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Shifting patterns of Aedes aegypti fine scale spatial clustering in Iquitos, Peru.

LaCon G, Morrison AC, Astete H, Stoddard ST, Paz-Soldan VA, Elder JP, Halsey ES, Scott TW, Kitron U, Vazquez-Prokopec GM - PLoS Negl Trop Dis (2014)

Bottom Line: The extent of clustering was used to quantify the probability of finding spatially correlated populations.Our findings have implications for understanding Ae. aegypti distribution and for the design of surveillance and control activities relying on household-level data.Focusing efforts in large geographic areas with historically high levels of transmission may be more effective than targeting Ae. aegypti hotspots.

View Article: PubMed Central - PubMed

Affiliation: Department of Environmental Sciences, Emory University, Atlanta, Georgia, United States of America.

ABSTRACT

Background: Empiric evidence shows that Aedes aegypti abundance is spatially heterogeneous and that some areas and larval habitats produce more mosquitoes than others. There is a knowledge gap, however, with regards to the temporal persistence of such Ae. aegypti abundance hotspots. In this study, we used a longitudinal entomologic dataset from the city of Iquitos, Peru, to (1) quantify the spatial clustering patterns of adult Ae. aegypti and pupae counts per house, (2) determine overlap between clusters, (3) quantify the temporal stability of clusters over nine entomologic surveys spaced four months apart, and (4) quantify the extent of clustering at the household and neighborhood levels.

Methodologies/principal findings: Data from 13,662 household entomological visits performed in two Iquitos neighborhoods differing in Ae. aegypti abundance and dengue virus transmission was analyzed using global and local spatial statistics. The location and extent of Ae. aegypti pupae and adult hotspots (i.e., small groups of houses with significantly [p<0.05] high mosquito abundance) were calculated for each of the 9 entomologic surveys. The extent of clustering was used to quantify the probability of finding spatially correlated populations. Our analyses indicate that Ae. aegypti distribution was highly focal (most clusters do not extend beyond 30 meters) and that hotspots of high vector abundance were common on every survey date, but they were temporally unstable over the period of study.

Conclusions/significance: Our findings have implications for understanding Ae. aegypti distribution and for the design of surveillance and control activities relying on household-level data. In settings like Iquitos, where there is a relatively low percentage of Ae. aegypti in permanent water-holding containers, identifying and targeting key premises will be significantly challenged by shifting hotspots of Ae. aegypti infestation. Focusing efforts in large geographic areas with historically high levels of transmission may be more effective than targeting Ae. aegypti hotspots.

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Related in: MedlinePlus

Probability of finding spatially correlated adult male and female Ae. aegypti populations at increasing distances from a household.Points integrate data from 9 entomologic surveys performed in the Maynas and Tupac Amaru neighborhoods during 2009–2011 and solid line shows exponential fit results together with its 95% confidence interval (dotted line). Refer to Table 4 for model fit results.
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pntd-0003038-g005: Probability of finding spatially correlated adult male and female Ae. aegypti populations at increasing distances from a household.Points integrate data from 9 entomologic surveys performed in the Maynas and Tupac Amaru neighborhoods during 2009–2011 and solid line shows exponential fit results together with its 95% confidence interval (dotted line). Refer to Table 4 for model fit results.

Mentions: We used the maximum distance of adult Ae aegypti local clustering in each neighborhood to estimate the cumulative probability distribution for finding spatially correlated populations at increasing distances from a household (Figure 5). A value of 0–5 meters in the X-axis of Figure 5 indicates that clustering did not exceed the household whereas values higher than 5 meters indicate that Ae. aegypti abundance was spatially correlated beyond the household. The probability of finding spatially correlated adult populations decreased significantly with increasing distances from the house, with patterns for both neighborhoods better explained by a negative exponential model of the form (Table 4). Model fit was very high (R2Maynas = 0.91; R2Tupac Amaru = 0.86; R2Both = 0.89). When data from both neighborhoods was combined, the probability of finding adults clustering beyond the household (>5 m) was 42% (95% CI,57.8–25.8%) and the finding of clusters of high adult abundance with an extent of 100 m was rare (6.1%, 95% CI, 0.0–21.0%) (Figure 5 and Table 4). Predicted values were very similar between neighborhoods (Table 4 and Figure S5).


