Human African trypanosomiasis cases diagnosed in non-endemic countries (2011-2020)

BACKGROUND

Sleeping sickness, or human African trypanosomiasis (HAT), is transmitted by tsetse flies in endemic foci in sub-Saharan Africa. Because of international travel and population movements, cases are also occasionally diagnosed in non-endemic countries.

METHODOLOGY/PRINCIPAL FINDINGS

Antitrypanosomal medicines to treat the disease are available gratis through the World Health Organization (WHO) thanks to a public-private partnership, and exclusive distribution of the majority of them enables WHO to gather information on all exported cases. Data collected by WHO are complemented by case reports and scientific publications. During 2011-2020, 49 cases of HAT were diagnosed in 16 non-endemic countries across five continents: 35 cases were caused by Trypanosoma brucei rhodesiense, mainly in tourists visiting wildlife areas in eastern and southern Africa, and 14 cases were due to T. b. gambiense, mainly in African migrants originating from or visiting endemic areas in western and central Africa.

CONCLUSIONS/SIGNIFICANCE

HAT diagnosis in non-endemic countries is rare and can be challenging, but alertness and surveillance must be maintained to contribute to WHO's elimination goals. Early detection is particularly important as it considerably improves the prognosis.

Monitoring the elimination of human African trypanosomiasis: Update to 2016

BACKGROUND

Human African trypanosomiasis (HAT) is a neglected tropical disease targeted for elimination 'as a public health problem' by 2020. The indicators to monitor progress towards the target are based on the number of reported cases, the related areas and populations exposed at various levels of risk, and the coverage of surveillance activities. Based on data provided by the National Sleeping Sickness Control Programmes (NSSCP), Non-Governmental Organizations (NGOs) and research institutions-and assembled in the Atlas of HAT-the World Health Organization (WHO) provides here an update to 2016 for these indicators, as well as an analysis of the epidemiological situation.

RESULTS

Trends for the two primary indicators of elimination are on track for the 2020 goal: 2,164 cases of HAT were reported in 2016 (as compared to the milestone of 4,000 cases), and for the period 2012-2016 280,000 km2 are estimated to be at moderate risk or higher (i.e. ≥ 1 case/10,000 people/year), as compared to the milestone of 230,000 km2. These figures correspond to reductions of 92% and 61% as compared to the respective baselines (i.e. 26,550 HAT cases in the year 2000, and 709,000 km2 exposed at various levels of risk for the period 2000-2004). Among the secondary indicators, an overall improvement in the coverage of at risk populations by surveillance activities was observed. Regarding passive surveillance, the number of fixed health facilities providing gambiense HAT diagnosis or treatment expanded, with 1,338 enumerated in endemic countries in 2017 (+52% as compared to the survey completed only sixteen months earlier). Concerning rhodesiense HAT, 124 health facilities currently provide diagnosis or treatment. The broadening of passive surveillance is occurring in a context of fairly stable intensity of active case finding, with between 1.8 million and 2.4 million people screened per year over the period 2012-2016.

DISCUSSION

Elimination of HAT as a public health problem by 2020 seems within reach, as the epidemiological trends observed in previous years are confirmed in this latest 2016 monitoring update. However, looking beyond 2020, and in particular to the 2030 goal of elimination of transmission as zero cases for the gambiense form of the disease only, there is no room for complacency. Challenges still abound, including ensuring the effective integration of HAT control activities in the health system, sustaining the commitment of donors and HAT endemic countries, and clarifying the extent of the threat posed by cryptic reservoirs (e.g. human asymptomatic carriers and the possible animal reservoirs in gambiense HAT epidemiology). WHO provides through the network for HAT elimination the essential coordination of the wide range of stakeholders to ensure synergy of efforts.

Inducible high-efficiency CRISPR-Cas9-targeted gene editing and precision base editing in African trypanosomes

The Cas9 endonuclease can be programmed by guide RNA to introduce sequence-specific breaks in genomic DNA. Thus, Cas9-based approaches present a range of novel options for genome manipulation and precision editing. African trypanosomes are parasites that cause lethal human and animal diseases. They also serve as models for studies on eukaryotic biology, including 'divergent' biology. Genome modification, exploiting the native homologous recombination machinery, has been important for studies on trypanosomes but often requires multiple rounds of transfection using selectable markers that integrate at low efficiency. We report a system for delivering tetracycline inducible Cas9 and guide RNA to Trypanosoma brucei. In these cells, targeted DNA cleavage and gene disruption can be achieved at close to 100% efficiency without further selection. Disruption of aquaglyceroporin (AQP2) or amino acid transporter genes confers resistance to the clinical drugs pentamidine or eflornithine, respectively, providing simple and robust assays for editing efficiency. We also use the new system for homology-directed, precision base editing; a single-stranded oligodeoxyribonucleotide repair template was delivered to introduce a single AQP2 - T791G/L264R mutation in this case. The technology we describe now enables a range of novel programmed genome-editing approaches in T. brucei that would benefit from temporal control, high-efficiency and precision.

