Human African trypanosomiasis amongst urban residents in Kinshasa: a case-control study

Tsetse fly ecology and risk of transmission of African trypanosomes related to a protected forest area at a military base in the city of Abidjan, Côte d'Ivoire

African trypanosomoses, whose pathogens are transmitted by tsetse flies, are a threat to animal and human health. Tsetse flies observed at the military base of the French Forces in Côte d'Ivoire (FFCI base) were probably involved in the infection and death of military working dogs. Entomological and parasitological surveys were carried out during the rainy and dry seasons using "Vavoua" traps to identify tsetse fly species, their distribution, favorable biotopes and food sources, as well as the trypanosomes they harbor. A total of 1185 Glossina palpalis palpalis tsetse flies were caught, corresponding to a high average apparent density of 2.26 tsetse/trap/day. The results showed a heterogeneous distribution of tsetse at the FFCI base, linked to more or less favorable biotopes. No significant variation in tsetse densities was observed according to the season. The overall trypanosomes infection rate according to microscopic observation was 13.5%. Polymerase chain reaction (PCR) analyses confirmed the presence of Trypanosoma vivax and T. congolense forest type, responsible for African animal trypanosomosis. Our findings suggest that there is a risk of introduction and transmission of T. brucei gambiense, responsible for human African trypanosomiasis, on the study site. This risk of transmission of African trypanosomes concerns not only the FFCI base, but also inhabited peripheral areas. Our study confirmed the need for vector control adapted to the eco-epidemiological context of the FFCI base.

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

BACKGROUND

Human African trypanosomiasis (HAT) is one of the world's classical neglected tropical diseases representing a major public health threat in sub-Saharan Africa. Although the parasitic disease is in decline in the Republic of Congo, the better understanding of the epidemiological situation of active foci is required to reduce the risk of disease resurgence which could impede progress registered so far. The aim of this study was to determine the prevalence of HAT and the associated risk factors in individuals living in remote areas of the Republic of Congo.

METHODS

A cross-sectional survey was carried out in volunteers living in rural settings from June 2020 to January 2021. Socio-demographic and Clinical parameters of the participants were recorded. The presence of HAT-specific antibodies was assessed in whole blood, and then confirmed in serial diluted plasma samples using Card-Agglutination Trypanosomiasis Test (CATT)/T.b. gambiense CATT. The Capillary Tube Centrifugation (CTC) and Lymph nodes (LN) examination were done for detecting trypanosome parasites in CATT-serum positive cases. The staging of positive participants was determined by cerebrospinal fluid (CSF) examination.

RESULTS

Out of 8556 enrolled participants, 48.5% were more than 15 years old, 57.7% were unschooled and 67.2% practiced peasant activities. The prevalence of HAT infection was 0.3% with the predominance of patients at stage 1 of the disease (84.0%). The districts of Mindouli (OR: 25.9 (5.2-468); p = 0.0016) and Mpouya (OR: 13.3 (2.5-246); p = 0.0140) was revealed as the foci of high risk of HAT infection. Several factors were associated with an increased risk of HAT infection mainly including the non-schooling (OR: 5.1 (1.2-21.9); p = 0.0268), the life in couple or married (OR: 3.3 (1.0-11.3); p = 0.0545) and the practice of peasant activities (OR: 6.9 (2.4-29.3); p = 0.0017).

CONCLUSION

This study highlights the need of revising and strengthening the strategies of HAT control in Republic of Congo, using an approach which will take into account the education level, the marital status and the occupation of the population at risk.

Case Report: Trypanosoma brucei Gambiense Human African Trypanosomiasis as the Cause of Fever in an Inpatient with Multiple Myeloma and HIV-1 Coinfection

We report the case of a 64-year-old woman found to have urban-acquired Trypanosoma brucei (T.b.) gambiense human African trypanosomiasis (HAT) as the cause of sustained fever starting 9 months after returning to Canada from Democratic Republic of the Congo, in the context of concomitant multiple myeloma and HIV-1 coinfection. Approaches for the management of both clinical stages of T.b. gambiense HAT are well defined for endemic settings using current diagnostics and treatments. However, few data inform the diagnosis and management of patients with bone marrow suppression from active malignancy, recent anticancer therapy, or HIV coinfection. We discuss the implications of immunosuppression for diagnosis and management of T.b. gambiense HAT.

