Molecular Characterization of a Novel Bovine Viral Diarrhea Virus Isolate SD-15.

As one of the major pathogens, bovine viral diarrhea virus caused a significant economic loss to the livestock industry worldwide. Although BVDV infections have increasingly been reported in China in recent years, the molecular aspects of those BVDV strains were barely characterized. In this study, we reported the identification and characterization of a novel BVDV isolate designated as SD-15 from cattle, which is associated with an outbreak characterized by severe hemorrhagic and mucous diarrhea with high morbidity and mortality in Shandong, China. SD-15 was revealed to be a noncytopathic BVDV, and has a complete genomic sequence of 12,285 nucleotides that contains a large open reading frame encoding 3900 amino acids. Alignment analysis showed that SD-15 has 93.8% nucleotide sequence identity with BVDV ZM-95 isolate, a previous BVDV strain isolated from pigs manifesting clinical signs and lesions resembling to classical swine fever. Phylogenetic analysis clustered SD-15 to a BVDV-1m subgenotype. Analysis of the deduced amino acid sequence of glycoproteins revealed that E2 has several highly conserved and variable regions within BVDV-1 genotypes. An additional N-glycosylation site (240NTT) was revealed exclusively in SD-15-encoded E2 in addition to four potential glycosylation sites (Asn-X-Ser/Thr) shared by all BVDV-1 genotypes. Furthermore, unique amino acid and linear epitope mutations were revealed in SD-15-encoded Erns glycoprotein compared with known BVDV-1 genotype. In conclusion, we have isolated a noncytopathic BVDV-1m strain that is associated with a disease characterized by high morbidity and mortality, revealed the complete genome sequence of the first BVDV-1m virus originated from cattle, and found a unique glycosylation site in E2 and a linear epitope mutation in Erns encoded by SD-15 strain. Those results will broaden the current understanding of BVDV infection and lay a basis for future investigation on SD-15-related pathogenesis.

Effect of constant exposure to cattle persistently infected with bovine viral diarrhea virus on morbidity and mortality rates and performance of feedlot cattle.

OBJECTIVE: To determine the effects of constant exposure to cattle persistently infected (PI) with bovine viral diarrhea virus (BVDV) on health and performance of feedlot cattle. DESIGN: 3 controlled trials. ANIMALS: Crossbred feedlot cattle (trial 1, n = 184; trial 2, 138; trial 3, 138). PROCEDURES: Weaned calves were or were not vaccinated against BVDV at feedlot arrival (trial 1) or 2 (trial 2) or 3 (trial 3) weeks before feedlot arrival. During trial 1, half of the calves were commingled with PI cattle throughout the feeding period. During trial 2, 63 calves were exposed to PI cattle before weaning and all calves were exposed to PI cattle throughout the feeding period. During trial 3, all study calves were exposed to PI cattle throughout the feeding period. Morbidity and mortality rates and average daily gain (ADG) data were analyzed. RESULTS: During trial 1, calves maintained with PI cattle had a higher morbidity rate regardless of BVDV vaccination than did calves not exposed to PI cattle; however, for calves maintained with PI cattle, the morbidity rate for those vaccinated against BVDV was less than that for those not vaccinated against BVDV. During trial 2, calves exposed to PI cattle before weaning or vaccinated against BVDV had lower morbidity and mortality rates and increased ADG, compared with those for calves not exposed to PI cattle before weaning or vaccinated against BVDV. During trial 3, health and performance did not vary between calves that were and were not vaccinated against BVDV. CONCLUSIONS AND CLINICAL RELEVANCE: Exposure of cattle to BVDV naturally or through vaccination before or at feedlot arrival mitigated the negative effects of constant exposure to PI cattle.

A stochastic risk-analysis model for the spread of bovine viral diarrhea virus after introduction to naïve cow-calf herds.

