Effect of water supply system installation on distribution of water storage containers and abundance of Aedes aegypti immatures in urban premises of Ho Chi Minh City, Viet Nam.

ABSTRACT

To assess the effect of installation of a water supply system on the distribution of water storage containers and abundance of Aedes aegypti immatures, we conducted two successive entomological surveys in October 2007 and July 2008 in an urban neighbourhood of Ho Chi Minh City, Viet Nam. In all, 850 water-holding containers, including plastic buckets, water jars, concrete basins, flower vases, ant-traps, outdoor discards, used tyres and plant saucers were observed in 122 premises. Of these, 44 premises already had a water supply system installed at the time of the first survey (i.e. control premises). In the remaining 78 premises, a water supply system was installed 3–6 months before the second survey (i.e. intervention premises). There was a drastic reduction in the number of water storage containers, except concrete basins, between the first and second surveys. We also observed that the distribution of water storage containers in the control and intervention premises was similar. This was probably because the construction of a water supply system before the second survey increased the reliability of the system not only for the residents in intervention premises but also in the control premises (i.e. increased water pressure in the water supply system). The number of plastic buckets and water jars was reduced in the second survey; however, these containers were still an important source of Ae. aegypti pupae. For effective control of dengue infection, it is necessary to conduct entomological monitoring considering the seasonal changes in vector abundance and dengue transmission threshold after installing a water supply system