The history of sleeping sickness
The big transcontinental epidemic
The apparent low frequency of the disease before the twentieth century is in sharp contrast with the severe outbreak that took place after the invasion into the interior of Africa by European explorers, missionaries, commercial agents, soldiers and colonial personnel during the late 19th century.
The colonial conquest meant an unprecedented biological, social and economical upheaval. Rural Africa was confronted with overwhelming novel industrial expansions. It meant porterage, soldiers and forced labour for instance for the construction of roads and railways, for collecting rubber, for mining. People moved or were moved to new hitherto unexplored environments. Imposition of taxes required extra cash crops and pressed people to open new lands in tsetse infested zones. Expropriations for industrial reasons obliged populations to establish new villages at locations selected by colonial responsibles, who of course had no notion of the risks of tsetse. The Belgian missionary school at Berghe St Marie set up at the river Congo border near Kwamouth was a notorious example. It had to close down in 1896 because yearly 100 out of the 1000 school children were dying of sleeping sickness.
Forced labour and new means of transport like roads and railways made people move more frequently hence enhancing the risk of transferring trypanosome strains from one area to another. Colonial pacification had brought tribal wars to an end and the long established micro eco-systems and traditional social relationships became disturbed. It caused the breakdown of the "sanitary barrier" maintained in the past by long distances between villages and limited contact between them.
In East Africa, during 1889-1896, a series of natural disasters coincided with the colonial expansion. A devastating panzootic of rinderpest killed more than 90% of the livestock and the greater part of wildlife. The tsetse populations, deprived of their primary source of food, were decimated and the remaining flies turned to humans. The situation worsened because of a severe drought that followed and made people, animals and tsetse concentrate around the scarce water sources and the lakeshores where tsetse was abundant.
The rapid spread of sleeping sickness as a result of the "opening up of Africa" followed precisely the sequence of the European invasion along the Congo River as far as the shores of Lake Victoria. The total number of deaths in the Congo basin has been estimated at half a million and in Uganda at 200.000 to 300.000. The uncontrollable spread and high death rates had a dramatic impact on the local populations as well as on the colonial administrations. The latter became seriously worried about the future exploitation of their colonies and as a matter of priority solicited for medical and biological research and recruited scientific missions to Africa.