Non-Bovine Species and the Risk to Effective Control of Bovine Viral Diarrhoea (BVD) in Cattle

Bovine viral diarrhoea virus (BVDV) is an economically important and highly prevalent virus of domestic cattle. Infections with BVDV may lead to both, reproductive and immunological effects that can result in widespread calf losses and increased susceptibility to diseases, such as mastitis and respiratory disease. While BVDV is generally considered to be host specific, it and other Pestivirus species, such as Border disease virus (BDV) in sheep, have been shown to be infecting species other than those from which they were originally isolated from. Recently BVDV was placed on the OIE’s list of notifiable disease and control and eradication programmes for BVDV have been developed throughout much of Europe, the United States, and the United Kingdom. While some countries, including Sweden and Ireland have successfully implemented eradication programmes, other countries such as New Zealand and Australia are still in the early stages of BVDV control. Despite effective control methods, incursions of BVDV into previously cleared herds still occur. While the cause of these incursions is often due to lapses in control methods, the ability of ruminant pestiviruses to infect species other than cattle poses the question as to whether non-bovine species could be impeding the success of BVDV eradication and control. As such, the aim of this review is to make mention of what is known about the cross-species transmission of BVDV, BDV and other pestiviruses between cattle and non-bovine ungulate species and draw conclusions as to the risk non-bovine species pose to the successful control and eradication of BVDV from cattle.

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.

Newly identified viral genomes in pangolins with fatal disease

Epizootic pathogens pose a major threat to many wildlife species, particularly in the context of rapidly changing environments. Pangolins (order Pholidota) are highly threatened mammals, in large part due to the trade in illegal wildlife. During July to August 2018 four sick wild pangolins (three Manis javanica and one Manis pentadactyla) exhibiting a variety of clinical symptoms were rescued by the Jinhua Wildlife Protection Station in Zhejiang province, China. Although three of these animals died, fortunately one recovered after 2 weeks of symptomatic treatment. Using meta-transcriptomics combined with reverse transcription polymerase chain reaction (RT-PCR), we identified two novel RNA viruses in two of the dead pangolins. Genomic analysis revealed that these viruses were most closely related to pestiviruses and coltiviruses, although still highly genetically distinct, with more than 48 and 25 per cent sequence divergence at the amino acid level, respectively. We named these Dongyang pangolin virus (DYPV) and Lishui pangolin virus (LSPV) based on the sampling site and hosts. Although coltiviruses (LSPV) are known to be transmitted by ticks, we found no evidence of LSPV in ticks sampled close to where the pangolins were collected. In addition, although DYPV was present in nymph ticks (Amblyomma javanense) collected from a diseased pangolin, they were not found in the local tick population. Epidemiological investigation revealed that both novel viruses might have been imported following the illegal international trade of pangolins. Hence, these data indicate that illegal wildlife trafficking not only threatens the status of pangolin populations, but may also spread epizootic pathogens.

Serological survey of wild cervids in England and Wales for bovine viral diarrhoea virus

BACKGROUND

Bovine viral diarrhoea (BVD) is a production disease commonly found in British cattle herds. Species other than cattle have been shown to be infected with the virus, thereby providing a potential source of infection for livestock. This study surveyed serum samples taken from 596 culled wild deer from England and Wales, between 2009 and 2010, for the presence of BVD antibodies.

METHODS

596 samples were tested with the SVANOVIR BVDV p80-Ab ELISA and a subset of 64 were tested with the IDEXX BVDV p80-Ab ELISA. ELISA results were confirmed using serum neutralisation tests.

RESULTS

2/596 samples (0.35 per cent) tested positive for BVD antibodies using the Svanova test and one of these tested positive and the other inconclusive using the IDEXX test; both were confirmed positive with serum neutralisation tests. These were both red deer stags, one from Devon and the other from East Anglia.

CONCLUSIONS

The results indicate that it is unlikely that BVD virus is widely circulating within the wild deer population and particularly unlikely that persistently infected deer are present in the populations surveyed. These results suggest that wild deer are unlikely to be a significant reservoir of BVD infection in cattle.

