Abstract
BackgroundPhlebotomus orientalis is the main sandfly vector of visceral leishmaniasis in the north and northwest of Ethiopia. CDC light traps and sticky traps are commonly used for monitoring sandfly populations. However, their trapping efficiency is greatly influenced by various environmental factors including moonlight and lunar periodicity. In view of that, the current study assessed the effect of moonlight and lunar periodicity on the performance of light traps in collecting P. orientalis.MethodsTrapping of P. orientalis and other Phlebotomus spp. was conducted for 7 months between December 2012 and June 2013 using CDC light traps and sticky traps from peri-domestic and agricultural fields. Throughout the trapping periods, collections of sandfly specimens were carried out for 4 nights per month, totaling 28 trapping nights that coincided with the four lunar phases (viz., first quarter, third quarter, new and full moon) distributed in each month.ResultsIn total, 13,533 sandflies of eight Phlebotomus species (P. orientalis, P. bergeroti, P. rodhaini, P. duboscqi, P. papatasi, P. martini, P. lesleyae and P. heischi) were recorded. The predominant species was P. orientalis in both trapping sites and by both methods of collection in all lunar phases. A significant difference (P < 0.05) was observed in the mean numbers of P. orientalis and other Phlebotomus spp. caught by CDC light traps among the four lunar phases. The highest mean number (231.13 ± 36.27 flies/trap/night) of P. orientalis was collected during the new moon phases, when the moonlight is absent. Fewer sandflies were attracted to light traps during a full moon. However, the number of P. orientalis and the other Phlebotomus spp. from sticky traps did not differ in their density among the four lunar phases (P = 0.122).ConclusionResults of the current study demonstrated that the attraction and trapping efficiency of CDC light traps is largely influenced by the presence moonlight, especially during a full moon. Therefore, sampling of sandflies using light traps to estimate population density and other epidemiological studies in the field should take the effect of moonlight and lunar periodicity into account on the trapping efficacy of light traps.
Highlights
Phlebotomus orientalis is the main sandfly vector of visceral leishmaniasis in the north and northwest of Ethiopia
A recent study in Italy [12] reported that P. perniciosus and Sergentomyia minuta were mainly collected during the full moon phases, while no significant differences in the capturing of sandflies was observed among lunar phases in Kenya [20]
The mean number of P. orientalis captured in light traps was higher than in sticky traps in paired collections; with mean ± SE of 122.06 ± 15.36 vs.6.23 ± 1.24 in light traps vs. sticky traps (Mann Whitney U-test, P < 0.05)
Summary
CDC light traps and sticky traps are commonly used for monitoring sandfly populations Their trapping efficiency is greatly influenced by various environmental factors including moonlight and lunar periodicity. Visceral leishmaniasis (VL) known as Kala-azar, caused by infection with Leishmania donovani complex is transmitted by the sandfly P. orientalis in Sudan, South Sudan, northern and south western Ethiopia [3,4,5] This species is frequently associated with Acacia-BalanitesZiziphus woodlands and vertisols (black cotton soils) [6,7]. Used techniques for monitoring sandfly populations are CDC light traps and sticky traps [8,9,10] Their trapping efficiency is greatly influenced by various environmental factors such as weather (wind speed, temperature, rainfall, relative humidity, night-length) and lunar illumination [11,12,13]. A recent study in Italy [12] reported that P. perniciosus and Sergentomyia minuta were mainly collected during the full moon phases, while no significant differences in the capturing of sandflies was observed among lunar phases in Kenya [20]
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