Ecological Dynamics of Sand Flies (Diptera: Psychodidae) in Two Leishmaniasis Endemic Foci in Sri Lanka

Background: Leishmaniasis has emerged as a significant global public health concern and has been notable in Sri Lanka since 1992, particularly in the Anuradhapura district, where Cutaneous Leishmaniasis is prevalent. The disease is caused by the Leishmania parasite, which is transmitted by sand flies of the genus Phlebotomus.
Objective: This study compared the diversity, dominance, and density of sandfly species in selected locations within the Anuradhapura and Kegalle districts.
Methods: Sand flies were collected monthly from January to March 2024 from locations identified through patient records from the Regional Epidemiologist’s unit. Collection was conducted using  cattle-baited traps (CBT), and identification was performed morphologically and through DNA analysis. Ecological indices, includ-ing Simpson’s Dominance Index for species dominance and Shannon’s diversity index for species diversity, were calculated using the collected data.
Results: A total of 154 sandflies were collected from ten locations in both areas. Among the collected samples, 87.6% (n=135) were P. argentipes and 5.19% (n=8) were P. stantoni, both of which belong to the genus Phle-botomus. Additionally, 7.4% (n=11) were Sergentomiya zelanica belonging to the genus Sergentomiya. P. ar-gentipes predominantly dominates locations in the Anuradhapura district, where Simpson’s dominance index is one (D=1), highlighting its high-risk status. In contrast, the Kegalle district showed higher species diversity with uneven distribution patterns. The Shannon Diversity Index reflected the highest diversity in Kegalle (H=0.6365), likely due to multiple species assemblages and ecological complexity.
Conclusions and Recommendations: This comparative study underscores the importance of understanding sandfly population dynamics for targeting integrated vector control strategies. Tailored vector control is essential to prevent the annual emergence of new endemic foci of leishmaniasis in Sri Lanka. This study also emphasizes the integration of environmental, entomological, and epidemiological approaches for effective leishmaniasis control in Sri Lanka.