It is well known that Japanese B encephalitis is a mosquito borne disease. Some Japanese investigators, however, have an idea that the alimentary canal may be an entry of Japanese B encephlitis virus similar to that in poliomyelitis virus. Hence the attempt was made to confirm whether or not the disease may develop following oral, intestinal al or rectal administration of the virus to hamsters.
Each of 2 hamsters was orally given two infected mouse brains. Out of these hamsters 6 (19%) got disease. Four hamsters each orally given five infected mouse brains were followed up as for the distribution of the virus in each organ (blood, liver, peritoneum, spleen, mesenterial lymphnodules, bulbus olfactorius, cerebrum, cerebellum and spinal cord), and the similar results to those following nasal infection in mouse were obtained.
Four hamsters had no encephalitis following direct injection of 0.3cc of 50% infected brain emulsion into surgically operated intestinal canal.
Out of 36 hamsters rectally injected with 5cc of 10% infected mouse brain emulsion without stopping anus with nippers, 12 hamsters (33%) got the disease. Whereas none out of 4 hamsters rectally injected with 5cc of 20% infected mouse brain emulsion stopping the anus with nippers for 24 hours and washed with acetic acid solution (pH 1.0) got the disease. The virus distribution in each organ was followed up daily after rectal injection of virus in the same condition as the above mentioned experiments and the virus was confirmed only in the contents of intestines, intestinal wall and blood in 2 hours after administration.
From the forgoing experiments it may be concluded that there is no evidence for the entry of the Japanese B encephalitis virus from alimentary canal into central nervous system in hamsters.
Four monkeys were orally given 6 mouse brains to each, and no symptoms indicating the onset of the disease were recognized. The viruses were not recovered from blood and feces. Rise of neither neutralising nor complement fixing antibody titers was not recognized.