Milk Replacers and Bovine Spongiform Encephalopathy in Calves, Japan

infection raise questions about the real pathogenic role of these viruses. As with other polyomaviruses, WUPyV and KIPyV could establish persistent and latent infections with likely asymptomatic reactivations (5), and detection of these viruses could also refl ect a long-term shedding from previous acute episode. Recently published studies have not shown a pathogenic role for these new polyomaviruses in respiratory tract disease (6,7); however, more comprehensive studies are needed to elucidate whether both KIPyV and WUPyV have any clinical relevance.