The Green Revolution has greatly contributed to the spread of Japanese encephalitis. Professor T Jacob John, professor of eminence at Christian Medical College, Vellore, in tracing its detection in several parts of India since 1954, shows the link between paddy cultivation and Japanese encephalitis.

"The prevalence of these diseases is determined by the population densities of their vectors, which in turn is determined by environmental factors," says John. A Culex mosquito-borne virus disease, Japanese encephalitis, has a transmission cycle which involves domestic pigs and wild birds as amplifying agents. Its spread is closely linked to the success of the Green Revolution.

"There has been a dramatic increase in rice fields since the Green Revolution," notes Jacob John. This has coincided with a rapid spread of encephalitis in India, specially in the rice-bearing regions as the Culex mosquito is closely associated with paddy fields which provide an excellent breeding ground for the insect. Despite this, there is no policy on vaccination against Japanese encephalitis, even though excellent vaccines are available.