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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., Competing Interests: Competing interests: None declared., (© British Veterinary Association 2020. No commercial re-use. See rights and permissions. Published by BMJ.)

Ruminant pestiviruses (family Flaviviridae) affect both wild and domestic ruminants worldwide, causing reproductive disorders and severe economic losses. Wild (n=1442) and domestic (n=373) ruminants from southern Spain were tested for the presence of antibodies to pestiviruses. Seropositivity was detected by both ELISA and virus neutralisation test in 1/892 (0.1 per cent) red deer, 29/125 (23.2 per cent) cattle and 17/157 (10.8 per cent) sheep. Pestivirus-specific antibodies to bovine viral diarrhoea virus (BVDV) and border disease virus (BDV) genotypes 1, 4 and 5 were detected. Significantly higher antibody titres to BDV-4 compared with BVDV-NADL were found in one cattle farm. Results indicate that wild ruminants may act as spillover hosts from domestic ruminants, and therefore they do not represent a risk for domestic ruminants in southern Spain. The wide distribution of pestiviruses among sheep and cattle suggests that transmission between these species may occur., (British Veterinary Association.)

The intention of this collaborative project was eradication of pestivirus from the Norwegian cattle population of about 30,000 dairy and beef herds, primarily by identification and culling of persistently infected (PI) animals. Testing was performed in four tiers, with examination for pestivirus antibodies by indirect ELISA in (1) bulk milk, (2) pooled milk from primiparous dairy cows and (3) pooled blood from young stock. The herds positive in the third tier were examined for pestivirus antigen in blood from all antibody-negative individuals by -antigen-capture ELISA, and these animal composed tier (4). Following culling of the PI animals, a herd was considered free from pestivirus when pooled blood from young stock was antibody-negative on two sampling occasions three months apart. Number of herds with PI animals peaked at about 3000 (10 per cent) in the 2nd project year, then decreased steadily; only three herds (0.01 per cent) contained PI animals 10 years later. Solid, continuous information flow to all relevant partners was crucial to project success. The project saved losses of between 50 million and 200 million Norwegian crowns (NOK) annually (approximately 4.5 million to 18 million GBP). Project running costs for 10 years were 52.4 million NOK. Following project completion, surveillance of the Norwegian cattle population for pestivirus has continued.

Bovine Viral Diarrhoea Virus (BVDV) is a pestivirus in the flaviviridae family which affects cattle worldwide. Bulk milk (BM) antibody testing is frequently used as a relatively quick method of assessing herd BVDV exposure; however, an understanding of the effects of vaccination and historic infection is essential for test interpretation. This study investigated the trends exhibited by monthly BM antibody analysis in 14 herds split into three categories. Category 1 herds (vaccinating/no persistently infected (PI) animals) began the study with mid-positive BM antibody titres and experienced an estimated increase of 0.007 optical density (OD) units per month (equating to a rise of 0.35 OD units in 50 months). Category 2 herds (not vaccinating/no PI animals) began the study with mid-positive BM antibody titres and experienced an estimated decrease of 0.005 OD units per month with antibody levels in one category 2 herd taking 1290 days to decrease from mid-positive to negative. Category 3 herds (vaccinating/PI animals present) began the study with high BM antibody titres which plateaued within this range throughout the 50-month observation period. Vaccination was observed to cause transient increases in BM antibody in a number of herds in categories 1 and 3.

Bulk tank milk samples were collected from 374 dairy farms in Scotland in 2007/2008 along with questionnaire data relating to the management of the farm. Milk samples were tested for antibodies to bovine viral diarrhoea virus (BVDV) using a commercially available (Svanova) kit and percentage positivity scores calculated according to the manufacturer's guidelines. There were 220 farms that did not routinely vaccinate for bovine viral diarrhoea (BVD), and these were distributed according to the Swedish BVD eradication classes as 12.7 per cent, 22.3 per cent, 44.5 per cent and 20.5 per cent for Classes 0, 1, 2 and 3, respectively. A more sophisticated statistical method (finite mixture modelling) which does not depend on arbitrary thresholds and categories suggested a 73 per cent prevalence of herds with high mean levels of antibodies. Risk factor analysis suggested that routine vaccination for BVD, suspicion of BVD, housing of pregnant cows with calves, total number of cows and the proportion of cows that were dry were all associated with increased BVDV antibodies in bulk milk. The inclusion of BVD within the farm's health plan was associated with decreased BVDV antibodies in the bulk milk.

