Respiratory Bovine Coronavirus Research Articles

Isolation and Characterization of Contemporary Bovine Coronavirus Strains.

Bovine coronavirus (BCoV) poses a threat to cattle health worldwide, contributing to both respiratory and enteric diseases. However, few contemporary strains have been isolated. In this study, 71 samples (10 nasal and 61 fecal) were collected from one farm in Ohio in 2021 and three farms in Georgia in 2023. They were screened by BCoV-specific real-time reverse transcription-PCR, and 15 BCoV-positive samples were identified. Among them, five BCoV strains from fecal samples were isolated using human rectal tumor-18 (HRT-18) cells. The genomic sequences of five strains were obtained. The phylogenetic analysis illustrated that these new strains clustered with US BCoVs that have been detected since the 1990s. Sequence analyses of the spike proteins of four pairs of BCoVs, with each pair originally collected from the respiratory and enteric sites of one animal, revealed the potential amino acid residue patterns, such as D1180 for all four enteric BCoVs and G1180 for three of four respiratory BCoVs. This project provides new BCoV isolates and sequences and underscores the genetic diversity of BcoVs, the unknown mechanisms of disease types, and the necessity of sustained surveillance and research for BCoVs.

Comprehensive genetic analysis of the first near-complete genome of bovine coronavirus and partial genome of bovine rotavirus in Türkiye through metagenomics.

Obtaining the complete or near-complete genome sequence of pathogens is becoming increasingly crucial for epidemiology, virology, clinical science and practice. This study aimed to detect viruses and conduct genetic characterization of genomes using metagenomics in order to identify the viral agents responsible for a calf's diarrhoea. The findings showed that bovine coronavirus (BCoV) and bovine rotavirus (BRV) are the primary viral agents responsible for the calf's diarrhoea. The current study successfully obtained the first-ever near-complete genome sequence of a bovine coronavirus (BCoV) from Türkiye. The G+C content was 36.31% and the genetic analysis revealed that the Turkish BCoV strain is closely related to respiratory BCoV strains from France and Ireland, with high nucleotide sequence and amino acid identity and similarity. In the present study, analysis of the S protein of the Turkish BCoV strain revealed the presence of 13 amino acid insertions, one of which was found to be shared with the French respiratory BCoV. The study also identified a BRV strain through metagenomic analysis and detected multiple mutations within the structural and non-structural proteins of the BRV strain, suggesting that the BRV Kirikkale strain may serve as an ancestor for reassortants with interspecies transmission, especially involving rotaviruses that infect rabbits and giraffes.

Detection of bovine coronavirus (BCoV) infection in cattle with clinical respiratory signs by PCR and investigation of the serological status of these animals

Aim: It was aimed to reveal the antigenic and serological prevalence of bovine coronavirus (BCoV) in cattle with clinically respiratory infection and to evaluate the relationship between virus shedding and serological status of animals in this study. Materials and Methods: In the study, nasal swab samples were collected from a total of 92 cattle of different gender between 0 and 2 years of age with clinical respiratory symptoms. These samples were subjected to RT-PCR using specific primer pairs. Furthermore, serum samples were also collected from the same animals and evaluated for BCoV-specific antibodies through an indirect ELISA method. Results: Ten (10.87%) swap samples were defined as positive for BCoV using RT-PCR. The seropositivity rate was 93.48% (86/92) in cattle by ELISA and 90% (9/10) in virus-shedding animals with nasal swab samples. Conclusion: The fact that 93.47% seropositivity was detected in unvaccinated animals against coronavirus in this study indicates that the animals were exposed to BCoV through colostrum or at a certain period of their lives. However the fact that 9 out of 10 animals with BCoV detected in swab samples also have BCoV-specific antibodies casts doubt on the efficacy of these antibodies in protecting against respiratory BCoV infections. We concluded that more detailed studies are needed to reveal the role of antibodies in respiratory coronavirus infections.

