Experimental infection of rabbits with bovine viral diarrhoea virus by a natural route of exposure

First study on genetic variability of bovine viral diarrhea virus isolated from Sapera dairy goats with reproductive disorders in Yogyakarta, Indonesia

Background and Aim:

Bovine viral diarrhea (BVD) virus (BVDV) is an important viral pathogen of cattle that can infect diverse artiodactyl species. The clinical manifestations caused by BVDV in heterologous hosts, as they do in cattle, vary, although respiratory and reproductive failures are commonly reported. BVDV infections commonly result in reproductive failure in goats, with abortion being the primary clinical sign. In central Java, Indonesia, BVDV infection has been reported in two clinically healthy local goat species, and the testing indicated infection by BVDV Type 1. However, the genetic diversity of viruses has not been described in healthy or ill goats. The objectives of the present study were as follows: (1) To investigate the genetic variation of BVDV isolated from Sapera dairy goats with naturally occurring reproductive disorders in Yogyakarta, Indonesia, using the 5’ untranslated region (5’ UTR) and (2) to study the possible correlation between reproductive disorders and the presence of BVDV in the flock.

Materials and Methods:

Blood samples were collected in October 2021 from 39 goats that had been individually reported to have reproductive disorders. The serum samples were subjected to molecular detection and genetic characterization of BVDV based on the 5’ UTR of the viral genome, followed by sequencing and phylogenetic analyses. Viral isolation was performed on BVDV-positive samples to analyze the viral biotypes.

Results:

BVDV infection was detected in five out of 39 female goats. The clinical status of the BVDV-infected goats was abortion (n=2), metritis (n=1), and repeated breeding (n=2). All antigen-positive samples were confirmed as BVDV type 1a (BVDV-1a) and noncytopathic (NCP)-BVDV biotype.

Conclusion:

The BVDV-1a and NCP biotypes are the main subtypes and biotypes present in Sapera dairy goats exhibiting reproductive failure. This result is consistent with previous results in dairy cattle in Yogyakarta. The reported results can facilitate the design of methods for the prevention and control of BVD circulating in Indonesia.

Bovine viral diarrhea virus: An updated American College of Veterinary Internal Medicine consensus statement with focus on virus biology, hosts, immunosuppression, and vaccination

Control of bovine viral diarrhea virus (BVDV) in cattle populations across most of the world has remained elusive in spite of advances in knowledge about this viral pathogen. A central feature of virus perseverance in cattle herds is the unique mechanism of persistent infection. Managing BVDV infection in herds involves controlling persistently infected carrier animals using a multidimensional approach of vaccination, biosecurity, and identification of BVDV reservoirs. A decade has passed since the original American College of Veterinary Internal Medicine consensus statement on BVDV. While much has remained the same with respect to clinical signs of disease, pathogenesis of infection including persistent infection, and diagnosis, scientific articles published since 2010 have led to a greater understanding of difficulties associated with control of BVDV. This consensus statement update on BVDV presents greater focus on topics currently relevant to the biology and control of this viral pathogen of cattle, including changes in virus subpopulations, infection in heterologous hosts, immunosuppression, and vaccination.

Bovine viral diarrhoea virus loses quasispecies diversity rapidly in culture

Bovine viral diarrhoea (BVD) is an important disease of cattle, with significant impacts on animal health and welfare. The wide host range of the causative pestiviruses may lead to formation of virus reservoirs in other ruminant or wildlife species, presenting a concern for the long-term success of BVD eradication campaigns. It is likely that the quasispecies nature of these RNA viruses contributes to their interspecies transmission by providing genetic plasticity. Understanding the spectrum of sequence variants present in persistently infected (PI) animals is, therefore, essential for studies of virus transmission. To analyse quasispecies diversity without amplification bias, we extracted viral RNA from the serum of a PI cow, and from cell culture fluid after three passages of the same virus in culture, to produce cDNA without amplification. Sequencing of this material using Illumina 250 bp paired-read technology produced full-length virus consensus sequences from both sources and demonstrated the quasispecies diversity of this pestivirus A genotype 1a field strain within serum and after culture. We report the distribution and diversity of over 800 SNPs and provide evidence for a loss of diversity after only three passages in cell culture, implying that cultured viruses cannot be used to understand quasispecies diversity and may not provide reliable molecular markers for source tracing or transmission studies. Additionally, both serum and cultured viruses could be sequenced as a set of 25 overlapping PCR amplicons that demonstrated the same consensus sequences and the presence of many of the same quasispecies variants. The observation that aspects of the quasispecies structure revealed by massively parallel sequencing are also detected after PCR and Sanger sequencing suggests that this approach may be useful for small or difficult to analyse samples.

