Human African Trypanosomiasis Transmission Research Articles

The elimination of human African trypanosomiasis: Monitoring progress towards the 2021-2030 WHO road map targets.

Human African trypanosomiasis (HAT) is a neglected tropical disease that usually occurs in rural areas in sub-Saharan Africa. It caused devastating epidemics during the 20th century. Sustained, coordinated efforts by different stakeholders working with national sleeping sickness control programmes (NSSCPs) succeeded in controlling the disease and reducing the number of cases to historically low levels. In 2012, WHO targeted the elimination of the disease as a public health problem by 2020. This goal has been reached and a new ambitious target was stated in the WHO road map for NTDs 2021-2030 and endorsed by the 73rd World Health Assembly: the elimination of gambiense HAT transmission (i.e. reducing the number of reported cases to zero). The interruption of transmission was not considered as an achievable goal for rhodesiense HAT, as it would require vast veterinary interventions rather than actions at the public health level. Data reported to WHO by NSSCPs were harmonized, verified, georeferenced and included in the atlas of HAT. A total of 802 cases were reported in 2021 and 837 in 2022. This is below the target for elimination as a public health problem at the global level (< 2000 HAT cases/year); 94% of the cases were caused by infection with T. b. gambiense. The areas reporting ≥ 1 HAT case/10 000 inhabitants/year in 2018-2022 cover a surface of 73 134 km2, with only 3013 km2 at very high or high risk. This represents a reduction of 90% from the baseline figure for 2000-2004, the target set for the elimination of HAT as a public health problem. For the surveillance of the disease, 4.5 million people were screened for gambiense HAT with serological tests in 2021-2022, 3.6 million through active screening and 0.9 million by passive screening. In 2021 and 2022 the elimination of HAT as a public health problem was validated in Benin, Uganda, Equatorial Guinea and Ghana for gambiense HAT and in Rwanda for rhodesiense HAT. To reach the next goal of elimination of transmission of gambiense HAT, countries have to report zero cases of human infection with T. b. gambiense for a period of at least 5 consecutive years. The criteria and procedures to verify elimination of transmission have been recently published by WHO. HAT elimination as a public health problem has been reached at global level, with seven countries already validated as having reached this goal. This achievement was made possible by the work of NSSCPs, supported by different public and private partners, and coordinated by WHO. The new challenging goal now is to reach zero cases by 2030. To reach this goal is crucial to maintain the engagement and support of donors and stakeholders and to keep the involvement and coordination of all partners. Along with the focus on elimination of transmission of gambiense HAT, it is important not to neglect rhodesiense HAT, which is targeted for elimination as a public health problem in the WHO road map for NTDs 2021-2030.

The evolving spectrum of human African trypanosomiasis.

Human African trypanosomiasis (HAT), or sleeping sickness, continues to be a major threat to human health in 36 countries throughout sub-Saharan Africa with up to 60 million people at risk. Over the last decade, there have been several advances in this area, some of which are discussed in this overview. Due to the concerted efforts of several bodies, including better identification and treatment of cases and improved tsetse fly vector control, the number of cases of HAT has declined dramatically. The clinical heterogeneity of HAT has also been increasingly recognized, and the disease, while usually fatal if untreated or inadequately treated, does not always have a uniformly fatal outcome. Improved methods of HAT diagnosis have now been developed including rapid diagnostic tests. Novel drug treatment of HAT has also been developed, notably nifurtimox-eflornithine combination therapy (NECT) for late-stage Trypanosoma brucei gambiense, oral fexinidazole for early and the early component of the late-stage of T.b. gambiense, and the new oral compounds of the oxaborole group, which have shown considerable promise in field trials. Advances in HAT neuropathogenesis have been steady, though largely incremental, with a particular focus on the role of the blood-brain barrier in parasite entry into the central nervous system and the relevant importance of both innate and adaptive immunity. While the World Health Organization goal of elimination of HAT as a public health problem by 2020 has probably been achieved, it remains to be seen whether the second more ambitious goal of interruption of transmission of HAT by 2030 will be attained.