Beginning in April 2006, 41 farms were recruited onto a pilot Bovine viral diarrhoea virus (BVDV) eradication programme across the south of England with the majority of study herds concentrated in Somerset. Each herd was assessed and where relevant cleared of persistently infected (PI) animals. Seven farms dropped out before whole herd screening could be performed. Of the remaining 34 farms, 20 (59 per cent) were classified as infected although two of these were initially misclassified as BVDV-free. Over the course of three years, 61 PIs were identified across 16 of the 20 infected farms. 72 per cent of PIs indentified on the first herd test were below two years of age. PI prevalence ranged from 0.2 to 3.1 per cent of infected herds and was highest in herds that did not vaccinate. By the end of 2009, 24/34 (71 per cent) of study farms were BVDV-free while 10 (29 per cent) remained infected.

During the period February to May 2008, bulk milk samples were collected from 57 dairy farms throughout Wales in the framework of a voluntary somatic cell count project. Bulk milk samples were tested for antibodies to bovine viral diarrhoea virus (BVDV), bovine herpesvirus type 1 (BHV-1) and Leptospira Hardjo, and samples were also tested for the presence of BVDV antigen by PCR. A questionnaire was used to determine whether the herd was open or closed, what the vaccination status was, and to obtain general farm information such as the herd size and average milk yield. Vaccination against BVD, infectious bovine rhinotracheitis and leptospirosis was practised on 37, 12 and 35 per cent of the farms, respectively. The presence of bulk milk antibodies on farms that did not use vaccination was 75 per cent for BVDV, 54 per cent for BHV-2 and 76 per cent for L Hardjo. Open herds had 10 times the odds (95 per cent confidence interval [CI] 1.7 to 59.4)of having bulk milk antibodies for BVDV and 16.7 times the odds (95 per cent CI 2.0 to 49.7) of having bulk milk antibodies to BHV-1 compared with closed herds. A farm with bulk milk antibodies to one disease had significantly higher odds of having bulk milk antibodies to a second disease (P<0.05).

Blood samples were collected from 1328 dairy cows of different parities in 46 herds in two regions of South Korea and tested for bovine viral diarrhoea virus (BVDV) by reverse transcriptase-PCR (RT-PCR) for the detection of viral sequences in whole blood and by a commercial elisa for the detection of bvdv-specific antibodies. None of the animals was positive by RT-PCR but 770 (58 per cent) were seropositive. The proportion of seropositive cows increased with their parity, but there was no difference between the seroprevalence of BVDV among the cows in the two regions.

Three alpacas (Vicugna pacos) aged two to 22 months with a history of illthrift and diarrhoea were examined postmortem, and tissues were collected for histology, including immunohistochemical labelling for pestivirus antigen, virus isolation and TaqMan reverse transcriptase-pcr assay. Blood samples from two clinical cases and the remaining herd members were tested for bovine viral diarrhoea virus (bvdv) antibody by serum neutralisation, antigen detection and pcr assay. The three affected alpacas were positive for bvdv by pcr of splenic tissue and/or heparinised blood. Non-cytopathic bvdv was isolated from several tissues and plasma of two of the alpacas. dna sequencing and phylogenetic analysis of the viral genome from the pcr product showed that the bvdv was of subgenotype 1b. Immunohistochemical examination of brain tissue was positive in two cases, consistent with a persistent infection. bvdv antibodies were detected in 16 of 25 clinically unaffected alpacas. There was no evidence of persistent infection in the in-contact animals. The source of the infection was not determined.