A stochastic SIR model was developed to simulate the spread of bovine viral diarrhea virus (BVDV) through a cow-calf herd and estimate the effect of the virus on the herd, including abortions, calf morbidity, and calf mortality. The model was applied with three herd sizes (400, 100, and 50 head) and four control strategies (no intervention, vaccination of breeding stock, testing all calves pre-breeding and culling of persistently infected calves, and both vaccination of adults and testing and culling of calves). When no control strategy was implemented the BVDV reproductive rate (R(E-PI)) of persistently infected calves (PI's), vertical transmission rate from cows to calves and the mortality rate of PI's were influential in the number of PI's produced in the herd. When a vaccination program alone was implemented the vaccine efficacy was influential in the number of PI's produced in the herd. All control strategies decreased the effects of BVDV on the herd at both 1 and 10 years compared to no control. In most cases the combination of adult vaccination and calf testing and culling resulted in the largest decrease in the both the median and 95% prediction interval for the range of effects from BVDV. The effect of control strategies was most apparent in the 400 head herds. All control strategies increased the probability of early clearance of PI's from the herd for all herd sizes. Fifty and 100 head herds cleared infection by 4 and 9 years respectively even without a control program but 400 head herds did not always clear infection after 10 years unless a testing program was implemented. The model presented is valuable in assessing the effect of control strategies and the effects of disease parameters on BVDV spread in beef herds.

Effect of the bovine viral diarrhoea virus (BVDV) infection on dairy calf rearing.

The aim of this study was to compare the cumulative incidence of mortality, clinical diarrhoea and respiratory disease in calves, during their first six months of age, in herds with different bovine viral diarrhoea virus (BVDV) infection status. Calves' health indicators were tested by comparing proportions in 101 farms with dissimilar infection condition. The results indicate that there was a significant relationship between the BVDV status (actively infected herd or not) and the cumulative incidence of mortality and respiratory disorders.

The effect of bovine viral diarrhea virus infections on health and performance of feedlot cattle.

The aim of this study was to investigate the effect of bovine viral diarrhea virus (BVDV) infections (unapparent acute infections and persistent infections) on the overall health and performance of feedlot cattle. Calves from 25 pens (7132 calves) were enrolled in the study. Overall and infectious disease mortality rates were significantly higher (P < 0.05) in pens categorized at arrival as positive for type I BVDV and lower in pens that were positive for type II BVDV than in negative pens. Mortality attributed to BVDV infection or enteritis was significantly more common (P < 0.05) in the pens containing persistently infected (PI) calves than in pens not containing PI calves (non-PI pens). There were no statistically detectable (P > or = 0.05) differences in morbidity, overall mortality, average daily gain, or the dry matter intake to gain ratio between PI and non-PI pens. Although type-I BVDV infections in feedlots appear to contribute to higher mortality rates, the presence of PI calves alone does not appear to have a strong impact on pen-level animal health and feedlot performance.

Severe malformations in calves associated with bovine viral diarrhoea (BVD) virus infection in a dairy cattle herd.

During late may 2004, Some dairy cows at Al-Kharj area of central Saudi Arabia, gave birth to severely malformed calves which died, few hours to few days following birth. Samples were collected from the affected calves and their dams of virological and serological investigations. Bovine viral diarrhoea virus was detected by capture enzyme linked immuno-sorbent assay (ELISA) in the brains of affected calves. Serum antibodies were detected in the dams. The present study indicated that in spite of vaccination against BVD in the country, still severe affections of the disease are encountered. Further insight epidemiological studies to elucidate the BVD situation in Saudi Arabia is urgently needed.

Prevalence of Neospora caninum and persistent infection with bovine viral diarrhea virus in dairy-breed steers in a feedlot.

OBJECTIVE: To determine the prevalence and effect of Neospora caninum infection and persistent infection (PI) with bovine viral diarrhea virus (BVDV) on weight gain, morbidity, and mortality rate in dairy-breed steer calves located on a feedlot in California. DESIGN: Prospective cohort observational study. ANIMALS: 900 dairy-breed steer calves in 2 pens. PROCEDURES: The 3- to 4-month-old calves were evaluated for serum antibodies against N caninum and infection with BVDV at entry to the feedlot. Five months later, sera were again analyzed for anti-N caninum antibodies; calves that were determined to have BVDV infection initially were retested to evaluate PI status. Average daily gain, morbidity, and deaths were recorded for all calves. RESULTS: Among 900 calves, prevalence of N caninum infection was 16.7% (95% confidence interval, 14.3% to 19.3%); prevalence of BVDV-associated PI was 0.2% (95% confidence interval, 0.03% to 0.9%). Morbidity rate and time to first illness were not significantly different between calves that were seropositive or seronegative for N caninum. At the second sample collection, weight and average daily gain of calves that were seropositive for N caninum was less than that of seronegative steers in 1 pen, whereas these measures did not differ between groups in the other pen. Statistical power was insufficient to evaluate the effect of BVDV PI on any outcome measurement. CONCLUSIONS AND CLINICAL RELEVANCE: Although N caninum serostatus had no significant effect on morbidity rate, some seropositive calves had reduced growth, compared with seronegative calves, 5 months after entry to the feedlot.