Host Immune Responses and Immune Evasion Strategies in African Trypanosomiasis

Parasites, including African trypanosomes, utilize several immune evasion strategies to ensure their survival and completion of their life cycles within their hosts. The defense factors activated by the host to resolve inflammation and restore homeostasis during active infection could be exploited and/or manipulated by the parasites in an attempt to ensure their survival and propagation. This often results in the parasites evading the host immune responses as well as the host sustaining some self-inflicted collateral tissue damage. During infection with African trypanosomes, both effector and suppressor cells are activated and the balance between these opposing arms of immunity determines susceptibility or resistance of infected host to the parasites. Immune evasion by the parasites could be directly related to parasite factors, (e.g., antigenic variation), or indirectly through the induction of suppressor cells following infection. Several cell types, including suppressive macrophages, myeloid-derived suppressor cells (MDSCs), and regulatory T cells have been shown to contribute to immunosuppression in African trypanosomiasis. In this review, we discuss the key factors that contribute to immunity and immunosuppression during T. congolense infection, and how these factors could aid immune evasion by African trypanosomes. Understanding the regulatory mechanisms that influence resistance and/or susceptibility during African trypanosomiasis could be beneficial in designing effective vaccination and therapeutic strategies against the disease.

Monitoring the presence of trypanosomes' DNA - Including Trypanosoma brucei gambiense DNA - From the midguts of riverine Glossina trapped in the south east outskirts of Kinshasa City (Democratic Republic of Congo)

Even if the number of Human African Trypanosomiasis (HAT) cases from Kinshasa province in DRC is going towards elimination for the last decade, cases still occur in the periphery of the city. The diagnosis of 21 cases in the south periphery of Kinshasa, between 2015 and 2017 gives evidence of the existence of an active focus in this area. Here, we present the results of a punctual entomological survey that was realized in july 2014 in the outskirts of the southeast of Kinshasa. Using pyramidal traps, we caught tsetse flies during 2 days, dissecting the fresh ones for further molecular analysis. The average Apparent Density of flies per Trap and per Day was three with a maximum of 5.6 flies in Nganda PIO. Polymerase chain reaction analysis of the midguts provided evidence of a high prevalence (57.2%) of infected flies. Ninety three percent of the trypanosomes that were identified belonged to the Nanomonas species, but Trypanozoon trypanosomes were also present in 24% of the infected flies, including mixed infections with Nanomonas, including 3 flies carrying Trypanosoma brucei gambiense, the human pathogen of trypanosomiasis. These results show that at the time of the field's study there was an active reservoir of trypanosomes, closed to pigsties, knowing that pig is a potential animal reservoir. It also demonstrates that xenomonitoring using the entomological approach can be an efficient tool for monitoring sleeping sickness. Finally, results are discussed in the frame of WHO's HAT elimination project. Regarding Kinshasa, it points out the need of regular epidemiologic surveys.

Human African trypanosomiasis

Human African trypanosomiasis (sleeping sickness) is a parasitic infection that almost invariably progresses to death unless treated. Human African trypanosomiasis caused devastating epidemics during the 20th century. Thanks to sustained and coordinated efforts over the past 15 years, the number of reported cases has fallen to an historically low level. Fewer than 3000 cases were reported in 2015, and the disease is targeted for elimination by WHO. Despite these recent successes, the disease is still endemic in parts of sub-Saharan Africa, where it is a considerable burden on rural communities, most notably in central Africa. Since patients are also reported from non-endemic countries, human African trypanosomiasis should be considered in differential diagnosis for travellers, tourists, migrants, and expatriates who have visited or lived in endemic areas. In the absence of a vaccine, disease control relies on case detection and treatment, and vector control. Available drugs are suboptimal, but ongoing clinical trials provide hope for safer and simpler treatments.