A literature review of economic evaluations for a neglected tropical disease: human African trypanosomiasis ("sleeping sickness")

Human African trypanosomiasis (HAT) is a disease caused by infection with the parasite Trypanosoma brucei gambiense or T. b. rhodesiense. It is transmitted to humans via the tsetse fly. Approximately 70 million people worldwide were at risk of infection in 1995, and approximately 20,000 people across Africa are infected with HAT. The objective of this review was to identify existing economic evaluations in order to summarise cost-effective interventions to reduce, control, or eliminate the burden of HAT. The studies included in the review were compared and critically appraised in order to determine if there were existing standardised methods that could be used for economic evaluation of HAT interventions or if innovative methodological approaches are warranted. A search strategy was developed using keywords and was implemented in January 2014 in several databases. The search returned a total of 2,283 articles. After two levels of screening, a total of seven economic evaluations were included and underwent critical appraisal using the Scottish Intercollegiate Guidelines Network (SIGN) Methodology Checklist 6: Economic Evaluations. Results from the existing studies focused on the cost-effectiveness of interventions for the control and reduction of disease transmission. Modelling was a common method to forecast long-term results, and publications focused on interventions by category, such as case detection, diagnostics, drug treatments, and vector control. Most interventions were considered cost-effective based on the thresholds described; however, the current treatment, nifurtomix-eflornithine combination therapy (NECT), has not been evaluated for cost-effectiveness, and considerations for cost-effective strategies for elimination have yet to be completed. Overall, the current evidence highlights the main components that play a role in control; however, economic evaluations of HAT elimination strategies are needed to assist national decision makers, stakeholders, and key funders. These analyses would be of use, as HAT is currently being prioritized as a neglected tropical disease (NTD) to reach elimination by 2020.

Treatment options for second-stage gambiense human African trypanosomiasis

Treatment of second-stage gambiense human African trypanosomiasis relied on toxic arsenic-based derivatives for over 50 years. The availability and subsequent use of eflornithine, initially in monotherapy and more recently in combination with nifurtimox (NECT), has drastically improved the prognosis of treated patients. However, NECT logistic and nursing requirements remain obstacles to its deployment and use in peripheral health structures in rural sub-Saharan Africa. Two oral compounds, fexinidazole and SCYX-7158, are currently in clinical development. The main scope of this article is to discuss the potential impact of new oral therapies to improve diagnosis-treatment algorithms and patients' access to treatment, and to contribute to reach the objectives of the recently launched gambiense human African trypanosomiasis elimination program.

Infections of the developing world

Access to critical care is rapidly growing in areas of the world where it was previously nonexistent and where infectious diseases often comprise the largest disease burden. Additionally, with crowding, mass migrations, and air travel, infectious diseases previously geographically confined are quickly spread across the planet, often in shorter time frames than disease incubation periods. Hence, critical care practitioners must be familiar with infectious diseases previously confined to the developing world. This article reviews selected tropical diseases that are seen in diverse locales and often require critical care services.

African trypanosomiasis

Trypanosomiasis remains one of the most serious constraints to economic development in sub-Saharan Africa and, as a consequence, related research has been subject to strong social and political as well as scientific influences. The epidemics of sleeping sickness that occurred at the turn of the 20th Century focussed research efforts on what became known as 'the colonial disease'. This focus is thought to have produced 'vertical' health services aimed at this one disease, while neglecting other important health issues. Given the scale of these epidemics, and the fact that the disease is fatal if left untreated, it is unsurprising that sleeping sickness dominated colonial medicine. Indeed, recent evidence indicates that, if anything, the colonial authorities greatly under-estimated the mortality attributable to sleeping sickness. Differences in approach to disease control between Francophone and Anglophone Africa, which in the past have been considered ideological, on examination prove to be logical, reflecting the underlying epidemiological divergence of East and West Africa. These epidemiological differences are ancient in origin, pre-dating the colonial period, and continue to the present day. Recent research has produced control solutions, for the African trypanosomiases of humans and livestock, that are effective, affordable and sustainable by small-holder farmers. Whether these simple solutions are allowed to fulfil their promise and become fully integrated into agricultural practice remains to be seen. After more than 100 years of effort, trypanosomiasis control remains a controversial topic, subject to the tides of fashion and politics.

