Evolution of Bovine viral diarrhea virus in Canada from 1997 to 2013.

Bovine viral diarrhea virus (BVDV) is a rapidly evolving, single-stranded RNA virus and a production limiting pathogen of cattle worldwide. 79 viral isolates collected between 1997 and 2013 in Canada were subjected to next-generation sequencing. Bayesian phylogenetics was used to assess the evolution of this virus. A mean substitution rate of 1.4×10-3 substitutions/site/year was found across both BVDV1 and BVDV2. Evolutionary rates in the E2 gene were slightly faster than other regions. We also identified population structures below the sub-genotype level that likely have phenotypic implications. Two distinct clusters within BVDV2a are present and can be differentiated, in part, by a tyrosine to isoleucine mutation at position 963 in the E2 protein, a position implicated in the antigenicity of BVDV1 isolates. Distinct clustering within all sub-genotypes, particularly BVDV2a, is apparent and could lead to new levels of genotypic classification. Continuous monitoring of emerging variants is therefore necessary.

Genetic Variability of Bovine Viral Diarrhea Virus and Evidence for a Possible Genetic Bottleneck during Vertical Transmission in Persistently Infected Cattle.

Bovine viral diarrhea virus (BVDV), a Pestivirus in the family Flaviviridae, is an economically important pathogen of cattle worldwide. The primary propagators of the virus are immunotolerant persistently infected (PI) cattle, which shed large quantities of virus throughout life. Despite the absence of an acquired immunity against BVDV in these PI cattle there are strong indications of viral variability that are of clinical and epidemiological importance. In this study the variability of E2 and NS5B sequences in multiple body compartments of PI cattle were characterized using clonal sequencing. Phylogenetic analyses revealed that BVDV exists as a quasispecies within PI cattle. Viral variants were clustered by tissue compartment significantly more often than expected by chance alone with the central nervous system appearing to be a particularly important viral reservoir. We also found strong indications for a genetic bottleneck during vertical transmission from PI animals to their offspring. These quasispecies analyses within PI cattle exemplify the role of the PI host in viral propagation and highlight the complex dynamics of BVDV pathogenesis, transmission and evolution.

Metadata beyond the sequence enables the phylodynamic inference of bovine viral diarrhea virus type 1a isolates from Western Canada.

Bovine viral diarrhea virus (BVDV) has been recognized as an important pathogen of livestock in Canada. The high mutation rate of this virus leads to a great degree of diversity between isolates resulting in the ability to infer precise evolutionary relationships. Many studies have attempted to elucidate the regional and global evolution of BVDV, but so far few have applied Bayesian methods to this end. We aimed to describe the molecular epidemiology and phylodynamics of BVDV 1a isolates in Western Canada using 5'UTR and E1-E2 sequence data, collection dates and locations. Sequences were obtained from isolates submitted to a diagnostic laboratory in Saskatoon, Canada. Path sampling and stepping stone model testing were employed to identify the model that best fit the data. We found that these Western Canadian isolates share a most recent common ancestor dated near 1909. Furthermore, the E1-E2 region shows a median substitution rate about ten times greater than the 5'UTR. It was also noted that caution should be exercised when inferring phylogenetic relationships using the 5'UTR alone, as it becomes difficult to resolve relationships within major clades. Phylogeographic and population size fluctuation estimates require more thorough sampling than was performed here to be reliable. We have found that there are significant gains to be made by utilizing a Bayesian analysis and by incorporating additional types of data beyond the sequence. These include the estimation of most common recent ancestor dates and the precise inference of transmission routes. Future work will expand upon these findings by more thoroughly sampling BVDV isolates spatially and temporally and further refining the Bayesian model employed here.

Rapid detection of neutralizing antibodies against bovine viral diarrhoea virus using quantitative high-content screening.

Bovine viral diarrhoea virus (BVDV) is an important cause of morbidity, mortality and economic losses in cattle worldwide. Humoral immunity to BVDV plays a major role in the protection against infection and disease. In vitro serum neutralization tests can quantify humoral responses, but standard protocols are time-consuming and labour-intensive. The objective of this study was to develop a highly sensitive assay based on high-content cell-by-cell screening that is faster and less subjective than the conventional protocols. It can detect a neutralizing antibody response within the first week after infection of an animal, takes less than 24h to complete and excludes operator bias by automated data acquisition and analysis.