Why JE is called Zoonotic Disease?

JE is basically a disease of animals. Pigs and birds, particularly those belonging to Family Ardeidae (e.g. cattle egrets, pond herons, etc.) are natural hosts. The virus is generally maintained in the enzootic cycle and appears as focal outbreaks under specific ecological conditions. Infection in human beings is caused as a result of spill-over of infection from zoonotic cycle. At low vector density level, the virus circulates in ardeid birds-mosquito ardeid bird cycle. However, at the commencement of monsoon season and/or increased availability of surface area mosquito breeding places e.g. rice field, irrigation canals  etc., the vector population builds up rapidly, the virus from wild birds through vector mosquito species spreads to peridomestic birds and then to mammals like cattles and pigs, etc. and eventually spills over to man.