High affinity nanobodies against the Trypanosome brucei VSG are potent trypanolytic agents that block endocytosis

The African trypanosome Trypanosoma brucei, which persists within the bloodstream of the mammalian host, has evolved potent mechanisms for immune evasion. Specifically, antigenic variation of the variant-specific surface glycoprotein (VSG) and a highly active endocytosis and recycling of the surface coat efficiently delay killing mediated by anti-VSG antibodies. Consequently, conventional VSG-specific intact immunoglobulins are non-trypanocidal in the absence of complement. In sharp contrast, monovalent antigen-binding fragments, including 15 kDa nanobodies (Nb) derived from camelid heavy-chain antibodies (HCAbs) recognizing variant-specific VSG epitopes, efficiently lyse trypanosomes both in vitro and in vivo. This Nb-mediated lysis is preceded by very rapid immobilisation of the parasites, massive enlargement of the flagellar pocket and major blockade of endocytosis. This is accompanied by severe metabolic perturbations reflected by reduced intracellular ATP-levels and loss of mitochondrial membrane potential, culminating in cell death. Modification of anti-VSG Nbs through site-directed mutagenesis and by reconstitution into HCAbs, combined with unveiling of trypanolytic activity from intact immunoglobulins by papain proteolysis, demonstrates that the trypanolytic activity of Nbs and Fabs requires low molecular weight, monovalency and high affinity. We propose that the generation of low molecular weight VSG-specific trypanolytic nanobodies that impede endocytosis offers a new opportunity for developing novel trypanosomiasis therapeutics. In addition, these data suggest that the antigen-binding domain of an anti-microbial antibody harbours biological functionality that is latent in the intact immunoglobulin and is revealed only upon release of the antigen-binding fragment.

Haemoparasites, such as African trypanosomes, have developed potent immune evasion mechanisms to avoid antibody-mediated elimination. Consequently, trypanosome surface antigen-specific immunoglobulins in the absence of complement are non-trypanocidal. In contrast, certain monovalent nanobodies (Nb), monomeric antigen-binding domains derived from camelid Heavy-Chain Antibodies (HCAb) and which have a much lower molecular weight (15 kDa) than classical antibodies (150 kDa), efficiently lyse trypanosomes both in vitro and in vivo. This is surprising as classically immunoglobulin effector functions are mediated via the Fc-domain, which is absent from the Nb. We demonstrate that the Nb-mediated trypanolysis depends on the low molecular weight, monovalency and high affinity and is associated with loss of motility, a major block to endocytosis, energy depletion and cell death. Overall, targeting the parasite surface with low molecular weight, high affinity Nbs is sufficient to exert a direct therapeutic action. Therefore, the exploitation of Nbs against African trypanosomiasis represents a novel therapeutic strategy. Furthermore, demonstration that a high affinity antigen-binding Nb or Fab fragment lacking an effector domain (i.e., Fc-domain or an attached toxin) can exert a direct biological function, suggests that intact antibodies likely harbour latent functionality which only become revealed upon removal of the Fc-domain.

Human African trypanosomiasis

Human African trypanosomiasis (sleeping sickness) occurs in sub-Saharan Africa. It is caused by the protozoan parasite Trypanosoma brucei, transmitted by tsetse flies. Almost all cases are due to Trypanosoma brucei gambiense, which is indigenous to west and central Africa. Prevalence is strongly dependent on control measures, which are often neglected during periods of political instability, thus leading to resurgence. With fewer than 12 000 cases of this disabling and fatal disease reported per year, trypanosomiasis belongs to the most neglected tropical diseases. The clinical presentation is complex, and diagnosis and treatment difficult. The available drugs are old, complicated to administer, and can cause severe adverse reactions. New diagnostic methods and safe and effective drugs are urgently needed. Vector control, to reduce the number of flies in existing foci, needs to be organised on a pan-African basis. WHO has stated that if national control programmes, international organisations, research institutes, and philanthropic partners engage in concerted action, elimination of this disease might even be possible.

Trypanosomiasis

African (sleeping sickness) and American (Chagas' disease) trypanosomiasis, caused by protozoa of the family Trypanosomatidae, are diseases that are endemic in parts of Africa and Latin America, respectively. Physicians in developed countries may occasionally see cases because of extensive travel and immigration from endemic countries. Although neurological involvement is common in both, its incidence and clinical presentation differ considerably. African trypanosomiasis, caused by subspecies of Trypanosoma brucei (T b rhodesiense, T b gambiense), is transmitted by the tsetse fly and causes meningoencephalitis, in which somnolence is a prominent feature. Parasites may reach the brain parenchyma through the choroid plexus or the Virchow Robin spaces. American trypanosomiasis, caused by Trypanosoma cruzi is transmitted by reduviid bugs. While lesions in the central nervous system are not prominent, except in the reactivated forms which occur in immunodeficient patients, the peripheral nerve, mainly the autonomic nervous system, is frequently involved, leading to the cardiomegaly and the digestive megaviscera. Congenital infections may also occur. In this paper we give an account of the epidemiology, clinical presentation and pathological features of these two protozoal infections based on human and experimental studies of both the central and peripheral nervous system.

