Cytopathic bovine viral diarrhea viruses (BVDV): emerging pestiviruses doomed to extinction

Abstract

Bovine viral diarrhea virus (BVDV), a Flaviviridae pestivirus, is arguably one of the most widespread cattle pathogens worldwide. Each of its two genotypes has two biotypes, non-cytopathic (ncp) and cytopathic (cp). Only the ncp biotype of BVDV may establish persistent infection in the fetus when infecting a dam early in gestation, a time point which predates maturity of the adaptive immune system. Such fetuses may develop and be born healthy but remain infected for life. Due to this early initiation of fetal infection and to the expression of interferon antagonistic proteins, persistently infected (PI) animals remain immunotolerant to the infecting viral strain. Although only accounting for some 1% of all animals in regions where BVDV is endemic, PI animals ensure the viral persistence in the host population. These animals may, however, develop the fatal mucosal disease, which is characterized by widespread lesions in the gastrointestinal tract. Cp BVD virus, in addition to the persisting ncp biotype, can be isolated from such animals. The cp viruses are characterized by unrestrained genome replication, and their emergence from the persisting ncp ones is due to mutations that are unique in each virus analyzed. They include recombinations with host cell mRNA, gene translocations and duplications, and point mutations. Cytopathic BVD viruses fail to establish chains of infection and are unable to cause persistent infection. Hence, these viruses illustrate a case of “viral emergence to extinction” – irrelevant for BVDV evolution, but fatal for the PI host.

Molecular identification and phylogenetic analysis of non-cytopathic bovine viral diarrhea virus isolate obtained from a local respiratory outbreak in Northern Turkey

“…Bovine Viral Diarrhea Virus that includes two species, BVDV-1 and BVDV-2, is a member of Pestivirus genus within Flaviviridae virus family together with Border Disease Virus (BDV) and Classical Swine Fever Virus (CSFV) (9). BVDV mainly affects dairy and beef cattle which are considered as its natural hosts (8).…”

“…BVDV species have two well-known biotypes commonly described as cytopathic (cp) and non-cytopathic (ncp) according to their effects on cultured cells in vitro (9). Ncp biotypes are responsible for the vast majority of BVDV infection in living cattle at some stage of their lives (4,9).…”

“…Ncp biotypes are responsible for the vast majority of BVDV infection in living cattle at some stage of their lives (4,9). Infection with BVDV is either asymptomatic or causes symptoms including mild enteric and respiratory symptoms, and results in seroconversion to protect from reinfection (9).…”

Bovine Viral Diarrhea-an Emerging Disease in Camelids a Review

“…Pestivirus infection has only been recently recognized as a potential cause of serious illness in both NWCs and OWCs (Evermann, 2006), indicating that members of the camelid group are susceptible to infection. In NWCs, Pestivirus has been intensively researched in North America (Byers, 2008;Kim et al, 2009), the UK (Mueller and Broadbent, 2007) as well as in Switzerland (Danuser et al, 2009). BVDV may cause a severe disease in alpacas and llamas, including diarrhea, reproductive loss, wastage and death, posing a significant threat to a herd's health as it does in bovines (Belknap et al, 2000).…”

“…Mueller and Broadbent (2007) reported that the oldest surviving PI alpaca survived 30 months. In bovines, more than 50% of PI animals die before they reach the age of one year.…”