Seasonal Abundance of Vectors at Outdoor Environments in Endemic and Nonendemic Districts of Dengue in Kaohsiung, South Taiwan
This study was designed to determine the seasonal variation in abundance of dengue vectors at open spaces, empty houses, parks, and markets in endemic and nonendemic districts of dengue. Ovitraps were placed in these sites from March 2003 to January 2004 in Kaohsiung Area (Kaohsiung City and Kaohsiung County), South Taiwan. The index peaked in May, June, and September in the endemic districts and in May and October in nonendemic districts. The egg production of the vectors increased from April on and peaked in September. Aedes albopictus had a significant higher proportion than A. aegypti throughout the study period and in both districts. Although ovitrap indices at open spaces, empty houses, and parks were significantly higher than those in nearby households, no significant difference was found between markets and households. Moreover, the outdoor ovitrap index was significantly higher than the indoor one. No significant difference was found between the endemic and nonendemic districts in egg production, vector maturation, vector abundance at the outdoor environments, or nearby households. These findings indicate the importance of the environmental conditions surrounding the human dwelling sites in the transmission of dengue. Measures applied to remove dengue vectors should include these sites but also outdoor environments as well.