A glycosylphosphatidylinositol-based treatment alleviates trypanosomiasis-associated immunopathology

The GPI-anchored trypanosome variant surface glycoprotein (VSG) triggers macrophages to produce TNF, involved in trypanosomiasis-associated inflammation and the clinical manifestation of sleeping sickness. Aiming at inhibiting immunopathology during experimental Trypanosoma brucei infections, a VSG-derived GPI-based treatment approach was developed. To achieve this, mice were exposed to the GPI before an infectious trypanosome challenge. This GPI-based strategy resulted in a significant prolonged survival and a substantial protection against infection-associated weight loss, liver damage, acidosis, and anemia; the latter was shown to be Ab-independent and correlated with reduced macrophage-mediated RBC clearance. In addition, GPI-based treatment resulted in reduced circulating serum levels of the inflammatory cytokines TNF and IL-6, abrogation of infection-induced LPS hypersensitivity, and an increase in circulating IL-10. At the level of trypanosomiasis-associated macrophage activation, the GPI-based treatment resulted in an impaired secretion of TNF by VSG and LPS pulsed macrophages, a reduced expression of the inflammatory cytokine genes TNF, IL-6, and IL-12, and an increased expression of the anti-inflammatory cytokine gene IL-10. In addition, this change in cytokine pattern upon GPI-based treatment was associated with the expression of alternatively activated macrophage markers. Finally, the GPI-based treatment also reduced the infection-associated pathology in Trypanosoma congolense and Trypanosoma evansi model systems as well as in tsetse fly challenge experiments, indicating potential field applicability for this intervention strategy.

Animal models of human African trypanosomiasis--very useful or too far removed?

Animal models of human African trypanosomiasis, also known as sleeping sickness, have been used for many years both to investigate disease pathogenesis and to test novel drug therapies. Model systems used have included mice, rats and non-human primates such as monkeys. Whilst such animal models have some definite but unavoidable limitations, it is argued that these are outweighed by their advantages. The latter include the ability to investigate disease pathogenesis mechanistically and the mechanisms of trypanosome traversal of the blood-brain barrier, as well as the identification of new potential drug targets and staging biomarkers, new drug therapies and combinations, and potential drug toxicity.

Expression, purification, characterization, and in vivo targeting of trypanosome CTP synthetase for treatment of African sleeping sickness

African sleeping sickness is a fatal disease caused by two parasite subspecies: Trypanosoma brucei gambiense and T. b. rhodesiense. We previously reported that trypanosomes have extraordinary low CTP pools compared with mammalian cells. Trypanosomes also lack salvage of cytidine/cytosine making the parasite CTP synthetase a potential target for treatment of the disease. In this study, we have expressed and purified recombinant T. brucei CTP synthetase. The enzyme has a higher K(m) value for UTP than the mammalian CTP synthetase, which in combination with a lower UTP pool may account for the low CTP pool in trypanosomes. The activity of the trypanosome CTP synthetase is irreversibly inhibited by the glutamine analogue acivicin, a drug extensively tested as an antitumor agent. There is a rapid uptake of acivicin in mice both given intraperitoneally and orally by gavage. Daily injection of acivicin in trypanosome-infected mice suppressed the infection up to one month without any significant loss of weight. Experiments with cultured bloodstream T. brucei showed that acivicin is trypanocidal if present at 1 mum concentration for at least 4 days. Therefore, acivicin may qualify as a drug with "desirable" properties, i.e. cure within 7 days, according to the current Target Product Profiles of WHO and DNDi.

Human African trypanosomiasis–neurological aspects

Human African Trypanosomiasis (HAT),which is also known as sleeping sickness, is a major cause of death and disability in 36 countries in sub-Saharan Africa. The disease is caused by the protozoan parasite of the Trypanosoma genus which is transmitted by the bite of the tsetse fly. The two types of HAT, the East African form due to Trypanosoma b.rhodesiensei (T. b.rhodesiensi) and the West African form due to T. b.gambiense, differ in their tempo of infection but in both cases the disease is always fatal if untreated. As well as multiple systemic features seen in the early (haemolymphatic) stage of disease, the late (encephalitic stage) stage, is associated with a wide range of neurological features including neuropsychiatric, motor and sensory abnormalities. Accurate staging of the disease is absolutely essential because of the potentially fatal complications of melarsoprol treatment of late-stage disease, the most important of which is a severe post-treatment reactive encephalopathy (PTRE) the pathogenesis of which is not fully understood. However, there is not a universal consensus as to how late-stage disease should be diagnosed using CSF criteria, and this has been very problematic in HAT. A more recent alternative drug for late stage gambiense disease is eflornithine (DFMO). There is a pressing need for a non-toxic oral drug for both early and late stage disease that would obviate many of the problems of staging, and various possible strategies to achieve this goal are currently underway. However, control of the disease will also require more effective measures of reducing man/fly contact and also the allocation of much greater financial and infrastructural resources than are currently available in Africa.