Vaccination of calves at day of birth with attenuated vaccines against bovine respiratory syncytial virus, bovine parainfluenza type 3 virus and respiratory bovine coronavirus

Vaccination of calves at day of birth with attenuated vaccines against bovine respiratory syncytial virus, bovine parainfluenza type 3 virus and respiratory bovine coronavirus

Bovine respiratory coronavirus enhances bacterial adherence by upregulating expression of cellular receptors on bovine respiratory epithelial cells

Bovine coronavirus (BCoV) is one of the agents causing bovine respiratory disease complex (BRDC), with single infection tending to be mild to moderate; the probability of developing pneumonia in BRDC may be affected by viral and bacterial combinations. Previously, we reported that bovine respiratory syncytial virus (BRSV) infection enhances adherence of Pasteurella multocida (PM) to cells derived from the bovine lower respiratory tract but that BRSV infection in cells derived from the upper respiratory tract reduces PM adherence. In this study, we sought to clarify whether the modulation of bacterial adherence to cells derived from the bovine upper and lower respiratory tract is shared by other BRDC-related viruses by infecting bovine epithelial cells from the trachea, bronchus and lung with BCoV and/or PM. The results showed that cells derived from both the upper and lower respiratory tract were susceptible to BCoV infection. Furthermore, all cells infected with BCoV exhibited increased PM adherence via upregulation of two major bacterial adhesion molecules, intercellular adhesion molecule-1 (ICAM-1) and platelet-activating factor receptor (PAF-R), suggesting that compared with BRSV infection, BCoV infection differentially modulates bacterial adherence. In summary, we identified distinct interaction between bovine respiratory viruses and bacterial infections.

Detección molecular de coronavirus bovino asociado al complejo respiratorio bovino en ganado de engorda del valle de Mexicali, Baja California, México

El complejo respiratorio bovino (CRB) es la principal causa de enfermedad y muerte en el ganado de engorda en todo el mundo. Es un síndrome infeccioso multifactorial provocado por distintos virus y bacterias que disminuyen la eficiencia productiva y ocasionan pérdidas económicas. En México, el CRB se ha reportado en todas las regiones donde se engorda ganado; sin embargo, esos reportes carecen de información sobre la presencia del coronavirus respiratorio bovino (CVB), haciendo necesario contar con herramientas de diagnóstico confiables y precisas para detectar la presencia de CVB en el ganado que se engorda en México, para proponer las medidas sanitarias apropiadas para su manejo clínico. En este trabajo, se desarrolló una plataforma de diagnóstico molecular de PCR en tiempo real (rt-PCR) que amplifica un fragmento de la proteína S del CVB en muestras de exudado nasal. Al aplicar la plataforma rt-PCR para CVB en bovinos de engorda en aparente estado de salud y con signos de enfermedad respiratoria asociados a CRB se encontró que 19/50 (38 %) resultaron positivos, confirmando la presencia de ese virus en el ganado de la región. Los resultados de este trabajo significan el primer reporte sobre la presencia del CVB asociado al CRB en la región ganadera del noroeste de México y sienta las bases para futuras investigaciones sobre papel que juega este virus en la presentación de la patología del CRB en los sistemas de explotación de bovinos de engorda en nuestra región y el país.

Molecular epidemiological survey and phylogenetic analysis of bovine respiratory coronavirus in Japan from 2016 to 2018.

Bovine coronavirus (BCoV) is an etiological agent of bovine respiratory disease (BRD). BRD is a costly illness worldwide; thus, epidemiological surveys of BCoV are important. Here, we conducted a molecular epidemiological survey of BCoV in respiratory-diseased and healthy cattle in Japan from 2016 to 2018. We found that 21.2% (58/273) of the respiratory-diseased cattle were infected with BCoV. The respiratory-diseased cattle had virus amounts 4.7 times higher than those in the asymptomatic cattle. Phylogenetic analyses showed that the BCoV identified in Japan after 2005 formed an individual lineage that was distinct from the strains found in other countries. These results suggest that BCoV is epidemic and has evolved uniquely in Japan.