Investigation of association between bovine viral diarrhoea virus and cervid herpesvirus type-1, and abortion in New Zealand farmed deer

This study tested for association between bovine viral diarrhoea virus (BVDv) and cervid herpesvirus type-1 (CvHV-1) exposure and abortion in New Zealand farmed red deer. Rising two-year-old (R2, n = 22,130) and mixed-age (MA, n = 36,223) hinds from 87 and 71 herds, respectively, throughout New Zealand were pregnancy tested using ultrasound early in gestation (Scan-1) and 55-89 days later (Scan-2) to detect mid-term abortion. Sera from aborted and non-aborted hinds at Scan-2 were tested for BVDv and CvHV-1 using virus neutralisation tests. Available uteri from aborted hinds and from hinds not rearing a calf to weaning were tested by PCR for herpesvirus DNA. In herds with aborted hinds, 10.3% of 639 R2 and 17.2% of 302 MA hinds were sero-positive for BVDv and 18.6% of 613 R2 and 68.5% of 232 MA hinds were sero-positive for CvHV-1. There was no association between BVDv sero-status and abortion at animal level (R2 p = 0.36, MA p = 0.76) whereas CvHV-1 sero-positivity was negatively associated with abortion in MA hinds (p = 0.01) but not in R2 hinds (p = 0.36), MA). Eleven of 108 uteri from aborted R2 hinds but no MA hinds were positive for herpesvirus DNA. Vaginal samples from four R2 and one MA aborted hinds tested were negative for herpesvirus DNA. A Cervid Rhadinovirus type-2 (CRhV-2) was identified in seven PCR positive uteri samples. Findings suggest that BVDv and CvHV-1 may not be associated with abortion in R2 hinds, but association needs to be tested further in MA hinds. The role of CRhV-2 requires clarification.

Detection of persistent pestivirus infection in pudú (Pudu puda) in a captive population of artiodactyls in Chile

Background

Bovine Viral Diarrhea Virus (BVDV) is the viral agent causing the most important economic losses in livestock throughout the world. Infection of fetuses before their immunological maturity causes the birth of animals persistently infected with BVDV (PI), which are the main source of infection and maintenance of this pathogen in a herd. There is evidence of susceptibility to infection with BVDV in more than 50 species of the order Artiodactyla, and the ability to establish persistent infection in wild cervid species of South America could represent an important risk in control and eradication programs of BVDV in cattle, and a threat to conservation of these wild species. In this study, a serological and virological study was performed to detect BVDV infection in a captive population of non-bovine artiodactyl species in a Chilean zoo with antecedents of abortions whose pathology suggests an infectious etiology.

Results

Detection of neutralizing antibodies against BVDV was performed in 112 artiodactyl animals from a zoo in Chile. Three alpacas (Vicugna pacos), one guanaco (Lama guanicoe) and seven pudús (Pudu puda) resulted seropositive, and the only seronegative pudú was suspected to be persistently infected with BVDV. Then two blood samples nine months apart were analyzed by a viral neutralization test and RT-PCR. Non-cytopathogenic BVDVs were isolated in both samples. A phylogenetic analysis showed that the virus was highly related to BVDV-1b strains circulating among Chilean cattle.

Conclusions

This is the first report of a South American deer persistently infected with Bovine Viral Diarrhea Virus. Further studies are needed to determine the possible role of BVDV as a pathogen in pudús and as a threat to their conservation.

Bovine Viral Diarrhea Virus (BVDV) in White-Tailed Deer (Odocoileus virginianus)

Bovine viral diarrhea virus (BVDV) is the prototypic member of the genus Pestivirus in the family Flaviviridae. Infections with BVDV cause substantial economic losses to the cattle industries, prompting various organized control programs in several countries. In North America, these control programs are focused on the identification and removal of persistently infected (PI) cattle, enhancement of BVDV-specific immunity through vaccination, and the implementation of biosecure farming practices. To be successful, control measures must be based on complete knowledge of the epidemiology of BVDV, including the recognition of other potential sources of the virus. BVDV does not possess strict host-specificity, and infections of over 50 species in the mammalian order Artiodactyla have been reported. Over 50 years ago, serologic surveys first suggested the susceptibility of white-tailed deer (Odocoileus virginianus), the most abundant free-ranging ruminant in North America, to BVDV. However, susceptibility of white-tailed deer to BVDV infection does not alone imply a role in the epidemiology of the virus. To be a potential wildlife reservoir, white-tailed deer must: (1) be susceptible to BVDV, (2) shed BVDV, (3) maintain BVDV in the population, and (4) have sufficient contact with cattle that allow spillback infections. Based on the current literature, this review discusses the potential of white-tailed deer to be a reservoir for BVDV.

