An investigation of the distribution of dengue vector
Aedes in the main urban areas of 129 counties (cities, districts) of Yunnan province, China
Objective To investigate mosquito in Yunnan province, China, as well as the population density, distribution, regional differences, and breeding habits of
Aedes aegypti and
Ae. albopictus in main urban areas.
Methods Breteau index (BI) was used to investigate
Aedes in the main urban areas of 129 counties, cities, and districts of Yunnan province, and all water containers in residential areas and special places (including park and green spaces in the urban area, recycling stations, tire collection stations, and hospitals) were checked. Water containers infested with larvae or pupae of
Aedes vector were marked as positive, and the larvae in positive containers were collected and morphologically identified. Descriptive statistics was used to describe general information; the Chi-square test was used to investigate the difference in
Aedes breeding sites between different areas and ecological environments, and the Chi-square test for trend was used to investigate the association between altitude and mosquito breeding density.
Results Among the 129 counties, cities, and districts of Yunnan province, 71 (55.04%) were found to have
Aedes vector, among which 68 (52.71%) were found to have
Ae. albopictus alone and 3 (2.33%) were found to have both
Ae. aegypti and
Ae. albopictus. A total of 37 198 households were investigated, among which 1 068 households were positive for
Aedes; a total of 167 206 water containers were found, among which 2 135 were positive, with a mean BI of 5.74, a house index of 2.87%, and a container index (CI) of 1.28%. Special places had significantly higher BI and CI than residential areas (
2=4 509.220 and 128.591, both
P<0.001). Tires were the most common type of water container and accounted for 44.84%, followed by other temporary containers (12.55%) and buckets (13.64%). Tires had the highest positive rate of 1.73%, followed by buckets (1.25%), other temporary containers (1.02%), waste bottles (0.95%), pool (0.59%), other permanent containers (0.56%), and vase (0.48%). In terms of water containers, Dehong Dai and Jingpo autonomous prefecture had the highest positive rate of 8.72% (583/6 689), followed by Honghe Hani and Yi autonomous prefecture (285/10 053, 2.83%), Xishuangbanna Dai autonomous prefecture (124/4 587, 2.70%), Wenshan Zhuang and Miao autonomous prefecture (271/10 662, 2.54%), and Pu'er city (308/12 691, 2.43%). Among the 2 135 positive containers, 1 849 (86.60%) were found to have
Ae. albopictus, 251 (11.76%) were found to have
Ae. aegypti, and 35 (1.64%) were found to have both
Ae. albopictus and
Ae. aegypti. The composition of
Ae. aegypti was 79.66% in Mengla county, 67.03% in Ruili city, and 34.55% in Jinghong city, and there was a significant difference between them (
P<0.001). The Chi-square test for trend showed a linear relationship between
Aedes breeding rate and altitude (
Aedes breeding rate gradually decreased with the increase in altitude.
Ae. albopictus is widely distributed in Yunnan province and
Ae. aegypti has become the dominant species in some areas. Special places have a higher breeding rate of
Aedes than residential areas, and border regions tend to have a high mosquito density. The density of
Aedes vector gradually decreases with the increase in altitude, and no
Aedes breeding is observed in the places with an altitude above 2 000 m. Buckets, tires, and waste cans are the main contributors for
Aedes breeding in residential areas, while tires and other waste containers are the main contributors for
Aedes breeding in special places.