Efficacy of different surveillance tools for leishmaniasis vector sand flies; A comparative field-based study

Abstract

Sand flies (Diptera: Psychodidae) are a significant public health concern due to their role as vectors of leishmaniasis. Although leishmaniasis was declared a notifiable disease in 2008, there is no systematized surveillance program to detect the abundance of vector sand flies. Therefore, this study was aimed at evaluating the suitability of different surveillance techniques to be used in a vector surveillance program in Sri Lanka. Entomological surveys were conducted monthly from December 2023 to June 2024 in two selected MOH areas, Divulapitiya and Mirigama in Gampaha District, Sri Lanka. Surveillance techniques used in this study included cattle baited net traps (CBNT), collection by hand (HC), light traps (LT) with 6 different sources (UV, white, green, blue, red, incandescent), human-baited double net traps (HDNT) and sticky traps (ST) with 5 colors (white, green, yellow, red, black). The sand fly densities were calculated for each month as per trap densities. A one-way ANOVA was conducted to compare the effectiveness of the different traps. A total of 732 sand flies (219 females, 513 males) from 6 species were found: Phlebotomus argentipes (44.0%), Sergentomyia zeylanica (52.9%), Sergentomyia punjabensis (2.3%), Sergentomyia dentata, Phlebotomus stantoni, and Sergentomyia rudnicki (each 0.3%). Males were predominant in all traps except in HDNTs. The highest species diversity was obtained from LTs although density was higher in CBNT (18.14 per trap) followed by HC (5.15), LT (4.25), HDNT (1.3) and ST (0.18). Mean captures in trap types were significantly different (P< 0.05). In LT sources, UV was identified as more attractive (43.9%; n=68) and white color STs were more productive for sand fly collection (65%; n=13). In conclusion, CBNT provides a higher collection rate. The LTs may be indicative of the diversity of the sand flies in an area. This study concludes to have a combination of different techniques to determine the diversity and abundance of vector sand flies.