First report of border disease virus in Melophagus ovinus (sheep ked) collected in Xinjiang, China.

Melophagus ovinus (sheep ked) is a blood-sucking ectoparasite that is parasitic primarily on sheep. It is widely distributed in different geographical regions worldwide. In China, it has been mainly found in Xinjiang, Gansu, and Tibet in recent years. In addition to causing direct damage to the animal hosts, M. ovinus also carries pathogens and serves as a vector for disease transmission. Border disease virus (BDV) is a positive-sense, single-stranded RNA pestivirus that mainly infects and causes border disease (BD) in sheep and goats worldwide. Since 2012, this disease has been reported in 4 provinces in China. In the present study, we investigated the presence of BDV in M. ovinus from Xinjiang and Gansu. Frozen M. ovinus collected during 2017 and 2018 from Xinjiang and Gansu and preserved in our laboratory were studied. First, total RNA of M. ovinus was extracted, followed by reverse transcription, PCR (RT-PCR) amplification of the 5'-UTR of BDV, and sequencing of the amplified products. Finally, the sequencing results were analyzed using DNAStar, MEGA 5.0 molecular biology software, and the BLAST online platform. The results from RT-PCR and sequencing analyses showed that among the samples included in the study, only the M. ovinus collected from Qinghe County in Alta, Xinjiang in 2018 tested positive for BDV. BLAST analysis showed that the viral strain with the most similar nucleotide identity to the sequence of the China/BDV/2018 fragment was the goat-derived BDV strain AH12-02 collected in Anhui, China, in 2012. A phylogenetic-tree analysis showed the strain to exhibit a BDV-3 genotype. This is the first report globally on BDV detected in M. ovinus and is also the first report of BDV discovered in Xinjiang, China. This study reconfirms the presence of BDV in China.

Distinct roles for the IIId2 sub-domain in pestivirus and picornavirus internal ribosome entry sites.

Viral internal ribosomes entry site (IRES) elements coordinate the recruitment of the host translation machinery to direct the initiation of viral protein synthesis. Within hepatitis C virus (HCV)-like IRES elements, the sub-domain IIId(1) is crucial for recruiting the 40S ribosomal subunit. However, some HCV-like IRES elements possess an additional sub-domain, termed IIId2, whose function remains unclear. Herein, we show that IIId2 sub-domains from divergent viruses have different functions. The IIId2 sub-domain present in Seneca valley virus (SVV), a picornavirus, is dispensable for IRES activity, while the IIId2 sub-domains of two pestiviruses, classical swine fever virus (CSFV) and border disease virus (BDV), are required for 80S ribosomes assembly and IRES activity. Unlike in SVV, the deletion of IIId2 from the CSFV and BDV IRES elements impairs initiation of translation by inhibiting the assembly of 80S ribosomes. Consequently, this negatively affects the replication of CSFV and BDV. Finally, we show that the SVV IIId2 sub-domain is required for efficient viral RNA synthesis and growth of SVV, but not for IRES function. This study sheds light on the molecular evolution of viruses by clearly demonstrating that conserved RNA structures, within distantly related RNA viruses, have acquired different roles in the virus life cycles.

A novel epidemiological model to better understand and predict the observed seasonal spread of Pestivirus in Pyrenean chamois populations.

Seasonal variations in individual contacts give rise to a complex interplay between host demography and pathogen transmission. This is particularly true for wild populations, which highly depend on their natural habitat. These seasonal cycles induce variations in pathogen transmission. The seasonality of these biological processes should therefore be considered to better represent and predict pathogen spread. In this study, we sought to better understand how the seasonality of both the demography and social contacts of a mountain ungulate population impacts the spread of a pestivirus within, and the dynamics of, this population. We propose a mathematical model to represent this complex biological system. The pestivirus can be transmitted both horizontally through direct contact and vertically in utero. Vertical transmission leads to abortion or to the birth of persistently infected animals with a short life expectancy. Horizontal transmission involves a complex dynamics because of seasonal variations in contact among sexes and age classes. We performed a sensitivity analysis that identified transmission rates and disease-related mortality as key parameters. We then used data from a long-term demographic and epidemiological survey of the studied population to estimate these mostly unknown epidemiological parameters. Our model adequately represents the system dynamics, observations and model predictions showing similar seasonal patterns. We show that the virus has a significant impact on population dynamics, and that persistently infected animals play a major role in the epidemic dynamics. Modeling the seasonal dynamics allowed us to obtain realistic prediction and to identify key parameters of transmission.

