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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.


Related in: MedlinePlus

Numbers of active breeding sites of Aedes vectors vs. dengue infections in each school.Each circle represents a school, and the size of the circle is proportional to the number of participating students. The regression line is weighted by the number of participating students in each school.
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pone.0161895.g004: Numbers of active breeding sites of Aedes vectors vs. dengue infections in each school.Each circle represents a school, and the size of the circle is proportional to the number of participating students. The regression line is weighted by the number of participating students in each school.

Mentions: Based on the surveys of breeding sites of Aedes vectors after the study, 6 out of the 10 schools were characterized as being located in rural or semi-rural areas surrounded by rice paddies and plantations with nearby villages while four schools were located in a semi-urban setting with household residences and commercial shops located in close proximity but not close enough to be classified as urban (Table 1). A total of 2,399 Aedes breeding containers filled with water were identified during the rainy season in all 10 schools during the follow-up breeding site inspection. The school with the highest number (368) of breeding containers with water was school S06 (rural) and that with the lowest number (122) was school S04 (semi-rural). Across all schools, 484 breeding sites (20.2%) were positive for mosquito larvae or pupae. The schools with the highest (106) and lowest (13) numbers of active breeding sites were schools S08 (semi-urban) and S05 (rural), respectively. In a regression of log-transformed number of active breeding sites against dengue infections, weighted for the number of participating students in each school, there was an overall correlation as shown in Fig 4 (R2 = 0.03, p <0.001), which was statistically significant but without a very strong association.


Spatial Variations in Dengue Transmission in Schools in Thailand
Numbers of active breeding sites of Aedes vectors vs. dengue infections in each school.Each circle represents a school, and the size of the circle is proportional to the number of participating students. The regression line is weighted by the number of participating students in each school.
© Copyright Policy
Related In: Results  -  Collection

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

pone.0161895.g004: Numbers of active breeding sites of Aedes vectors vs. dengue infections in each school.Each circle represents a school, and the size of the circle is proportional to the number of participating students. The regression line is weighted by the number of participating students in each school.
Mentions: Based on the surveys of breeding sites of Aedes vectors after the study, 6 out of the 10 schools were characterized as being located in rural or semi-rural areas surrounded by rice paddies and plantations with nearby villages while four schools were located in a semi-urban setting with household residences and commercial shops located in close proximity but not close enough to be classified as urban (Table 1). A total of 2,399 Aedes breeding containers filled with water were identified during the rainy season in all 10 schools during the follow-up breeding site inspection. The school with the highest number (368) of breeding containers with water was school S06 (rural) and that with the lowest number (122) was school S04 (semi-rural). Across all schools, 484 breeding sites (20.2%) were positive for mosquito larvae or pupae. The schools with the highest (106) and lowest (13) numbers of active breeding sites were schools S08 (semi-urban) and S05 (rural), respectively. In a regression of log-transformed number of active breeding sites against dengue infections, weighted for the number of participating students in each school, there was an overall correlation as shown in Fig 4 (R2 = 0.03, p <0.001), which was statistically significant but without a very strong association.

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.


Related in: MedlinePlus