Social-ecological factors and preventive actions decrease the risk of dengue infection at the household-level: Results from a prospective dengue surveillance study in Machala, Ecuador

<div><p>Background</p><p>In Ecuador, dengue virus (DENV) infections transmitted by the <i>Aedes aegypti</i> mosquito are among the greatest public health concerns in urban coastal communities. Community- and household-level vector control is the principal means of controlling disease outbreaks. This study aimed to assess the impact of knowledge, attitudes, and practices (KAPs) and social-ecological factors on the presence or absence of DENV infections in the household.</p><p>Methods</p><p>In 2014 and 2015, individuals with DENV infections from sentinel clinics in Machala, Ecuador, were invited to participate in the study, as well as members of their household and members of four neighboring households located within 200 meters. We conducted diagnostic testing for DENV on all study participants; we surveyed heads of households (HOHs) regarding demographics, housing conditions and KAPs. We compared KAPs and social-ecological factors between households with (n = 139) versus without (n = 80) DENV infections, using bivariate analyses and multivariate logistic regression models with and without interactions.</p><p>Results</p><p>Significant risk factors in multivariate models included proximity to abandoned properties, interruptions in piped water, and shaded patios (p<0.05). Significant protective factors included the use of mosquito bed nets, fumigation inside the home, and piped water inside the home (p<0.05). In bivariate analyses (but not multivariate modeling), DENV infections were positively associated with HOHs who were male, employed, and of younger age than households without infections (p<0.05). DENV infections were not associated with knowledge, attitude, or reported barriers to prevention activities.</p><p>Discussion</p><p>Specific actions that can be considered to decrease the risk of DENV infections in the household include targeting vector control in highly shaded properties, fumigating inside the home, and use of mosquito bed nets. Community-level interventions include cleanup of abandoned properties, daily garbage collection, and reliable piped water inside houses. These findings can inform interventions to reduce the risk of other diseases transmitted by the <i>Ae</i>. <i>aegypti</i> mosquito, such as chikungunya and Zika fever.</p></div

KAPs in households with versus without acute or recent DENV infections.

<p>KAPs in households with versus without acute or recent DENV infections.</p

A map of the study site and distribution of study households.

<p>(A) Location of Ecuador in the Americas (B) location of the city of Machala, El Oro Province, Ecuador, (C) and the distribution of households surveyed in this study. Household locations were aggregated to the neighborhood level for de-identification. Some clusters (5 households) have been disaggregated across block boundaries. This figure was created in ArcGIS version 10.3.1 (ESRI, 2016) using shape files from the GADM database of Global Administrative Areas, version 2.8, freely available at <a href="http://gadm.org" target="_blank">gadm.org</a>. Streets are derived from data available at the OpenStreetMap project (<a href="http://openstreetmap.org" target="_blank">openstreetmap.org</a>) for the municipality of Machala, El Oro, Ecuador. Neighborhood polygons were manually digitized by AMSI, and the shape file data are available upon request to the authors.</p

Social-ecological factors in households with versus without acute or recent DENV infections.

<p>Social-ecological factors in households with versus without acute or recent DENV infections.</p

Multivariate logistic regression model of predictors of acute or recent DENV infections in the household.

<p>Multivariate logistic regression model of predictors of acute or recent DENV infections in the household.</p

Unadjusted associations of DENV illness severity and JEV antibody status.

*<p>Non-hospitalized infections incorporate both non-hospitalized DF and asymptomatic seroconversions.</p>**<p>Non-DHF infections incorporate both non-hospitalized and hospitalized DF and asymptomatic seroconversions.</p>†<p>P-values were calculated using the Mantel-Haenzel chi-square statistic.</p

Factors associated with JEV seropositivity among those experiencing dengue (DENV) infection.

*<p>Refers to first-detected DENV infections in the cohort that occurred during the active surveillance period each year (June 1 – November 1) and had neutralizing antibody data available.</p>**<p>Statistical tests considered the association between variables of interest and the presence or absence of JEV NAbs in the pre-infection sample. p-values were obtained using the Pearson chi-square test for categorical variables, with α = 0.05 as the level of significance. ‘Missing’ categories were not included in statistical comparisons.</p

Positive and negative strand DENV RNA levels in unfractionated PBMC.

<p>Quantitative PCR for positive and negative strand viral RNA was performed with RNA extracted from unfractionated PBMC collected on fever day-2 from subjects infected with DENV1 (A), DENV2 (B), DENV3 (C), or DENV4 (D). The range of the positive strand DENV RNA was 0 to 6069 copies/million cells. Negative strand DENV RNA was detected in 6 of 18 samples with detectable positive strand RNA and the levels ranged from 5 to 35 copies/million cells.</p

Duration of DENV illness (days) by JEV NAb status.

*<p>Duration of illness was calculated as the number of days elapsed from first day of febrile illness to the last day that a child reported any fever, muscle or joint pain, headache, nauseas, vomiting, diarrhea, or any signs of bleeding or hemorrhage.</p>**<p>P-values were calculated using 2-way analysis of variance testing (ANOVA), with α = 0.05 as the level of significance.</p

Cohort characteristics associated with symptomatic DENV illness.

*<p>Refers to first-detected DENV infections in the cohort that occurred during the active surveillance period each year (June 1–November 1) and had neutralizing antibody data available</p>**<p>Statistical tests considered the association between variables of interest and the occurrence of symptomatic versus asymptomatic infection. p-values were obtained using the Pearson chi-square test for categorical variables, with α = 0.05 as the level of significance. ‘Missing’ categories were not included in statistical comparisons.</p