Variant surface glycoprotein RNA interference triggers a precytokinesis cell cycle arrest in African trypanosomes

Trypanosoma brucei is a protozoan parasite that causes African sleeping sickness. T. brucei multiplies extracellularly in the bloodstream, relying on antigenic variation of a dense variant surface glycoprotein (VSG) coat to escape antibody-mediated lysis. We investigated the role of VSG in proliferation and pathogenicity by using inducible RNA interference to ablate VSG transcript down to 1-2% normal levels. Inhibiting VSG synthesis in vitro triggers a rapid and specific cell cycle checkpoint blocking cell division. Parasites arrest at a discrete precytokinesis stage with two full-length flagella and opposing flagellar pockets, without undergoing additional rounds of S phase and mitosis. A subset (<10%) of the stalled cells have internal flagella, indicating that the progenitors of these cells were already committed to cytokinesis when VSG restriction was sensed. Although there was no obvious VSG depletion in vitro after 24-h induction of VSG RNA interference, there was rapid clearance of these cells in vivo. We propose that a stringent block in VSG synthesis produces stalled trypanosomes with a minimally compromised VSG coat, which can be targeted by the immune system. Our data indicate that VSG protein or transcript is monitored during cell cycle progression in bloodstream-form T. brucei and describes precise precytokinesis cell cycle arrest. This checkpoint before cell division provides a link between the protective VSG coat and cell cycle progression and could function as a novel parasite safety mechanism, preventing extensive dilution of the protective VSG coat in the absence of VSG synthesis.

Controlling malaria and African trypanosomiasis: The role of the mouse

Malaria and trypanosomiasis are vector-borne protozoal diseases which disproportionately affect the poor. Both give rise to immense human suffering; malaria exerts its effect directly on human health, while trypanosomiasis causes damage largely though its effect on the health and productivity of the livestock on which so many poor people depend. These diseases both have multifaceted and poorly understood mechanisms of pathogenesis, combined with relatively complex life cycles characterised by multiple stages in both insect vector and mammalian host. In both cases, there is a dramatic effect of host genotype on disease progression. This effect is apparent in both the human and cattle hosts and among inbred mouse strains. This provides an opportunity to use the mouse to probe the mechanisms underlying resistance or susceptibility to pathology. The availability of high-density linkage maps, the genome sequence and transcriptomics tools has transformed the power of the mouse to illuminate such fundamental aspects of the host--parasite interaction.

History of sleeping sickness (African trypanosomiasis)

Infections with subspecies of the protozoan parasite Trypanosoma brucei cause important wasting diseases in Africa (nagana in cattle and sleeping sickness in humans). These diseases were little known until the end of the nineteenth century when serious epidemics of nagana were reported and raised concern among the colonial powers. The early history of sleeping sickness revolves around the discovery of the causative organism, its mode of transmission,and its life cycle in the tsetse fly. The history continues into the twentieth century with the discovery of how the parasites evade the immune response, frustrating the development of a vaccine; the failure to develop cheap and effective drugs; and the development of alternative approaches to control the tsetse fly vector.

East African sleeping sickness in Chennai

A traveler to East Africa developed fever, an eschar on his forearm and thrombocytopenia shortly after returning home to Chennai, India. Trypanosoma brucei rhodesiense infection was diagnosed on examination of his peripheral smear. He made a full recovery after receiving a course of suramin.

[Sleeping sickness: forgotten research?]

Has research on sleeping sickness, i.e., human African trypanosomiasis (HAT), been forgotten? To get an idea on funding, we consulted the Medline bibliographic database for the last 14 years. The number of publications on HAT was stagnant over the study period. By comparison there was a steady increase in the number of publications dealing with malaria. These findings suggest that interest in HAT research waned in favor of other endemics even though government or other funding agencies continued to finance research networks. To illustrate this situation, we present the funding and findings of our multidisciplinary working group in a wide range of domains including sleep, endocrine rhythms, identification of biological markers, research on physiopathologic mechanisms of the host-pathogen relationship, and development on new medications. Over the last 14 years, a total of 1 million Euros was spent to produce 68 publications on Medline, i.e., roughly 15000 [symbol: see text] per publication.

[Geographic distribution of trypanosomiasis treated in Ivory Coast from 1993 to 2000]

Human African Trypanosomosis (HAT, or sleeping sickness) caused by Trypanosoma brucei gambiense develops chronically in Côte d'Ivoire. From 1993 to 2000, a total of 1616 patients were taken in charge in the three treatment centres of the country, which means an average of 202 patients a year. The patients came from two main areas in the Centre West of the country in the Marahoué region: the districts of Sinfra, South of Bouaflé, and Bonon, West of Bouaflé. In the Centre West and in the South East of the country (Aboisso-Ayamé), patients are still struck by the disease, although these foci are less active. The remaining foci seem to be controlled, although no active survey has been carried out. The areas where the greatest number of patients were recorded are the ones where rental crops are located (cocoa and coffee mainly) and where rural activities tend to bring humans and tsetse flies in contact. In this study, are figured the number of treated patients, the endemic and risk areas. It will help to design control strategies and decision makers to know where priority control programs should be implemented.

