Field investigation of Aedes vectors during dengue outbreak in Araceli, Palawan, the Philippines

บทคัดย่อ

Importance of work: In mid-2023, the municipality of Araceli in Palawan, the Philippines,
experienced a major dengue outbreak, prompting an urgent field entomological investigation.
Objective: To determine the density, distribution and breeding habitats of Aedes mosquito
vectors in the two most affected barangays (the smallest administrative divisions in the
Philippines) of Poblacion and Dagman to inform evidence-based control strategies.
Materials and Methods: In total, 279 structures were surveyed, followed by the collection
of both immature and adult mosquitoes in the two barangays in Araceli. These samples were
identified morphologically per container and per house. In addition, all female Aedes vectors
collected were tested for dengue virus detection based on real-time polymerase chain reaction (PCR).
Results: In total, 3,439 mosquito specimens were collected, comprising larvae (74.41%), pupae
(12.88%) and adults (12.71%). Aedes aegypti (Linnaeus, 1762) and Aedes albopictus (Skuse,
1894) were the predominant species identified. Key breeding containers were mainly outdoor
artificial water storage items such as pails, drums and discarded items. The entomological
indices—House Index (HI), Container Index (CI), Breteau Index (BI), Pupal Index (PI),
Pupae per Person Index (PPI) and Adult House Index (AHI)—all exceeded national and World
Health Organization threshold values, confirming high dengue transmission risk. Two-sample
proportion tests revealed no significant differences in larval indices between households with
and without dengue history (all p > 0.05); however, lower AHI (p = 0.041) and PPI (p = 0.006)
values in the case-history households suggested post-intervention suppression.
Main findings: Although no dengue virus was detected in adult mosquitoes based on PCR
analysis, the sustained presence of vectors suggested ongoing transmission potential. These
f
indings underscore the importance of integrating larval, pupal and adult surveillance, insecticide
resistance monitoring and community engagement into local vector control programs.