Nocturnal activity of Phlebotomus species (Diptera: Psychodidae) in a visceral leishmaniasis endemic area of northwest Ethiopia

Abstract

Phlebotomus orientalis is the most likely vector of Leishmania donovani causing visceral leishmaniasis in northwest Ethiopia. Understanding of sand fly night activities is very essential to design appropriate sand fly control methods in order to reduce Leishmania infection. The aim of this study was to determine the nocturnal activity of Phlebotomus species. This study was conducted for six consecutive months from January to June 2013 in Adebay village where visceral leishmaniasis is endemic. Sandflies were collected using CDC Light traps changed at one hour interval, in periphery village (peridomestic area) and farm field. The traps were activated from 18:00 to 7:00 hours. Overall, 5,902 sandflies were collected. Eight Phlebotomus species representing four subgenera were indentified: Phlebotomus (Larroussius) orientalis, P.(Phlebotmus) papatasi, P.(Phlebotmus) bergeroti, P. (Phlebotomus)duboscqi, P. (Paraphlebotomus) alexanderi, P. (Anaphlebotomus) rodhani and other two Parvidens species(P. lesleyae and P. heischi). Among eight species of sand flies collected P.orientalis were the most predominant species followed by P. papatasi and P. lesleyae. The result indicated that female and male P.orientalis showed similar activity pattern (19:00-05:00hrs). Both sexes were active throughout the night (19:00-06:00 hours), reaching a peak between 01:00 and 03:00hrs (mean density of 16.46 females/trap/hour/night; and 33.83 males/trap/hour/night). Male P. papatasi were the dominant having two peaks, an early smaller peak between 21:00-22:00 hrs and a larger second one around midnight (24:00-02:00 hrs). Females displayed similar activity patterns, with an early peak at 21:00-22:00 and a late smaller peak at 02:00-03:00 hours. Hourly collections of P.orientalis and P. papatasi, the corresponding temperatures revealed no significant correlations. In conclusion, P.orientalis and P. papatasi remained active throughout the night. High risk of VL transmissions is likely concentrated during the peak hours and local inhabitants could reduce the risk of infection by using appropriate personal protective measures such as repellents and bed nets.

Keywords: visceral leishmaniasis, Phlebotomus species, nocturnal activity, northwest Ethiopia