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Epidemiological studies on swine japanese encephalitis in south korea 1. epizootic patterns of japanese encephalitis in pigs

Cho, K.S.

Bulletin of Azabu University Veterinary Medicine 1(2): 241-256

1980


Accession: 005375506

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During a 2 yr period from 1968 and 1969, the incidence of Japanese encephalitis (JE) virus infections in pigs in South Korea was studied by seroepidemiological and virological investigations. The meteorological aspect was also surveyed. Antibody responses to JE virus in pigs were first observed between mid June and early Aug., and these positive rates were significantly different according to the serum specimens collected from pigs in different years and in various districts. In 1969, the response generally appeared later and at a lower level compared with that in 1968 and did not occur simultaneously even in the same litters. According to the monthly data of the maximum and minimum temperatures and rainfall in Junbuk-do, difference in variation of temperature was not recognized between both years, but the amount of rainfall was significantly prevalent in 1969. Almost all river basins were unsuitable for the reproduction of mosquitoes, because they were continuously full of running water in the summer of 1969. Outbreaks of abortion in sows were recognized as follows; the first case occurred in 6 primary pregnant sows of a farm in Anyang area, Gyunggi-do, during Jan. and Feb., 1969. New-borns (51) or fetuses, 49 (96.1%) were stillborn or died within 5 days after parturition. These abortions and stillbirths were considered to have been caused by epizootic field viruses in 1968. Two JE viral strains [Anyang (ASF-M) and Anyang (ASF-C)] were isolated from stillborn fetuses. The 2nd case appeared in primary pregnant sows from a farm in the Sosa area, Gyunggi-do, during June-Sept., 1969. These 5 litters showed 71.9% (23/32) mortality within 5 days after parturition. Three JE viral strains [Sosa (ASF-M1), Sosa (ASF-M2) and SOsa (ASF-C)] were also isolated from stillborn fetuses.

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