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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

Temporal instability in Ae. aegypti clusters.Maps show the number of surveys (out of 9 total surveys) a house was a hot-spot of high adult male and female Ae. aegypti abundance for (A) Maynas and (B) Tupac Amaru neighborhoods. Inset in each panel show the result of weighted k-function analysis performed on the number of times a house was a hot-spot. Global clustering occurs when observed values (solid black line) are higher than the expected 95% CI under a random distribution (red dotted lines).
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pntd-0003038-g004: Temporal instability in Ae. aegypti clusters.Maps show the number of surveys (out of 9 total surveys) a house was a hot-spot of high adult male and female Ae. aegypti abundance for (A) Maynas and (B) Tupac Amaru neighborhoods. Inset in each panel show the result of weighted k-function analysis performed on the number of times a house was a hot-spot. Global clustering occurs when observed values (solid black line) are higher than the expected 95% CI under a random distribution (red dotted lines).

Mentions: There was no obvious consistent temporal pattern of adult clusters in both neighborhoods; i.e., the location of clusters in one survey differed from the location of clusters in future or prior surveys. The temporal instability in Ae. aegypti hotspots is shown in Figure 4. Most houses in Maynas and Tupac Amaru (80.9% and 87.9%, respectively) were identified as hotspots only once in the 9 survey periods. The maximum number of survey dates when a house was identified as a hotspot was 3 (out of 9 surveys) in Maynas and 2 (out of 9 surveys) in Tupac Amaru (Figure 4). The spatial location of hotspots did not follow any apparent spatial pattern; the distribution of hotspots within both neighborhoods did not differ from a random distribution (Figure 4).


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)

Temporal instability in Ae. aegypti clusters.Maps show the number of surveys (out of 9 total surveys) a house was a hot-spot of high adult male and female Ae. aegypti abundance for (A) Maynas and (B) Tupac Amaru neighborhoods. Inset in each panel show the result of weighted k-function analysis performed on the number of times a house was a hot-spot. Global clustering occurs when observed values (solid black line) are higher than the expected 95% CI under a random distribution (red dotted lines).
© Copyright Policy
Related In: Results  -  Collection

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

pntd-0003038-g004: Temporal instability in Ae. aegypti clusters.Maps show the number of surveys (out of 9 total surveys) a house was a hot-spot of high adult male and female Ae. aegypti abundance for (A) Maynas and (B) Tupac Amaru neighborhoods. Inset in each panel show the result of weighted k-function analysis performed on the number of times a house was a hot-spot. Global clustering occurs when observed values (solid black line) are higher than the expected 95% CI under a random distribution (red dotted lines).
Mentions: There was no obvious consistent temporal pattern of adult clusters in both neighborhoods; i.e., the location of clusters in one survey differed from the location of clusters in future or prior surveys. The temporal instability in Ae. aegypti hotspots is shown in Figure 4. Most houses in Maynas and Tupac Amaru (80.9% and 87.9%, respectively) were identified as hotspots only once in the 9 survey periods. The maximum number of survey dates when a house was identified as a hotspot was 3 (out of 9 surveys) in Maynas and 2 (out of 9 surveys) in Tupac Amaru (Figure 4). The spatial location of hotspots did not follow any apparent spatial pattern; the distribution of hotspots within both neighborhoods did not differ from a random distribution (Figure 4).

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