CAO Yang, WEI Ling-ya, WANG Hui-min, KONG Qing-xin
Objective To study the correlation between the Breteau index (BI) method, double mosquito net method, and lamp trapping method, and to explore the applicability of these surveillance methods for larval and adult mosquitoes in the urban environment of Hangzhou, Zhejiang province, China. Methods We selected five urban districts of Shangcheng, Xiacheng, Xihu, Jianggan, and Gongshu in Hangzhou as surveillance points, and conducted surveillance two times, respectively, in the first and last ten days of each month from April to November of 2017 and 2018. The density of immature mosquitoes was surveyed by the BI method and the density of adult mosquitoes were surveyed by the double mosquito net method and lamp trapping method. BI, double mosquito net index(DMNI), and lamp trapping mosquito index (LTMI) were calculated. The correlations between these surveillance indicators were analyzed by Spearman rank correlation. Results During April to November, 2017, seasonal variation in BI of Hangzhou showed a single-peak pattern, with BI gradually increasing from April to June and then declining rapidly from July to November; the change in LTMI also displayed a single-peak pattern, with the peak at 2.05 mosquitoes/trap·night in June; the DMNI increased gradually from April to June, reaching a maximum of 2.93 mosquitoes/net·hour in June; in 2017, BI, DMNI, and LTMI averaged 9.28, 1.41 mosquitoes/net·hour, and 0.97 mosquitoes/trap·night, respectively; there was a positive correlation between BI, DMNI, and LTMI (BI and DMNI, rs=0.398, P=0.012; BI and LTMI, rs=0.681, P<0.001; DNMI and LTMI, rs=0.517, P=0.001). During April to November, 2018, BI in Hangzhou was generally at a low level, and there was no obvious seasonal variation; LTMI showed a single-peak pattern, with the peak at 1.06 mosquitoes/trap·night in September; DNMI increased gradually from April to July, reaching a maximum of 4.88 mosquitoes/net·hour in July; BI, DNMI, and LTMI in 2018 averaged 3.83, 2.39 mosquitoes/net·hour, and 0.53 mosquitoes/trap·night, respectively; there was a positive correlation between DNMI and LTMI (rs=0.478, P=0.002), but neither of the two indicators was correlated with BI (BI and DNMI, rs=0.249, P=0.122; BI and LTMI, rs=0.165, P=0.308). Conclusion There is a certain correlation between surveillance methods for larval and adult mosquitoes, and both types of surveillance methods can effectively reflect the abundance of mosquito vectors in urban areas. At the same time, mosquito surveillance methods are susceptible to external conditions, and should be used under strict quality control.