Brazilian strain of bovine respiratory coronavirus is derived from dual enteric and respiratory tropism

Bovine coronavirus (BCoV) is a pathogen related to enteric and respiratory diseases in cattle worldwide. Enteric (BECoV) strains of BCoV are predominant in South America, and genetic investigations have been conducted to identify its relationship with isolates of respiratory origin (BRCoV). In this study, we used a BRCoV strain (BR-UEL11) derived from an outbreak of respiratory disease in feedlot cattle in southern Brazil, and compared the partial sequence of the polymorphic region of Spike (which was detected and sequenced by two distinct reverse transcription-polymerase chain reactions) with those of other BCoV strains. The phylogenetic relationship of BR-UEL11 with Brazilian BCoV, which is associated with calf diarrhea and winter dysentery (enteric, BECoV; respiratory, BRCoV), and classical reference prototypes was analyzed. The analysis showed that the BRCoV strains from Brazil clustered with a clade that was distinct from most isolates associated with calf diarrhea (BECoV) and ancestral prototype strains such as Mebus, Nebraska, and LYVB. Furthermore, the BRCoV strains from Brazil clustered with a clade that contained recent strains associated with winter dysentery, showing 98-99% nucleotide identity with those strains. These results suggested that the Brazilian BCoV evolved from being solely enteric to a dual enteric and respiratory tropic virus.

Genetic variability of the S1 subunit of enteric and respiratory bovine coronavirus isolates.

Bovine coronavirus (BCoV) is considered an important pathogen in cattle worldwide. It is a causative agent of enteric and respiratory diseases of cattle. The S1 subunit of the viral S glycoprotein is responsible for virus binding to host-cell receptors, induction of neutralizing antibody and hemagglutinin activity. The entire S1 genomic region (2304 bp) of two enteric bovine coronavirus isolates from Austria, one respiratory and one enteric isolate from Slovakia were analyzed at the genetic level. The comparative analysis of those four isolates revealed 97.1-98.6% similarity at the nucleotide and 95.6-98.6% at the amino acid level. No differences between enteric and respiratory isolates were observed at the genetic level. The isolates were clustered in the phylogenetic tree with European isolates independently of their enteric or respiratory origin.

Complete Genome Analysis of Canine Respiratory Coronavirus

The canine respiratory coronavirus (CRCoV) K37 strain of the family Coronaviridae, group 2, was isolated in South Korea. Its genome was analyzed by nucleotide sequencing and was determined to have 31,029 bp. The small open reading frames situated between the spike and envelope genes of most of the CRCoV strains (except the CRCoV 4180 strain) were found to encode three nonstructural proteins (4.9 kDa, 2.7 kDa, and 12.8 kDa), while those of bovine coronavirus (BCoV) encode another three nonstructural proteins (4.9 kDa, 4.8 kDa, and 12.7 kDa) and those of a recently isolated bovine respiratory coronavirus (BRCoV) were found to encode only two nonstructural proteins (4.9 kDa and 12.7 kDa). The differences in the genes encoding these small nonstructural proteins may be associated with the emergence of highly similar viruses in different hosts.

Molecular analysis of the bovine coronavirus S1 gene by direct sequencing of diarrheic fecal specimens

