Persistence of Viral RNA in Chikungunya Virus-Infected Aedes aegypti (Diptera: Culicidae) Mosquitoes after Prolonged Storage at 28°C

Experiments were conducted to determine the persistence of chikungunya viral (CHIKV) RNA in experimentally infected Aedes aegypti mosquitoes stored for prolonged periods at 28°C. Intra-thoracically inoculated mosquitoes with confirmed positivity were killed by quick freezing at -80°C, applied to sticky tape, and stored at 28°C with 80 ± 5% relative humidity (RH). At weekly intervals, five mosquitoes were removed from the tape randomly and assayed individually for detection of viral RNA by reverse transcriptase-polymerase chain reaction (RT-PCR). CHIKV RNA was detected up to 12 weeks in dry mosquitoes by RT-PCR. Virus could not be isolated either in cell culture or in the suckling Swiss-albino mouse system at any stage. This study demonstrated the persistence of CHIKV viral RNA up to 12 weeks when stored at 28°C with RH 80 ± 5%. This finding will have significance in CHIKV surveillance programs in mosquito populations or field-based studies in countries where maintenance of a cold chain is a concern.