Spatial Variations in Dengue Transmission in Schools in Thailand

Pitcha Ratanawong; Pattamaporn Kittayapong; Phanthip Olanratmanee; Annelies Wilder-Smith; Peter Byass; Yesim Tozan; Peter Dambach; Carlos Alberto Montenegro Quiñonez; Valérie R Louis

doi:10.1371/journal.pone.0161895

Spatial Variations in Dengue Transmission in Schools in Thailand

PLoS One. 2016 Sep 26;11(9):e0161895. doi: 10.1371/journal.pone.0161895. eCollection 2016.

Authors

Affiliations

¹ Institute of Public Health, Heidelberg University Medical School, Heidelberg, Germany.
² Center of Excellence for Vectors and Vector-Borne Diseases, Faculty of Science, Mahidol University at Salaya, Nakhon Pathom, Thailand.
³ Faculty of Science and Technology, Rajabhat Rajanagarindra University, Chachoengsao, Thailand.
⁴ Epidemiology and Global Health, Department of Public Health and Clinical Medicine, Umeå University, Umeå 90187, Sweden.
⁵ Lee Kong Chian School of Medicine, Nanyang Technological University, Singapore, Singapore.
⁶ Medical Research Council/Wits University Rural Public Health and Health Transitions Research Unit (Agincourt), School of Public Health, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg 2193, South Africa.
⁷ College of Global Public Health, New York University, New York, New York, United States of America.

Abstract

Background: Dengue is an important neglected tropical disease, with more than half of the world's population living in dengue endemic areas. Good understanding of dengue transmission sites is a critical factor to implement effective vector control measures.

Methods: A cohort of 1,811 students from 10 schools in rural, semi-rural and semi-urban Thailand participated in this study. Seroconversion data and location of participants' residences and schools were recorded to determine spatial patterns of dengue infections. Blood samples were taken to confirm dengue infections in participants at the beginning and the end of school term. Entomological factors included a survey of adult mosquito density using a portable vacuum aspirator during the school term and a follow up survey of breeding sites of Aedes vectors in schools after the school term. Clustering analyses were performed to detect spatial aggregation of dengue infections among participants.

Results: A total of 57 dengue seroconversions were detected among the 1,655 participants who provided paired blood samples. Of the 57 confirmed dengue infections, 23 (40.0%) occurred in students from 6 (6.8%) of the 88 classrooms in 10 schools. Dengue infections did not show significant clustering by residential location in the study area. During the school term, a total of 66 Aedes aegypti mosquitoes were identified from the 278 mosquitoes caught in 50 classrooms of the 10 schools. In a follow-up survey of breeding sites, 484 out of 2,399 water containers surveyed (20.2%) were identified as active mosquito breeding sites.

Discussion and conclusion: Our findings suggest that dengue infections were clustered among schools and among classrooms within schools. The schools studied were found to contain a large number of different types of breeding sites. Aedes vector densities in schools were correlated with dengue infections and breeding sites in those schools. Given that only a small proportion of breeding sites in the schools were subjected to vector control measures (11%), this study emphasizes the urgent need to implement vector control strategies at schools, while maintaining efforts at the household level.

Grants and funding

This research is part of the DengueTools Consortium, funded under the health theme of the Seventh Framework Programme of the European Commission (Grant Agreement Number 282589) (PI-Dr. Annelies Wilder-Smith), and Mahidol University Grant (PI-Dr. Pattamaporn Kittayapong). All funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.