Relationships between dengue vector abundance, household water storage practices and new water supply infrastructure in southern Vietnam

Phuc Hau Tran (2011). Relationships between dengue vector abundance, household water storage practices and new water supply infrastructure in southern Vietnam PhD Thesis, School of Population Health, The University of Queensland.

       
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s4126977_PhD_finalthesis.docx Final thesis Word document Click to show the corresponding preview/stream application/vnd.openxmlf... 9.46MB 3
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Author Phuc Hau Tran
Thesis Title Relationships between dengue vector abundance, household water storage practices and new water supply infrastructure in southern Vietnam
School, Centre or Institute School of Population Health
Institution The University of Queensland
Publication date 2011-03
Thesis type PhD Thesis
Supervisor Brian Kay
Peter O'Rourke
Jon Adams
Total pages 201
Total colour pages 21
Total black and white pages 180
Subjects 11 Medical and Health Sciences
Abstract/Summary The container-breeding mosquito Aedes aegypti (L.) is the major global vector of dengue. In Vietnam, proliferation of this mosquito species has been favoured by poor water supply which forces residents to store water in containers, or poor sanitation or refuse collection, which results in the accumulation of potential water-holding discards suitable as larval habitats. In rural areas in Vietnam, water for household use is often stored in 50 – 2,000 litre artificial containers, most of which are not insect proof and therefore provide suitable development sites for Ae. aegypti immatures. These water storage containers usually account for > 90% of all infested containers and > 95% of the immature productivity. Since 2000, the Government of Vietnam has committed to providing rural communities with increased access to safe water through a variety of household water supply schemes including water tanks and jars and piped water, with the aim of providing 85% of rural households with access to at least 60 litres of water per person per day. The effect of new infrastructure (tanks, jars and piped water) on householder water-storage behaviours and dengue vector abundance is unknown. To understand community behaviours and perceptions relating to their preferred water source, water storage practices and water usage patterns, nine focus group discussions (FGDs) were conducted in three communes located in the Mekong Delta area in southern Vietnam. Through FGDs, most participants identified poorly screened or uncovered water containers (including household water storage containers and other types of artificial containers) as habitats for mosquitoes that transmit dengue viruses, and thereby demonstrated a clear understanding of the links between household water storage practices and the threat of dengue. These qualitative analyses also revealed broader community-based concerns about the limited availability of water and strong preferences for storage of rainwater based upon perceptions of cost, quality and security of supply. These perceptions were central to shaping householders’ responses to water infrastructure projects. The limited availability of water during the dry season and insufficient numbers of water storage containers were over-riding community concerns which provided an important context to understanding community behaviour and responses to public health interventions against dengue. Understanding such concerns will help to maximise the benefits of future water supply projects and to inform potential intervention methods for dengue. To quantify effects of the new water supply infrastructure (WSI) on households' water storage and usage patterns and entomological risk factors for dengue, a quantitative cohort study was undertaken in houses that received new WSI. The study revealed that large tanks provided by the water supply project represented a significant proportion of householders' water storage capacity (23 –65% of total water storage), however they represented a disproportionally low contribution in terms of production of Aedes aegypti immatures (0 – 20.8% III/IV instars; 0 – 11.8% pupae), compared with other types of containers such as standard jars > 100 litres (48.5 – 90.9% III/IV instars; 66.3 – 98.2% pupae). Interestingly, householders stored significant volumes of tap water in their containers, particularly in standard jars (tap water represented between 15 – 51 % of water held in standard jars) in both dry and wet season. Standard jars accounted for 60 – 100% productivity of immatures of all container types in households receiving tap water. Moreover, standard jars holding tap water accounted for 23 – 46% III/IV instars and 42 – 50% pupae. Although many containers were covered with fitted lids, up to 11% of project tanks with lids and 19% of standard jars with lids were positive for III/IV instars. Lids were absent or became damaged and ill-fitting soon after installation. This raised a policy question as to whether the provision of lids is sound expenditure in water supply schemes. The entomological surveys also showed that project tanks that were positive for Mesocylops spp. were less likely to be infested with Ae. aegypti immatures. Mesocyclops and fish were found in 13 – 26% of tanks and 9 – 18% of standard jars in the three communes. The former had been inadvertently introduced by water transference from river to container probably during the tank conditioning process, whereas fish had been added as a local attempt by some householders to effect control. These naturally occurring organisms could be developed further into community-based biological control programs against immatures of dengue mosquitoes in the Mekong Delta area in Southern Vietnam. From these investigations, it is evident that future water supply programs should consider: a) improving the reliability of tap water supplies to minimise the need for householders to store tap water in containers; b) devising effective container designs that are acceptable to householders in terms of accessibility and durability, and also offer protection from infestation with dengue mosquito immatures; c) and providing practical instructions to householders regarding protection of their existing containers against Aedes mosquitoes.
Keyword household water supply, water storage, dengue, quantitative research, qualitative research, entomology, Aedes aegypti immatures
Additional Notes Pages that should be printed in colour: 8-9, 13, 27, 35-38, 55, 57, 59, 64, 68-69, 82, 97-99, 112, 118, 125 Pages that should be printed in lanscape: 8, 10, 26, 55, 57, 59, 62, 67-69, 81, 83, 103, 106-107, 109, 111, 117, 131-132, 137-138

 
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Created: Fri, 01 Jul 2011, 18:19:05 EST by Mr Phuc Hau Tran on behalf of Library - Information Access Service