Sheep serve as amplifying hosts of Japanese encephalitis virus, increasing the risk of human infection

The transmission cycle of Japanese encephalitis virus (JEV), involving pigs and birds as amplifying hosts and mosquitoes as vectors, was elucidated in the 1950s. However, factors contributing to this cycle remain unclear. Here, sheep were infected with a JEV strain isolated from sheep exhibiting neurological symptoms. The results revealed that sheep are susceptible to JEV infection and develop viremia, with levels and duration comparable to those observed in pigs, a known JEV-amplifying host. Mosquitoes fed viremic sheep blood showed an infection rate of 40.6 to 57.1%. These findings indicate that sheep can serve as amplifying hosts for JEV, potentially contributing to JEV transmission and increasing the public health risk of human infections. We propose an alternative, sheep-associated rural domestic JEV transmission cycle, which may be prevalent in specific regions where sheep are bred but pigs are not. This cycle exists along with the well-known pig-associated rural domestic and bird-associated wild cycles.