Authors: Dominique Legros, Gaëlle Ollivier, Marc Gastellu-Etchegorry, Christophe Paquet, Christian Burri, Jean Jannin, and Philippe Büscher
Human African Trypanosomiasis (HAT), or sleeping sickness, is an old tropical disease transmitted through the bites of infected tsetse flies. The disease was largely controlled in the 1960s; however, a lack of human and financial resources and years of conflict in the most affected countries have hampered efforts to monitor and control the disease. Sleeping sickness, therefore, re-emerged in the 1980s. The drugs that are available to treat it are scarce, highly toxic, and encounter parasite resistance. Very little progress has been made in developing new drugs in recent decades, and, as a result, we may soon be confronted with a complete absence of effective drugs to treat HAT patients.
There are two forms of HAT. The first, Trypanosoma brucei gambiense (Tbg), is primarily a human disease and causes a chronic infection. It is endemic in West and Central African countries. The second, Trypanosoma brucei rhodesiense (Tbr), has a huge animal reservoir and is primarily an animal disease. It causes an acute illness in humans in eastern and southern African countries.
Sleeping sickness has two clinical stages. The first corresponds to the multiplication of the trypanosomes in the blood and in the lymphatic system and very often goes undiagnosed. When the parasites cross the blood-brain barrier, the disease progresses to the second stage, which is characterized by neurological symptoms and, without treatment, evolves toward body wasting, somnolence, coma, and death.