Wing Interferential Patterns (WIPs) and machine learning, a step toward automatized tsetse (Glossina spp.) identification

A simple method for accurately identifying Glossina spp in the field is a challenge to sustain the future elimination of Human African Trypanosomiasis (HAT) as a public health scourge, as well as for the sustainable management of African Animal Trypanosomiasis (AAT). Current methods for Glossina species identification heavily rely on a few well-trained experts. Methodologies that rely on molecular methodologies like DNA barcoding or mass spectrometry protein profiling (MALDI TOFF) haven’t been thoroughly investigated for Glossina sp. Nevertheless, because they are destructive, costly, time-consuming, and expensive in infrastructure and materials, they might not be well adapted for the survey of arthropod vectors involved in the transmission of pathogens responsible for Neglected Tropical Diseases, like HAT. This study demonstrates a new type of methodology to classify Glossina species. In conjunction with a deep learning architecture, a database of Wing Interference Patterns (WIPs) representative of the Glossina species involved in the transmission of HAT and AAT was used. This database has 1766 pictures representing 23 Glossina species. This cost-effective methodology, which requires mounting wings on slides and using a commercially available microscope, demonstrates that WIPs are an excellent medium to automatically recognize Glossina species with very high accuracy.

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

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

Monitoring the elimination of human African trypanosomiasis at continental and country level: Update to 2018.

BackgroundIn 2012 human African trypanosomiasis (HAT), also known as sleeping sickness, was targeted for elimination as a public health problem, set to be achieved by 2020. The World Health Organization (WHO) provides here the 2018 update on the progress made toward that objective. Global indicators are reviewed, in particular the number of reported cases and the areas at risk. Recently developed indicators for the validation of HAT elimination at the national level are also presented.Methodology/Principal FindingsWith 977 cases reported in 2018, down from 2,164 in 2016, the main global indicator of elimination is already well within the 2020 target (i.e. 2,000 cases). Areas at moderate or higher risk (i.e. ≥ 1 case/10,000 people/year) are also steadily shrinking (less than 200,000 km2 in the period 2014–2018), thus nearing the 2020 target [i.e. 90% reduction (638,000 km2) from the 2000–2004 baseline (709,000 km2)]. Health facilities providing diagnosis and treatment of gambiense HAT continued to increase (+7% since the previous survey), with a better coverage of at-risk populations. By contrast, rhodesiense HAT health facilities decreased in number (-10.5%) and coverage. At the national level, eight countries meet the requirements to request validation of gambiense HAT elimination as a public health problem (i.e. Benin, Burkina Faso, Cameroon, Côte d’Ivoire, Ghana, Mali, Rwanda, and Togo), while for other endemic countries more efforts are needed in surveillance, control, or both.Conclusions/SignificanceThe 2020 goal of HAT elimination as a public health problem is within grasp, and eligible countries are encouraged to request validation of their elimination status. Beyond 2020, the HAT community must gear up for the elimination of gambiense HAT transmission (2030 goal), by preparing for both the expected challenges (e.g. funding, coordination, integration of HAT control into regular health systems, development of more adapted tools, cryptic trypanosome reservoirs, etc.) and the unexpected ones.

An Active Follow-up Strategy for Serological Suspects of Human African Trypanosomiasis with Negative Parasitology Set up by a Health Zone Team in the Democratic Republic of Congo.