Chinese border disease virus strain JSLS12-01 infects piglets and down-regulates the antibody responses of classical swine fever virus C strain vaccination.

During 2012 and 2013, several border disease virus (BDV) strains were identified from Chinese goat and sheep herds. At the same time, pigs from the same areas were found to be seropositive to BDV by ELISA, without showing clinical signs (unpublished data). To examine the susceptibility of pigs to the Chinese BDV strains, BDV isolate JSLS12-01, isolated from naturally infected sheep, was used to infect pigs. Antibody responses, viremia, clinical signs and pathological changes of the infected animals were examined. It confirmed that the current BDV strain could infect the domestic pigs, the animals showed viremia during 4 to 14 days post infection (dpi) and sero-conversion from 14dpi; no clinical and pathological changes were observed. In addition, CSFV maternal antibody did not influence BDV infection. Subsequently, pigs were infected with the BDV isolate and vaccinated with Hog cholera lapinized virus (HCLV) 21 days later to determine the effect of BDV infection on antibody induction of CSFV vaccination. The specific CSFV antibody and neutralizing antibody titers of the BDV infected group remained negative after the primary vaccination. Even after the boost vaccination, they were still significantly lower than those of the uninfected groups (p<0.05). These results indicated that BDV infection could down-regulate the antibody responses of CSFV C-strain vaccination. It should be paid attention that BDV prevalence in pig herds and in live vaccines might hamper the vaccination of CSF.

Transmission of border disease virus from a persistently infected calf to seronegative heifers in early pregnancy.

BACKGROUND: This study describes the transmission of border disease virus (BDV) from a persistently infected calf to seronegative heifers in early pregnancy, resulting in persistently infected fetuses. On day 50 of pregnancy (= day 0 of the infection phase), six heifers were co-housed in a free stall with a bull calf persistently infected with BDV (pi BVD) for 60 days. The heifers underwent daily clinical examination, and blood samples were collected regularly for detection of pestiviral RNA and anti-pestivirus antibodies. After day 60 (= day 110 of pregnancy), the heifers were slaughtered, and the fetuses and placentae underwent post-mortem and immunohistochemical examination and RT-PCR for viral RNA detection. RESULTS: Three heifers had mild viraemia from day 8 to day 14, and by day 40 all heifers had pestivirus antibodies identified as anti-BDV antibodies in the serum neutralisation test. The placenta of the three viraemic heifers had histological evidence of inflammation, and fetal organs from these heifers were positive for pestivirus antigen by immunohistochemical examination and for BD viral RNA by RT-PCR and sequencing. Thus, co-housing of heifers in early pregnancy with a pi-BDV calf led to seroconversion in all heifers and persistent fetal infection in three. CONCLUSIONS: Considering that pi-BDV cattle can infect other cattle and lead to persistent infection of the fetus in pregnant cows, BDV should not be ignored in the context of the mandatory BVDV eradication and monitoring program. This strongly suggests that BDV should be taken into account in BVD eradication and control programs.

Short communication: Transmission of border disease virus to seronegative cows inseminated with infected semen.

The goal of this study was to investigate the transmissibility of border disease (BD) virus to seronegative cows via artificial insemination with cryopreserved semen from a bull persistently infected with BD virus. Five pestivirus naive cows were inseminated with BD virus-infected semen. Blood was collected for detection of pestivirus antibody by means of an ELISA on day 0 (day of insemination) and then every 7 days until day 56, at which time a serum neutralisation test (SNT) for differentiation of BD and BVD virus was carried out. Seroconversion was first noticed in two cows on day 14, in two cows on day 21 and in one cow on day 28. In the SNT, all cows had distinctly positive titres against BD virus. Therefore, BD virus is readily transmitted by infected semen, but none of the cows conceived, most likely because of poor semen quality.