Sensitivity analysis to identify key-parameters in modelling the spread of bovine viral diarrhoea virus in a dairy herd.

Models have been developed to represent the spread of bovine viral diarrhoea virus (BVDV) in cattle herds. Whereas the herd dynamics is well known, biological data are missing to estimate the parameters of the infection process. Our objective was to identify the parameters of the infection process that highly influence the spread of BVDV in a dairy herd. A stochastic compartmental model in discrete time represented BVDV infection in a typical Holstein dairy herd structured into five groups (calves, young versus older heifers, lactating versus dry cows). Model sensitivity was analysed for variations in the probability of birth of persistently infected (P) calves (b(P)), mortality of P animals (m(P)), within- and between-group transmission rates for P and transiently infected (T) animals (respectively, beta(w)(P),beta(b)(P),beta(w)(T),beta(b)(T)). Three to five values were tested per parameter. All possible combinations of parameter values were explored, representing 3840 scenarios with 200 runs for each. Outputs were: virus persistence 1 year after introduction, time needed to reach a probability of 80% for the herd to be virus-free, epidemic size, mean numbers of immune dams carrying a P foetus, of P and of T animals in infected herds. When considered together, m(P) and beta(b)(P) accounted for 40-80% of variance of all outputs; b(P) and beta(w)(T) accounted each for less than 20% of variance; beta(b)(T) and beta(w)(P) accounted for almost no percent of variance of the outputs. Parameters beta(w)(T) and b(P) needed to be more precisely estimated. The influence of m(P) indicated the effectiveness of culling P calves, the influence of beta(b)(P) indicated the role of the herd structure in BVDV spread, whereas the influence of b(P) indicated the possible role of vaccination programs in controlling within-herd BVDV spread.

Naturally occurring Mycoplasma bovis-associated pneumonia and polyarthritis in feedlot beef calves.

Mycoplasma bovis is perceived as an emerging cause of mortality in feedlot beef cattle. This study examined the lesions and infectious agents in naturally occurring M. bovis-associated bronchopneumonia and arthritis and the relationship of this condition with bovine viral diarrhea virus (BVDV) infection. Standardized pathologic, immunohistochemical, and microbiologic investigations were conducted on 99 calves that died or were euthanized within 60 days after arrival in 72 feedlots. Cranioventral bronchopneumonia with multiple foci of caseous necrosis was identified in 54 of 99 calves, including 30 with concurrent fibrinosuppurative bronchopneumonia typical of pneumonic pasteurellosis. Mycoplasma bovis was consistently identified in these lesions by culture and immunohistochemistry, but also commonly in healthy lungs and those with pneumonia of other causes. Focal lesions of coagulation necrosis, typical of pneumonic pasteurellosis, were often infected with both Mannheimia haemolytica and M. bovis. Arthritis was present in 25 of 54 (46%) calves with M. bovis pneumonia, and all calves with arthritis had pneumonia. BVDV infection was more common in calves with lesions of bacterial pneumonia than in those dying of other causes, but BVDV infection was not more common in calves with caseonecrotic bronchopneumonia than those with fibrinosuppurative bronchopneumonia. Retrospective analysis identified cases of M. bovis pneumonia in the early 1980s that had milder lesions than the current cases. The findings suggest that, in at least some calves, M. bovis induces caseonecrotic bronchopneumonia within the lesions of pneumonic pasteurellosis.

