Abundance, composition, peak active-period and vertical flight range of sand flies (Diptera: Psychodidae), the vector of leishmaniasis in Kurunegala district

Background: Leishmaniasis is identified as a neglected tropical disease in the world and considered a notifiable disease in Sri Lanka. It has shown an upward trend in Kurunegala district since 2008. Studies on vector bionomics, although important for implementing effective vector control, are still limited in Sri Lanka.

Objective: To describe the abundance, composition, peak active-period and vertical flight range of sand flies in the Kurunegala district

Methods: A descriptive study was conducted in two selected disease-endemic areas in Rideegama and Ibbagamuwa Medical Officer of Health areas in Kurunegala district during February-March, 2019. sand flies were collected using different standard sampling techniques (CDC Light-traps, Sticky-traps and Cattle-Baited-Net-Traps and by hand collections). The identification of sand flies was done up to Genus level. Sticky traps were set up at different heights on walls of houses to determine the vertical flight range of sand flies. The hourly sand fly collections were used to determine the active peak times. The abundance was calculated as per trap density and hourly collections were monitored to identify peak active-period of sand flies.

Results: The total number of sand flies collected during the study period was 773. The light- traps were found to be more productive than other collection methods. The numbers of sand flies belonging to geni Phlebotomus and Sergentomyia were 525 and 248 respectively. The average vertical flight range of flies was less than two feet from the ground level. A higher percentage of sand flies was collected from outdoors (n = 74%) than indoors (n = 26%). The highest active period of sand flies was between 18.00 hr and 22.00 hr of the day, although it was slightly different in Phlebotomus (from 18.00 hr to 20.00 hr) species and Sergentomyia species (from 18.00.00 hr to 22.00 hr).

Conclusions and Recommendations: Sand flies belonging to the genus Phlebotomus and Sergentomyia were present in the area. The peak aggregation time was at night starting at 18.00 hrs in the day for both genera. The vertical flight range of sand fly was approximately less than two feet from the ground level.