[Technical reasons for the re-emergence of sleeping sickness]

In the 1920s the epidemic outbreak of human African trypanosomiasis was so deadly that government authorities decided to take large-scale action. It was by giving Jamot absolute administrative and financial autonomy to apply his ideas that the disease was successfully controlled. After Jamot determined efforts against the disease continued so that, by the dawn of decolonization, many considered the problem of sleeping sickness as resolved. Control programs progressively slowed and virtually ceased. Neglected and all but forgotten, the disease has able to make a natural and forceful comeback. Obvious attempts have been made to explain this comeback in terms of poor commitment on the part of health authorities, disappearance of competent work groups, and lack of money and personnel. True as these issues may be, it is just not that simple. Many other problems prevent disease management from being delegated to primary healthcare workers including the difficulty of clinical, serological, and parasitological diagnosis, inability to implement effective widespread vector control, paucity of therapeutic modalities, and irrationality of vaccination. Under these conditions, re-emergence of the disease was unavoidable and future control efforts will be difficult.

Stage determination and follow-up in sleeping sickness

In order to select a correct treatment after primary diagnosis of trypanosomiasis infection, accurate assessment of the disease stage, haemo-lymphatic or meningo-encephalitic, is essential. This is achieved by lumbar puncture and subsequent examination of the cerebrospinal fluid. These examinations have to be repeated during 2 years after treatment, and only after the cerebrospinal fluid has normalized one can decide on complete cure. The currently used cerebrospinal fluid parameters, i.e. white blood cell count, total protein determination and finding of trypanosomes, and practical problems encountered using these parameters are discussed. Alternative markers for stage determination and follow-up include trypanosome specific antibodies, anti-galactocerebroside antibodies and IgM measurement in CSF.

[Control of human African trypanosomiasis: back to square one]

The natural history of sleeping sickness is cyclic. The first epidemic outbreak in the 19th century devastated the population and resolved spontaneously for lack of victims. Intensive development during the colonial period and the movement of population that it spawned led to another epidemic in the early 1920s that reached such severe proportions that drastic steps had to be taken. At that time, Jamot was given complete political, administrative, and financial freedom to combat the disease. This program led to the development of the mobile team concept and so-called vertically structured vector control strategy and was so successful that sleeping sickness ceased to be considered as a major public health problem at the beginning of the 1960s. In the ensuing years sleeping sickness was largely neglected. Monitoring the disease required specialized teams that were no longer considered as cost-effective. One by one the measures that had been implemented to control the disease disappeared, thus setting the scene for a new outbreak grew. In 1995, the incidence of sleeping sickness reached the same levels as in the 1920s. The current situation is a classic example of a neglected disease with a paucity of competent specialists, diagnostic tests, effective drugs, and operational facilities. It was not until 2001 that new hope appeared thanks to a combined public- and private-sector initiative allowing restructuring of treatment teams, renovation of facilities, free distribution of drugs, and research to develop new therapeutic agents. Also thanks to the PATTEC initiative, the governments of the African affected nations are showing new in interest in sleeping sickness. However the battle is far from won and much effort will be required. Time is running out and the stakes are high.

[Sleeping sickness, a reemerging sickness]

Human African Trypanosomiasis (THA) has reappeared in most intertropical countries of Black Africa and an estimated 400,000 new cases are reported every year. Genetic tests which now make possible the differentiation of morphologically similar trypanosome subspecies showed that a large variety of game and domestic animals act as reservoir hosts of Trypanosoma brucei gambiense, thus making it even more difficult to fight the disease. The detection of cases and their treatment are absolutely necessary in preventing the spread of the disease. This can only be carried out with mobile medical teams which seek out patients. This detection currently calls on techniques which isolate trypanosomes and serological techniques. The collection of data with regards to different geographical positions, makes it possible to determine exactly which regions are affected, possibly affected or sound. Although the diagnosis of the hemo-lymphatic stage can be determined without any great problem nowadays, the point at which the trypanosome invades CNS tissues and the ways in which it occurs are as yet unknown, even though the role of nitric oxyde and cytokines is better understood. Antibodies, anti-neurofilaments and anti-galactocerebrosides when found in the cerebro-spinal fluid are characteristic of the nervous stage of the disease. This condition is really sleeping sickness, not only hypersomnia. The more seriously the patient is affected the shorter the sleep-wake cycles are during the nycthemeron. These early disorders can be quickly reversed thanks to therapy, which to day uses melarsoprol, an arsenical drug, which cannot be of great promise as it is very toxic. Current research into nitro-imidazole derivatives (particularly megazol) seems a promising therapy as they were effective in vitro and in vivo, in rodents and primates.

