Field evaluation of entomological surveillance techniques for leishmaniasis vector sand flies (Diptera: Psychodidae)

Leishmaniasis remains a major public health concern in Sri Lanka, as emphasized in the first National Strategic Plan for the Prevention and Control of Leishmaniasis. The lack of a systematic surveillance plan was identified as one of the key challenges to implementing a control programme. Therefore, this study evaluated the efficacy of different entomological techniques for leishmaniasis vector surveillance. Monthly collections were conducted from December 2023 to June 2024 in two Medical Officer of Health areas, Divulapitiya and Mirigama, in the Gampaha District. The surveillance techniques included Cattle Baited Net Trap (CBNT), Hand Collection (HC), Light Trap (LT) with six different light sources (UV, white, green, blue, red, incandescent), Human-baited Double Net Trap (HDNT), and Sticky Trap (ST) with five different colours (white, green, yellow, red, black). A one-way ANOVA was used to compare trap efficiency. A total of 732 sand flies (219 females and 513 males) of six species were collected: Phlebotomus argentipes (43.98%), Sergentomyia zeylanica (52.87%), Sergentomyia punjabensis (2.33%), Sergentomyia dentata (0.27%), Phlebotomus stantoni (0.27%), and Sergentomyia rudnicki (0.27%). Males predominated in all traps except HDNT. The highest species diversity was obtained from LTs, while sand fly density was highest in CBNT (18.14 per trap), followed by HC (5.15), LT (4.25), HDNT (1.3), and ST (0.18). The CBNT was most effective for evaluating sand fly abundance in the study area, while the LT was productive in determining species diversity. The findings of this study emphasize the importance of integrating multiple surveillance techniques to improve the accuracy and effectiveness of leishmaniasis vector monitoring in Sri Lanka.