Bovine viral diarrhea virus 1b fetal infection with extensive hemorrhage

75 years of bovine viral diarrhea virus: Current status and future applications of the use of directed antivirals

Bovine viral diarrhea virus (BVDV) was first reported 75 years ago and remains a source of major financial and production losses in the North American cattle industry. Currently, control methods in North America primarily center around biosecurity and vaccination programs; however, despite high levels of vaccination, the virus persists in the cattle herd due at least in part to the often-insidious nature of disease and the constant viremia and viral shedding of persistently infected animals which act as a reservoir for the virus. Continued development of targeted antivirals represents an additional tool for the prevention of BVDV-associated losses. Currently, in vivo studies of BVDV antivirals are relatively limited and have primarily been directed at the RNA-dependent RNA polymerase which represents the viral target with the highest potential for commercial development. Additional live animal studies have explored the potential of exogenous interferon treatment. Future research of commercial antivirals must focus on the establishment and validation of in vivo efficacy for compounds with demonstrated antiviral potential. The areas which provide the most viable economic justification for the research and development of antivirals drugs are the fed cattle sector, outbreak control, and wildlife or animals of high genetic value. With further development, targeted antivirals represent an additional tool for the management and control of BVDV in North American cattle herds.

Comparison of the Ability of High and Low Virulence Strains of Non-cytopathic Bovine Viral Diarrhea Virus-1 to Modulate Expression of Interferon Tau Stimulated Genes in Bovine Endometrium

Bovine Viral Diarrhea virus (BVDV) is a pestivirus with a single-stranded, positive sense RNA genome. It is endemic in many cattle populations, causing major economic losses in part due to reduced fertility. BVDV exhibits great genetic diversity and is classified as type 1 or 2 (BVDV-1, BVDV-2) with either non-cytopathogenic (ncp) or cytopathogenic (cp) biotypes. Differing strains of ncpBVDV differ in virulence, affecting clinical outcome. BVDV replicates in the reproductive tract, affecting host immunity and embryo survival. This study used an in vitro model of primary bovine endometrial cell cultures to compare the effects of two BVDV ncp type 1a strains of differing virulence (termed HO and KY) on endometrial transcription of candidate interferon stimulated genes (ISG) using qPCR. Half the cultures were stimulated with interferon tau (IFNT, the conceptus produced pregnancy recognition factor) in the presence or absence of viral infection. Cultures were replicated on cells from 10 BVDV-free cows. IFNT treatment stimulated transcription of 10 candidate ISGs, whereas both ncpBVDV-1 strains alone inhibited transcription of 8/10 ISGs. In combined BVDV-1+IFNT cultures, the stimulatory effect of IFNT on expression of GBP4, ISG15, HERC5, RSAD2, IFIH1, IFIT3, and MX1 was significantly inhibited by HO, but only ISG15, RSAD2, IFI27, and IFIT3 were decreased by KY. Inhibition by HO was generally greater. The IFNT-induced expression of TRIM56 was, however, increased by HO. These data show that HO, the more virulent ncpBVDV-1 strain, has a greater capacity to inhibit key antiviral pathways. These differences need confirmation at the protein level but may influence immune tolerance of the host. They could also reduce fertility by increasing uterine susceptibility to bacterial infection and disrupting IFNT-mediated pregnancy recognition.

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

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