[Clinical signs and diagnosis of a severe primary infection with BVDV subtype 1b in a dairy herd]. / Klinische verschijnselen en diagnostiek bij een ernstige primaire BVD-virus subtype 1b-infectie in een melkveekoppel.

As a result of a BVDV infection in a herd consisting of 95 adult cattle 17 cows aborted their calves within a period of 3.5 months, one third got severe diarrhoea, 3 cows died and an increased percentage of the cattle got lochiometra after calving or abortion. The disease was diagnosed by paired serological testing of cattle with diarrhoea or abortion and post mortem examination of several aborted calves. From one foetus BVDV virus was isolated and subsequently subtyped by sequencing. Of aborting cattle, the testing results were influenced by the interval between infection and abortion. These results indicate that a primary infection with BVDV subtype 1b can cause severe clinical symptoms in a dairy herd.

Outbreak of foetal infection with bovine pestivirus in a central Queensland beef herd.

OBJECTIVE: To describe a significant outbreak of foetal infection and subsequent losses due to bovine pestivirus on a 5200 ha beef breeding and fattening property in central Queensland. DESCRIPTION OF THE HERD: The affected herd consisted of 656 cows, including 269 recently purchased cows, and 221 heifers that were joined in December/January 1995/96. There were approximately 2500 cattle on the property. INVESTIGATION: Following the purchase of 269 cows in October 1995, which were mingled with the existing cow herd, losses were experienced due to foetal infection with bovine pestivirus. These losses were recorded between 1996 and 1999 as: reduced pregnancy rates, losses between pregnancy testing (midpregnancy) and branding (calves averaged 3 months-of-age), losses due to pneumonia and ill-thrift between branding and approximately 12 months-of-age, and losses due to ill-thrift and the chronic wasting form of mucosal disease thereafter. All surviving calves were tested for bovine pestivirus in 1997 at an average of 10 months. Fifty-three calves were identified as persistently infected with bovine pestivirus. A further 110 calf losses could reasonably be attributed to bovine pestivirus infection. Persistently infected cattle were always unthrifty compared to their virus negative counterparts. Only one persistently infected calf was identified, on the basis of severe ill thrift, in the 1997 birth cohort and none in 1998. CONCLUSIONS: This outbreak of foetal infection with bovine pestivirus resulted in significant production losses. These losses were recorded over the three years subsequent to the outbreak. Significant numbers of persistently infected calves were not evident among calves born in the two years after this outbreak.

[Comparison of performance of dairy herds that were or were not vaccinated with a bovine herpes virus 1 marker vaccine in 1998]. / Vergelijking van de bedrijfskengetallen van melkveebedrijven die in 1998 wel of niet hebben gevaccineerd met BHV1 markervaccin.

This study analysed the effects of the use of bovine herpesvirus 1 (BHV1) marker vaccine on the performance of dairy cattle. In Spring of 1999, vaccination of 12 herds with the BHV1 marker vaccine resulted in severe animal health problems and mortality. The vaccines used on these farms were all from a batch that appeared to be contaminated with bovine virus diarrhoea virus type 2. This led to a general call to farmers and veterinary practitioners to report side-effects of this vaccine. As a result, more than 7000 farmers reported symptoms. The information was obtained by means of a questionnaire; there was no control group. To determine the effects of the use of the marker vaccine, it was necessary to perform a study based on objectively acquired information. The information collected by the Royal Dutch Cattle Syndicate and the office of Identification and Registration was complied into herd indices on production, udder health, reproduction, and culling. Two groups of dairy farms that had used the BHV1 marker vaccine (attenuated and inactivated vaccine) were compared with farms that were certified BHV1-free. The analyses were performed based on intra-herd comparisons, meaning that per herd each index calculated over a certain period of time after the use of the marker vaccine was compared to a similar period of time prior to the use of the marker vaccine. A total of 144 comparisons were made. Seven comparisons were statistically significant. In two comparisons, the results were in favour of the BHV1-free farms and in five comparisons, the result were in favour of the vaccinated farms. Thus use of the BHV1 marker vaccine could not be proven to affect herd performance. The sensitivity of the tests was very high, so with a high level of probability even very small differences in indices between groups would have been detected.