Challenges in Identifying and Determining the Impacts of Infection with Pestiviruses on the Herd Health of Free Ranging Cervid Populations

Although most commonly associated with the infection of domestic livestock, the replication of pestiviruses, in particular the two species of bovine viral diarrhea virus (BVDV), occurs in a wide range of free ranging cervids including white-tailed deer, mule deer, fallow deer, elk, red deer, roe deer, eland and mousedeer. While virus isolation and serologic analyses indicate that pestiviruses are circulating in these populations, little is known regarding their impact. The lack of regular surveillance programs, challenges in sampling wild populations, and scarcity of tests and vaccines compound the difficulties in detecting and controlling pestivirus infections in wild cervids. Improved detection rests upon the development and validation of tests specific for use with cervid samples and development and validation of tests that reliably detect emerging pestiviruses. Estimation of impact of pestivirus infections on herd health will require the integration of several disciplines including epidemiology, cervid natural history, veterinary medicine, pathology and microbiology.

Evidence of Bovine viral diarrhea virus Infection in Three Species of Sympatric Wild Ungulates in Nevada: Life History Strategies May Maintain Endemic Infections in Wild Populations

Evidence for bovine viral diarrhea virus (BVDV) infection was detected in 2009–2010 while investigating a pneumonia die-off in Rocky Mountain bighorn sheep (Ovis canadensis, canadensis), and sympatric mountain goats (Oreamnos americanum) in adjacent mountain ranges in Elko County, Nevada. Seroprevalence to BVDV-1 was 81% (N = 32) in the bighorns and 100% (N = 3) in the mountain goats. Serosurveillance from 2011 to 2015 of surviving bighorns and mountain goats as well as sympatric mule deer (Odocoileus hemionus), indicated a prevalence of 72% (N = 45), 45% (N = 51), and 51% (N = 342) respectively. All species had antibody titers to BVDV1 and BVDV2. BVDV1 was isolated in cell culture from three bighorn sheep and a mountain goat kid. BVDV2 was isolated from two mule deer. Six deer (N = 96) sampled in 2013 were positive for BVDV by antigen-capture ELISA on a single ear notch. Wild ungulates and cattle concurrently graze public and private lands in these two mountain ranges, thus providing potential for interspecies viral transmission. Like cattle, mule deer, mountain goats, and bighorn sheep can be infected with BVDV and can develop clinical disease including immunosuppression. Winter migration patterns that increase densities and species interaction during the first and second trimester of gestation may contribute to the long term maintenance of the virus in these wild ungulates. More studies are needed to determine the population level impacts of BVDV infection on these three species.

Bovine Viral Diarrhea Virus Infections

Bovine viral diarrhea virus (BVDV) continues to be of economic significance to the livestock industry in terms of acute disease and fetal loss. Many of the lesions relating to BVDV infection have been well described previously. The virus is perpetuated in herds through the presence of calves that are persistently infected. Relationships between various species and biotypes of BVDV and host defenses are increasingly understood. Understanding of the host defense mechanisms of innate immunity and adaptive immunity continues to improve, and the effects of the virus on these immune mechanisms are being used to explain how persistent infection develops. The noncytopathic biotype of BVDV plays the major role in its effects on the host defenses by inhibiting various aspects of the innate immune system and creation of immunotolerance in the fetus during early gestation. Recent advances have allowed for development of affordable test strategies to identify and remove persistently infected animals. With these improved tests and removal strategies, the livestock industry can begin more widespread effective control programs.

Spatial point pattern analyses of Bovine viral diarrhea virus infection in domestic livestock herds and concomitant seroprevalence in wild white-tailed deer (Odocoileus virginianus) in New York State, USA

Bovine viral diarrhea virus (BVDV) is an economically important disease of domestic cattle that is capable of infecting cervids. A first step in the formulation of a regional BVDV management plan is a local assessment of the likelihood of pathogen transmission from wildlife to domestic livestock. To achieve this, blood samples were collected from hunter-harvested white-tailed deer (Odocoileus virginianus) throughout New York State in the fall of 2009 and 2010. The SVANOVIR BVDV p80-AB enzyme-linked immunosorbent assay (ELISA; Svanova Biotech AV, Uppsala, Sweden) was used to screen sera for anti-BVDV antibodies. Because this ELISA is not validated for use in white-tailed deer, sera that tested positive were tested again using serum neutralization to verify the presence of antibodies. Spatial data describing the geographic location of BVDV antigen-positive cattle and camelid herds and BVDV-seropositive white-tailed deer were analyzed via the dual kernel density estimation method. In white-tailed deer, 7.48% (80/1,069) were BVDV-seropositive, whereas 3.43% (144/4,195) of tested herds were positive for BVDV antigen. An exploratory cluster analysis revealed 1 significant cluster of BVDV antigen-positive herds and 2 significant clusters of BVDV-seropositive deer. There was no spatial overlap between the clusters. The spatial point pattern and exploratory cluster analyses suggest that BVDV is maintained independently in domestic livestock herds in the western part of the state and in the white-tailed deer population in the northwestern part of the state.

