Altitudinal cross-sectional study of the sand fly fauna of the highlands of Tigray Region, northern Ethiopia.

BACKGROUND: Cutaneous leishmaniasis (CL), caused by Leishmania aethiopica and transmitted by Phlebotomus longipes, is endemic in northern Ethiopia. However, sand fly fauna is poorly documented in the northern Tigray region. High-altitude CL cases have also been observed, but their local acquisition is uncertain. To identify the faunal composition, their geographical and altitudinal distribution, cross-sectional surveys were conducted in ten villages (average altitude range: 2411 - 3186 meters) with confirmed CL cases across four endemic districts of the region. A total of 170 light trap-nights and 1700 sticky trap-nights of sand fly collections were made.

RESULTS: Totally, 1477 sand flies (52% males & 48% females) comprising five species of Phlebotomus (38%) and six species of Sergentomyia (62%) were identified morphologically. The Phlebotomus species included Phlebotomus longipes (73%), one confirmed (Phlebotomus sergenti (6%), and two potential vectors of Leishmania tropica: Phlebotomus arabicus (18%), and Phlebotomus guggisbergi (2%); the latter is a new record for Ethiopia. Phlebotomus longipes is widely distributed and predominated in caves (43%), animal sheds (28%), and bedrooms (15%). Phlebotomus longipes and three Sergentomyia species were found at average elevations reaching 3186 meters, setting a new altitude record for Ethiopia. Phlebotomus arabicus was also found up to 3045 meters in hyrax habitats.

CONCLUSION: The risk of CL in Tigray reaches up to 3200 meters. Phlebotomus longipes habitats suggest the potential for domestic and peri-domestic transmission of CL. Further research is needed to determine if the new high-altitude presence of the sand fly species is due to climate change or other factors.