Shifting patterns of Aedes aegypti fine scale spatial clustering in Iquitos, Peru.

LaCon G, Morrison AC, Astete H, Stoddard ST, Paz-Soldan VA, Elder JP, Halsey ES, Scott TW, Kitron U, Vazquez-Prokopec GM - PLoS Negl Trop Dis (2014)

Probability of finding spatially correlated adult male and female Ae. aegypti populations at increasing distances from a household.Points integrate data from 9 entomologic surveys performed in the Maynas and Tupac Amaru neighborhoods during 2009–2011 and solid line shows exponential fit results together with its 95% confidence interval (dotted line). Refer to Table 4 for model fit results.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC4125221&req=5

pntd-0003038-g005: Probability of finding spatially correlated adult male and female Ae. aegypti populations at increasing distances from a household.Points integrate data from 9 entomologic surveys performed in the Maynas and Tupac Amaru neighborhoods during 2009–2011 and solid line shows exponential fit results together with its 95% confidence interval (dotted line). Refer to Table 4 for model fit results.
Mentions: We used the maximum distance of adult Ae aegypti local clustering in each neighborhood to estimate the cumulative probability distribution for finding spatially correlated populations at increasing distances from a household (Figure 5). A value of 0–5 meters in the X-axis of Figure 5 indicates that clustering did not exceed the household whereas values higher than 5 meters indicate that Ae. aegypti abundance was spatially correlated beyond the household. The probability of finding spatially correlated adult populations decreased significantly with increasing distances from the house, with patterns for both neighborhoods better explained by a negative exponential model of the form (Table 4). Model fit was very high (R2Maynas = 0.91; R2Tupac Amaru = 0.86; R2Both = 0.89). When data from both neighborhoods was combined, the probability of finding adults clustering beyond the household (>5 m) was 42% (95% CI,57.8–25.8%) and the finding of clusters of high adult abundance with an extent of 100 m was rare (6.1%, 95% CI, 0.0–21.0%) (Figure 5 and Table 4). Predicted values were very similar between neighborhoods (Table 4 and Figure S5).

Bottom Line: The extent of clustering was used to quantify the probability of finding spatially correlated populations.Our findings have implications for understanding Ae. aegypti distribution and for the design of surveillance and control activities relying on household-level data.Focusing efforts in large geographic areas with historically high levels of transmission may be more effective than targeting Ae. aegypti hotspots.

View Article: PubMed Central - PubMed

Affiliation: Department of Environmental Sciences, Emory University, Atlanta, Georgia, United States of America.

ABSTRACT

Background: Empiric evidence shows that Aedes aegypti abundance is spatially heterogeneous and that some areas and larval habitats produce more mosquitoes than others. There is a knowledge gap, however, with regards to the temporal persistence of such Ae. aegypti abundance hotspots. In this study, we used a longitudinal entomologic dataset from the city of Iquitos, Peru, to (1) quantify the spatial clustering patterns of adult Ae. aegypti and pupae counts per house, (2) determine overlap between clusters, (3) quantify the temporal stability of clusters over nine entomologic surveys spaced four months apart, and (4) quantify the extent of clustering at the household and neighborhood levels.

Methodologies/principal findings: Data from 13,662 household entomological visits performed in two Iquitos neighborhoods differing in Ae. aegypti abundance and dengue virus transmission was analyzed using global and local spatial statistics. The location and extent of Ae. aegypti pupae and adult hotspots (i.e., small groups of houses with significantly [p<0.05] high mosquito abundance) were calculated for each of the 9 entomologic surveys. The extent of clustering was used to quantify the probability of finding spatially correlated populations. Our analyses indicate that Ae. aegypti distribution was highly focal (most clusters do not extend beyond 30 meters) and that hotspots of high vector abundance were common on every survey date, but they were temporally unstable over the period of study.

Conclusions/significance: Our findings have implications for understanding Ae. aegypti distribution and for the design of surveillance and control activities relying on household-level data. In settings like Iquitos, where there is a relatively low percentage of Ae. aegypti in permanent water-holding containers, identifying and targeting key premises will be significantly challenged by shifting hotspots of Ae. aegypti infestation. Focusing efforts in large geographic areas with historically high levels of transmission may be more effective than targeting Ae. aegypti hotspots.

Show MeSH
Related in: MedlinePlus