Epidemiological and entomological survey in a focus of visceral leishmaniasis in Pap district (Fergana Valley) of Namangan region, Uzbekistan

Abstract

An active focus of human visceral leishmaniasis (VL) is present in Uzbekistan, Namangan region, Pap district, situated along the Fergana Valley at an altitude of 900–1300 m a.s.l. An overall total of 19 VL cases, all recorded in children less than 14 years of age, have been reported during the period of 1987–99 in three villages, namely Oltinkon (9 cases), Chodak (7 cases) and Guliston (3 cases). Clinical and epidemiological features suggest that the disease is zoonotic in nature and that it is possibly caused by Leishmania infantum, though no characterization of the causative agent was performed due to the failure in isolating the parasite. Currently, diagnosis is made exclusively on the basis of clinical manifestations followed by demonstration of parasites in bone marrow aspirates. Standardized monthly sandfly collections (July–September 1999) were made with sticky traps and hand captures from houses and peri-domestic areas. Twenty houses were monitored over two consecutive days every month in five villages scattered along the valley, three of which were the VL foci (Oltinkon, Chodak, Guliston) and the other two, Kandigan and Khonabad, were located at the top (>1300 m a.s.l.) and at the bottom of the valley (740 m a.s.l.), respectively. Among the sandfly species identified, Phlebotomus sergenti (46.0%) was the most prevalent species through the entire period, followed by P. papatasi (18.8%), P. longiductus (15.5%), P. alexandri (10.3%), P. angustus (6.6%), S. sumbarica (2.2%), P. keshishiani (0.6%) and S. grekovi (0.1%). The role of the suspected vector, P. longiductus in the transmission of VL cases in the Fergana focus is discussed in relation to its abundance and distribution in the valley.