Human African trypanosomiasis in the Democratic Republic of the Congo: disease distribution and risk

Background

For the past three decades, the Democratic Republic of the Congo (DRC) has been the country reporting the highest number of cases of human African trypanosomiasis (HAT). In 2012, DRC continued to bear the heaviest burden of gambiense HAT, accounting for 84 % of all cases reported at the continental level (i.e., 5,968/7,106). This paper reviews the status of sleeping sickness in DRC between 2000 and 2012, with a focus on spatio-temporal patterns. Epidemiological trends at the national and provincial level are presented.

Results

The number of HAT cases reported yearly from DRC decreased by 65 % from 2000 to 2012, i.e., from 16,951 to 5,968. At the provincial level a more complex picture emerges. Whilst HAT control in the Equateur province has had a spectacular impact on the number of cases (97 % reduction), the disease has proved more difficult to tackle in other provinces, most notably in Bandundu and Kasai, where, despite substantial progress, HAT remains entrenched. HAT prevalence presents its highest values in the northern part of the Province Orientale, where a number of constraints hinder surveillance and control.

Significant coordinated efforts by the National Sleeping Sickness Control Programme and the World Health Organization in data collection, reporting, management and mapping, culminating in the Atlas of HAT, have enabled HAT distribution and risk in DRC to be known with more accuracy than ever before. Over 18,000 locations of epidemiological interest have been geo-referenced (average accuracy ≈ 1.7 km), corresponding to 93.6 % of reported cases (period 2000–2012). The population at risk of contracting sleeping sickness has been calculated for two five-year periods (2003–2007 and 2008–2012), resulting in estimates of 33 and 37 million people respectively.

Conclusions

The progressive decrease in HAT cases reported since 2000 in DRC is likely to reflect a real decline in disease incidence. If this result is to be sustained, and if further progress is to be made towards the goal of HAT elimination, the ongoing integration of HAT control and surveillance into the health system is to be closely monitored and evaluated, and active case-finding activities are to be maintained, especially in those areas where the risk of infection remains high and where resurgence could occur.

Electronic supplementary material

The online version of this article (doi:10.1186/s12942-015-0013-9) contains supplementary material, which is available to authorized users.

Epidemiology of human African trypanosomiasis

Human African trypanosomiasis (HAT), or sleeping sickness, is caused by Trypanosoma brucei gambiense, which is a chronic form of the disease present in western and central Africa, and by Trypanosoma brucei rhodesiense, which is an acute disease located in eastern and southern Africa. The rhodesiense form is a zoonosis, with the occasional infection of humans, but in the gambiense form, the human being is regarded as the main reservoir that plays a key role in the transmission cycle of the disease. The gambiense form currently assumes that 98% of the cases are declared; the Democratic Republic of the Congo is the most affected country, with more than 75% of the gambiense cases declared. The epidemiology of the disease is mediated by the interaction of the parasite (trypanosome) with the vectors (tsetse flies), as well as with the human and animal hosts within a particular environment. Related to these interactions, the disease is confined in spatially limited areas called “foci”, which are located in Sub-Saharan Africa, mainly in remote rural areas. The risk of contracting HAT is, therefore, determined by the possibility of contact of a human being with an infected tsetse fly. Epidemics of HAT were described at the beginning of the 20th century; intensive activities have been set up to confront the disease, and it was under control in the 1960s, with fewer than 5,000 cases reported in the whole continent. The disease resurged at the end of the 1990s, but renewed efforts from endemic countries, cooperation agencies, and nongovernmental organizations led by the World Health Organization succeeded to raise awareness and resources, while reinforcing national programs, reversing the trend of the cases reported, and bringing the disease under control again. In this context, sustainable elimination of the gambiense HAT, defined as the interruption of the transmission of the disease, was considered as a feasible target for 2030. Since rhodesiense HAT is a zoonosis, where the animal reservoir plays a key role, the interruption of the disease’s transmission is not deemed feasible.