Background: The World Health Organization aims for the elimination of Human African Trypanosomiasis (HAT) as a public health problem by 2020 and for full elimination (absence of new cases) by 2030. One of strategies to achieve this is the active follow-up of all HAT serological suspects found during passive screening who have never been re-tested for parasitology. This is important because these cases can maintain HAT transmission and may be responsible for reemergence of the disease. Methods: In order to improve case finding at low cost in the targeted population, a general recall was transmitted to aparasitemic serological suspects about the availability of confirmation services at the general referral hospital. Transport was facilitated for re-testing. The initial examinations were carried out in Health Centers from Bagata Health Zone (HZ) in the Democratic Republic of the Congo between January 2017 and April 2019. This strategy of using a HZ team has not been previously documented. Results: From a total sample of 74 serological suspects listed by the health centers, 36 cases were re-examined at the general reference hospital; 19% (7/36) self-presented and 81% (29/36) were actively followed up by HZ personnel. Of those re-examined at the general reference hospital, 39% (14/36) resulted in a parasitologically confirmed case. Of the 14 people diagnosed with HAT, 14% (2/14) self-presented and the remaining 86% (12/14) were diagnosed in suspects who were actively followed up. This new strategy of facilitating transport from the villages added value by contributing to the detection of 12 HAT cases, compared to the passive approach, waiting for self-reference, which resulted in the detection of 2 new HAT cases. The cost per detected patient was 70 USD from the group of 7 suspects who self-presented for testing at the hospital and 346 USD per detected case for the group of 29 patients who were actively followed up by health zone staff. Conclusion: Targeted active follow-up of aparasitemic serological suspects by HZ teams is a cost-effective and promising approach to identifying additional cases of HAT in areas of very low prevalence, which would contribute to the HAT elimination goal set by the World Health Organization.

Assessing the impact of aggregating disease stage data in model predictions of human African trypanosomiasis transmission and control activities in Bandundu province (DRC).

Since the turn of the century, the global community has made great progress towards the elimination of gambiense human African trypanosomiasis (HAT). Elimination programs, primarily relying on screening and treatment campaigns, have also created a rich database of HAT epidemiology. Mathematical models calibrated with these data can help to fill remaining gaps in our understanding of HAT transmission dynamics, including key operational research questions such as whether integrating vector control with current intervention strategies is needed to achieve HAT elimination. Here we explore, via an ensemble of models and simulation studies, how including or not disease stage data, or using more updated data sets affect model predictions of future control strategies.

Molecular identification of Trypanosoma brucei gambiense in naturally infected pigs, dogs and small ruminants confirms domestic animals as potential reservoirs for sleeping sickness in Chad.

Human African trypanosomiasis (HAT) has been targeted for zero transmission to humans by 2030. Animal reservoirs of gambiense-HAT could jeopardize these elimination goals. This study was undertaken to identify potential host reservoirs for Trypanosoma brucei gambiense by detecting its natural infections in domestic animals of Chadian HAT foci. Blood samples were collected from 267 goats, 181 sheep, 154 dogs, and 67 pigs. Rapid diagnostic test (RDT) and capillary tube centrifugation (CTC) were performed to search for trypanosomes. DNA was extracted from the buffy coat, and trypanosomes of the subgenus Trypanozoon as well as T. b. gambiense were identified by PCR. Of 669 blood samples, 19.4% were positive by RDT and 9.0% by CTC. PCR revealed 150 animals (22.4%) with trypanosomes belonging to Trypanozoon, including 18 (12%) T. b. gambiense. This trypanosome was found in all investigated animal species and all HAT foci. Between animal species or villages, no significant differences were observed in the number of animals harboring T. b. gambiense DNA. Pigs, dogs, sheep and goats appeared to be potential reservoir hosts for T. b. gambiense in Chad. The identification of T. b. gambiense in all animal species of all HAT foci suggests that these animals should be considered when designing new control strategies for sustainable elimination of HAT. Investigations aiming to decrypt their specific role in each epidemiological setting are important to achieve zero transmission of HAT.

Human African trypanosomiasis: current status and eradication efforts

Abstract Epidemics of human African trypanosomiasis (HAT) in the twentieth century led to millions of deaths. However, since the start of the twenty-first century, there has been a continued decline in the number of reported cases, due to increased investment and prioritisation of control efforts. Systematic screening of at-risk areas and widespread access to increasingly advanced diagnostics and treatments, along with much improved vector control, has all helped to make disease elimination achievable in the near future. Despite the progress, the danger of disease resurgence is well known for HAT, and continued surveillance and treatment availability are essential. Additionally, many uncertainties regarding HAT transmission remain and combine to make potential disease eradication a complete unknown.