Increased expressions of ADAMTS-13, neuronal nitric oxide synthase, and neurofilament correlate with severity of neuropathology in Border disease virus-infected small ruminants.

Border Disease (BD), caused by Pestivirus from the family Flaviviridae, leads to serious reproductive losses and brain anomalies such as hydranencephaly and cerebellar hypoplasia in aborted fetuses and neonatal lambs. In this report it is aimed to investigate the expression of neuronal nitric oxide synthase (nNOS), A Disintegrin And Metalloprotease with Thrombospondin type I repeats-13 (ADAMTS-13), and neurofilament (NF) in the brain tissue in small ruminants infected with Border Disease Virus (BDV) and to identify any correlation between hypomyelinogenesis and BD neuropathology. Results of the study revealed that the levels of ADAMTS-13 (p<0.05), nNOS (p<0.05), and NF (p<0.05) were remarkably higher in BDV-infected brain tissue than in the uninfected control. It was suggested that L-arginine-NO synthase pathway is activated after infection by BDV and that the expression of NF and nNOS is associated with the severity of BD. A few studies have focused on ADAMTS-13 expression in the central nervous system, and its function continues to remain unclear. The most prominent finding from our study was that ADAMTS-13, which contain two CUB domains, has two CUB domains and its high expression levels are probably associated with the development of the central nervous system (CNS). The results also clearly indicate that the interaction of ADAMTS-13 and NO may play an important role in the regulation and protection of the CNS microenvironment in neurodegenerative diseases. In addition, NF expression might indicate the progress of the disease. To the best of the authors'knowledge, this is the first report on ADAMTS-13 expression in the CNS of BDV-infected small ruminants.

Molecular, biological, and antigenic characterization of a Border disease virus isolated from a pig during classical swine fever surveillance in Japan.

In the current study, molecular, biological, and antigenic analyses were performed to characterize Border disease virus (BDV) strain FNK2012-1 isolated from a pig in 2012 in Japan. The complete genome comprises 12,327 nucleotides (nt), including a large open reading frame of 11,685 nt. Phylogenetic analysis revealed that FNK2012-1 was clustered into BDV genotype 1 with ovine strains. FNK2012-1 grew in porcine, bovine, and ovine primary cells and cell lines, but grew better in bovine and ovine cells than in porcine cells. Specific pathogen-free pigs inoculated with FNK2012-1 did not show any clinical signs. Noninoculated contact control pigs also did not show clinical signs and did not seroconvert. The results suggest that FNK2012-1 may be of ruminant origin and is poorly adapted to pigs. Such observations can provide important insights into evidence for infection and transmission of BDV, which may be of ruminant origin, among pigs.

Sheep persistently infected with Border disease readily transmit virus to calves seronegative to BVD virus.

Bovine viral diarrhea- and Border disease viruses of sheep belong to the highly diverse genus pestivirus of the Flaviviridae. Ruminant pestiviruses may infect a wide range of domestic and wild cloven-hooved mammals (artiodactyla). Due to its economic importance, programs to eradicate bovine viral diarrhea are a high priority in the cattle industry. By contrast, Border disease is not a target of eradication, although the Border disease virus is known to be capable of also infecting cattle. In this work, we compared single dose experimental inoculation of calves with Border disease virus with co-mingling of calves with sheep persistently infected with this virus. As indicated by seroconversion, infection was achieved only in one out of seven calves with a dose of Border disease virus that was previously shown to be successful in calves inoculated with BVD virus. By contrast, all calves kept together with persistently infected sheep readily became infected with Border disease virus. The ease of viral transmission from sheep to cattle and the antigenic similarity of bovine and ovine pestiviruses may become a problem for demonstrating freedom of BVD by serology in the cattle population.

Neuropathologic study of border disease virus in naturally infected fetal and neonatal small ruminants and its association with apoptosis.