The occurrence of Bovine viral diarrhea virus in hunter-harvested white-tailed deer (Odocoileus virginianus) in the state of Georgia, southeastern United States

The prevalence of Bovine viral diarrhea virus (BVDV) in free-ranging white-tailed deer (WTD, Odocoileus virginianus) in the state of Georgia was evaluated using ear notches collected from hunter-harvested deer during the hunting season of 2010-2011. From September to December 2010, 367 ear samples from WTD were collected from 37 counties in Georgia. The samples were from 178 (48.5%) female deer, 187 (51%) male deer, and 2 (0.5%) of unknown sex. The age of the animals varied from 6 months to 6.5 years. The age was not recorded in 34 animals (9.3%). Of the animals with known ages, 42% were under 2 years. Screening of 367 samples for BVDV using an antigen-capture enzyme-linked immunosorbent assay (AgELISA) resulted in 364 negative samples and 3 suspect samples. The 3 suspect samples were negative for BVDV reverse transcription polymerase chain reaction (RT-PCR), virus isolation, and immunohistochemistry. A subpopulation of samples (n = 89) selected from various geographical regions also tested negative for BVDV RT-PCR. In conclusion, although a few of the samples were suspect for the presence of BVDV by AgELISA, the presence of the virus within the deer population studied could not be confirmed further.

Distribution of bovine viral diarrhoea virus antigen in persistently infected white-tailed deer (Odocoileus virginianus)

Infection with bovine viral diarrhoea virus (BVDV), analogous to that occurring in cattle, is reported rarely in white-tailed deer (Odocoileus virginianus). This study evaluated the distribution of BVDV antigen in persistently infected (PI) white-tailed deer and compared the findings with those from PI cattle. Six PI fawns (four live-born and two stillborn) from does exposed experimentally to either BVDV-1 or BVDV-2 were evaluated. Distribution and intensity of antigen expression in tissues was evaluated by immunohistochemistry. Data were analyzed in binary fashion with a proportional odds model. Viral antigen was distributed widely and was present in all 11 organ systems. Hepatobiliary, integumentary and reproductive systems were respectively 11.8, 15.4 and 21.6 times more likely to have higher antigen scores than the musculoskeletal system. Pronounced labelling occurred in epithelial tissues, which were 1.9-3.0 times likelier than other tissues to contain BVDV antigen. Antigen was present in >90% of samples of liver and skin, suggesting that skin biopsy samples are appropriate for BVDV diagnosis. Moderate to severe lymphoid depletion was detected and may hamper reliable detection of BVDV in lymphoid organs. Muscle tissue contained little antigen, except for in the cardiovascular system. Antigen was present infrequently in connective tissues. In nervous tissues, antigen expression frequency was 0.3-0.67. In the central nervous system (CNS), antigen was present in neurons and non-neuronal cells, including microglia, emphasizing that the CNS is a primary target for fetal BVDV infection. BVDV antigen distribution in PI white-tailed deer is similar to that in PI cattle.

Evaluation of three experimental bovine viral diarrhea virus killed vaccines adjuvanted with combinations of Quil A cholesterol and dimethyldioctadecylammonium (DDA) bromide

Bovine viral diarrhea virus (BVDV) infections cause respiratory, reproductive, and enteric disease in cattle. Vaccination raises herd resistance and limits the spread of BVDV among cattle. Both killed and modified live vaccines against BVDV are available. While modified live vaccines elicit an immune response with a broader range and a longer duration of immunity, killed vaccines are considered to be safer. One way to improve the performance of killed vaccines is to develop new adjuvants. The goal of this research was evaluate new adjuvants, consisting of combinations of Quil A cholesterol and dimethyldioctadecylammonium (DDA) bromide, for use in killed vaccines. Responses to three novel killed vaccines, using combinations of Quil A and DDA as adjuvants, were compared to responses to a commercial modified live and a commercial killed vaccine. Vaccination response was monitored by measuring viral neutralizing antibodies (VN) levels and by response to challenge. All three novel vaccines were efficacious based on reduction in virus isolation, pyrexia, and depression. Compared to a commercial killed vaccine, the three novel vaccines elicited higher VN levels and reduced injection site inflammation.