Prevalence of trypanosome infection in tsetse flies from Oji River and Emene axis of Enugu State, Nigeria: A preliminary report.

Introduction:Trypanosomes are protozoan parasites of vertebrates transmitted by blood-sucking tsetse fly. Trypanosomes remain a constant threat to the lives of humans and animals throughout large regions of Africa.Aims and Objectives:This study investigated the presence, prevalence, and species of trypanosome parasite in tsetse flies caught in two areas of no previous documented history of trypanosome infection.Materials and Methods:For this purpose, 63 and 77 nonterenal tsetse flies were collected from Oji River and Emene areas of Enugu State Nigeria, respectively. Genomic DNA was isolated from the whole tsetse fly using genomic DNA extraction kit. Identification and characterization of trypanosome were done using two approaches: the amplification of internal transcribed spacer 1 of ribosomal DNA and the use of primers specific to Trypanozoon.Results:In Oji River, of 63 tsetse flies collected, the identification of trypanosome parasite was done on 57 flies and 6 (10.71%) tsetse flies were infected with trypanosome parasite. Six flies were infected with Trypanosoma Congolense, 2 with Trypanosoma Vivax, and 1 with Trypanosoma brucei. Two mixed infections of T. vivax and T. congolense and 1 mixed infection of T. brucei and T. congolense was also identified. In Emene, of 77 tsetse flies collected, the identification of trypanosome parasite was done on 66 flies and 11 (16.6%) tsetse flies were infected with trypanosome parasite. Nine flies were infected with T. congolense, 2 with T. vivax, and 3 with T. brucei. Mixed infections identified include 2 mixed infections of T. brucei and T. congolense and 1 mixed infections of T. vivax and T. brucei. None of the subspecies of T. brucei were detected using species specific primers.Discussion:This study shows the parasitological evidence on the occurrence of animal African trypanosomiasis and also demonstrated that there is likely no active transmission of human African trypanosomiasis in the study areas.Conclusion:This study shows that there is likely no active transmission of human African trypanosomiasis going on in these localities since no human infective form of the parasite was detected.

Human African Trypanosomiasis: Challenges in the Diagnosis of Trypanosoma Brucei Rhodesiense – Case Report

Introduction: Trypanosoma brucei rhodesiense has been known to be responsible for transmission of Human African Trypanosomiasis (HAT) in Zambia for decades, affecting predominantly rural districts and communities. Despite a decline in cases of T.b. rhodesiense HAT in the country over the years, sporadic cases are still being reported in some rural areas. Despite years of dealing with the disease challenges are still being experienced on diagnosis. This article on a HAT case highlights challenges in the diagnosis of T.b. rhodesiense. Case history: A 27 year old black African male developed malaria-like symptoms and signs, followed by palpable swellings in the neck and skin rash. The patient was initially diagnosed of malaria and treated with artemether lumefantrine, according to national guidelines. The patient later developed central nervous system (CNS) manifestations and was diagnosed as bacterial meningo-enchephalitis and put on several antibiotics. Thirty five days (35) after admission Trypanosoma brucei rhodesiense parasites were confirmed in the spinal fluid with fatal outcome despite commencing the patient with definitive treatment. Conclusions: The diagnosis of Trypanosoma brucei rhodesiense continues to experience challenges resulting into delayed treatment. Improved capacities to diagnose treat, and map the disease are vital elements to effective control in endemic areas.

Sleeping sickness and its relationship with development and biodiversity conservation in the Luangwa Valley, Zambia.

