Flavivirus which is produced in mosquitoes is responsible for infection in humans and horses. Pregnant infected sow shows no symptoms and signs of infection in pregnancy, while pigs demonstrate abortions and stillbirths. In nature JEV is amplified in wild creatures like pigs, birds and mosquitoes. Culex tritaeniorhynchus species, a mosquito vector of JEV is wide spread in various parts of Asia. Horses and humans are called as dead-end hosts because they do not transmit virus to mosquitoes by its bite. Japanese Encephalitis virus is most commonly found in south-eastern and southern countries of Asia, Northern Australia, Papua New Guinea and Indonesian Archipelago.