Dengue fever is the most rapidly spreading mosquito-transmitted viral disease in the world. It causes ca. 390 million infections and 22,000 deaths annually in >100 countries. There is currently no cure and a recently licensed vaccine does not give complete protection. Disease prevention is done by mosquito vector control. Outbreaks occur periodically in most endemic countries, but outbreak detection is not accurate or timely enough to initiate control interventions in time. Critical gaps in knowledge remain. There is an urgent need to develop cost-effective and practical tools that can reliably measure dengue transmission and predict outbreaks. The project will assess human exposure to mosquito bites by detecting antibodies to mosquito saliva in human blood samples and detect dengue virus in mosquito adults and pupae. The project will be done during 2016-2019 in northeastern Thailand. It employs an integrated approach, where Study 1 is a prospective hospital-based case-control study (yr 1) to evaluate indices and dengue risk factors in positive and negative households. Study 2 is a cluster randomized controlled trial (yr 2-3) applying these indices to assess the effect of a vector control intervention consisting of treating household containers with a pyriproxyfen-spinosad mixture on epidemiological and entomological outcomes. The anticipated results will help authorities to forecast epidemics to plan and execute appropriate and timely interventions. The project is a partnership of international and national experts in the fields of entomology, virology, immunology, and epidemiology working with the Ministry of Public Health. Capacity building is an integral part of the project. As of November 2016, data on more than 100 human cases and controls in Study 1 had been collected, including blood samples, adult and immature mosquitoes, and household information. Data analysis is ongoing.
Long-term primary objective
Contribute to the development of practical early warning systems for dengue epidemics by evaluating novel entomological and immunological indices that accurately represent dengue incidence.
- Assess the accuracy of indices in identifying dengue positive and negative households (Study 1).
- Identify risk factors that may distinguish dengue positive from dengue negative households (Study 1).
- Assess the relationships between indices and dengue incidence longitudinally (Study 2).
- Assess the relationships between indices and the impact of vector control interventions (Study 2).
This study will be carried out in Khon Kaen and Roi Et provinces in north-eastern Thailand. It will employ a prospective hospital-based case-control study, comprising epidemiological, entomological, immunological, and virological methodologies. The project is organized into four work packages. WP1. Epidemiology: Dengue surveillance, clinical case detection, human blood sample collections (including blood spots for WP3), and DENV and serotype detection. WP2. Entomology: Mosquito collections, DENV detection in mosquitoes, climatic and environmental data collection, vector control intervention. WP3. Immunology: Dried human blood spot samples (collected under WP1) analyzed in the laboratory to assess human exposure to Aedes mosquito bites. WP4. Data Management and Statistical Analysis: Logistic regression analysis to identify factors, in particular entomological variables, associated with risk of dengue.