Evaluation of long-term preservation methods for viral RNA in mosquitoes at room temperature

Mosquitoes are important vectors of various pathogenic viruses. Almost all viruses transmitted by mosquitoes are RNA viruses. Therefore, to detect viral genes, mosquito samples must be kept at low temperatures to prevent RNA degradation. However, prolonged transport from the field to laboratory can pose challenges for temperature control. The aim of this study was to evaluate methods for preserving viral RNA in mosquito bodies at room temperature. Virus-infected mosquito samples were immersed in ethanol, propylene glycol, and a commercially available nucleic acid preservation reagent at room temperature, and viral RNA stability was compared. As a result, for the two RNA viruses (San Gabriel mononegavirus and dengue virus 1) subjected to this experiment, no significant decrease in the viral RNA was observed for at least eight weeks after immersion in the reagents, and the amount of RNA remaining was equivalent to that of samples stored at - 80 °C. These results indicate that immersion storage in these reagents used in this study is effective in preserving viral RNA in mosquitoes under room temperature conditions and is expected to be implemented in epidemiologic surveillance that is not limited by the cold chain from the field to the laboratory.