Analytical tools for planning cost-effective surveillance in Gambiense sleeping sickness

The re-emergence of sleeping sickness as a major health problem in parts of Africa, combined with the new sources of financial support and provision of drugs means that an investigation of the cost-effectiveness of the different approaches is timely. There has been very little work done on the economics of controlling either form of sleeping sickness. This paper builds on work done for WHO by the authors on developing a framework for analysing the cost-effectiveness of different methods for surveillance in gambiense sleeping sickness. The framework has been used to build a spreadsheet which makes it possible to simulate the effects of controlling the disease at different prevalences, for example using mobile teams or various forms of fixed post surveillance and screening different proportions of the population in a year. Prices, control strategies, prevalence, sensitivity and specificity of tests are all variables which can be altered to suit different situations or investigate how different approaches perform. As new research is beginning to produce calculations of the burden of sleeping sickness, in terms of disability-adjusted life years (DALY) potentially averted by controlling the disease, it is possible to combine these DALY estimates with the analyses of cost-effectiveness undertaken in these exercises to look at the cost-utility of the work, both to compare different approaches and demonstrate that controlling sleeping sickness represents good value for money as an investment in health.

The GPI biosynthetic pathway as a therapeutic target for African sleeping sickness

African sleeping sickness is a debilitating and often fatal disease caused by tsetse fly transmitted African trypanosomes. These extracellular protozoan parasites survive in the human bloodstream by virtue of a dense cell surface coat made of variant surface glycoprotein. The parasites have a repertoire of several hundred immunologically distinct variant surface glycoproteins and they evade the host immune response by antigenic variation. All variant surface glycoproteins are anchored to the plasma membrane via glycosylphosphatidylinositol membrane anchors and compounds that inhibit the assembly or transfer of these anchors could have trypanocidal potential. This article compares glycosylphosphatidylinositol biosynthesis in African trypanosomes and mammalian cells and identifies several steps that could be targets for the development of parasite-specific therapeutic agents.

Neurobiology of cerebral malaria and African sleeping sickness

This review is aimed at emphasizing the need for basic neuroscience research on two tropical diseases, malaria and sleeping sickness (African trypanosomiasis), that still represent major health problems and in which severe involvement of the nervous system is frequently the direct cause of death. The life cycles of the two parasites, the protozoan Plasmodium and Trypanosoma brucei, which are the causative agents of malaria and sleeping sickness, respectively, are briefly reviewed. The historical contribution to the pathogenesis and therapy of malaria by a renowned pioneer in neuroscience, Camillo Golgi, is pointed out. The different strategies for survival in the host by the intracellular Plasmodium and the extracellular African trypanosomes are summarized; such strategies include sites favorable for hiding or replication of the parasites in the host, antigenic variation, and interactions with the cytokine network of the host. In particular, tumor necrosis factor-alpha and interferon-gamma may play a role in these infections. The parasites may paradoxically interact with cytokines to their benefit. However, cytokine receptors are expressed on neuronal subsets sensitive to cytokine action, and stimulation of these subsets may cause neuronal dysfunctions during the infections. Finally, the clinical symptoms of cerebral malaria and African trypanosomiasis and research aiming at deciphering their pathogenetic mechanisms that could affect the nervous system at a molecular level are described. The need for neuroscientists in this endeavor is emphasized.

Targeting proteins to the glycosomes of African trypanosomes

Glycosomes are microbodies found in protozoa belonging to the order Kinetoplastida. These highly specialized organelles compartmentalize most of the glycolytic enzymes normally located in the cytosol of other eukaryotic cells. The recent success in expressing foreign proteins in Trypanosoma brucei has permitted a detailed analysis of glycosomal protein targeting signals in these organisms. These studies have revealed that the previously identified C-terminal tripeptide peroxisomal targeting signal also functions in the import of proteins into the glycosomes of T. brucei. However, the glycosomal and peroxisomal targeting signals differ in a few important ways. The C-terminal tripeptide sequence requirements for glycosomal protein targeting are comparatively relaxed. Of the three C-terminal amino acids, the first can be any small, neutral amino acid; the second should be capable of forming hydrogen bondings, whereas the third is a hydrophobic amino acid. This degenerate tripeptide sequence differs significantly from the more stringent requirements observed for the import of proteins into mammalian peroxisomes and thus represents an opportunity for designing peptide analogues that specifically block the glycosomal protein import for a possible antitrypanosomal chemotherapy. A recently described N-terminal signal that targets thiolase to the mammalian peroxisomes does not appear to function in import into the glycosomes. However, a novel internal targeting signal has tentatively been identified in at least one of the glycosomal proteins that can target a reporter protein to the glycosomes of T. brucei. Glycosome-deficient mutants have been isolated recently, which will aid in the identification of genes involved in the biogenesis of the glycosome.

Depletion of CD8+ T cells suppresses growth of Trypanosoma brucei brucei and interferon-gamma) production in infected rats

Sprague-Dawley rats infected with Trypanosoma brucei brucei showed a strong and rapid induction of splenocyte IFN-gamma (within 12 h post-infection) as measured by a single cell assay for IFN-gamma secretion. Depletion of CD8+ cells in infected rats abrogated the IFN-gamma production, suppressed parasite growth and increased survival of the animals. Induction of MHC class I antigens in the paraventricular and supra-optic hypothalamic nuclei caused by the trypanosome infection was also inhibited by the CD8+ cell depletion. It is suggested that the CD8+ cells are involved directly or indirectly in growth regulation of the parasite and that IFN-gamma induced by the parasite may be one of the factors that trigger MHC expression and immunosuppression.

