Evidence of Transmission Capability in UK Culex pipiens for Japanese Encephalitis Virus (JEV) Genotype I and Potential Impact of Climate Change

Japanese encephalitis virus (JEV) is a mosquito-borne orthoflavivirus and a major cause of human encephalitis throughout Asia, although it is currently not reported in Europe. To assess the potential impact of climate change, such as increased temperatures, and the potential for native Cx. pipiens to transmit JEV genotype I in the United Kingdom (UK), we have investigated vector competence at two different temperatures. Culex pipiens f. pipiens were provided a bloodmeal containing JEV genotype I at 7.8 × 108 PFU/mL. Mosquitoes were maintained for 14 days at 21 °C or 25 °C, and rates of infection, dissemination, and transmission potential were assessed. There was no evidence for virus infection, dissemination, or potential for transmission at 21 °C. However, at 25 °C, virus infection was detected in 5 of 36 mosquitoes (13.9%). Of these, JEV disseminated to legs and wings in three specimens (3/5) and viral RNA was detected in saliva from one specimen (1/3). These data indicate that at elevated temperatures of 25 °C, UK Cx. pipiens f. pipiens could transmit JEV genotype 1.