Sleeping sickness survey in Musoma district, Tanzania. I. Investigation of the incidence of sleeping sickness in the human population.

In a survey of sleeping sickness in the Ikoma-Serengeti area, carried out in October and November 1970, about 3,000 people living in the area were examined and none was found infected. Introduction Rhodesian sleeping sickness was introduced into the Musoma District mainly in the Ikoma area in the 1920's. It is believed to have been an extension of an epidemic in Maswa, Mwanza District, which lies to the south. The outbreak of Rhodesian sleeping sickness in Maswa probably began in 1919-1921 during a period of famine but early patients were first diagnosed in 1922 (Davey 1924). Glossina swynnertoni was incriminated as the main vector of the outbreak. The spread of the disease was thought to be due to infected persons and the main¬ tenance of intensive man-fly contact as the game population was quite small and scattered (Swynnerton 1923, 1925). Davey and McClean, however, having trav¬ elled in the affected area during an investigation of the same outbreak, found ample evidence that game was quite abundant in the area (Davey 1924). From 1925 the yearly incidence of sleeping sickness in Ikoma ranged between 12 and 265 (Fairbairn 1948). The endemic situation continued until 1954 when the last 3 cases of sleeping sickness were notified from the area. It is reported that a large number of cases of sleeping sickness was diagnosed during the endemic period 1 E.A.T.R.O., Tororo, Uganda. 2 University of Guelph, Guelph, Canada. 182 Acta Tropica XXVIII, 3,1971 Epidemiology largely among goldmine workers in the Kilimafedha and associated mines in the district. One possible reason for the disappearance of the disease in the mid-fifties is that a number of mines had been closed because of their unprofitability; conse¬ quently the population moved away (Young 1968). In 1964, 2 patients suffering from sleeping sickness were notified from the Musoma District, one of them a resident of Seronera, the administrative centre of Serengeti National Park. From 1964 to date the following cases have been notified: 1 case in 1965; 4 in 1966; 6 in 1967; 14 in 1968 and 6 in 1969. Of these, 2 were tourists. The reappearance of sleeping sickness into this heavily tsetseinfested area caused some concern particularly as this area had been developed as a tourist centre. For this reason a survey of human trypanosomiasis (sleeping sickness) in the Musoma District was undertaken mainly in the Serengeti National Park, Ikoma Game Reserve and populated areas surrounding the game sanctuary particularly those to the north and north west about 10 miles from the borders of the Park. The aims of the survey were to find out the mechanism and the extent of transmission of sleeping sickness in this part of Tanzania. To achieve this objective it was necessary to examine people living in the area for evidence of parasitaemia; to examine the tsetse species so as to ascertain the rates and types of their infections and also their feeding habits; and to determine the infection rates in a limited number of game species and cattle with pathogenic trypanosomes particularly those of the Trypanosoma brucei subgroup. Full ac¬ counts of the investigations and their results are reported in this paper in four parts. In the first part an account is given of the investigations undertaken among the human population living in the survey area.