Bovine coronavirus (BCoV) causes severe diarrhea in newborn calves, is associated with winter dysentery in adult cattle and respiratory infections in calves and feedlot cattle. The BCoV S protein plays a fundamental role in viral attachment and entry into the host cell, and is cleaved into two subunits termed S1 (amino terminal) and S2 (carboxy terminal). The present study describes a strategy for the sequencing of the BCoV S1 gene directly from fecal diarrheic specimens that were previously identified as BCoV positive by RT-PCR assay for N gene detection. A consensus sequence of 2681 nucleotides was obtained through direct sequencing of seven overlapping PCR fragments of the S gene. The samples did not undergo cell culture passage prior to PCR amplification and sequencing. The structural analysis was based on the genomic differences between Brazilian strains and other known BCoV from different geographical regions. The phylogenetic analysis of the entire S1 gene showed that the BCoV Brazilian strains were more distant from the Mebus strain (97.8% identity for nucleotides and 96.8% identity for amino acids) and more similar to the BCoV-ENT strain (98.7% for nucleotides and 98.7% for amino acids). Based on the phylogenetic analysis of the hypervariable region of the S1 subunit, these strains clustered with the American (BCoV-ENT, 182NS) and Canadian (BCQ20, BCQ2070, BCQ9, BCQ571, BCQ1523) calf diarrhea and the Canadian winter dysentery (BCQ7373, BCQ2590) strains, but clustered on a separate branch of the Korean and respiratory BCoV strains. The BCoV strains of the present study were not clustered in the same branch of previously published Brazilian strains (AY606193, AY606194). These data agree with the genealogical construction and suggest that at least two different BCoV strains are circulating in Brazil.

Quasispecies of bovine enteric and respiratory coronaviruses based on complete genome sequences and genetic changes after tissue culture adaptation

The genetic diversity of 2 pairs (AH65 and AH187) of wild type bovine coronaviruses (BCoV) sequenced directly from nasal (respiratory) and rectal (enteric) swabs of two feedlot calves with respiratory and enteric symptoms [Hasoksuz, M., Sreevatsan, S., Cho, K.O., Hoet, A.E., Saif, L.J., 2002b. Molecular analysis of the S1 subunit of the spike glycoprotein of respiratory and enteric bovine coronavirus isolates. Virus Res. 84 (1–2), 101–109.]. was analyzed. Sequence analysis of the complete genomes revealed differences at 123 and 149 nucleotides (nt) throughout the entire genome between the respiratory and enteric strains for samples AH65 and AH187, respectively, indicating the presence of intra-host BCoV quasispecies. In addition, significant numbers of sequence ambiguities were found in the genomes of some BCoV-R and BCoV-E strains, suggesting intra-isolate quasispecies. The tissue culture (TC) passaged counterparts of AH65 respiratory BCoV (AH65-R-TC) and enteric BCoV (AH65-E-TC) were also sequenced after 14 and 15 passages and 1 plaque purification in human rectal tumor cells (HRT-18), respectively. Compared to the parental wild type strains, tissue culture passage generated 104 nt changes in the AH65-E-TC isolate but only 8 nt changes in the AH65-R-TC isolate. Particularly noteworthy, the majority of nucleotide changes in the AH65-E-TC isolate occurred at the identical positions as the mutations occurring in the AH65-R strain from the same animal. These data suggest that BCoV evolves through quasispecies development, and that enteric BCoV isolates are more prone to genetic changes and may mutate to resemble respiratory BCoV strains after tissue culture passage.

Molecular analysis of S gene of spike glycoprotein of winter dysentery bovine coronavirus circulated in Korea during 2002–2003

Since the molecular analysis of spike (S) glycoprotein gene of bovine coronavirus (BCoV) has been conducted and compared mainly among American and Canadian isolates and/or strains, it is unclear whether BCoV circulated in the other countries are distinctive in genetic characteristics. In the present study, we analyzed the S glycoprotein gene to characterize 10 winter dysentery (WD) coronavirus strains circulated in Korea during 2002–2003 and compared the nucleotide (nt) and deduced amino acid (aa) sequences with the other known BCoV. The phylogenetic analysis of the entire S glycoprotein gene revealed that the aa sequences of all Korean WD strains were more homologous to each other and were very closely related to respiratory bovine coronavirus (RBCV) strain OK and enteric bovine coronavirus (EBCV) strain LY-138, but were distinct from the other known BCoVs. Based on the phylogenetic analysis of the hypervariable region of the S1 subunit, all Korean WD strains clustered with the respiratory strain OK, BCQ3994 and the enteric strain LY-138, while the Canadian BCQ calf diarrhea and WD strains, and the American RBCV LSU, French EBCV F15 and avirulent VACC, L9, and Mebus strains clustered on a separate major branch. These data suggest that the WD strains circulated in Korea had a genetic property of both RBCV and EBCV and were significantly distinct from the ancestral enteric strain.

