| 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) |