EXPERIMENTAL TRANSMISSION OF THE WEST NILE VIRUS BY THE MOSQUITO

Abstract

Smithburn and others (1) have described that nine out of ten mice proved fatal showing a cerebral symptom 6-8 days after intracerebral inoculation with the serum obtained from an African native woman aged 37, having suffered from fever at Omogo, West Nile District, Uganda, in December 1937. The virus was identified later as of a neurotropic nature and named the West Nile virus through its characteristics made clear in experiments on mice and monkeys, and the case mentioned above was in the event also ascertained to have been as such through the fact that the neutralizing antibody against the virus was proved in the serum, although no cerebral symptom were then complained of. The virus is known to have a relation to some extent to Japanese B encephalitis virus (2), as it is found neutralized more or less by the immune sera of those viruses. The same results were obtained by us as to its character and the immunological aspects having received the strain through the courtesy of Dr. Hammon. Furthermore it is of interest to make clear that mosquitoes would be also responsible for spreading the West Nile virus as in the other arthropod borne encephalitis. The most encephalitis which would break out during summer time are known to be spread by mosquitoes (Simmons (3) ), as have reported repeatedly in our previous papers (Mitamura (4) and Kitaoka (5) ) . Anyway an experimental transmission of the West Nile virus was undertaken by us. While carrying out experiment we realized that Philip and Smadel (6) reported that the West Nile virus was experimentally transmissible by Aedes albopictus and Smithburn (7) proved by means of the neutralization test that the virus was found inconceivably wide spread throughout Central Africa.