Epidemiological evidence for immunity following Trypanosoma brucei gambiense sleeping sickness

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.

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“…It has been described that certain protective immunity exists against new infections in humans after suffering from the disease 107,108…”

Section: Risk Factorsmentioning

confidence: 99%

Epidemiology of human African trypanosomiasis

Franco¹,

Simarro²,

Diarra³

et al. 2014

CLEP

259

230

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“…gambiense infection and it is also known that results of the CATT may remain positive for some time. 14,15 Furthermore, the positive predictive value of the CATT dilutions is uni i known and may vary over the length of a control programme. Perhaps a higher threshold of even 1/16 or 1/32 should be considered especially when the overall prevalence of the disease is moderate to low.…”

Section: Discussionmentioning

confidence: 99%

Treatment outcomes and risk factors for relapse in patients with early-stage human African trypanosomiasis (HAT) in the Republic of Congo

Balasegaram

Harris

Checchi

et al. 2006

Bull World Health Organ

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“…However, another explanation could be that people from areas where the disease is absent are more susceptible to infection that individuals originating from endemic areas. One interesting epidemiologic feature of sleeping sickness is that the epidemics of the 1970s and 1980s appeared in the same foci as the major epidemics seen 50 years earlier (Khonde et al . 1995; Hide 1999).…”

Section: Discussionmentioning

confidence: 99%

“…1986a) and their interactions in this cyclic evolution have been studied but are not clearly identified (Hide 1999). Khonde et al . (1995) suggested than despite the persistence of ecological conditions favouring human–fly contact in these areas, low prevalence rates observed during several decades could be because of the appearance of an immune population.…”

Section: Discussionmentioning

confidence: 99%

Host age and time of exposure in Trypanosoma brucei gambiense Human African Trypanosomiasis

Garcia

Jamonneau

Sané

et al. 2002

Tropical Med Int Health

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Human African Trypanosomiasis is related to behavioural risk factors but complex interactions exist between (i) environmental and behavioural risk factors, (ii) vector and (iii) human host. Our aim was to investigate the interrelationships between previously analysed risk factors and the roles of age and time of exposure according to ethnic group and migration status. However, this descriptive and retrospective study is based on cases only (no controls) and our results must therefore be regarded as hypothesis-generating. Individuals originating from areas where sleeping sickness is absent and who settle in an endemic area seem to develop the disease after a shorter time of exposure than native subjects from endemic areas. Our results emphasise the complexity of vector-transmitted disease epidemiology, involving behavioural and/or environmental risk factors on the one hand, and more individual ones such as ageing, immunity and genetic background on the other hand.

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Epidemiological evidence for immunity following Trypanosoma brucei gambiense sleeping sickness

Cited by 27 publications

References 14 publications

Epidemiology of human African trypanosomiasis

Epidemiology of human African trypanosomiasis

Treatment outcomes and risk factors for relapse in patients with early-stage human African trypanosomiasis (HAT) in the Republic of Congo

Host age and time of exposure in Trypanosoma brucei gambiense Human African Trypanosomiasis

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