA positivity rates were similar to those of other screening techniques currently used and Immune Trypanolysis was highly specific. Hence for surveillance in HAT endemic areas, collecting dried blood samples followed by centralized testing could become an alternative to the current strategy of active screening by mobile teams with on the spot confirmation. It has also potential for post-elimination surveillance to monitor resurgence and for exploratory surveillance in historic foci. Though highly specific, Immune Trypanolysis remains too complex for use in intermediate level laboratories, to further expand this strategy an alternative second step test is required.