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Water level flux in household containers in Vietnam--a key determinant of Aedes aegypti population dynamics.

Jeffery JA, Clements AC, Nguyen YT, Nguyen le H, Tran SH, Le NT, Vu NS, Ryan PA, Kay BH - PLoS ONE (2012)

Bottom Line: We calculated the probability of the water volume of a large container (>500 L) increasing or decreasing by ≥20% to be 0.05 and 0.07 per day, respectively, and for small containers (<500 L) to be 0.11 and 0.13 per day, respectively.These human water-management behaviors are important determinants of Ae. aegypti production during the dry season.This has implications for choosing a suitable Wolbachia strain for release as it appears that prolonged egg desiccation does not occur in this village.

View Article: PubMed Central - PubMed

Affiliation: Queensland Institute of Medical Research, PO Royal Brisbane Hospital, Brisbane, Queensland, Australia.

ABSTRACT
We examined changes in the abundance of immature Aedes aegypti at the household and water storage container level during the dry-season (June-July, 2008) in Tri Nguyen village, central Vietnam. We conducted quantitative immature mosquito surveys of 171 containers in the same 41 households, with replacement of samples, every two days during a 29-day period. We developed multi-level mixed effects regression models to investigate container and household variability in pupal abundance. The percentage of houses that were positive for I/II instars, III/IV instars and pupae during any one survey ranged from 19.5-43.9%, 48.8-75.6% and 17.1-53.7%, respectively. The mean numbers of Ae. aegypti pupae per house ranged between 1.9-12.6 over the study period. Estimates of absolute pupal abundance were highly variable over the 29-day period despite relatively stable weather conditions. Most variability in pupal abundance occurred at the container rather than the household level. A key determinant of Ae. aegypti production was the frequent filling of the containers with water, which caused asynchronous hatching of Ae. aegypti eggs and development of cohorts of immatures. We calculated the probability of the water volume of a large container (>500 L) increasing or decreasing by ≥20% to be 0.05 and 0.07 per day, respectively, and for small containers (<500 L) to be 0.11 and 0.13 per day, respectively. These human water-management behaviors are important determinants of Ae. aegypti production during the dry season. This has implications for choosing a suitable Wolbachia strain for release as it appears that prolonged egg desiccation does not occur in this village.

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Related in: MedlinePlus

Absolute counts of pupae every 2 days, in relation to water flux, water storage and weather conditions.
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pone-0039067-g001: Absolute counts of pupae every 2 days, in relation to water flux, water storage and weather conditions.

Mentions: For the water volume analyses, 171 containers within the 41 properties were classified as either large (>500 L, n = 119) or small (<500 L, n = 52). A variable was created to indicate water flux, categorized according to whether the volume of water had increased by >20%, decreased by >20% or neither increased or decreased by >20%, relative to the previous survey. Daily rainfall (mm) and daily minimum, mean and maximum temperatures (°C) were obtained from Nha Trang city weather station (Figure 1). June/July is the dry and hot season in central Vietnam and there were only three rain events >5 mm during the survey period.


Water level flux in household containers in Vietnam--a key determinant of Aedes aegypti population dynamics.

Jeffery JA, Clements AC, Nguyen YT, Nguyen le H, Tran SH, Le NT, Vu NS, Ryan PA, Kay BH - PLoS ONE (2012)

Absolute counts of pupae every 2 days, in relation to water flux, water storage and weather conditions.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3404066&req=5

pone-0039067-g001: Absolute counts of pupae every 2 days, in relation to water flux, water storage and weather conditions.
Mentions: For the water volume analyses, 171 containers within the 41 properties were classified as either large (>500 L, n = 119) or small (<500 L, n = 52). A variable was created to indicate water flux, categorized according to whether the volume of water had increased by >20%, decreased by >20% or neither increased or decreased by >20%, relative to the previous survey. Daily rainfall (mm) and daily minimum, mean and maximum temperatures (°C) were obtained from Nha Trang city weather station (Figure 1). June/July is the dry and hot season in central Vietnam and there were only three rain events >5 mm during the survey period.

Bottom Line: We calculated the probability of the water volume of a large container (>500 L) increasing or decreasing by ≥20% to be 0.05 and 0.07 per day, respectively, and for small containers (<500 L) to be 0.11 and 0.13 per day, respectively.These human water-management behaviors are important determinants of Ae. aegypti production during the dry season.This has implications for choosing a suitable Wolbachia strain for release as it appears that prolonged egg desiccation does not occur in this village.

View Article: PubMed Central - PubMed

Affiliation: Queensland Institute of Medical Research, PO Royal Brisbane Hospital, Brisbane, Queensland, Australia.

ABSTRACT
We examined changes in the abundance of immature Aedes aegypti at the household and water storage container level during the dry-season (June-July, 2008) in Tri Nguyen village, central Vietnam. We conducted quantitative immature mosquito surveys of 171 containers in the same 41 households, with replacement of samples, every two days during a 29-day period. We developed multi-level mixed effects regression models to investigate container and household variability in pupal abundance. The percentage of houses that were positive for I/II instars, III/IV instars and pupae during any one survey ranged from 19.5-43.9%, 48.8-75.6% and 17.1-53.7%, respectively. The mean numbers of Ae. aegypti pupae per house ranged between 1.9-12.6 over the study period. Estimates of absolute pupal abundance were highly variable over the 29-day period despite relatively stable weather conditions. Most variability in pupal abundance occurred at the container rather than the household level. A key determinant of Ae. aegypti production was the frequent filling of the containers with water, which caused asynchronous hatching of Ae. aegypti eggs and development of cohorts of immatures. We calculated the probability of the water volume of a large container (>500 L) increasing or decreasing by ≥20% to be 0.05 and 0.07 per day, respectively, and for small containers (<500 L) to be 0.11 and 0.13 per day, respectively. These human water-management behaviors are important determinants of Ae. aegypti production during the dry season. This has implications for choosing a suitable Wolbachia strain for release as it appears that prolonged egg desiccation does not occur in this village.

Show MeSH
Related in: MedlinePlus