A large-scale outbreak of disease characterized by neurological symptoms such as astasia, ataxia, tremor, nystagmus, opisthotonus, and hypersensitivity occurred in beef and dairy cattle in southern Japan from summer to autumn in 2006. Nonsuppurative encephalomyelitis was observed in these clinical cases by histopathological findings. Akabane viral antigen and genome were detected in the central nervous system of the affected cattle. Akabane virus was isolated not only from these cattle but also from the blood samples of cohabitated and sentinel cattle in the epidemic area. The isolates were closely related to the Iriki strain in genogroup Ia, which caused encephalitis in calves in 1984. Most of the affected cattle possessed the neutralizing antibody against Akabane virus. Seroconversion of the sentinel calves was also confirmed during an outbreak of the disease. No evidence of Akabane virus circulation was observed in 2005 in a nation-wide serological surveillance, suggesting that a new strain belonging to genogroup Ia invaded southern Japan from overseas in the summer of 2006 and caused an epizootic outbreak of encephalomyelitis in cattle. We recommend that an advanced vaccine be developed to control the disease properly.
(Research Team for Environmental/Enzootic Diseases, Kyushu Research Station, TEL +81-29-838-7708)
- Kono, R., et al. (2008) BMC Vet. Res. 4: 20.
- Hirata, M., et al. (2008) J. Jpn. Vet. Med. Assoc. 61: 771-776.