The present study describes the pathologic changes and cellular apoptosis in the central nervous system (CNS) of fetal and neonatal small ruminants infected with border disease virus (BDV), as demonstrated by immunohistochemistry and in situ hybridization. Abortions of ewes and goats were observed, as were births of lambs and kids with poor survival rates and nervous signs. Lesions included cerebellar hypoplasia, porencephaly, hydranencephaly, and nonsuppurative meningoencephalomyelitis with hypomyelinogenesis. Viral antigens and RNA were present in neuropil, glial, and neuronal cells, especially in periventricular areas, cerebellum, and brainstem. TUNEL positivity and labeling of anti-bax and anti-caspases 3, 8, and 9 were detected in BDV-infected CNSs, especially in glial and neuronal cells. The double immunostaining and TUNEL assay revealed that in BDV-infected animals, not only were BDV-infected glial and neuronal cells undergoing apoptosis, but so were uninfected cells in close vicinity of BDV-infected cells. The expression of activated caspases 3, 8, 9; bax; and TUNEL in glial and neuronal cells of the infected fetal and neonatal kids were significantly (P < .05) higher than those of the infected fetal and neonatal lambs. Yet, the expression of bcl-2 in the CNSs of the infected fetal and neonatal lambs was higher (P < .05) in neuronal and glial cells than in those of the infected fetal and neonatal kids. The results suggest that cell death in the BDV-infected CNS is induced by intrinsic and extrinsic cascades of apoptotic pathways.

Clinical and laboratorial findings in pregnant ewes and their progeny infected with Border disease virus (BDV-4 genotype).

To evaluate the pathogenicity of local isolates of ovine pestiviruses (BDV-4 genotype), 13 virus- and antibody-negative, artificially inseminated pregnant ewes were challenged on days 108 (5 ewes), 76 (5 ewes) and 55 of pregnancy (3 ewes) with 2 ml of ovine pestivirus containing 10(6) TCID(50). Viraemia was detected by RT-PCR from 2 to 15 days pi in most ewes. No abortion due to the infection was observed but the number of stillbirths was high (32%), and bodyweight at lambing was significantly reduced compared to the experimental flock of origin used as control. Clinical symptoms in live lambs consisted on tremors, gait anomalies and inability to stand unaided. Skeletal abnormalities (brachygnathia, prognathia, arthrogryposis) were present in 44% of the lambs. Only 20% of the lambs were clinically normal. RT-PCR was a very sensitive technique compared to antigen ELISA in detecting viral presence in experimentally infected ewes and their progeny.

Border disease of sheep and goats.

Border disease (BD) is a congenital virus disease of sheep and goats first reported in 1959 from the border region of England and Wales. BD virus (BDV) is a pestivirus in the genus Flaviviridae and is closely related to classical swine fever virus and bovine virus diarrhoea virus (BVDV). Nearly all isolates of BDV are non-cytopathogenic (ncp) in cell culture. There are no defined serotypes but pestiviruses isolated from sheep exhibit considerable antigenic diversity and three distinct antigenic groups have been identified. Distribution of the virus is worldwide. Prevalence rates vary in sheep from 5 to 50% between countries and from region-to-region within countries. The disease in goats is rare and characterized by abortion. Clinical signs in sheep include barren ewes, abortions, stillbirths and the birth of small weak lambs. Affected lambs can show tremor, abnormal body conformation and hairy fleeces (so-called 'hairy-shaker' or 'fuzzy' lambs). Vertical transmission plays an important role in the epidemiology of the disease. Infection of fetuses can result in the birth of persistently infected (PI) lambs. These PI lambs are viraemic, antibody negative and constantly excrete virus. The virus spreads from sheep to sheep with PI animals being the most potent source of infection. Apparently healthy PI sheep resulting from congenital infection can be identified by direct detection of viral antigen or viral RNA in leukocytes or by isolation of ncp virus from blood or serum in laboratory cell cultures. Isolation of virus is unreliable in lambs younger than 2 months old that have received colostral antibody. The isolation of virus from tissues of aborted or stillborn lambs is difficult but tissues from PI sheep contain easily detectable levels of virus. To detect the growth of virus in cell cultures it is essential to use an immune-labelling method. Acute infection is usually subclinical and viraemia is transient and difficult to detect. Sheep may also be infected following close contact with cattle excreting the closely related BVDV.