A questionnaire on the health, management, and performance of cow-calf herds in Québec.

Questionnaires were mailed to 520 cow-calf producers in Québec in order to compare management practices and herd performance according to herd size (small: < 40 females, or large: > or = 40 females) and in 4 geographic areas for the 1995 calving season. Owners of large herds adopted management practice and preventive measures more often than did owners of small herds. Average calving and weaning rates were 95% and 87% respectively. Average perinatal and preweaning mortality rates were between 4.9% and 5.6%. A greater percentage of owners with large herds than owners of small herds reported diarrhea and pneumonia problems. Among large herds, the number of herds experiencing pneumonia and calf mortality associated with diarrhea tended to be higher in areas of the northwest. Calf mortality due to pneumonia was higher in the northeast. No regional variation was found among small herds. Further research is needed to identify diseases risk factors.

[Pestivirus as causative agent of abortion and perinatal mortality in cattle and sheep in Switzerland]. / Ursächliche Beteiligung von Pestiviren an Aborten und perinatalen Todesfällen bei Rindern und Schafen in der Schweiz.

The causal involvement of bovine viral diarrhoea virus (BVDV) and border disease virus (BDV) infection in bovine and ovine abortion and perinatal mortality remain unclear. From 1992 until 1994, 213 bovine and 31 ovine foetuses as well as 36 calves and 25 lambs which had died perinatally were investigated. Tissue samples were tested for the presence of pestiviruses and serum or fluid from the body cavities were analysed for the presence of pestivirus antibodies. Detection of pestiviruses was performed by (i) cell culture isolation, (ii) antigen ELISA and (iii) immunohistochemical staining for viral antigen. For antibody-testing an indirect ELISA was used. In nine bovine foetuses and in two calves BVDV was isolated. Pestiviruses, most likely BDV were detected in one ovine foetus and three lambs. In 6% of the bovine and 11% of the ovine foetuses anti-pestivirus antibodies were detected. However, clinical features and history of bovine cases did not show a correlation with the diagnostic results, In contrast, the presence of central nervous system signs in neonatal lambs and the detection of BDV was correlated.

Insertion of a sequence encoding light chain 3 of microtubule-associated proteins 1A and 1B in a pestivirus genome: connection with virus cytopathogenicity and induction of lethal disease in cattle.

Pestiviruses represent the first RNA viruses for which recombination with cellular protein-coding sequences has been reported. As a result of such recombinations cytopathogenic (cp) pestiviruses can develop from noncytopathogenic (noncp) viruses. In the case of bovine viral diarrhea virus (BVDV), the generation of cp mutants is linked to the induction of the lethal syndrome mucosal disease (MD) in cattle. The cp BVDV JaCP was isolated from an animal which had come down with MD. The genome of JaCP contains a novel kind of cellular insertion (LC3*) which is flanked by duplicated pestivirus sequences. Neither insertion nor duplication is present in the genome of the accompanying noncp virus JaNCP. As part of the viral polyprotein, the insertion in the JaCP genome is translated into a polypeptide almost identical to a fragment of light chain 3, a subunit of the microtubule-associated proteins 1A and 1B from the rat. Transient-expression studies revealed that the LC3* sequence is able to induce an additional cleavage of the viral polyprotein. The respective cleavage occurs directly downstream of the LC3*-encoded sequence and is not dependent on the NS3 serine protease. Insertion of LC3* into an infectious noncp pestivirus cDNA clone without duplicated viral sequences resulted in recovery of a defective cp virus able to replicate only in the presence of a noncp helper virus. In contrast, introduction of both insertion and duplication led to an autonomously replicating cp virus.

Losses over a 2-year period associated with fetal infection with the bovine viral diarrhea virus in a beef cow-calf herd in Saskatchewan.

