A PROSPECTIVE SEROEPIDEMIOLOGIC STUDY OF VISCERAL LEISHMANIASIS IN BARINGO DISTRICT, RIFT-VALLEY PROVINCE, KENYA

The incidence of visceral leishmaniasis (VL) was studied in 30 clusters with an average of 98 individuals in each cluster in a defined, endemic rural area of Baringo District, Kenya. The clusters were centred around recent cases of VL. Anti-leishmanial antibodies were measured by the direct agglutination test (DAT) and a clinical examination was performed on 2 occasions between April 1991 and May 1993. Of 2934 individuals tested by the DAT during the first visit, 78 (2.7%) were seropositive, 54 with and 24 without a history of VL. The seroconversion rate was 9/1000 person-years of observation (95% confidence interval 5.1-12.92) among 2332 seronegative individuals retested the following year. During the entire study period, VL was diagnosed in 10 patients, with an incidence rate of 2.2/1000 person-years of observation (95% confidence interval 0.8-3.6). Household contacts of individuals with previously confirmed VL had a higher frequency of DAT positivity than the rest of the population. This difference was significant for both sexes. These results suggest transmission in and around houses.