Comparative studies on bionomics and behavior of phlebotomine sandflies in highland and lowland areas of kala-azar transmission, northwest Ethiopia

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Addis Ababa University


The aim of this study was to investigate and compare the bionomics, ecology and behaviors of the vector (s) of visceral leishmaniasis (VL) in two endemic and ecologically distinct areas of northwestern Ethiopia. This included species composition, population dynamics, habitat preference, host preference, vectorial potential and nocturnal activity studies in the field. Phlebotomine sandflies were collected using CDC light traps, sticky traps and pyrethrum space spray catches from Libo-Kemkem district (May 2011-April 2012) and Metema district (October 2012-September 2013). A total of 51,411 sandfly specimens were collected: 10,776 from highland and 40, 635 from the lowland areas. Seven species were found in the highland area: two Phlebotomus sandflies (P. orientalis and P. rodhaini) and five Sergentomyia species, whereas 19 species were found in the lowland area: six Phlebotomus (P. orientalis, P. rodhaini, P. bergeroti, P. duboscqi, P. papatasi and P. martini) and 13 Sergentomyia species. Of the Phlebotomus spp., P. orientalis was the predominant species in both the highland (99.9%) and lowland (93.7%) areas. In both areas, this species showed seasonal a occurrence and mainly abundant during the dry months (March-May/June) of the year and increasing in numbers till the rains began, when numbers dropped dramatically. In both areas, P. orientalis exhibits both strong exophilic and exophagic behaviors and its parous rates of the species were 45.6% and 66.2% in highland and lowland, respectively. Identification of blood meals in wild caught blood fed P. orientalis using cytochrome b polymerase chain reaction (Cyt b –PCR) and reverse iv line blotting (RLB) and enzyme linked immunosorbent assay (ELISA) showed that this species has strong predilection for bovine in both the highland (67.8%) and the lowland (49.8%) areas. A total of 1087 P. orientalis from the highland area and 344 Phlebotomus spp. from lowland area were dissected for detection of natural infection, but none of them was infected. A similar result was obtained in 347 P. orientalis females processed using PCR for detection of L. donovani from the highland area. Hourly activity period of the two populations of P. orientalis showed variation. The nocturnal activity of P. orientalis in the highland peaked between 22:00 and 23:00hours for both sexes; whereas in the lowland area, this peak was between 3:00 and 4:00hours. Although natural infection was not detected in the current study, P. orientalis is strongly implicated as vector of VL in both study areas due to its abundance and other circumstantial evidences. Therefore, control of the disease in these particular areas should involve tools that mainly target the vector of the disease by considering its seasonal abundance, ecology and behaviors in the respective areas



Comparative studies on bionomics, and behavior of phlebotomine