Understanding sand fly sampling methods: sticky traps are attraction-based and not interceptive sampling tools of...

Area of Science:

• Medical entomology
• Vector-borne disease research
• Behavioral ecology

Background:

• Sticky traps are commonly used for sand fly sampling, but their mechanism (interception vs. attraction) is not experimentally proven.
• Phlebotomus orientalis is the primary vector of visceral leishmaniasis in East Africa.
• Previous assumptions about sticky trap functionality lacked experimental evidence.

Purpose of the Study:

• To experimentally determine if sticky traps function as interceptive or attractive sampling tools for Phlebotomus orientalis.
• To investigate the reasons behind the highly male-biased collection observed with sticky traps.
• To provide insights for optimizing sand fly vector surveillance strategies.

Main Methods:

• Field experiments were conducted in Sudan from 2016-2019.
• Compared sand fly capture rates on sticky traps of different colors (black, red, transparent, white, yellow, green, blue) under varying lunar light conditions.
• Evaluated trap placement (horizontal/vertical on ground, horizontal on stool) and observed mating behavior on non-sticky surfaces.

Main Results:

• Phlebotomus orientalis showed significant attraction to white, yellow, and transparent traps, with minimal catch on black and red traps.
• Horizontal trap placement on the ground yielded 8-fold higher efficacy than vertical placement; elevated placement reduced attraction.
• Males successfully lured females for copulation on un-sticky surfaces, a process hindered by sticky oil on traps.

Conclusions:

• Sticky traps for P. orientalis operate primarily as attractant-based tools, not solely interceptive.
• Male sand flies use trap surfaces for mating displays, attracting females.
• The sticky nature of the traps interferes with mating rituals, leading to low female capture rates and biased sex ratios.