All issues > Volume 4(1); 1961

Original Article

J Korean Pediatr Soc. 1961;4(1):42-49. Published online March 31, 1961.

STUDIES OE JAPANESE B ENCEPHALITIS IN COLD BLOODED ANIMALS

Ik Chin Chang¹

¹Yonsei University, College of Medicine, Seoul, Korea

Abstract

1.Experimental Infection of Frog, Rana rugosa Schlegel,with Japanese B Encephalitis Virus 2.Epidemiological Significance and Persisting Period of Japanese B Encephalitis Virus in Frog. 3.Isolation of Japanese B Encephlitis Virus from Naturally Infected Frogs, Rana nigromaculata Hallowell, Collected in Chollapuk-To. (Following is an abstract from the article presented at the Ninth General Meeting of the Korean Medical Association on July 8 th, 1957) One of the most perplexing problems of the natural life cycle of Japanese B encephalitis virus (JEV) is its whereabouts during the interepidemic period or the winter months when Culex tritaeniorhynchus (Ct.) is not active. Ct. which become infected with JEV apparently keep the virus for the duration of their life span. The Ct. may hibernate in protected places, such as ceilings, caves and hay in the southern parts of Korea throught the winter and may be capable of carrying and transmitting the virus tha next spring by biting sasoeptible animal hostes. It has been believed that migratory birds reintroduce active infection to Korea each spring from endemic areas in warmer places where conditions permit year around mosquito breeding. However, the short period of viremia in JEV reservoirs (about one -week) and the certain period (August and September, usually) during which the epidemic occurs seem to make unlikely the theory of rointrodaction annually by mospuitoes coming out of hibernation or by migratory birds. Birds, mites or othei ectoparasites hibernate during the cold months and possibly may play some part in maintenance of the virus of St. Louis and equine encephalomyelitis during the interepidemic period. The extensive studies of many workers have shown that their role is minor compaired wich that of the mosquitoes- In addition there has been no successful isolation JEV from them If it can be accepted that the culex has an equal appetite for blood from birds, warm and cold blooded animals, frogs and snakes, they would acquire infection of encephalitis by the biting of culex. In our laboratory, frogs, Rana rugosa Schlegel, which were experimentally inoculated with JEV acquired the latent infection. For two reasons, we prefered to use organs rather than blood inoculating the virus. First, because we feel that the organs are more significant as carriers of the organisms and second, because of the relative small proportion of blood in the frogs body. The virus multiplied within three days in the organs of frogs after in oculation of JEV. The virus isolated from the organs of inoculated frogs was used to inoculate mice, and was recovered in mice of the first generation up to the end of the third week and was isolated in the mice of the second and third generations by blind subculture up to as many as 12 to 24 weeks. The subculture of virus through frogs was successful through only two or three generations and was easily transfered to mice from second and third generation of frogs. We have successfully isolated JEV from frogs, Raaa nigromaculata Hallowell, which were found in the endemic areas, Kimje, Kaichung, and Chongoop, Cholapukto, during the eqidemic of Japanese B encephalitis in 1956. The character of the virus is similar to JEV, Nakayama strain which is kept in our laboratory, except that the incubation period is prolonged one or two days in the mouse test. Experimental infection of Japanese B encephalitis with the strain of Nakayama virus was also successful in snakes, Elaphe rufodorsata (Cantor) and Natrix tigrina lateralis (Berthold). Cold blooded animals have chronic latent infections of Japanese B encephalitis and may serve as long term reservoir of JEV and infection sources for arthroped vectors season after season. (Author's Abstract) (1957年 5月 1日 接受 )

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