The Luangwa Valley has a long historical association with Human African Trypanosomiasis (HAT) and is a recognised geographical focus of this disease. It is also internationally acclaimed for its high biodiversity and contains many valuable habitats. Local inhabitants of the valley have developed sustainable land use systems in co-existence with wildlife over centuries, based on non-livestock keeping practices largely due to the threat from African Animal Trypanosomiasis. Historical epidemics of human sleeping sickness have influenced how and where communities have settled and have had a profound impact on development in the Valley. Historical attempts to control trypanosomiasis have also had a negative impact on conservation of biodiversity.Centralised control over wildlife utilisation has marginalised local communities from managing the wildlife resource. To some extent this has been reversed by the implementation of community based natural resource management programmes in the latter half of the 20th century and the Luangwa Valley provides some of the earliest examples of such programmes. More recently, there has been significant uncontrolled migration of people into the mid-Luangwa Valley driven by pressure on resources in the eastern plateau region, encouragement from local chiefs and economic development in the tourist centre of Mfuwe. This has brought changing land-use patterns, most notably agricultural development through livestock keeping and cotton production. These changes threaten to alter the endemically stable patterns of HAT transmission and could have significant impacts on ecosystem health and ecosystem services.In this paper we review the history of HAT in the context of conservation and development and consider the impacts current changes may have on this complex social-ecological system. We conclude that improved understanding is required to identify specific circumstances where win-win trade-offs can be achieved between the conservation of biodiversity and the reduction of disease in the human population.

On the road to elimination of Rhodesiense human African trypanosomiasis: first WHO meeting of stakeholders.

On the road to elimination of Rhodesiense human African trypanosomiasis: first WHO meeting of stakeholders.

Integration of diagnosis and treatment of sleeping sickness in primary healthcare facilities in the Democratic Republic of the Congo.

Control of human African trypanosomiasis (HAT) in the Democratic Republic of Congo (DRC) has always been a vertical programme, although attempts at integration in general health services were made in recent years. Now that HAT prevalence is declining, the integration question becomes even more crucial. We studied the level of attainment of integration of HAT case detection and management in primary care centres in two high-prevalence districts in the province of Bandundu, DRC. We visited all 43 first-line health centres of Mushie and Kwamouth districts, conducted structured interviews and inspected facilities using a standardised checklist. We focused on: availability of well trained staff - besides HAT, we also tested for knowledge on tuberculosis; availability of equipment, consumables and supplies; and utilisation of the services. All health centres were operating but most were poorly equipped, and attendance rates were very low. We observed a median of 14 outpatient consultations per facility (IQR 8-21) in the week prior to our visit, that is two patients per day. The staff had good knowledge on presenting symptoms, diagnosis and treatment of both HAT and tuberculosis. Nine centres were accredited by the national programme as HAT diagnosis and treatment centres, but the most sensitive diagnostic confirmation test, the mini-anion exchange centrifugation technique (mAECT), was not present in any. Although all nine were performing the CATT screening test, only two had the required cold chain in working order. In these high-prevalence districts in DRC, staff is well-acquainted with HAT but lack the tools required for an adequate diagnostic procedure. Attendance rates of these primary care centres are extremely low, making timely recognition of a resurgence of HAT unlikely in the current state of affairs.

The journey towards elimination of gambiense human African trypanosomiasis: not far, nor easy

Considering the epidemic situation of gambiense human African trypanosomiasis (HAT) at the end of the twentieth century, the World Health Organization (WHO) and partners strengthened disease control and surveillance. Over the last 15 years, the activities implemented through the National Control Programmes have brought gambiense HAT under control and now its elimination is deemed as an achievable goal. In 2012, WHO targeted gambiense HAT for elimination as a public health problem by 2020. The final goal will be the sustainable disease elimination by 2030, defined as the interruption of the transmission of gambiense HAT. The elimination is considered feasible, because of the epidemiological vulnerability of the disease, the current state of control, the availability of strategies and tools and international commitment and political will. Integration of activities in the health system is needed to ensure the sustainability of the elimination. The development of user-friendly diagnostic and treatment tools will facilitate the integration process. Adequate funding is needed to implement activities, but also to support research that will make the elimination sustainable. A long-term commitment by donors is needed and ownership of the process by endemic countries is critical.

