Relationships between dengue virus infection in mosquito vector, (Aedes aegypti), dengue cases and weather conditions in Samut Sakhon Province, Thailand

Abstract

Background : Dengue is commonly found in the tropical and subtropical regions. The disease is still affecting the population of the world especially in Southeast Asia. The current increase in both morbidity and mortality rates was associated with the potentiality of the viral transmission. Surveillance focusing on the virus infection in principal dengue vector, weather conditions and number of dengue cases should be evaluated to develop an effective control approach, therefore reduce the emergence of dengue disease within the endemic and/or new areas.

Objectives : To characterize the transmission pattern of dengue virus in the mosquito vector (Aedes aegypti) according to the seasons and to determine the relationship between dengue virus infections in the mosquito, monthly dengue case reports and weather conditions in a highly endemic area of Thailand.

Research design : Descriptive study.

Setting : Ban Phaeo District, Samut Sakhon Province, Thailand

Methods : Ae. aegypti mosquitoes were collected from the study site during the rainy season of 2012, winter, dry and rainy seasons of 2013. Dengue infection in the mosquitoes was determined by nested reverse-transcription polymerase chain reaction. The seasonal prevalence pattern of dengue in the mosquitoes was compared to the dengue cases, and also with to local-weather condition within the same periods.

Results : Four dengue serotypes were detected in the individual mosquito samples. The highest rate of infection was shown in the rainy season of 2012 (August - November). The infection rate in mosquitoes declined in the winter and dry season of 2013. However, the infection rate in the mosquitoes was increasing in the rainy season of 2013. The trend of the dengue cycle in mosquito vector likely associated with that from the cycle of dengue cases or the morbidity rate in the study area. Interestingly, those were also associated with the changes of local weather conditions, i.e. temperature and relative humidity.

Conclusions : The result showed significant association between the pattern of dengue case, morbidity and the dengue infection in the mosquito vectors. Incidence trends of the disease were also accompanied with the consecutive data of both humidity and temperature. Therefore, the data could improve the surveillance and contribute to better prediction of the magnitude for the dengue outbreak.