Colostral transmission of bluetongue virus nucleic acid among newborn dairy calves in California.

There have been substantial recent changes in the global distribution and nature of bluetongue virus (BTV) infection of ungulates, perhaps as a result of climate change. To evaluate the epidemiology of BTV infection in California, an area historically endemic for the virus, we monitored newborn dairy calves at different sites for one year for the presence of BTV RNA and virus-specific antibodies. The data confirm both localized, vector-mediated, seasonal transmission of BTV as well as dissemination of BTV and/or viral nucleic acid to newborn calves following ingestion of colostrum.