Introduction to the Special Issue on Epidemiology and Ecology of Parasitic Diseases

Human African Trypanosomiasis (HAT), commonly known as sleeping sickness is a vector-borne parasitic infection caused by protozoa of the genus Trypanosoma. It can be fatal if left untreated. HAT is found in sub-Saharan Africa, but is restricted to the range of its tsetse vector. In recent decades, the foci of HAT infections have changed and it has been suggested that climate change and changes to the habitats of the tsetse vectors have influenced the observed changes. The paper by Tongue et al. clearly demonstrates the effects of habitat change on the transmission of African trypanosomiasis. Certain subspecies of Glossina have adjusted to the decrease in natural habitats by exhibiting peri-domestic behaviors that allow them to live in urban and suburban habitats near humans. The increase in urban and suburban habitats for subspecies of the tsetse vector Glossina has reduced the effectiveness of efforts to control, much less eliminate, transmission of the causative species Trypanosoma brucei rhodesiense (causes the acute form of the disease) and Trypanosoma brucei gambiense (causes the chronic from of the disease). This study provides a cautionary tale about the influence of habitat changes and climate change on the future of HAT transmission (and other pathogens), assuming these changes continue to occur. In the next study, we move west off of the continent of Africa to consider a species of mosquito in the genusCulex and its possible role in the transmission of Dirofilaria immitis, the primary causative agent of heartworm disease. Although the Canary Islands are a known endemic focus of Dirofilaria immitis, the mosquito vector on the island has, heretofore, not been identified. This article by Morchon Garcia et al. provides convincing evidence that they found the mosquito species that serves as the vector of D. immitis on the islands. Five potential vector species of mosquitoes were collected on the islands. Using molecular biological techniques, the authors identified one species of mosquito, Culex theileri, which was infected with D. immitis. Recent studies in Iran [4] and Spain [5] suggest that C. theileri is a competent vector species. In addition, comparing analyses of the mtDNA in the cox1 gene between C. theileri populations in the Canary Islands and Iran suggest that the two populations are molecularly similar. Although the results of this study are supportive of the role of C. theileri in the transmission of D. immitis in the Canary Islands, the authors caution that additional studies are required to conclusively support their suggestions. Our next study takes us to Asia and consideration of the status of Visceral Leishmaniasis (VL) in Iran. In his review, Mohebali combines his personal experience with numerous (>3,000) cases of leishmaniasis in Iran with results obtained from a search of databases from 1996 through 2010. The author’s results suggest that canids serve as the primary reservoir hosts of infection of humans a result found in previous studies [6]. Several species of Phlebotomus serve the insect vectors in Iran. In Iran, VL appears to be a disease of the young as children 12 years of age and younger made up 92.8% of the reported cases of VL during the time span under review. Mohebali found that the direct agglutination test was an effective means of detecting antiLeishmania antibodies and recommended it as a surveillance tool. The author concluded that VL is a serious zoonotic threat in Iran with sporadic prevalence in most geographic zones while being endemic in northwestern and southern Iran. Finally, we go further east and north to Mongolia where Papageorgiou et al. examined the epidemiology of tick-borne pathogens in two of the country’s provinces (aimags). Livestock were investigated using serology and PCR to identify exposure and infection

An exploratory GIS-based method to identify and characterise landscapes with an elevated epidemiological risk of Rhodesian human African trypanosomiasis

BackgroundSpecific land cover types and activities have been correlated with Trypanosoma brucei rhodesiense distributions, indicating the importance of landscape for epidemiological risk. However, methods proposed to identify specific areas with elevated epidemiological risk (i.e. where transmission is more likely to occur) tend to be costly and time consuming. This paper proposes an exploratory spatial analysis using geo-referenced human African trypanosomiasis (HAT) cases and matched controls from Serere hospital, Uganda (December 1998 to November 2002) to identify areas with an elevated epidemiological risk of HAT.MethodsBuffers 3 km from each case and control were used to represent areas in which village inhabitants would carry out their daily activities. It was hypothesised that the selection of areas where several case village buffers overlapped would enable the identification of locations with increased risk of HAT transmission, as these areas were more likely to be frequented by HAT cases in several surrounding villages. The landscape within these overlap areas should more closely relate to the environment in which transmission occurs as opposed to using the full buffer areas. The analysis was carried out for each of four annual periods, for both cases and controls, using a series of threshold values (number of overlapping buffers), including a threshold of one, which represented the benchmark (e.g. use of the full buffer area as opposed to the overlap areas).ResultsA greater proportion of the overlap areas for cases consisted of seasonally flooding grassland and lake fringe swamp, than the control overlap areas, correlating well with the preferred habitat of the predominant tsetse species within the study area (Glossina fuscipes fuscipes). The use of overlap areas also resulted in a greater difference between case and control landscapes, when compared with the benchmark (using the full buffer area).ConclusionsThese results indicate that the overlap analysis has enabled the selection of areas more likely to represent epidemiological risk zones than similar analyses using full buffer areas. The identification of potential epidemiological risk zones using this method requires fewer data than other proposed methods and further development may provide vital information for the targeting of control measures.

