Bovine viral diarrhoea virus 1b infection associated with congenital tremor and hypomyelination in Holstein calves

• Hypomyelination is a rare consequence of in utero BVDV infection cattle. A high prevalence congenital tremor and hypomyelination BVD outbreak described. The complete genome causing reported for the first time. Type number viral genomic mutations differ between brain blood samples. Genetic variability host factors contributed to unusual outbreak. bovine diarrhoea virus (BVDV) infection. We describe naïve Holstein dairy herd northern Italy, with an unusually calves neurological signs, generalised tremors ataxia. Histological analysis showed that was predominant lesion most typical neuropathological findings (e.g. cerebellar hypoplasia) were absent. Virological molecular analyses non-cytopathic genotype 1b associated calves’ signs excluded other viruses responsible or disorders. Whole-genome sequencing BVDVs from calf whole persistently infected herd-mate no such sign >99.7 % sequence identity. Analysis quasispecies distribution revealed greatest variation rates regions coding structural proteins E1 E2. Variation slightly greater brain- than blood-derived occurred at different sites, suggesting occurrence distinct evolutionary processes two calves. Molecular characterisation genomes five same farm confirmed E2 variable. Several factors, including genetic appear have observed unique disease phenotype, characterised by signs.