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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

Numbers of adult male and female Ae. aegypti collected per house and entomologic survey in Tupac Amaru neighborhood, Iquitos, Peru.Refer to Table 1 for information about each entomologic survey.
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pntd-0003038-g002: Numbers of adult male and female Ae. aegypti collected per house and entomologic survey in Tupac Amaru neighborhood, Iquitos, Peru.Refer to Table 1 for information about each entomologic survey.

Mentions: Maynas households had a significantly higher average number of water-holding containers than Tupac Amaru (Two-sample Wilcoxon test, W = 224207, P<0.001). Across both neighborhoods, most (98.9%) houses had at least one water holding container throughout the study period. The proportion of houses with positive containers ranged between 0.04–0.12 in Maynas and 0.03–0.10 in Tupac Amaru (Figure S2). A total of 5,833 Ae. aegypti pupae (3,192 in Maynas and 2,641 in Tupac Amaru) and 8,709 adult males and females (5,671 in Maynas and 3,038 in Tupac Amaru) were collected over the nine surveys. Forty-nine percent of all Ae. aegypti adults collected were females. Adult abundance was highly overdispersed, 91% of all Maynas houses and 94.9% of all Tupac Amaru houses were infested with 5 or less adult Ae. aegypti mosquitoes. The median number of adult Ae. aegypti per house was significantly higher in Maynas than in Tupac Amaru (Figure S3, W = 1544194, P<0.001). There was, however, considerable variation embedded in these estimates (Figure 1 and Figure 2). The number of adults and pupae collected per house ranged from 0 to 163 and from 0 to 681, respectively. Infested houses were found throughout the study neighborhoods (Figure 1 and Figure 2).


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)

Numbers of adult male and female Ae. aegypti collected per house and entomologic survey in Tupac Amaru neighborhood, Iquitos, Peru.Refer to Table 1 for information about each entomologic survey.
© Copyright Policy
Related In: Results  -  Collection

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

pntd-0003038-g002: Numbers of adult male and female Ae. aegypti collected per house and entomologic survey in Tupac Amaru neighborhood, Iquitos, Peru.Refer to Table 1 for information about each entomologic survey.
Mentions: Maynas households had a significantly higher average number of water-holding containers than Tupac Amaru (Two-sample Wilcoxon test, W = 224207, P<0.001). Across both neighborhoods, most (98.9%) houses had at least one water holding container throughout the study period. The proportion of houses with positive containers ranged between 0.04–0.12 in Maynas and 0.03–0.10 in Tupac Amaru (Figure S2). A total of 5,833 Ae. aegypti pupae (3,192 in Maynas and 2,641 in Tupac Amaru) and 8,709 adult males and females (5,671 in Maynas and 3,038 in Tupac Amaru) were collected over the nine surveys. Forty-nine percent of all Ae. aegypti adults collected were females. Adult abundance was highly overdispersed, 91% of all Maynas houses and 94.9% of all Tupac Amaru houses were infested with 5 or less adult Ae. aegypti mosquitoes. The median number of adult Ae. aegypti per house was significantly higher in Maynas than in Tupac Amaru (Figure S3, W = 1544194, P<0.001). There was, however, considerable variation embedded in these estimates (Figure 1 and Figure 2). The number of adults and pupae collected per house ranged from 0 to 163 and from 0 to 681, respectively. Infested houses were found throughout the study neighborhoods (Figure 1 and Figure 2).

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