| Summary |
Nonsuppurative eneephaltits has been deteeted sporadically in Taiwan since 1985. However, the exact causative agent was not recognized inti! July of 1990, when Ibaraki disease virus was first isolated from cerebellum of a cattle with nonsuppurative encephalitis in Chia-Yi district in Taiwan. During the prevailing period of the disease, epidemilolgical survey was conducted on 72 young calves aged under 1 year, from 8 farms located in Chia-Yi District. Result showed that 10 calves (14 %) suffered from the disease. Nine sick calves culled or died within a few days after the onset of clinical signs. Virus isolation was further performed on 73 blood samples from epizootic farms, and results showed that 28 plasma samples and 11 blood ecll samples contained the Orbivirus, respectively. During the period of September to October, virus were isolated from the nasal discharge and blood of infected cattle, with the symptoms mainly in the respiratory tracts, of two farms in Pingutn. Furthermore, Orbivirus was also isolated from a newborn calf with nurvous signs in Kaohsiung district in December of 1991. The viruses isolated from field cases were pathogenic to suckling mice. Experimental infection of isolated virus to cattle also induced clinical sign in respiratory tract. Furthermore, virus could be recovered from blood of the infected cattle even 54 days post inoculation. A four consecutive years of serological survey on antibodies against lbaraki diseease in cattle in Taiwan was conducted from 1987 to 1990. The antibody-positive rate of dairy cattle in Taiwan increased from 25% in 1987 to 85 % in 1!)90. The result indicated that the disease was epizootic in cattle population in Taiwan.
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