Identifying research questions to support the drive to eliminate Human African Trypanosomiasis

Following an online Scientific Research Meeting joint-hosted by LCNTDR, The HAT Platform and RSTMH on 'Achieving Human African Trypanosomiasis elimination' last month, Kathryn Forbes and Tim Jesudason have written up a summary of the event and its findings.

Human African trypanosomiasis (HAT), also known as sleeping sickness, is a vector-borne parasitic disease that affects some of the world’s poorest, most marginalised populations. Without diagnosis and treatment, HAT is considered fatal.  Symptoms include confusion, changes in behaviour (often aggressive), extreme fatigue, joint pain and headaches, convulsions and other neurological conditions which, unless treated, progress until the patient dies. Transmitted by the tsetse fly, the disease takes on one of two forms, depending on the subspecies of the parasite involved: 

•  Trypanosoma brucei gambiense, found in 24 countries in west and central Africa and accounts for 97% of reported cases of sleeping sickness. A person can be infected for months or even years without major signs or symptoms of the disease. When more evident symptoms emerge, the patient is often already in an advanced disease stage where the central nervous system is affected.
•  Trypanosoma brucei rhodesiense, found in 13 countries in eastern and southern Africa and causes under 3% of reported cases. First signs and symptoms are observed a few months or weeks after infection. The disease develops rapidly and invades the central nervous system. Only Uganda presents both forms of the disease, but in separate zones .

Ending the neglect to attain the Sustainable Development Goals: a road map for neglected tropical diseases 2021-2030, published by the World Health Organization in 2021, targets HAT for elimination (interruption of transmission) by 2030. The target follows sustained progress globally. In 2009 the number of cases reported dropped below 10 000 for the first time in 50 years, and there were 992 and 663 cases reported in 2019 and 2020 respectively.

As the prevalence of HAT continues to decline, however, new challenges are emerging that threaten the achievement of the WHO NTD road map target. To discuss these challenges and identify important research questions that will need to be answered if we are to meet the target, in February 2022, the London Centre for NTD Research, the HAT Platform, DNDi and the Royal Society of Tropical Medicine & Hygiene hosted three virtual roundtable meetings over three consecutive days. Key research areas identified included:

Case finding and diagnostics: Case-finding is becoming more challenging as the prevalence of HAT declines and new strategies are needed to combine passive and reactive case-finding approaches. New diagnostic tools are needed that can be easily implemented in communities, but are sensitive and specific enough to ensure all cases are identified.  The potential for a PCR test for HAT needs further research and investigation in terms of sensitivity and specificity, but also ensuring that any test developed is suitable for use in settings with poor health infrastructure, or at a central laboratory to confirm cases or help to identify when to stop screen and treat strategies.

Since HAT has an animal reservoir, diagnostics and treatment for animals was also discussed. A specific research question raised addressed was: “If we can prove that domestic animals act as a reservoir, however small, can we treat animals for trypanosomiasis to reduce the transmission to humans?”

Vector control: Vector control is an effective intervention to protect vulnerable populations, including refugees and internally displaced persons. Notably, in Uganda, an intervention for tsetse control was implemented in refugee settlements. This protected by those arriving and those already resident. It could be implemented quickly on short notice in addition to clinical interventions.  

Climate change: Climate change was discussed along with the anthropogenic change on the environment having an effect on HAT transmission. In Zimbabwe, for example, there is strong evidence that hotter weather has resulted in increased tsetse fly populations, and therefore a rise in HAT cases. Climate change will also affect livestock and significant research is needed in this area. 

People-centred approaches: It is essential that messages about HAT prevention, treatment and care are received from people trusted by communities, as HAT anthropologists acknowledged that the person conveying a message can be as important as the message itself. At times, local knowledge is not sufficiently acknowledged, and researchers impose knowledge on communities. Better collaboration is needed, including a need to recognise that indigenous knowledge is scientific, real and logical and often better received. 

The roundtable research sessions attracted a diverse audience of stakeholders interested in the elimination of human African trypanosomiasis, importantly, researchers not normally working in the field of HAT.  Participants joined from over 60 countries. The meetings generated rich discussions which identified research areas that will need to be explored to achieve WHO road map targets. To learn more about the role of research in the elimination of human African trypanosomiasis, watch the roundtable recordings below. 

•    Watch day one here.
•    Watch day two here.
•    Watch day three here.