Field evaluation of four commercial light traps, trap placement, and effect of carbon dioxide on phlebotomine sand fly collection in Thailand

Abstract

Background Several light trap devices have been invented and developed to assess the abundance of sand flies. Traps available in the market have different designs and attractant combinations to catch sand fly vectors. We evaluated the efficacy of four commercial light traps and determined the effect of trap placement and carbon dioxide (CO2) on sand fly collection in northern Thailand. Methods Trap evaluations were conducted at two natural caves located in Chiang Rai province, Thailand. In the first part of the study, the efficacies of four trap types including the Centers for Disease Control miniature light trap (CDC LT), Encephalitis Vector Survey trap (EVS), CDC Updraft Blacklight trap (CDC UB), and Laika trap (LK) were evaluated and compared using a Latin square experimental design. The second half of the study evaluated the influence of trap placement and CO2 on sand fly collection. Additionally, CDC LT were placed inside, outside, and at the entrance of caves to compare the number of sand flies collected. Results For the trap efficacy experiment, a total of 11,876 phlebotomine sand flies were collected over 32 trap-nights. Results demonstrated that CDC LT, CDC UB, and LK collected significantly more sand flies than EVS (P > 0.05). However, there were no significant differences between the numbers of sand flies collected by CDC LT, CDC UB, and LK. A total of 6,698 sand flies were collected from the trap placement and CO2 experiment over 72 trap-nights. Results showed that CO2 did not influence the numbers of sand flies captured (P < 0.05), whereas trap placement at the entrance of the caves resulted in collection of significantly more sand flies than traps placed inside and outside of the caves. Conclusion We found the CDC LT, CDC UB, and LK without CO2 captured the greatest amount of sand flies. This was particularly observed when traps were placed at the entrance of a cave, perhaps because of the greater passage of stimuli caused by wind flow at the entrance of the cave. The light traps in this study can be used effectively to collect sand fly vectors in northern Thailand.