The Mechanism of Abortion caused by Arboviruses in Domestic Animals and the Ecology of the Viruses

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The mechanism of abortion in domestic animals caused byarboviruses, Japanese encephalitis virus (JEV), Getah virus (GTV), Akabane virus (AKV), Chuzan virus (CZV) and bovine viral diarrhoea-mucosal disease virus (BVD-MDV) was studied by virological, pathological and epizzotiological examinations.1) Outbreaks of abortion and stillbirth caused by JEV were observed in swine population in Hokkaido. JE antibody positive farms were found at the same site in negative farms in 3 years continuously. This result indicates that the JEV was maintained in a distinct endemic focus.2) Vertical transmission of JE virus in Aedes japonicas was demonstrated with a minimum rate of 0.7%.3) Dot-immunobinding assay has been evaluated as a useful method for the detection of anti-GTV antibody in horses.4) Pathological studies were performed on bovine Akabane disease occurred in Iwate. Arthrogriposis was recognized in 14 out of 70 cattle involved in the occurrence.5) AKV was isolated from the biting midge, Culicooides oxystoma, collected in a cowshed in Kagoshima.6) Chuzan virus classified as a new member of the Playah subgroup of the genus Orbivirus was isolated from healthy calves and from Culiooides oxystoma. The virus caused epidemic of congenital abnormalities of calves characterized by the hydroencephally-cerebellar hydroplasia which occurred in Kyushu.7) When cattle persistently infected with non-cytopathic BVD-MDV were challenged to cytopathid strain, some of them developed mucosal disease and morbund. All control cattle showed transit fever but no diarrhea, and recovered from infection.8) Two newborn calves with congenital malformation by in utero infection with BVD-MDV also showed ataxia and blindness. At autopsy, cerebellar hypoplasia and reduction insize of the optic nerves were observed in both cases in addition to severe hydrocephalus in one case.