Changing landscapes, changing practice: negotiating access to sleeping sickness services in a post-conflict society

For several decades, control programmes for human African trypanosomiasis (HAT, or sleeping sickness) in South Sudan have been delivered almost entirely as humanitarian interventions: large, well-organised, externally-funded but short-term programmes with a strategic focus on active screening. When attempts to hand over these programmes to local partners fail, resident populations must actively seek and negotiate access to tests at hospitals via passive screening. However, little is known about the social impact of such humanitarian interventions or the consequences of withdrawal on access to and utilisation of remaining services by local populations. Based on qualitative and quantitative fieldwork in Nimule, South Sudan (2008-2010), where passive screening necessarily became the predominant strategy, this paper investigates the reasons why, among two ethnic groups (Madi returnees and Dinka displaced populations), service uptake was so much higher among the latter. HAT tests were the only form of clinical care for which displaced Dinka populations could self-refer; access to all other services was negotiated through indigenous area workers. Because of the long history of conflict, these encounters were often morally and politically fraught. An open-door policy to screening supported Dinka people to 'try' HAT tests in the normal course of treatment-seeking, thereby empowering them to use HAT services more actively. This paper argues that in a context like South Sudan, where HAT control increasingly depends upon patient-led approaches to case-detection, it is imperative to understand the cultural values and political histories associated with the practice of testing and how medical humanitarian programmes shape this landscape of care, even after they have been scaled down.

Human African trypanosomiasis in endemic populations and travellers

Human African trypanosomiasis (HAT) or sleeping sickness is caused by the protozoan parasites Trypanosoma brucei (T.b.) gambiense (West African form) and T.b. rhodesiense (East African form) that are transmitted by the bite of the tsetse fly, Glossina spp.. Whereas most patients in endemic populations are infected with T.b. gambiense, most tourists are infected with T.b. rhodesiense. In endemic populations, T.b. gambiense HAT is characterized by chronic and intermittent fever, headache, pruritus, and lymphadenopathy in the first stage and by sleep disturbances and neuro-psychiatric disorders in the second stage. Recent descriptions of the clinical presentation of T.b. rhodesiense in endemic populations show a high variability in different foci. The symptomatology of travellers is markedly different from the usual textbook descriptions of African HAT patients. The onset of both infections is almost invariably an acute and febrile disease. Diagnosis and treatment are difficult and rely mostly on old methods and drugs. However, new molecular diagnostic technologies are under development. A promising new drug combination is currently evaluated in a phase 3 b study and further new drugs are under evaluation.

Population-dynamics focussed rapid rural mapping and characterisation of the peri-urban interface of Kampala, Uganda

In developing countries, cities are rapidly expanding and urban and peri-urban agriculture (UPA) has an important role in feeding these growing urban populations; however such agriculture also carries public health risks such as zoonotic disease transmission. It is important to assess the role of UPA in food security and public health risks to make evidence-based decisions on policies. Describing and mapping the peri-urban interface (PUI) are the essential first steps for such an assessment. Kampala, the capital city of Uganda is a rapidly expanding city where the PUI has not previously been mapped or properly described. In this paper we provide a spatial representation of the entire PUI of Kampala economic zone and determine the socio-economic factors related with peri-urbanicity using a population-dynamics focussed rapid rural mapping. This fills a technical gap of rapid rural mapping and offers a simple and rapid methodology for describing the PUI which can be applied in any city in developing countries for wide range of studies.

Characterization of sleeping sickness transmission sites in rural and periurban areas of Kinshasa (République Démocratique du Congo)

To characterize the potential transmission sites of sleeping sickness in Kinshasa, two entomologic surveys were carried out during the dry and the rainy seasons in rural and periurban areas of Kinshasa in 2005. About 610 pyramidal traps were set up, and 897 Glossina fuscipes quanzensis were captured. Environmental and biologic factors were reported, and relationships between these factors were evaluated using logistic regression and multiple correspondence analysis. The biologic factors (the presence of tsetse flies, human blood meals, and teneral flies) were progressively accumulated at each capture site to permit the characterization of the sleeping sickness transmission risk. The dry season was found to be a more favorable period for the disease transmission than the rainy season. Moreover, the landscapes characterized by the presence of argillaceous soils, raised ground cover with forest residues and rivers, were identified as types of environments with greater risk of sleeping sickness transmission. Pig breeding appeared as an important factor increasing the disease transmission. If vector control is continuously performed along rivers segments at high risk, the transmission of sleeping sickness in rural and periurban areas of Kinshasa will considerably decrease.

