The roles of Phlebotomus martini and P.celiae (Diptera: Phlebotominae) as vectors of visceral leishmaniasis in the Aba Roba focus, southern Ethiopia

Abstract

During field studies (December 1988 to April 1990) to determine the vectors of visceral leishmaniasis (kala-azar) in the Aba Roba (Segen Valley) focus of southern Ethiopia, a total of 40,770 sandflies (Diptera: Psychodidae: Phlebotominae) were collected and identified as six species of Phlebotomus and seventeen Sergentomyia spp. Nine of these species were anthropophilic (four Phlebotomus and five Sergentomyia spp.), the dominant being Phlebotomus (Synphlebotomus) martini, P.(S.)celiae and Sergentomyia (Sergentomyia) schwetzi. P.celiae adult populations increased during the rainy season. Of 2326 P.martini and 1044 P.celiae dissected, the parous rate was 29.9% and 24.4%, respectively. Leishmania promastigotes were detected in sixteen P.martini (eleven identified as L.donovani by isoenzyme analysis and/or a DNA probe) and in three P.celiae (two identified by DNA probe), giving overall infection rates of 0.7% (1.9% parous infection rate) and 0.3% (1.2% parous infection rate), respectively. Four isolates from P.martini were typed by their isoenzyme profile as L.donovani zymodeme MON-37 = LON-44, identical to one of the zymodemes isolated from patients in this focus. This is the first evidence that P.celiae is a vector and the first time that P.martini has been implicated in Ethiopia. Based on observations of abundance, seasonality and prevalence of infection of the two Synphlebotomus spp., it is concluded that P.martini is the major vector and P.celiae a secondary vector in the Aba Roba focus. The risk of infection with L.donovani is greatest during the wet season.