One beef cattle died of sheep-associated malignant catarrhal fever (SA-MCF) on a farm. The 25 cattle which were kept with the affected one were regularly checked for OHV-2 DNA in peripheral blood leukocytes (PBL) by PCR. None of the cattle showed any symptoms of SA-MCF, but 10 cattle showed PCR-positive at the time of the outbreak. Afterward, 8 of the 10 cattle were tested as PCR-negative the following month. On the other hand, the remaining 2 cattle successively showed PCR-positive for at least 11 and 13 months, respectively. It was suggested that these cattle were persistently infected with OHV-2. We examined the effect of dexamethasone injections in the one of persistently infected cattle. It showed no symptoms of SA-MCF during the whole period, however, OHV-2 DNA in PBL increased for about 3 weeks after the dexamethasone injections. It showed the possibility that persistently infected cattle develop SA-MCF a few years later in an environment without sheep.
(Clinical Microbiology Section, Hokkaido Research Station TEL +81-11-851-5226)
Katsuragi et al. (2003) J. Jpn. Vet. Med. Assoc. 56:793-797 (in Japanese with English summary).