[Re-emergence of human African trypanosomiasis in Kinshasa, Democratic Republic of Congo (DRC)]

BACKGROUND

The incidence of human African trypanosomiasis (HAT) or sleeping sickness in Kinshasa has been increasing since 1996. The objectives of this study were first to identify the optimal levels of knowledge, and then to determine the risk factors for HAT in the city of Kinshasa.

METHODS

This case/control study was based on a structured questionnaire. Case-patients were detected and treated between 1 January 2004 and 31 December 2005. Each case-patient was paired with two seronegative controls of the same age and sex, living in the same type of environment. The study included 437 case-patients and 874 controls.

RESULTS

The optimal level of knowledge defined by the list of elementary notions related to HAT was 44% for the case-patients and 37.0% for controls (p<0.0001). The majority of individuals (86.7%) was favorable to passive screening. The patients living in peripheral areas were more at risk than other groups, in rural areas (odds-ratio 12.1; 95% IC: 5.7-21.7), and remote areas (odds-ratio 8.9; 9% IC: 2.1-38.8). A family history of HAT (odds-ratio 12.9; 95% IC: 7.9-20.8), ignoring the transmission route (odds-ratio 11.2; 95% IC: 5.8-21.7), and the water supply in natural points (odds-ratio 6.9; 95% IC: 2.8-17.2) were also risk factors.

CONCLUSION

The results identified avoidable factors, which could be taken into account, to decrease the incidence of new contamination, the morbidity, and mortality of HAT.

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.

Thermal tolerance in a south-east African population of the tsetse fly Glossina pallidipes (Diptera, Glossinidae): implications for forecasting climate change impacts

For tsetse (Glossina spp.), the vectors of human and animal trypanosomiases, the physiological mechanisms linking variation in population dynamics with changing weather conditions have not been well established. Here, we investigate high- and low-temperature tolerance in terms of activity limits and survival in a natural population of adult Glossina pallidipes from eastern Zambia. Due to increased interest in chilling flies for handling and aerial dispersal in sterile insect technique control and eradication programmes, we also provide further detailed investigation of low-temperature responses. In wild-caught G. pallidipes, the probability of survival for 50% of the population at low-temperatures was at 3.7, 8.9 and 9.6 degrees C (95% CIs: +/-1.5 degrees C) for 1, 2 and 3 h treatments, respectively. At high temperatures, it was estimated that treatments at 37.9, 36.2 and 35.6 degrees C (95% CIs: +/-0.5 degrees C) would yield 50% population survival for 1, 2 and 3 h, respectively. Significant effects of time and temperature were detected at both temperature extremes (GLZ, p<0.05 in all cases) although a time-temperature interaction was only detected at high temperatures (p<0.0001). We synthesized data from four other Kenyan populations and found that upper critical thermal limits showed little variation among populations and laboratory treatments (range: 43.9-45.0 degrees C; 0.25 degrees C/min heating rate), although reduction to more ecologically relevant heating rates (0.06 degrees C/min) reduce these values significantly from approximately 44.4 to 40.6 degrees C, thereby providing a causal explanation for why tsetse distribution may be high-temperature limited. By contrast, low-temperature limits showed substantial variation among populations and acclimation treatments (range: 4.5-13.8 degrees C; 0.25 degrees C/min), indicating high levels of inter-population variability. Ecologically relevant cooling rates (0.06 degrees C/min) suggest tsetses are likely to experience chill coma temperatures under natural conditions (approximately 20-21 degrees C). The results from acute hardening experiments in the Zambian population demonstrate limited ability to improve low-temperature tolerance over short (hourly) timescales after non-lethal pre-treatments. In flies which survived chilling, recovery times were non-linear with plateaus between 2-6 and 8-12 degrees C. Survival times ranged between 4 and 36 h and did not vary between flies which had undergone chill coma by comparison with flies which had not, even after factoring body condition into the analyses (p>0.5 in all cases). However, flies with low chill coma values had the highest body water and fat content, indicating that when energy reserves are depleted, low-temperature tolerance may be compromised. Overall, these results suggest that physiological mechanisms may provide insight into tsetse population dynamics, hence distribution and abundance, and support a general prediction for reduced geographic distribution under future climate warming scenarios.

