High infection rate of Zika virus in mosquitoes collected from an area of active Zika virus transmission in eastern Thailand

Zika virus (ZIKV), chikungunya virus (CHIKV) and dengue virus (DENV) are emerging and re-emerging arboviral diseases. These viruses are transmitted to humans through the bites of Aedes mosquitoes. Recently, ZIKV infection has been described as an emerging disease in Thailand and many countries, especially in tropical and subtropical areas. Specific drugs and vaccines against these infections are unavailable; therefore, effective disease control relies on vector control measures only. To understand the transmission cycle of these viruses and mosquito vectors, this study is designed to investigate the natural infection of ZIKV, CHIKV and DENV in field-caught mosquitoes by molecular techniques. Adults and larvae of mosquitoes were collected in and around the patients' homes in the Klaeng District, Rayong Province, Thailand. CHIKV and DENV were detected by Multiplex Real-time RT-PCR and ZIKV was detected by Hemi-nested RT-PCR. ZIKV RNA was detected in 8 (10.3%) samples (5 (6.4%) females and 2 (2.6%) males of Aedes aegypti and 1 (1.3%) female Armigeres subalbatus) and CHIKV RNA in 5 (6.4%) (3 (3.8%) females and 2 (2.6%) larvae of Ae. aegypti), while DENV RNA was not detected in any samples. The Maximum Likelihood tree of nucleotide sequences of positive samples showed that ZIKV in mosquitoes were cladded within the Asian lineage. This study was a preliminary survey of the potential vectors of ZIKV, CHIKV and DENV in an affected area. Information obtained from this study helps to understand the natural infection rates in mosquitoes with ZIKV, CHIKV and DENV and may be valuable in creating the most effective mosquito vector control strategies in the future.