Comparison of four outdoor trapping methods as alternatives to human landing catch for Anopheles surveillance

Vector surveillance is a critical component of malaria control, particularly with the increasing importance of outdoor transmission. This study evaluated the performance of four outdoor trapping methods, the human landing catch (HLC), human double net trap (HDNT), human decoy trap (HDT), and UV light trap (UVLT), as potential alternatives to the HLC, which raises ethical concerns due to pathogen exposure risk for human collectors. Fieldwork was conducted over 48 nights across three seasons (cool-dry, hot-dry, and rainy) at a malaria-endemic area in Kanchanaburi Province, Thailand. A total of 3,734 mosquitoes were collected, of which 1,266 (33.90%) were identified as Anopheles species, including the primary malaria vectors: Anopheles baimaii, Anopheles dirus, Anopheles minimus, Anopheles aconitus, and Anopheles sawadwongporni. The results showed that HLC collected the highest number of mosquitoes overall. However, HDNT was the most effective method to capture Anopheles (538; 42.50%), compared with UVLT (359, 28.36%), HLC (340, 26.85%), and HDT (29, 2.29%). Due to temporal dynamics of mosquitoes, HDNT was particularly effective for collecting An. harrisoni and An. sawadwongporni across different seasons. However, HLC remained superior for capturing An. dirus s.l. The results suggest that HDNT is a promising and safer alternative than HLC for outdoor surveillance of Anopheles mosquitoes, while the use of multiple or seasonally tailored methods could further enhance surveillance strategies.