Spatial Patterns of High Aedes aegypti Oviposition Activity in Northwestern Argentina

Elizabet Lilia Estallo,Mario Alberto Lanfri,Guillermo Más,Carlos Marcelo Scavuzzo,Mario Zaidenberg,María Virginia Introini,Walter Ricardo Almirón,Carolina Vergara-Cid,Francisco Ludueña-Almeida,Abdisalan Mohamed Noor

doi:10.1371/journal.pone.0054167

Abstract

BackgroundIn Argentina, dengue has affected mainly the Northern provinces, including Salta. The objective of this study was to analyze the spatial patterns of high Aedes aegypti oviposition activity in San Ramón de la Nueva Orán, northwestern Argentina. The location of clusters as hot spot areas should help control programs to identify priority areas and allocate their resources more effectively.MethodologyOviposition activity was detected in Orán City (Salta province) using ovitraps, weekly replaced (October 2005–2007). Spatial autocorrelation was measured with Moran’s Index and depicted through cluster maps to identify hot spots. Total egg numbers were spatially interpolated and a classified map with Ae. aegypti high oviposition activity areas was performed. Potential breeding and resting (PBR) sites were geo-referenced. A logistic regression analysis of interpolated egg numbers and PBR location was performed to generate a predictive mapping of mosquito oviposition activity.Principal FindingsBoth cluster maps and predictive map were consistent, identifying in central and southern areas of the city high Ae. aegypti oviposition activity. A logistic regression model was successfully developed to predict Ae. aegypti oviposition activity based on distance to PBR sites, with tire dumps having the strongest association with mosquito oviposition activity. A predictive map reflecting probability of oviposition activity was produced. The predictive map delimitated an area of maximum probability of Ae. aegypti oviposition activity in the south of Orán city where tire dumps predominate. The overall fit of the model was acceptable (ROC = 0.77), obtaining 99% of sensitivity and 75.29% of specificity.ConclusionsDistance to tire dumps is inversely associated with high mosquito activity, allowing us to identify hot spots. These methodologies are useful for prevention, surveillance, and control of tropical vector borne diseases and might assist National Health Ministry to focus resources more effectively.

Highlights

In 1986, re-infestation of Aedes aegypti was detected in northeastern region of Argentina [1], and in a few years it reached even higher levels than before eradication campaign, affecting central and northern region of the country [2]
The overall fit of the model was acceptable (ROC = 0.77), obtaining 99% of sensitivity and 75.29% of specificity
Distance to tire dumps is inversely associated with high mosquito activity, allowing us to identify hot spots

Summary

Introduction

In 1986, re-infestation of Aedes aegypti was detected in northeastern region of Argentina (provinces of Misiones and Formosa) [1], and in a few years it reached even higher levels than before eradication campaign, affecting central and northern region of the country [2]. Evidence of dengue 2 (DEN-2) virus circulating in northwestern Argentina was reported, with autochthonous cases occurring in Salta Province during 1997 in the localities of Oran Cases affected 14 jurisdictions, 10 of them registering autochthonous cases for the first time (Buenos Aires, Ciudad Autonoma de Buenos Aires, Catamarca, Chaco, Cordoba, Entre Rıos, La Rioja, Santa Fe, Santiago del Estero and Tucuman). This outbreak started in the Oran Department (province of Salta), with the first autochthonous cases being detected during the epidemiologic week (EW) 53 in 2008 and extending until the EW 21 in 2009, when the disease spread south and east, reaching the 35th parallel. The location of clusters as hot spot areas should help control programs to identify priority areas and allocate their resources more effectively

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