Assessment of Dengue Fever Emergency Control Task Carried Out in Kaohsiung City in 2006

Wei-Tai Hsia

2008 Vol.24 NO.1

Correspondence Author： Wei-Tai Hsia

Abstract：

The objective of this emergency control task was to rapidly eradicate local virus-borne female mosquitoes to interrupt the route of transmission for an indigenous dengue fever endemic. All measures taken during this task were centered on this purpose.
This study aimed to evaluate the efficacy of an emergency pesticide spray operation for dengue fever carried out in Cianjhen and Lingya Districts of Kaohsiung City in 2006 using knockdown rate, mortality rate, adult mosquito index, relative control efficiency, and dosage of pesticide used. The results showed that after applying the two commercially available pesticides, “Perdelta E.C.” and “Deltamethrin 2.8% E.C.,” (both using the same type of thermal fogger (PulsFog K10)) to Cianjhen and Lingya Districts respectively, the knockdown and mortality rate of Aedes aegypti L. in either district were above
90%. However, the disease control in a few households was not satisfacfied,
probably due to inexperienced workers with unfamiliar spraying techniques leading to insufficient pesticides used. In the meantime, within one day of the spray operation, the adult pest index dropped rapidly to a zero reading, making an 100% relative control efficiency. However, if the breeding source was not eliminated after the first two days of spray operation, the mosquito density would rise again, subsequently making the relative control efficiency dropped back to around 65%. Furthermore, there was noticeably a significant difference from the actual flow or output rate of the thermal fogger (p < 0.05) to the original machine specification when the real amount of pesticide applied at each household site was measured during the spray. Also, the spray workers tended to make the pesticide solution in somewhat higher concentration than instructed. And to make things worse, some spray workers were not properly trained. These factors resulted in somewhat uneven spray quality across the board, with a common tendency for over spraying (from 1 up to 8 times of the intended amount). In conclusion, despite evidence showing drug resistance has occurred with the local Aedes aegypti L. mosquito population in Kaohsiung’s Cianjhen and Lingya Districts, with correct decisions made by the city government, right timing of the pesticide spray operation, plus Taiwan CDC’s on-site instruction to improve the workers’ spray skills, the overall outcome of this operation was seen as successful and effective in preventing the dengue fever endemic from getting worse.
Keywords: Aedes aegypti L., drug effect evaluation, control efficiency, adult mosquito index