Evaluation of concurrent shedding of bovine coronavirus via the respiratory tract and enteric route in feedlot cattle.

To assess the relationship between shedding of bovine coronavirus (BCV) via the respiratory tract and enteric routes and the association with weight gain in feedlot cattle. 56 crossbred steers. Paired fecal samples and nasal swab specimens were obtained and were tested for BCV, using antigen-capture ELISA. Paired serum samples obtained were tested for antibodies to BCV, using antibody-detection ELISA. Information was collected on weight gain, clinical signs, and treatments for enteric and respiratory tract disease during the study period. Number of samples positive for bovine respiratory coronavirus (BRCV) or bovine enteric coro navirus (BECV) was 37/224 (17%) and 48/223 (22%), respectively. Some cattle (25/46, 45%) shed BECV and BRCV. There were 25/29 (86%) cattle positive for BECV that shed BRCV, but only 1/27 (4%) cattle negative to BECV shed BRCV. Twenty-seven of 48 (56%) paired nasal swab specimens and fecal samples positive for BECV were positive for BRCV. In contrast, only 10/175 (6%) paired nasal swab specimens and fecal samples negative for BECV were positive for BRCV. Only shedding of BECV was associated with significantly reduced weight gain. Seroconversion to BCV during the 21 days after arrival was detected in 95% of the cattle tested. Feedlot cattle infected with BCV after transport shed BCV from the respiratory tract and in the feces. Fecal shedding of BCV was associated with significantly reduced weight gain. Developing appropriate control measures for BCV infections could help reduce the decreased weight gain observed among infected feedlot cattle.

Bovine coronaviruses associated with enteric and respiratory diseases in Canadian dairy cattle display different reactivities to anti-HE monoclonal antibodies and distinct amino acid changes in their HE, S and ns4.9 protein

Bovine coronavirus isolates associated with recent outbreaks of respiratory disease in Ontario and Quebec dairy farms were compared to reference strains known to be responsible for neonatal calf diarrhea (NCD) or winter dysentery (WD) of adult cattle. In respect to their hemagglutinating properties and their higher RDE activities with rat erythrocytes, WDBCoV strains differed from NCDBCoV strains and respiratory bovine coronaviruses RBCoV strains. Serologically, three MAbs directed to the HE glycoprotein of the WDBCoV strain BCQ.2590 recognized two serogroups amongst NCDBCoV strains by hemagglutination inhibition, whereas only one of the MAbs failed to react toward three of the four RBCoV isolates tested. Sequencing analysis of the S (S1 portion), HE, ORF4 and ORF5 genes of BCoV isolates associated with different clinical syndromes indicated that neither insertions or deletions could explain their distinct tropism. For the HE glycoprotein, a total of 15 amino acids (aa) substitutions were identified by comparing field isolates to the prototype Mebus strain. Two specific proline substitutions were identified for virulent strains being located in the signal peptides (aa 5) and aa position 367; one specific aa change was revealed at position 66 for RBCoV field isolates. Analysis of the S1 portion of the S glycoprotein revealed a total of eight aa changes specific to enteropathogenic (EBCoV) strains and eight aa changes specific to RBCoV strains. For all BCoV isolates studied, the region located between the S and M genes (ORF4) apparently encodes for two non-structural (ns) proteins of 4.9 and 4.8 kDa. A specific non-sense mutation was identified for the nucleotide at position 88 of the putative 4.9 kDa protein gene of RBCoV isolates resulting in 29 rather that 43 aa residues. The ORF5, which encodes a 12.7 ns protein and the 9.5 kDa E protein, was highly conserved amongst the BCoV field isolates.