Acute infection of calves, previously vaccinated with bacille Calmette-Guerin (BCG), with non-cytopathic viral diarrhoea virus (BVDV) resulted in the temporary suppression of two in vitro assays used to monitor Mycobacterium bovis infection. Lymphocyte proliferation and interferon-gamma production by whole blood cultures containing purified protein derivatives prepared from Mycobacterium avium (PPD-A) and M bovis (PPD-B) were markedly suppressed. The implication is that acute infections of cattle with non-cytopathic BVDV may temporarily compromise diagnostic tests for M. bovis infections and result in a failure to identify cattle with tuberculosis.

Bulk tank milk samples collected from 929 Northern Ireland dairy herds were classified according to their geographical location, somatic cell count and milk yield. Each sample was tested by ELISA for antibody levels to bovine viral diarrhoea virus (BVDV) and the herds were assigned to four groups with increasing antibody levels. In nine herds (1 per cent) no antibodies were detectable in the milk samples (group 1) and they were detectable at low levels in the milk from 90 herds (9.7 per cent, group 2), at moderate levels in 369 herds (39.7 per cent, group 3), and at high levels in the remaining 461 herds (49.6 per cent, group 4). The testing of samples from 90 herds in groups 1 and 2 after an interval of 12 months showed that the annual incidence risk for new infections with BVDV was in the range 0.133 to 0.477. There were significant relationships (P < 0.001) between the mean corrected optical density in the ELISA and herd location and somatic cell count, but not yield; the relationship with somatic cell count was linear (P < 0.01). Forty-three group 3 herds and 49 group 4 herds were selected at random and bulk milk samples were tested for BVDV by reverse transcriptase polymerase chain reaction. None of the group 3 herds was positive, but five group 4 herds were positive.

Milk samples from 135 herds in Brittany were tested by a blocking ELISA for antibodies to bovine viral diarrhoea virus (BVDV) and used to assess the relationship between the bulk milk result and the within-herd prevalence of antibody-positive lactating cows. This relationship was first quantified by using a general linear model and controlling for the number of cows contributing milk to the bulk tank, for the percentage of primiparous cows in the herds and for the number of milkings contributing to the bulk tank. Receiver operating characteristic (ROC) analysis was then used to define classes of percentage inhibition in the bulk milk associated with minimum intraclass and maximum between-class variances of the within-herd prevalence. Only the percentage inhibition of bulk milk had a significant positive effect on within-herd prevalence (R2 = 0.85). The ROC analysis provided three classes of bulk milk results corresponding to different expected levels of within-herd prevalence. Herds with bulk milk percentage inhibitions of 0 to 35 per cent, 35 to 60 per cent and 60 to 100 per cent had mean (sd) observed prevalences of 4.8 (5.7) per cent, 21.6 (14.6) per cent and 66.0 (29.3) per cent, respectively. Herds with a bulk milk inhibition of 0 to 35 per cent were expected to be BVDV-free. A herd with two consecutive bulk milk results four months apart of 60 per cent or more was likely to have a very high prevalence (median of 93 per cent) and could be suspected of harbouring an active infection.

Neutralising serum antibodies against bovine virus diarrhoea virus (BVDV) were monitored for three years in 35 cattle that were infected with the virus as calves; 24 of the calves were inoculated intramuscularly or intranasally, and 11 contracted the infection naturally. All the experimentally infected calves seroconverted within 14 to 28 days after inoculation, and all the animals still had high serum levels of antibodies to BVDV three years after infection. Determinations of antibody levels in milk and blood samples excluded the possibility that the calves had been reinfected with BVDV during the study.

Bulk tank milk samples from 1070 dairy herds in England and Wales were tested by ELISA for antibodies to bovine virus diarrhoea virus (BVDV). A subset of 341 herds was tested by ELISA for antibodies to bovine herpesvirus 1 (BHV-1), bovine respiratory syncytial virus (BRSV) and bovine coronavirus (BCV). None of the herds had less than 40 dairy cows and none had been vaccinated against BVDV. The prevalence of BVDV antibody-positive herds in the national population was estimated at 95 per cent and approximately 65 per cent of the herds had a high level of bulk tank antibody suggestive of recent infection with BVDV. Dairy herds in East Anglia and the south-east of England had a significantly lower risk of being BVDV antibody-positive than herds in the rest of England and Wales. However, these regional differences tended to diminish with increasing herd size. Around 69 per cent of the herds were BHV-1 antibody-positive and all the herds were antibody positive to BRSV and BCV. Comparison with earlier serological surveys revealed that there had been little change in the prevalence and distribution of BVDV antibody-positive herds in England and Wales over the last 20 years, but that there had been an increase in the prevalence of BHV-1 antibody-positive herds.

