Relationship Between Japanese B and Russian Spring-Summer Encephalitis and Birds

It is apparent by the confirmation of viremia in 2 out of 126 sparrows (Mitamura) that birds get infected with Japanese B encephalitis (JBE) virus in the form of inapparent infection. This can also be presumed by the results of positive neutralization test against JBE virus in some birds. Hammon considered, through neutralization test, that St. Louis encephalitis (SLE) might be widely spread in nature. Smith stated that SLE virus is found among chicken mites (Dermanyssus gallinae) . Encephalitis virus is recognized to spread among birds without mosquitoes. In other words, birds being the original virus reservoir, man and animal get occasional infection with encephalitis virus in the mode of bird-mosquito-human cycle transmission, and birds are playing an important role as a source of infection. Regarding Russian spring-summer encephalitis (RSSE), Solobiev discovered that siskin and finch are susceptible to it. Concerning the epidemiology of encephalitis, Mitamura suspected the existence of some relationship between JBE and birds, and further advanced into setting up a hypothesis that JBE might be tfansmitted from one area to another through migratory birds. Experimental viremia on wild birds has also been carried out by Kobayashi and Kawashima in Japan. Still, the relationship between birds and encephalitis necessitates further investigations. Experiments were carried out from three angles.(1) Onset and duration of viremia when birds are experimentally infected.(2) Whether birds caught in fields develop viremia or preserve virus in brain spontaneously or not.(3) Frequency and extent of the presence of neutralizing and complement fixing antibodies in the blood of birds in situ.