In 1992, significant calf losses occurred between birth and weaning in a 650-cow Saskatchewan beef herd. These losses occurred subsequent to ill-thrift and disease, and every calf necropsied was found to be persistently infected with bovine viral diarrhea virus (BVDV). The objectives of this study were to describe the losses associated with fetal infection with BVDV in this herd and to determine why they occurred. For investigative purposes, blood samples were collected from the entire cow herd and the surviving calves at pregnancy testing in 1992, and tested by virus isolation for BVDV. Between 51 and 71 persistently infected calves were born in 1992. Bovine viral diarrhea virus was only isolated from calves. The only confirmed fetal infections with BVDV were recorded as the birth of persistently infected calves. However, abortions, reduced pregnancy rates, and delayed calvings were also recorded in the cow herd and may have been the result of fetal infections. The herd was monitored again in 1993. Fetal infections with BVDV were recorded as the birth of stunted, deformed, and persistently infected calves. The greatest losses due to fetal infection with BVDV in the 2 years of this study occurred in cows that were 3-years-old at calving (second calves). Bovine viral diarrhea virus appears to have remained endemic in this herd by transmission from persistently infected calves on young 3- and 4-year-old cows to naive calved 2-year-old cows that were mingled with them annually for rebreeding. Significant numbers of the 2-year-old cows remained naive to BVDV, because they were segregated from persistently infected calves at weaning, preventing cross-infection with BVDV.

Performance, survival, necropsy, and virological findings from calves persistently infected with the bovine viral diarrhea virus originating from a single Saskatchewan beef herd.

Fifty-one calves from 652 cows and heifers that calved on a Saskatchewan ranch in 1992 were identified as persistently infected with bovine viral diarrhea virus (BVDV), based on virological and necropsy findings. Herd records suggested a further 20 calves that died between birth and weaning were probably also persistently infected. Subsequent to weaning, all surviving persistently infected calves were transferred to one pen in a 10,000 head commercial feedlot, to mimic normal management practice in western Canadian beef herds. On average, when compared with healthy, BVDV-negative herdmates, persistently infected calves were "poor doers" and had poor survivability, with only 4 persistently infected calves surviving to 1 year of age. There was no difference (P > 0.05) in survival between male and female persistently infected calves. The clinical, pathological, and virological findings from these persistently infected calves varied over time. The majority of persistently infected calves had gross pathological lesions at necropsy, consistent with mucosal disease. However, approximately 25% of the persistently infected calves had gross pneumonic lesions at necropsy, with no or only mild lesions of mucosal disease. A wide variety of other lesions were also noted in persistently infected calves at necropsy. Therefore, the possibility that BVDV-induced lesions can be misdiagnosed is very real. The results of this study indicate that persistent infection with BVDV should always be considered in calves with chronic ill thrift, chronic enteritis, or respiratory disease.

Identification of a new group of bovine viral diarrhea virus strains associated with severe outbreaks and high mortalities.

New BVDV strains associated with very high mortalities, which killed about 25% of the veal calves in Quebec in 1993, have been isolated. In this study, characterization of the last two-thirds of the 5' untranslated region (5'UTR) of their genome and virus neutralization experiments with polyvalent antisera raised in different animals both demonstrated that these strains formed a distinct group. Despite a difference of about 25% in the 5'UTR sequence with that of the classical strains, these 5'UTRs maintained the same secondary structure albeit with a higher stability. Serological crossreactivity between the classical and new BVDV strains was relatively low and suggest that new strains should also be included to obtain efficient BVDV vaccines. Based upon the distinct characteristics of these new BVDV strains, we propose to divide BVDV into two groups. Group I comprises the classical BVDV isolates including commonly used laboratory and vaccine strains, and group II comprises the newly described BVDV strains and those associated with thrombocytopenia and hemorrhaging.

Infection of pigs and cattle with bovine viral diarrhoea virus on a farm in England.

Deaths within a litter of sucking pigs led to a suspicion of hog cholera, but pestiviruses isolated from both dead and live piglets appeared to be bovine viral diarrhoea virus. Persistent viraemia with bovine viral diarrhoea virus was demonstrated in living littermates and also in a bought-in calf, housed in a nearby pen on the same farm. Only two of the littermates survived, both of which had been virus negative and seropositive from the outset of testing. Porcine and bovine virus isolates grew well in calf testicular cells and were neutralised equally by sera collected at the farm from cattle and pigs. However, a comparison by means of their reactivity to monoclonal antibodies showed that they were similar but not identical, and only the porcine isolates grew well in a porcine kidney cell line.