Two days after being imported into the United Kingdom one of a group of 30 pregnant dairy heifers showed clinical signs of bovine viral diarrhoea virus (BVDV) infection and subsequently died. Before it died the heifer was BVDV antigen-positive and antibody-negative. The gross post mortem findings were suggestive of mucosal disease but in addition to noncytopathic BVD virus, Salmonella typhimurium DT104 was cultured from tissues and gut contents. The other heifers were screened for S typhimurium by culturing faeces, and serology showed that 13 (45 per cent) of the group seroconverted to BVDV in the three weeks between samplings and the remainder were seropositive, indicating previous exposure. During this period four heifers showed clinical signs of acute BVDV infection but recovered uneventfully. Four animals (14 per cent) were positive for S typhimurium DT104 on faecal culture, and three of these excretors concurrently seroconverted to BVDV. Of the 29 heifers remaining in the group, one aborted in late gestation, 26 bore live calves and two delivered stillborn calves. Pre-colostral blood samples from the calves showed that their dams' pre-existing antibody titres correlated well with in utero fetal protection. In non-immune dams, exposure to BVDV between 69 and 120 days of gestation led to the birth of live persistently viraemic calves. Infection between 120 and 140 days of gestation led to the birth of live calves with evidence of congenital damage to the central nervous system, and infection later than 140 days of gestation led to the birth of live, normal calves with high pre-colostral antibody titres to BVDV. One calf which sucked colostrum was antibody and virus antigen-positive when sampled at 12 hours old but regular blood sampling failed to detect viraemia again until the calf was seven weeks old when it became persistently viraemic.

A model is described for the validation of vaccines designed to protect the bovine fetus from bovine viral diarrhoea virus (BVDV). The fetopathic nature of the challenge strain of virus was confirmed and the method used to test a commercial vaccine (Bovidec) developed from a Compton prototype. Heifers were vaccinated two or three times about the time of impregnation and challenged when they were between 25 and 80 days of gestation. There was no evidence of a viraemia in the heifers after the challenge, or of infection with BVDV of 13 liveborn calves or two aborted fetuses.

During the certification of the bulls at an artificial breeding centre for freedom from pestivirus infection, a single viraemic bull was identified, and further testing confirmed that it was persistently infected. The two-year-old bull was healthy and of similar bodyweight to its peers. Its semen was of normal quality on the basis of density, motility and morphological criteria. Approximately 600 doses of semen had been distributed for sire evaluation purposes to 97 dairy farms. An examination of the breeding records indicated a first service conception rate of 38 per cent. All but one of the 162 cows inseminated with the bull's semen were seropositive compared with 95 of 143 cows (66.4 per cent) inseminated with semen from other bulls. Virological studies of the 61 calves sired by the persistently infected bull revealed that two were persistently infected, but that the others were healthy and uninfected. It was concluded that the semen from this bull was a potential source of pestivirus infection for 'clean' herds.

A positive relationship was found between the prevalence of cows in a herd which were antibody-positive for bovine viral diarrhoea virus (BVDV) and the level of antibodies to the virus in bulk tank milk as determined by an indirect enzyme-linked immunosorbent assay (ELISA). In herds with an ELISA absorbance value of up to 0.20 there were very few or no antibody-positive cows, whereas in herds with an ELISA absorbance value of at least 0.81, 87 to 100 per cent of the lactating cows were antibody-positive to BVDV. An analysis of the level of antibodies to BVDV in milk samples from Sweden and Finland showed that of 123 Swedish herds, 83.7 per cent had detectable antibodies to BVDV in their bulk milk whereas only 3.1 per cent of the 291 Finnish samples were antibody-positive. The incidence of BVDV infection in 105 herds in one area of Sweden was determined by analysing two samples of bulk tank milk taken one year apart. The infection had apparently occurred recently in five of these dairy herds.