Identification of specific variations within the HE, S1, and ORF4 genes of bovine coronaviruses associated with enteric and respiratory diseases in dairy cattle.

The bovine Coronavirus (BCV) is the causative agent of enteric diseases including neonatal calf diarrhea (NCD) (Dea et al., 1980; Mebus et al., 1973), winter dysentery (WD) (Benfield and Saif, 1990; Dea et al., 1995), and chronic shedding in adult cattle (AD) (Tsunemitsu et Saif, 1995). BCV can also infect the upper respiratory tract of growing calves causing pneumonia (Chouljenko et al., 1998; Reynolds et al., 1985). The respiratory BCV (RBCV) is now recognized as an important agent associated to shipping fever (Storz et al., 1996). The virion possesses a single stranded, non segmented RNA genome of positive polarity, and is made of 5 structural proteins: the nucleocapsid phosphoprotein (N: 52 kDa), the matrix glycoprotein (M: 25 kDa), the peplomer glycoprotein (S: 200 kDa), the small membrane protein (E: 9.5 kDa) and the hemagglutinin esterase glycoprotein (HE: 140 kDa) (Spaan et al., 1988). Both S and HE are able to agglutinate red blood cells and elicit production of neutralizing antibodies (Dea et Tijssen, 1989; Deregt and Babiuk, 1987; Vautherot et al, 1992). The S protein has an important role to play in tropism being responsible for binding to the host cell (Spaan et al., 1988). The regions situated between the S and M genes (ORF4 and ORF5) may also be implicated in the tropism of coronaviruses (Mounir et al., 1992).

Elucidation of the genomic nucleotide sequence of bovine coronavirus and analysis of cryptic leader mRNA fusion sites.

Over the last few years numerous respiratory bovine coronaviruses (RBCV) were isolated from respiratory infections of cattle including two shipping fever epizootics (Storz et al., 1996; Storz et al., 2000). The RBCV strain 98TXSF-110-LU (LU) and the enteric strain 98TXSF-110-ENT (ENT) were isolated from lung and intestinal samples, respectively, from an animal experiencing fatal respiratory disease during a 1998 shipping fever epizootic. We obtained and compared the entire genomic sequences of the LU and ENT isolates to delineate nucleotide (nt) and amino acid (aa) differences between them. In addition, we analyzed the leader-mRNA junction sequences of the S and 12.7 kDa mRNAs specified by different BCV strains.KeywordsSingle Nucleotide SubstitutionJunction SequenceFusion SiteEntire Genomic SequenceGenomic Nucleotide SequenceThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

Temperature-sensitive acetylesterase activity of haemagglutinin-esterase specified by respiratory bovine coronaviruses.

Numerous respiratory bovine coronaviruses (RBCV) were isolated recently from nasal swab samples and lung tissues of feedlot cattle with acute respiratory tract disease. These newly emerging RBCV isolates exhibited distinct phenotypic features that differentiated them from enteropathogenic bovine coronaviruses (EBCV). The RBCV strains had a receptor-destroying enzyme function mediated by acetylesterase (AE) activity of the haemagglutinin-esterase (HE) glycoprotein. The HE genes of wild-type EBCV strain LY138 and RBCV strains OK-0514 (OK) and LSU-94LSS-051 (LSU) were cloned, sequenced and transiently expressed in COS-7 cells. The enzymic properties of HE proteins in COS-7 cellular extracts and in purified virus preparations were assayed at room temperature, 37 degrees C and 39 degrees C by two different assays. One assay used p-nitrophenyl acetate (PNPA) as substrate and detected serine-esterase activity; the second assay monitored AE function with bovine submaxillary mucin (BSM) as substrate. The PNPA tests confirmed that HE proteins of EBCV and RBCV were functionally expressed in transfected COS-7 cells. Time-dependent determination of the AE activity of purified RBCV OK and LSU particles showed lower AE activity at 39 degrees C than at 37 degrees C, whereas the purified EBCV LY particles retained full AE activity at both 37 degrees C and 39 degrees C. Transiently expressed RBCV HE exhibited a marked reduction of AE activity after 40 min of assay time at 37 degrees C. In contrast, the AE activity of the transiently expressed EBCV HE remained stable beyond 40 min. The deduced amino-acid sequences of the HE proteins specified by the RBCV strains OK and LSU contained specific amino-acid changes in comparison with the EBCV LY strain, which may be responsible for the observed enzymic differences. These results are consistent with the hypothesis that RBCV strains have evolved to selectivelyreplicate in respiratory tissues and that HE may play a role in this tissue tropism.

