Epidemiology and clinical manifestations of Leishmania donovani infection in two villages in an endemic area in eastern Sudan.

We conducted a longitudinal study in an endemic area for visceral leishmaniasis (VL) in eastern Sudan to compare the epidemiology and clinical spectrum of Leishmania donovani infection in two populations differing in ethnic background and duration of residence in the area. The study took place in two villages from April 1994 to April 1996. In Um-Salala village, which is inhabited by members of the Masaleet tribe, half of the villagers had previous exposure to cutaneous leishmaniasis (Leishmaria major) before moving there. The population of the second village, Mushrau Koka, belong to the Hausa tribe and most were born there. The incidence of VL was 20.4/1000 person-years in 1994/1995 and increased sharply to 38.3/1000 person-years in 1995/1996 in Um-Salala. A rise in the incidence of VL was also observed in Mushrau Koka but with a lower incidence, 3.3/1000 person-years to 4.6/1000 person-years. The incidence rate of confirmed VL reflects only a limited part of the total infection rate which includes various forms of subclinical infection. The ratio of clinical to subclinical infection in Um-Salala was 1.2 : 1 in 1994/1995 compared with 2.6 : 1 in 1995/1996. This ratio was 1 : 11 in 1994/1995 and 1 : 2.5 in 1995/1996 in Mushrau Koka. In both villages the mean age of subclinical cases was higher, but in Mushrau Koka the mean age of subclinical cases also was higher than that of subclinical cases in Um-Salala. The leishmanin skin test (LST) was positive in 56% of individuals in Um-Salala and in 33% in Mushrau Koka. VL only occurred in leishmanin-negative individuals. Post kala-azar dermal leishmaniasis (PKDL) followed in 58% of confirmed VL patients in Um-Salala; the low incidence of VL for Mushrau Koka did not permit to estimate a PKDL rate. The clinical manifestations resulting from exposure to L. donovani range from subclinical infection to VL and PKDL. No firm conclusion as to the difference in incidence of VL between the two villages could be reached but differences in exposure to VL and cutaneous leishmaniasis (CL) as well as other factors such as ethnic background and differences in nutritional status may play a role.