An experiment was carried out to study the effect of the infection with Japanese encephalitis virus on spermatogenesis in boars. Two boars were inoculated subcutaneously with a field strain of the virus. They presented viremia and produced hemagglutination-inhibiting antibody after inoculation. One of them showed hyperemia of the scrotum and a rather hard consistency of the head of the epididymis. These boars were examined for characteristics of the semen. Consequently, they exhibited a decrease in number of sperms, a drop in percentage of motile sperms, and an increase in number abnormal sperms. In one of them, azoospermia was found for a month since the 29th day after infection.
In a boar, the virus was recovered from the semen collected on the 3rd and 17th day after infection. It was assumed that sows might have been infected with the virus by way of insemination. Then gilts were inseminated artificially with semen containing the virus and inserted into the cervical canal of the uterus. They manifested viremia and antibody production, and were not fertilized.
From the results mentioned above, it was considered that in boars infected with Japanese encephalitis virus spermatogenesis might be disturbed and the virus discharged into the semen. It was also presumed that virus infection and infertility might be induced in gilts which had received the contaminated semen by mating or artificial insemination.

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The QS^- and QS⁺ strains of Japanese encephalitis (JE) virus were examined for characteristics on primary quail embryo cell cultures. The following results were obtained.
1) The attenuated QS^- strain showed a higher titer when incubated at 30°C than when incubated at either of two temperatures, 37 and 40°C. There was, however, no distinct difference in titer of the QS⁺ strain among these three temperatures of incubation.
2) The QS^- strain was much less pathogenic than the QS⁺ strain both for suckling mice by the subcutaneous route and for adult mice by the intracerebral route.
3) A high infectivity and ability to cause hemagglutination were found infractions of each strain with a buoyant density of 1.25-1.26g/ml. The plaque was 4 and 1mm in diameter with the QS⁺ and QS^- strain, respectively.
These results indicate that the QS^- strain has satisfactory characteristics of attenuated JE virus. The hemagglutinating activity of the QS⁺ strain was maintained or enhanced about two times by addition of Tween 80 to a final concentration of 1w/v%, while that of the QS^- strain decreased markedly or was lost. The sensitivity to Tween 80 presented a good parallelism with other characteristics of the attenuated strain so far as the two strains examined are concerned.

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1. Susceptibility to Japanese encephalitis (JE) virus was compared among 4 species of mosquitoes, Culex tritaeniorhynchus, C. pipiens pallens, C. orientalis and Aedes albopictus, by examining the larval infection. It was confirmed in a preliminary experiment that the larval infection was accomplished effectively by dipping 4th instar larvae into virus suspension (JaGAr 01 strain of JE virus at a titer of 10⁶-10⁷ icLD₅₀/0.02ml in suckling mice) at 27°C for 1hr and then rearing them until the harvest when checked 10 days after the treatment.
2. It was observed that 1-day chicks engorged by the above-mentioned infected mosquitoes presented viremia and subsequently produced HI antibody against JE virus. This indicates that mosquitoes infected by the above-mentioned procedure were not only retentive of the virus, but also fully capable of transmitting the virus.
3. C. tritaeniorhynchus, C. pipiens pallens, and C. orientalis were susceptible to JE virus, although the latter two were less susceptible than the former one. Aedes albopictus was not susceptible to this virus.

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