Human visceral leishmaniasis: Seroprevalence survey of asymptomatic adults in an endemic area of Northwestern Iran

Visceral leishmaniasis (VL) or kala-azar is a protozoan disease caused by some species of Leishmania donovani complex. Mediterranean type of the disease is endemic in various parts of Iran. A cross-sectional study was designed to determine the seroprevalence of VL among asymptomatic adult population in Meshkin-Shahr area from the Northwest of Iran as an endemic focus of VL.
Methods & Materials: Altogether, 180 blood samples were collected from asymptomatic adults’ population throughout 2015. Before sampling, a questionnaire was separately completed for each individual. All the collected blood samples were examined by direct agglutination test (DAT) after plasma separation. Anti-Leishmania infantum antibodies at titers 1:100 to 1:1600 was considered as L. infantum infection, while the cut-off titer of ≥ 1:3200 with specific signs and symptoms was considered as VL.
From 180 collected plasma samples, nine (5%) of them showed anti-Leishmania antibodies at titers 1:400 and higher. Distribution of anti-Leishmania antibodies titers was 1:400 (n = 2), 1:800 (n = 4), and 1:1600 (n = 3). All of the seropositive cases were observed among females. All the seropositive individuals had not a history of kala-azar. The highest seropositivity rate was observed among the age group of 13-23 years old. No changes in titers of anti-Leishmania antibodies observed after collected the seropositive blood samples again and tested by DAT with 1-month interval.
Visceral Leishmania infection is relatively high among adult people reside in Meshkin-Shahr area without any clinical manifestations. Asymptomatic VL infection is very important in immunocompromized individuals such as HIV-positive cases; these patients are at risk to manifesting clinical signs and symptoms of VL. Therefore continuing serological surveillance for detection of visceral Leishmania infection should be recommended in the endemic foci of VL.