Evidence for a long-term increase in the incidence of Leishmania tropica in Aleppo, Syria.

We report the results of a short study of the epidemiology of Leishmania tropica in the Sheikh Maksoud District of Aleppo, Syria. The present and past status of infection in a community of about 100,000 people are assessed from prevalence and incidence data obtained by active and passive case detection, and from a skin test survey. L. tropica has apparently been endemic for at least 2-3 human generations in Aleppo, and incidence has increased over the past decade. The current estimated force of infection is 0.174/year, the incidence is about 5%, and the average age of infection is 14 years. L. tropica has the essential characteristics of a cyclic infectious disease, and the recent rise in incidence could be part of a long period cycle. A survey of leishmanial scars seriously underestimated the fraction of persons immune, as scar surveys usually do. We estimate that a passive case registration scheme, which has been established in response to growing concern about leishmaniasis in Aleppo, succeeds in recording and treating about one in 4 cases.