Human African trypanosomiasis transmission, Kinshasa, Democratic Republic of Congo

To investigate the epidemiology of human African trypanosomiasis (sleeping sickness) in Kinshasa, Democratic Republic of Congo, 2 entomologic surveys were conducted in 2005. Trypanosoma brucei gambiense and human-blood meals were found in tsetse fly midguts, which suggested active disease transmission. Vector control should be used to improve human African trypanosomiasis control efforts.

Special infectious disease risks of expatriates and long-term travelers in tropical countries. Part II: infections other than malaria

A wide range of viral, bacterial, and protozoal diseases pose risk to long-term tropical travelers. Risk varies geographically and with lifestyle. For some infections, risk increases with duration of stay, coming to resemble that of the local population. Risk management strategies include vaccination, chemoprophylaxis, avoidance measures, and screening, where appropriate. Vaccination against hepatitis A and B, typhoid, and rabies is recommended for all long-term travelers to (sub-)tropical areas. Lowering of the vaccination threshold for Japanese encephalitis is suggested. Meningococcal disease is rare in travelers, but vaccination is safe and acceptable. The efficacy of Bacillus Calmette-Guérin (BCG) is uncertain; immunological testing avoids BCG's confounding of tuberculin testing. Diarrhea is common, and self-treatment may be recommended. Sexually transmitted infections including human immunodeficiency virus (HIV) are serious risks; education, screening, and HIV postexposure prophylaxis following involuntary exposure are recommended. Many infections are chronic or asymptomatic, and appropriate screening is recommended on return or after prolonged exposure.

Trypanosomiasis in Kinshasa: distribution of the vector, Glossina fuscipes quanzensis, and risk of transmission in the peri-urban area

Abstract. Because human and animal cases of African trypanosomiasis have been reported in and around the city of Kinshasa for a long time, the likelihood of local transmission was examined. A georeferenced image of the city was produced, based on a satellite image (SPOT 4). Urban, peri-urban and rural areas were delineated. All recent data on captures of Glossina fuscipes quanzensis Pires (Diptera: Glossinidae) between 1999 and 2004, as well as epidemiological data on a 1999 outbreak of human trypanosomiasis by Trypanosoma brucei gambiense in the Kisenso District, were entered in a geographical information system (GIS). Tsetse flies were mainly found along some of the major rivers in the rural and peri-urban area of Kinshasa. Unsupervised classification of the satellite image allowed identification of riverine habitats suitable for tsetse flies and indicated sites where further entomological surveys were needed. The study produced strong indications that local transmission of human trypanosomiasis had occurred in the recent past in the peri-urban zone of Kinshasa.

African trypanosomiasis: Changing epidemiology and consequences

Human African trypanosomiasis has re-emerged as a serious public health threat after near-elimination because of diminished investment in previously successful control programs. The continued, occasional importation of African trypanosomiasis to the United States can be expected as tourists and immigrants travel from high-risk areas. No vaccine or chemoprophylaxis is available for this disease, and travelers to affected areas should be counseled on tsetse fly avoidance. New diagnostic and staging tests are promising but have not replaced the classical method of examining body fluids for trypanosomes. Prompt diagnosis and staging is essential because if untreated, East African and West African sleeping sickness are fatal. Drug regimens are toxic and cumbersome, and short-term prospects for therapeutic advances are limited.