Urban Transmission of Human African Trypanosomiasis, Gabon

To the Editor: We describe a confirmed case of human African trypanosomiasis (HAT) in an expatriate returning to France from Gabon after a probable tsetse fly bite in the urban setting of Libreville. This case indicates a possible urban transmission of HAT in Gabon and stresses the need for entomologic studies in Libreville. HAT is endemic to sub-Saharan Africa. Trypanosoma brucei rhodesiense (eastern Africa) and T.b. gambiense (western Africa) parasites are transmitted to humans by tsetse flies of the Glossina morsitans group (T.b. rhodesiense) and of the G. palpalis group (T.b. gambiense), which are found only in Africa. T.b. gambiense represents >90% of all reported cases of HAT worldwide. HAT has always been a travel-associated disease. It is a rare cause of fever, cutaneous lesions, and neurologic signs in travelers returning from disease-endemic areas and involves T.b. rhodesiense in 70% of the cases, resulting mostly from an exposure during safari in game parks (1,2). A 58-year-old previously healthy Portuguese man who worked in Gabon for 13 years for a French company was admitted to the tropical and infectious diseases ward because of a 2-month history of intermittent fever, fatigue, and a 10-kg weight loss. The patient recalled a painful unidentified insect bite on his right thigh 2 months before in his garden in Libreville (Lalala quarter). A 8-cm, indurated, erythematous, and painful plaque (chancre) progressively developed (Figure) in the following weeks after the assumed insect bite. When admitted to the hospital, the patient had a temperature of 39°C, anorexia, insomnia, pruritus of the left arm, and paresthesia of the hands and feet. Two additional large annular erythematous macules, centrally pale (trypanids), were found on his back (Figure). A subclavicular 0.5-cm lymph node was observed. There was no hepatosplenomegaly. Figure Thigh chancre (1) and back trypanids (2 and 3) in a patient with human African trypanosomiasis infection, Gabon. His laboratory results showed moderate anemia (hemoglobin 11.8 g/dL) and thrombopenia (134,000 platelets/mm3) and elevated levels of C-reactive protein (30.6 mg/L) and gammaglobulins (23.9 g/L). A thick-blood smear showed no malaria parasites but a few trypomastigotes of Trypanosoma spp. PCR of blood identified T.b. gambiense. A cerebrospinal fluid sample showed moderate elevation of total proteins (0.43 g/L) and albumin (291 mg/L), 11 leukocytes, and no IgM elevation. Direct examination and PCR showed no trypanosome in the cerebrospinal fluid. Specific antibodies were found in the blood by indirect immunofluorescence (titer 200). Biopsies of 2 skin lesions (thigh, back) showed a lymphoplasmocytic vasculitis consistent with cutaneous locations of HAT; no parasite was observed in situ. The patient was treated successfully with a 7-day course of pentamidine. The case was reported to World Health Organization Control of Neglected Tropical Diseases Department. A total of 328 HAT cases were reported to the World Health Organization in Gabon during 2000–2009; most infections were acquired in the mangrove swamp Atlantic coast focus in Noya (Estuaire Province) and some in the focus of Bendje (Ogooue-Maritime Province) (3). Four of 6 cases of T.b. gambiense imported to Europe during 2005–2009 were in expatriates with a travel history to Gabon (1). In the 4 case-patients infected in Gabon, an exposure in rural forest areas was assessed (4–6; D. Malvy, pers. comm.). In the fifth case reported here, the tsetse bite likely occurred in the urban setting of Libreville. The patient did not report occupational exposure to tsetse bites outside Libreville during the previous year. He occasionally went in Pointe Denis during weekends but did not remember having been bitten by a tsetse fly. Although the patient did not identify the insect in his garden, the chronology of his clinical history and the presence of a typical chancre at the place of the insect bite that occurred before symptoms provide strong arguments in favor of this hypothesis. The bite occurred during the morning hours, in the patient’s home garden in the Lalala area of Libreville (0.357568N, 9.475365E) near the Ogombie River. This area is located 125 km and 75 km from the Bendje and Noya HAT foci, respectively. Two studies provided evidence for urban transmission of HAT in Kinshasa (Democratic Republic of Congo) and in Bonon (Cote d’Ivoire) (7,8). Concurrently, some tsetse species, such as G. palpalis, adapt to high human densities and are found in the largest urban centers of western Africa (9). Entomologic studies in Libreville should prompt further investigation into a possible urban transmission of HAT in Gabon, as we suspect in the case reported.