Antibody responses to respiratory coronavirus infections of cattle during shipping fever pathogenesis

Summary. Antibody responses against respiratory bovine coronavirus (RBCV) infections were monitored in cattle from the onset of a naturally occurring severe shipping fever (SF) epizootic to complete recovery of affected cattle or fatal outcomes. The infection with RBCV was detected in nasal secretions of 86 cattle, and 81 of them developed acute respiratory tract disease, including fatal pneumonia. Cattle nasally shedding RBCV at the beginning of the epizootic experienced characteristic primary immune responses with specific antibodies for hemagglutinin-esterase (HE) and spike (S) glycoproteins. Virus shedding in nasal secretions of the majority of the cattle ceased between days 7 and 14 with the appearance of HE- and S-specific antibodies. Nasal samples and lung tissues from 9 of the 10 fatal cases had high titers of RBCV, but these cattle had only IgM responses to RBCV infections. Cattle remaining negative in RBCV isolation tests entered this epizootic with antibodies against HE and S. Protection against respiratory tract disease was apparently associated with high level of opsonic and virus-neutralizing IgG2. The HE and S glycoproteins were recognized earliest by the bovine immune system while the N protein induced antibody responses during the later stage of initial infection and the early stage of reinfection. The membrane (M) glycoprotein was the least immunogenic of the major viral structural proteins.

Isolation of respiratory bovine coronavirus, other cytocidal viruses, and Pasteurella spp from cattle involved in two natural outbreaks of shipping fever.

To identify cytocidal viruses and Pasteurella spp that could be isolated from cattle involved in 2 natural outbreaks of shipping fever. 105 and 120 castrated male 4- to 8-month-old feedlot cattle involved in 1997 and 1998 outbreaks, respectively. Nasal swab specimens and blood samples were collected, and cattle were vaccinated on arrival at an order-buyer barn from 4 local auction houses. Four days later, they were transported to a feedlot, and additional nasal swab specimens and blood samples were collected. Nasal swab specimens were submitted for virus isolation and bacterial culture; blood samples were submitted for measurement of respiratory bovine coronavirus (RBCV) hemagglutinin inhibition titers. 93 of 105 cattle and 106 of 120 cattle developed signs of respiratory tract disease during 1997 and 1998, respectively, and RBCV was isolated from 81 and 89 sick cattle, respectively, while at the order-buyer's barn or the day after arrival at the feedlot. During the 1997 outbreak, bovine herpesvirus 1 was isolated from 2 cattle at the order-buyer's barn and from 5 cattle 7 and 14 days after arrival at the feedlot, and parainfluenza virus 3 was isolated from 4 cattle 14 days after arrival at the feedlot. During the 1998 outbreak, bovine herpesvirus 1 was isolated from 2 cattle at the order-buyer's barn and on arrival at the feedlot and from 5 cattle 7 and 14 days after arrival at the feedlot, and parainfluenza virus 3 was isolated from 1 animal the day of, and from 18 cattle 7 and 14 days after, arrival at the feedlot. Pasteurella spp was cultured from 4 and 6 cattle at the order-buyer's barn and from 92 and 72 cattle on arrival at the feedlot during the 1997 and 1998 outbreaks, respectively. Results suggest that RBCV may play a causative role in outbreaks of shipping fever in cattle. More than 80% of the sick cattle shed RBCV at the beginning of 2 outbreaks when the Pasteurella spp infection rate was low.