[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.