Japanese encephalitis (JE) is an acute arbovirus disease which causes encephalitis in horses and humans, and abortion in pigs. It is caused by infection with the japanese encephalitis virus (JEV), a mosquito-borne virus which occurs in widely dispersed areas in eastern Asia, including Papua New Guinea and Indonesia. The virus was introduced into the Torres Straight Islands in 1995 and to the Australian mainland in 1998. JE originated in Japan, with first known outbreaks occurring as early as 1871 and the virus was first isolated in 1935. Three types of manifestations of JEV can occur---transitory, lethargic, or hyperexcitable. Clinical signs, if present, vary; disease usually presents itself in sporadic or localized clusters.

How JE is Transmitted to Horses

The virus is transmitted to horses through biting insects. One of the main mosquito vectors is Culex annulirostris in Queensland, Australia.