Bovine viral diarrhea virus: global status

Despite the success of regional bovine viral diarrhea viruses (BVDV) eradication programs, infections remain a source of economic loss for producers. The wide variation among BVDV results in differences in genotype, biotype, virulence, and types of infections. BVDV infect a range of domestic and wild ruminants. Clinical presentation varies depending on strain of virus, species of host, immune status of host, reproductive status of host, age of host, and concurrent infections. Recent advances in BVDV research and diagnostics have led to the development of regional eradication/control programs, the most efficacious of which focus on biosecurity, surveillance, and control.

Prevalence and antigenic differences observed between Bovine viral diarrhea virus subgenotypes isolated from cattle in Australia and feedlots in the southwestern United States

Bovine viral diarrhea virus (BVDV) is divided into 2 different species within the Pestivirus genus, BVDV type 1 (BVDV-1) and BVDV type 2 (BVDV-2). Further phylogenetic analysis has revealed subgenotype groupings within the 2 types. Thus far, 12 BVDV-1 subgenotypes (a-l) and 2 BVDV-2 subgenotypes (a and b) have been identified. The purpose of the current study was to determine the prevalence of BVDV subgenotypes in the United States and Australia and to determine if there are detectable antigenic differences between the prevalent subgenotypes. To determine prevalence, phylogenetic analysis was performed on 2 blinded panels of isolates consisting of 351 viral isolates provided by the Elizabeth Macarthur Laboratory, New South Wales, and 514 viral isolates provided by Oklahoma State University. Differences were observed in the prevalence of BVDV subgenotypes between the United States (BVDV-1b most prevalent subgenotype) and Australia (BVDV-1c most prevalent subgenotype). To examine antigenic differences between the subgenotypes identified in samples from the United States and Australia, polyclonal antisera was produced in goats by exposing them at 3-week intervals to 2 noncytopathic and 1 cytopathic strain of either BVDV-1a, BVDV-1b, BVDV-1c, BVDV-2a, or Border disease virus (BDV). Virus neutralization (VN) assays were then performed against 3 viruses from each of the 5 subgenotypes. Comparison of VN results suggests that there are antigenic differences between BVDV strains belonging to different subgenotypes. The present study establishes a foundation for further studies examining whether vaccine protection can be improved by basing vaccines on the BVDV subgenotypes prevalent in the region in which the vaccine is to be used.

Transmission of bovine viral diarrhea virus among white-tailed deer (Odocoileus virginianus)

Cattle persistently infected (PI) with bovine viral diarrhea virus (BVDV), a pestivirus in the family Flaviviridae, are an important source of viral transmission to susceptible hosts. Persistent BVDV infections have been identified in white-tailed deer (Odocoileus virginianus), the most abundant free-ranging ruminant in North America. As PI deer shed BVDV similarly to PI cattle, maintenance of BVDV within white-tailed deer populations may be possible. To date, intraspecific transmission of BVDV in white-tailed deer has not been evaluated, which prompted this study. Six pregnant white-tailed deer were captured in the first trimester of pregnancy and cohabitated with a PI white-tailed deer. Cohabitation with the PI deer resulted in BVDV infection in all does, as indicated by seroconversion. All does gave birth to live fawns and no reproductive losses were observed. At birth, evidence of BVDV infection was identified in two singlet fawns, of which one was determined to be PI by repeated serum reverse transcription nested PCR, whole blood virus isolation and immunohistochemistry. This study demonstrates for the first time that BVDV transmission may occur among white-tailed deer. The birth of a PI fawn through contact to a PI white-tailed deer indicates that under appropriate circumstances, BVDV may be maintained in white-tailed deer by congenital infection.

Bovine viral diarrhea virus infections in heterologous species

Infections with Bovine viral diarrhea virus (BVDV) are not limited to cattle, but may be detected in various species in the mammalian order Artiodactyla. Despite epidemiological evidence of BVDV infections in species other than cattle, current knowledge regarding the impact of BVDV on heterologous species is incomplete. In heterologous hosts, BVDV infections with clinical signs analogous to those in cattle have been described and include disease of multiple organ systems, most notably the reproductive tract and immune system. Clinical infections may negatively impact the health and well-being of heterologous species, including camelids and captive and free-ranging wildlife. Of additional importance are BVDV infections in small ruminants and swine where difficulties arise in laboratory testing for Border disease virus (BDV) and Classical swine fever virus (CSFV), respectively. Pestiviruses are antigenically closely related and their cross-reactivity requires additional efforts in virological testing. In cattle populations, persistently infected animals are considered the main source of BVDV transmission. This phenomenon has also been detected in heterologous species, which could facilitate reservoirs for BVDV that may be of great importance where control programs are in progress. This review summarizes the current epidemiological and clinical knowledge on heterologous BVDV infections and discusses their implications.