Morphometric analysis of growth retardation in fetal lambs following experimental infection of pregnant ewes with border disease virus.

The onset of growth retardation was investigated in fetal lambs following experimental infection of pregnant ewes with Border Disease virus (BDV) on day 53 of pregnancy. Fetuses from control and infected ewes were harvested at weekly intervals between day 60 and day 95 of gestation and morphometric studies were completed on tibial radiographs and tibial growth cartilage metaphyseal junctions. Mean tibial areas were significantly reduced (P < 0.01) in fetuses from infected ewes at 35 and 42 days after infection and growth cartilage metaphyseal junctions were less mature in fetuses from infected ewes at 42 days after infection. Positive immunostaining for BDV antigen was demonstrated in the brains of all fetuses from infected ewes between 14 and 42 days after infection. Attempts to demonstrate BDV antigen in bone proved unsuccessful. It is concluded that intrauterine growth retardation is an early manifestation of BDV infection in lambs and that the process is initiated shortly following infection of the fetus.

Swine and ruminant pestiviruses require the same cellular factor to enter bovine cells.

Pestiviruses initiate infection of susceptible cells by receptor-mediated endocytosis. Cellular plasma membrane or endosomal molecules involved in translocation of these viruses into the cytosol have not been unequivocally identified. We reported previously that a mutant cell line derived from Madin-Darby bovine kidney (MDBK) cells, termed CRIB-1, was resistant to infection with bovine viral diarrhoea virus. CRIB-1 cells were also resistant to infection with classical swine fever virus and border disease virus of sheep, suggesting that entry of these three different pestiviruses into bovine cells requires a common cell membrane function. The resistance is pestivirus-specific: CRIB-1 cells were as susceptible as the parental MDBK cells to 14 other viruses of cattle and swine belonging to unrelated families. The resistance of CRIB-1 cells to pestivirus infection involves a block in virus entry since transfection of virus RNA or virus inoculation in the presence of PEG resulted in productive infection. Furthermore, quantitative analyses of the outcome of PEG-mediated infection of CRIB-1 cells indicated that the intracellular milieu was fully permissive for pestivirus replication. Binding studies revealed that virus attachment to CRIB-1 cells was not completely abrogated. These results indicate that entry of pestiviruses into MDBK cells depends on a common plasma membrane or endosomal function, which is lacking in CRIB-1 cells.

Border disease in sheep.

The current knowledge on border disease in sheep is reviewed. This is a congenital and teratogenic disorder induced by pestivirus. The history, etiology, epidemiology, clinical aspects, and pathologic lesions at postnatal and intrauterine infections (as well as in congenitally affected animals), pathogenesis, immunity, diagnosis, and control and prevention of the syndrome are discussed.

Replication of border disease virus in ovine lymphocytes and monocytes in vitro.

Adherent and non-adherent mononuclear cells obtained from the peripheral blood of normal sheep supported the in vitro replication of a non-cytopathic and a cytopathic strain of Border disease virus (BDV) with no apparent cytopathic effects. There was a significant rise in virus titres in adherent mononuclear cells (monocyte) and non-adherent (lymphocyte) cultures infected with both non-cytopathic and cytopathic strains of BDV 24 hours after inoculation. Peak virus titres of 5.36 log10 TCID50 ml-1 were recorded in adherent samples incubated for 48 hours while peak titres of 6.17 log10 TCID50 ml-1 were recorded in lymphocyte culture after 72 hours of incubation. Both the non-cytopathic and the cytopathic strains of BDV produced significantly higher titres in non-adherent (lymphocyte) cultures than in adherent (monocyte) cultures (P < 0.001) but the replication in adherent cells was faster than in nonadherent cell cultures. The addition of virus on both types of mononuclear cell cultures had no effect on cell viability but it had a significant inhibitory effect on the blastogenic responses of lymphocytes to phytohaemagglutinin.