The epidemiology of sleeping sickness in East Africa: Part I. A sleeping sickness outbreak in Uganda in 1957

Abstract

1. 1) In 1957 an epidemic of Gambian sleeping sickness carried by Glossina palpalis broke out on the Aswa River, draining the Lango and Acholi Districts of Northern Uganda. 2. 2) The first appearance of the disease on this river was only 20 years ago, and followed a series of epidemics, each one caused by a big movement of people including infected persons, which had traversed Acholi from west to east, originating in an outbreak on the Albert Nile in 1909. 3. 3) Two previous outbreaks had occurred on the Aswa River close to the site of the present epidemic; one, in 1935, resulted from the first introduction of the disease, and one, in 1945, followed an abnormal increase in man-fly contact during an exceptionally dry season. 4. 4) Data are given showing the remarkably rapid development of the 1957 epidemic, in which a tenfold increase in the number of cases took place in 18 months. 5. 5) The causes of the outbreak are discussed. A dense human population was occupying a part of the tsetse-infested river where the contact with G. palpalis was so close as to be almost inescapable. The absence of other food for the fly, and the people's habits of fishing and travelling, tended to increase the intensity and amount of their contact with the tsetse. Finally a very dry season in 1956–1957 aggravated still further this close man-fly contact and caused an existing low endemic of T. gambiense to flare up at the alarmingly rapid rate recorded. 6. 6) Control, by mass survey and treatment of cases plus a temporary and local elimination of G. palpalis by Dieldrin spraying, kept the epidemic from developing into what might have been a dangerously wide outbreak, but the actual rate of reduction in the epidemic centre was slow. The underlying reasons are discussed.