Human African trypanosomiasis in Angola: clinical observations, treatment, and use of PCR for stage determination of early stage of the disease

Biological and clinical observations are described for 224 patients infected by human African trypanosomiasis (HAT) in Angola in 2007 and 2008. Seven patients were initially classified in stage 1 (S1), 17 intermediate stage (IS) (WBC <20 lymphocytes/μl with absence of trypanosomes in cerebrospinal fluid (CSF) and no neurological signs), and 200 in stage 2 (S2). Out of 224 patients, 165 (73.6%) presented one or more neurological signs. During treatment with eflornithine, six deaths of S2 patients occurred, five of which were because of an encephalopathy syndrome. Nine patients were diagnosed with a relapse or suspected treatment failure during the follow-up: eight patients after treatment with eflornithine (relapse rate 4.1%) and one patient after pentamidine (6.6%). The contribution of PCR for stage determination evaluated for S1 and IS confirms the difficulty of stage determination, as one S1 patient and two IS patients were carriers of trypanosomes detected a posteriori by PCR in CSF but were treated with pentamidine while follow-up did not confirm treatment efficacy. Since 2001 in Angola, either by passive or active mode detection, approximately 80% of the new cases every year were in S2, whereas the annual number of cases has regressed, probably because the transmission of HAT is decreasing. However, stage determination and treatment remain two major issues for the chronic form of sleeping sickness.

Transmission of human African trypanosomiasis in the Komo-Mondah focus, Gabon

Knowledge about transmission of sleeping sickness in a given focus is of a great importance since it governs the efficacy and the cost-effectiveness of control strategy. The Komo-Mondah focus is the most endemic sleeping sickness focus of Gabon. This focus has hardly been investigated and available publications are more than thirty years old. In order to update transmission features of sleeping sickness in that focus, we have conducted epidemiological and entomological surveys in March-April 2008. Epidemiological investigation relied on a case-control study using a quantitative and qualitative methodology (a structured questionnaire). Cases were affected people (parasitological positive) diagnosed by the national control program from 2004 to 2007, controls were those found disease-free after clinical examination and biological tests in the same period. They were asked to respond to a standard questionnaire concerning their activities after having signed a written consent. An unvaried analysis was first performed and then a multivariate analysis using the conditional logistic regression for matching method. Traps were then set out for four days in areas where people were working. Tsetse flies captured were identified and dissected; their density and human-fly contact points were determined. A risk of infection was associated with fishing activities (Odds-ratio: 5.69; CI95%: 3.38-9.57). Three species of Glossina were captured: Glossina palpalis palpalis, Glossina fuscipes fuscipes and G. Caliginea. Human-fly contact points were mainly landing stages. A combined strategy of case-detection and vector control targeted at landing stages should be efficient against the disease.