[Cost of the individual treatment of Trypanosoma brucei gambiense trypanosomiasis in a focus of infection in Niari (Congo)]

A survey carried out on 101 patients has shown that the treatment of human sleeping sickness, theoretically free, is relatively costly. The average total cost amount to 58,000 F C.F.A., ranging from free treatment up to much as 110,000 F C.F.A. This high cost in part explains the cases where treatment is refused, something which has frequently been observed in the Congo. It would therefore be desirable for patients, who are significant epidemiological reservoirs of T. b. gambiense, to receive economic aid.

[Strategy of sleeping sickness control in the Peoples' Republic of Congo: research and perspectives]

The authors review the different strategies applied nowadays in the Popular Republic of Congo to eradicate sleeping sickness. They underline the problems encountered on the field as well as researches carried out to solve them. Recent progress at both levels of screening and trapping opened interesting prospects. Success of the Congo in its fight against sleeping sickness depends now mainly on means made available to apply on a large scale these new methods.

Evaluation of immunoassays for diagnosis and management of sleeping sickness in Liberia

Nineteen parasitologically confirmed Liberian sleeping sickness patients were observed for up to 40 months. Efficacy of suramin therapy was indicated by decrease of serum and CSF immunoglobulins as well as by decreasing IgG and IgM serum antibody levels as determined by ELISA and fluorescence antibody tests. The tendency of serum antibody concentrations to increase again during the second and third years after treatment could be explained in one patient only who experienced relapse or reinfection, confirmed by demonstration of blood trypanosomes. Known endemic and nonendemic areas in Liberia could not be discriminated by the prevalence of Trypanosoma IgG antibodies. Furthermore, IgM antibody was present in 18% of a random sample of sera from non-endemic ares. The possibility of trypanosomes other than T.b. gambiense to stimulate antibody production in man is discussed.

Cytotoxicity of monoclonal antibodies to Trypanosoma brucei

Monoclonal antibodies (McAbs) were raised against Metacyclic Variable Antigen Types (M-VATs) of the AnTAR 1 and ETAR 1 serodemes of Trypanosoma brucei. Two dominant M-VATs, one from each serodeme, were labelled by two of the McAbs using the indirect immunofluorescence technique. These McAbs were of the IgM class, and labelled exposed epitopes on living trypanosomes. They showed lytic activity in vitro towards their respective homologous VAT trypanosomes, both in the presence and absence of complement. In vivo, the McAbs promoted lysis and clearance of trypanosomes from the bloodstream of infected mice. Prevention of reinfection with trypanosomes expressing the same VAT was conferred by the McAbs.

Cure of mice infected with Trypanosoma rhodesiense by cis-diamminedichloroplatinum (II) and disulfiram rescue

Mice infected with Trypanosoma rhodesiense were treatment concurrently with cis-diamminedichloroplatinum (II) (DDP), disulfiram, and hydration. Most of the mice (92.5 percent) were cured; inoculation of blood or suspensions of brain or heart from these animals did not produce disease in recipient mice. The dose of DDP needed to eliminate the trypanosomes, 3 milligrams per kilogram of body weight per day for 7 days, was lethally toxic unless the animals received disulfiram orally and subcutaneous injections of physiologic saline, which reduced the acute renal necrosis caused by DDP alone. Some mild to moderate reversible renal damage was noted upon pathologic examination of the treated mice.

Control of sleeping sickness due to Trypanosoma brucei gambiense*

Sleeping sickness due to Trypanosoma brucei gambiense is endemic in 23 African countries and an estimated 45 million people are exposed to infection. The relatively low incidence of the disease (about 10 000 new cases each year) is mainly a result of 50 years of regular medical surveillance and treatment in combination with tsetse control where indicated and possible. The present article considers the significant developments in research in the field and assesses the impact of these findings on techniques used in the control of the disease. The World Health Organization has recently established an action programme for sleeping sickness control to organize and coordinate medical surveillance, treatment of infected individuals, and vector control activities. Among its objectives, the programme aims to provide support for national control services in the form of technical expertise, training of staff, and provision of newly developed equipment for diagnosis and treatment. The programme is also closely associated with the research activities supported by the UNDP/World Bank/WHO Special Programme for Research and Training in Tropical Diseases.

[Post-therapeutic evolution of patients presenting an immunological suspicion of trypanosomiasis without parasitological proof in support of it (author's transl)]

The authors have recently preconised systematic treatment of every human being who is fluorescent positive. The evolution of antibodies of 26 subjects parasitologically negative and positive only in FAT test is described here after treatment with Arsobal. Statistically the antibodies decrease progressively like antibodies of Sleeping Sickness patients of first period usually did. Therefore it is possible to conclude that immunological suspects who were treated were realy sick and rightly cured.