Unmated heifers seronegative to bovine pestivirus were used to investigate the effects on conception and embryo-fetal survival of pestivirus infection around the time of artificial insemination. The reproductive performances of three groups were compared; the control group did not become infected during pregnancy, group 1 heifers were infected by contact with a persistently infected cow and calf four days after insemination and group 2 heifers were infected intranasally nine days before insemination. Conception rates and embryo-fetal survival were monitored by serial serum progesterone assays, transrectal ultrasonography and manual palpation of the uterus. The conception rates (determined 20 days after insemination) of 60 per cent (nine of 15) and 44 per cent (eight of 18) for groups 1 and 2 were lower than the 79 per cent (11 of 14) achieved by the control group. The group 1 heifers subsequently experienced significant embryo-fetal loss, resulting in a pregnancy rate (determined 77 days after insemination) of 33 per cent (five of 15), significantly lower than the control group's 79 per cent (11 of 14). The pregnancy rate of the group 2 heifers (39 per cent, seven of 18) was also significantly lower than that of the controls, largely as a result of the group's poor conception rate. All the heifers diagnosed pregnant 275 days after insemination were induced to calve. No persistently infected calves were born.

Epidemiological aspects of bovine viral diarrhoea virus (BVDV) infections were studied longitudinally in a large dairy herd for three years. At the start of the study, practically all the cows more than four years old had BVDV antibody titres, whereas the younger stock were almost all seronegative. The spread of the virus was monitored in a part of the population that contained only transiently viraemic cattle and in another part that contained persistently viraemic calves. Among the lactating cows the virus circulated for two-and-a-half years, although they had no direct contact with persistently viraemic cattle during this period. The highest transmission rate occurred when a large number of susceptible heifers was added to the population of cows that contained transiently viraemic cattle. The circulation of BVDV among the lactating cows ceased while 27 seronegative cows were still present. Both findings are in accordance with predictions from simple epidemic models. The susceptibility of the cows that remained seronegative was confirmed experimentally. In contrast with the limited circulation of BVDV caused by transiently viraemic cattle, virtually all susceptible cattle that came into contact with a persistently viraemic calf became seropositive within three months. Transplacental BVDV infections were not detected in the calves born to cows that had antibodies against the virus due to an infection that had occurred at least four years earlier. Transplacental transmission of BVDV did not occur in most of the pregnant cows that were infected before approximately the 60th day of gestation, but when cows became infected later in gestation the virus virtually always invaded the fetus.(ABSTRACT TRUNCATED AT 250 WORDS)

A one-week-old Brown Swiss calf had fractures of the metaphyseal regions of the left femur and right tibia, and a generalised, severe derangement of osteogenesis. Alternating zones of sclerosis and radiolucency in the metaphysis of all the long bones was visible radiographically. A histopathological examination revealed a segmental disruption of trabecular modelling, with subsequent fracture. Immunohistochemistry using a monoclonal antibody for bovine viral diarrhoea (BVD) virus revealed abundant viral antigen in the pituitary gland, hypothalamus and thyroid gland. Intestinal tissue was positive on fluorescent antibody testing for the virus. The lesions indicate that transplacental infection with BVD virus can result in severe skeletal abnormalities and fractures.

Two outbreaks of border disease occurred on farms with sheep flocks and breeding cattle. The infection of the pregnant sheep was probably caused by transmission of virus from calves persistently infected with non-cytopathic bovine virus diarrhoea virus (BVDV) which were kept in close confinement with the ewes during mid-pregnancy. Border disease was also induced experimentally in eight lambs by exposing their dams at 38 to 78 days of gestation to a heifer persistently infected with BVDV. Both the natural and the experimental infections were characterised by typical signs such as 'hairy-shaker' lambs and high lamb mortality. The diagnosis was confirmed by virus isolations from live-born lambs, seroconversion and pathology. The study supports the assertion that cattle persistently infected with BVDV and in close contact with pregnant sheep, are an important source of strains of virus capable of causing border disease.