Assessment of listing and categorisation of animal diseases within the framework of the Animal Health Law (Regulation (EU) No 2016/429): bovine viral diarrhoea (BVD)

Bovine viral diarrhoea (BVD) has been assessed according to the criteria of the Animal Health Law (AHL), in particular criteria of Article 7 on disease profile and impacts, Article 5 on the eligibility of BVD to be listed, Article 9 for the categorisation of BVD according to disease prevention and control rules as in Annex IV and Article 8 on the list of animal species related to BVD. The assessment has been performed following a methodology composed of information collection and compilation, expert judgement on each criterion at individual and, if no consensus was reached before, also at collective level. The output is composed of the categorical answer, and for the questions where no consensus was reached, the different supporting views are reported. Details on the methodology used for this assessment are explained in a separate opinion. According to the assessment performed, BVD can be considered eligible to be listed for Union intervention as laid down in Article 5(3) of the AHL. The disease would comply with the criteria as in Sections 4 and 5 of Annex IV of the AHL, for the application of the disease prevention and control rules referred to in points (d) and (e) of Article 9(1). The assessment here performed on compliance with the criteria as in Section 3 of Annex IV referred to in point (c) of Article 9(1) is inconclusive. The animal species to be listed for BVD according to Article 8(3) criteria are mainly species of the families Bovidae, Cervidae and Camelidae as susceptible species and several mammalian species as reservoirs.

Perspective on BVDV control programs

Programs for control and eradication of bovine viral diarrhea virus (BVDV) are often considered prudent when the expense of a control program within a specified time frame effectively prevents loss due to disease and the expense of control does not exceed the costs associated with infection. In some geographic areas, concerns about animal welfare or desires to reduce antibiotic usage may motivate BVDV control even when control programs are associated with a lack of financial return on investment. In other geographic areas, concerns about financial return on investment may be the key motivating factor in considering implementation of BVDV control programs. Past experiences indicate that systematic, well-coordinated control programs have a clear potential for success, while voluntary control programs in cultures of distributed decision-making often result in notable initial progress that ultimately ends in dissolution of efforts. Segmentation of the cattle industry into cow-calf producers, stocker/backgrounders, and feedlot operators amplifies the distribution of decision-making regarding control programs and may result in control measures for one industry segment that are associated with significant costs and limited rewards. Though the host range of BVDV extends well beyond cattle, multiple eradication programs that focus only on testing and removal of persistently infected (PI) cattle have proven to be effective in various countries. While some individuals consider education of producers to be sufficient to stimulate eradication of BVDV, research surrounding the adoption of innovative health care procedures suggests that the process of adopting BVDV control programs has a social element. Collegial interactions and discussions may be crucial in facilitating the systematic implementation necessary to optimize the long-term success of control programs. Compulsory control programs may be considered efficient and effective in some regions; however, in a nation where individual identification of cattle remains voluntary, the likelihood of effective compulsion to control BVDV within a farm or ranch appears to be very unlikely. While currently available diagnostic tests are sufficient to support BVDV eradication via systematic, well-coordinated programs, the development of a diagnostic procedure to safely and consistently detect the gestation of a PI fetus after 5 months of gestation would be a valuable research breakthrough. This desired testing modality would allow diagnosis of PI calves, while the dam continues to provide biocontainment of the infected fetus. This development could speed the progress of control programs in achieving the goal of BVDV control and eventual eradication.

Assessment of the rabbit as a wildlife reservoir of bovine viral diarrhea virus: serological analysis and generation of trans-placentally infected offspring

Eradication of bovine viral diarrhea virus (BVDV) is ongoing in many European countries and is based on removal of persistently infected (PI) cattle. In this context, low-level risks, including alternative reservoirs of infection, may become more important as the number of BVDV-free herds increases. Alternative reservoirs include livestock, such as sheep and goats, as well as wildlife, including deer and rabbits. Due to the extensive nature of the beef industry in Scotland, where an eradication program started in 2010, contact between cattle and alternative reservoir hosts is common. Seroprevalence to BVDV in rabbit populations can be high. In addition, rabbits can be infected with BVDV by natural routes, indicating that they could be a wildlife reservoir of infection. We analyzed the potential risk to livestock from rabbit populations in the UK by two approaches. First, ∼260 serum samples from free-ranging wild rabbits in Scotland and northern England were tested for BVDV-specific antibodies by ELISA. Only three samples exhibited low level BVDV-specific reactivity, suggesting that BVDV infection of rabbits was not frequent. Second, rabbits were challenged with BVDV at day 7 or 12 of pregnancy. This did not lead to any clinical signs in the infected animals or obvious increases in abortion or stillbirth in the infected dams. Samples from the dams, placental material and ∼130 offspring were tested by BVDV-specific RT-PCR and antibody ELISA. Positive PCR results in the placentas and in the tissues and body fluids of rabbits up to 10 days old showed that trans-placental infection of rabbits with BVDV had occurred. Many of the offspring had BVDV-specific antibodies. These data support the view that a wildlife reservoir of BVDV in rabbit poses a small but non-zero risk of re-infection for BVDV-free cattle herds. Rabbits are susceptible to infection with BVDV but only a small proportion of free-living rabbits in the UK appear to have been infected.