Bovine viral diarrhoea virus type 3: A new threat to italian cattle industry? [Virus della diarrea virale bovina (BVDV) tipo 3: Una minaccia emergente per i bovini?]

We report the clinical, pathogenetic and immunological features of the infection caused by a novel bovine pestivirus, namely Hobi virus or bovine viral diarrhea virus (BVDV) type 3, in Italy. This emerging pestivirus, first detected more than 10 years ago in a commercial batch of foetal bovine serum produced in Brazil, has been reported so far only in southern America and Asia. In 2010, Hobi-like viruses were detected in Italy in association with outbreaks of respiratory disease and reproductive failures occurring in a cattle herd of the Calabria region. A virus pair consisting of cytopathogenic (cp) and noncytopathogenic (ncp) BVDV-3 was isolated from a heifer dead as a consequence of respiratory distress. At the genetic level the two viruses differed for the presence in the cp strain of an insertion displaying high similarity to a bovine sequence previously associated to other cp BVDVs. By screening the cattle herd affected by clinical forms induced by the novel pestivirus, a BVDV-3 persistently infected (PI) calf was detected, which was monitored for about 6 months with regards to clinical conditions, viremia and viral shedding. Experimental infection of cattle, sheep and swine showed that BVDV-3 is able to infect all those species, although only ruminants displayed clinical signs and virus shedding. The poor serological cross-reactivity existing between BVDV-1 and BVDV-3, which was assessed in the sheep model, raised some concerns about the ability of currently available vaccines, mostly containing BVDV-1, to protect effectively against the new pestiviral species. To overcome the limitations of available diagnostic assays, a new tool (nested PCR) was developed which ensures unambiguous molecular characterisation of all BVDV species, including BVDV-3, in clinical samples. Future studies will assess the real circulation of this pestivirus in Italian cattle herds and evaluate the BVDV-3 impact on animal productions.