The Lambwe Valley and its people

By 1936 the Lambwe Valley, which had been heavily populated in the early years of this century, was nearly devoid of people. Population since that time has increased markedly as a result of a settlement scheme and efforts made to control and eradicate Glossina pallidipes and trypanosomiasis. The formation of a game reserve (now a National Park) prevented the completion of a tsetse eradication programme and has provided an unmolested habitat for both G. pallidipes and large numbers of game animals which act as a reservoir for trypanosomiasis. Rhodesian sleeping sickness, as well as animal trypanosomiasis, have been severe problems for the local farmers who live around the boundaries of the National Park.

Sleeping sickness in the Lambwe Valley in 1978

Even though tsetse control measures were discontinued in the Lambwe Valley in 1974 the prevalence of Rhodesian sleeping sickness remained at low levels. A survey conducted in 1978 verified a low prevalence of disease (0.1%). Thirty-four per cent of the individuals tested were positive for malaria with the highest prevalence (44%) in children aged 0-9 years. Thirteen of 1340 individuals (0.97%) tested and found negative for sleeping sickness in 1978 developed the disease by 1985. Fourteen individuals with moderate titres (2+) in the IFAT but who showed no evidence of disease were traced and found to be alive and well seven years later. Three of these patients still had positive titres but the others had converted to negative. Sera from four patients infected and treated in 1978 were also positive, but only one of five patients treated in 1977 reacted in the test. The CFT as described did not appear useful as a diagnostic test.

Diagnosis of Rhodesian sleeping sickness in the Lambwe Valley (1980-1984)

In primary Rhodesian sleeping sickness patients, parasitological diagnosis was best performed by rodent inoculation of blood (98.5%+) followed by Giemsa-stained thick blood smears (93.3%+). Parasitological diagnosis in relapse patients was sometimes impossible and clinical diagnosis based on CSF examination was necessary. Early during a disease outbreak in 1980, 89% of the infections were detected by mobile field teams, but once established in the endemic area a stationary diagnostic facility detected most of the cases. A total number of 23,751 examinations for Rhodesian sleeping sickness and malaria were made by mobile field teams during 1980-1984; 102 primary cases (0.43%) and 25 (0.10%) relapse cases were diagnosed. A total of 9339 individuals (39%) had patent malaria infections. The IFAT was positive in 89% of the primary sleeping sickness patients and 77% of the relapse patients. Seventy-nine per cent of the primary patients were positive in a CFT test, and 77% of the relapse patients were considered positive.