Limits...
Spatial Variations in Dengue Transmission in Schools in Thailand

View Article: PubMed Central - PubMed

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.

No MeSH data available.


Numbers of mosquitoes caught in schools during school terms using portable vacuum aspirators.Schools are classified by rural, semi-rural or semi-urban status and ranked by the number of students.
© Copyright Policy
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC5036884&req=5

pone.0161895.g002: Numbers of mosquitoes caught in schools during school terms using portable vacuum aspirators.Schools are classified by rural, semi-rural or semi-urban status and ranked by the number of students.

Mentions: In-classroom mosquito surveys were conducted in June 2012. A total of 66 Ae. aegypti were identified among 278 mosquitoes (amounting to 24%), collected from 50 classrooms. The highest number of 83 mosquitoes per catch day collected in a school by a portable vacuum aspirator came from school S04 (semi-rural). However, the highest number of Ae. aegypti collected was 31 from school S01 (semi-urban) (Fig 2). There was a strong and significant correlation between dengue infection and the number of mosquitoes caught by a portable vacuum aspirator in classrooms, as shown in Fig 3 (R2 = 0.50, p<0.001), allowing for the difference in the number of participants per school using a weighted regression.


Spatial Variations in Dengue Transmission in Schools in Thailand
Numbers of mosquitoes caught in schools during school terms using portable vacuum aspirators.Schools are classified by rural, semi-rural or semi-urban status and ranked by the number of students.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC5036884&req=5

pone.0161895.g002: Numbers of mosquitoes caught in schools during school terms using portable vacuum aspirators.Schools are classified by rural, semi-rural or semi-urban status and ranked by the number of students.
Mentions: In-classroom mosquito surveys were conducted in June 2012. A total of 66 Ae. aegypti were identified among 278 mosquitoes (amounting to 24%), collected from 50 classrooms. The highest number of 83 mosquitoes per catch day collected in a school by a portable vacuum aspirator came from school S04 (semi-rural). However, the highest number of Ae. aegypti collected was 31 from school S01 (semi-urban) (Fig 2). There was a strong and significant correlation between dengue infection and the number of mosquitoes caught by a portable vacuum aspirator in classrooms, as shown in Fig 3 (R2 = 0.50, p<0.001), allowing for the difference in the number of participants per school using a weighted regression.

View Article: PubMed Central - PubMed

ABSTRACT

Background: Dengue is an important neglected tropical disease, with more than half of the world&rsquo;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&rsquo; 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.

No MeSH data available.