Detection of bovine coronaviruses from adult cows with epizootic diarrhea and their antigenic and biological diversities

Brain invasion of bovine coronavirus: molecular analysis of bovine coronavirus infection in calves with severe pneumonia and neurological signs

IMPORTANCE

Although the role of bovine coronavirus (BCoV) in calf diarrhea and respiratory disorders is well documented, its contribution to neurological diseases is unclear.

OBJECTIVE

This study conducted virological investigations of calves showing diarrhea and respiratory and neurological signs.

METHODS

An outbreak of diarrhea, respiratory, and neurological disorders occurred among the 12 calves in July 2022 in Istanbul, Türkiye. Two of these calves exhibited neurological signs and died a few days after the appearance of symptoms. One of these calves was necropsied and analyzed using molecular and histopathological tests.

RESULTS

BCoV RNA was detected in the brain, lung, spleen, liver, and intestine of the calf that had neurological signs by real-time reverse transcription polymerase chain reaction. Immunostaining was also observed in the intestine and brain. A 622 bp S1 gene product was noted on gel electrophoresis only in the brain. Phylogenetic analysis indicated that the BCoV detected in this study had a high proximity to the BCoV strain GIb with 99.19% nucleotide sequence homology to the strains detected in Poland, Israel, Türkiye, and France. No distinct genetic lineages were observed when the brain isolate was compared with the respiratory and enteric strains reported to GenBank. In addition, the highest identity (98,72%) was obtained with the HECV 4408 and L07748 strains of human coronaviruses.

CONCLUSIONS AND RELEVANCE

The strain detected in a calf brain belongs to the GIb-European lineage and shares high sequence homology with BCoV strains detected in Europe and Israel. In addition, the similarity between the human coronaviruses (4408 and L07748) raises questions about the zoonotic potential of the strains detected in this study.

Coronaviruses in cattle

Bovine coronaviruses are spread all over the world. They cause two types of clinical manifestations in cattle either an enteric, calf diarrhoea and winter dysentery in adult cattle, or respiratory in all age groups of cattle. The role of coronaviruses in respiratory infections is still a hot topic of discussion since they have been isolated from sick as well as healthy animals and replication of disease is rarely successful. Bovine coronavirus infection is characterised by high morbidity but low mortality. The laboratory diagnosis is typically based on serological or molecular methods. There is no registered drug for the treatment of virus infections in cattle and we are limited to supportive therapy and preventative measures. The prevention of infection is based on vaccination, biosecurity, management and hygiene. This paper will cover epidemiology, taxonomy, pathogenesis, clinical signs, diagnosis, therapy, economic impact and prevention of coronavirus infections in cattle.

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.

Surveillance of diarrhea-causing pathogens in dairy and beef cows in Yamagata Prefecture, Japan from 2002 to 2011

The economic consequences of bovine diarrhea are serious. Few long‐term epidemiological data are available concerning the causative pathogens of bovine diarrhea in Japan. From 2002 to 2011, surveillance of enteric pathogens was performed in cows of various breed and age from 302 farms in which diarrhea had occurred in Yamagata Prefecture, Japan. Differences between dairy and beef cows in the number of cases of diarrhea and rates of infection by Salmonella spp. and Eimeria spp. were found. Clinical symptoms (duration of epidemic, hematochezia and complications) caused by bovine rotavirus infection were milder than those caused by bovine coronavirus infection.

Antigenic variation among recent Japanese isolates of bovine coronaviruses belonging to phylogenetically distinct genetic groups

Bovine coronaviruses (BCoVs) isolated in Japan consist of four genetic groups, as determined by phylogenetic analysis using the polymorphic region (aa 456–592) of the S glycoprotein gene. Japanese field isolates of BCoV, reference Kakegawa strain, and vaccine strain 66/H were analyzed for their antigenic properties by indirect immunofluorescence and neutralization testing. There were no significant differences observed among these BCoVs in direct immunofluorescence tests. However, antigenic differences were observed between BCoVs in the neutralization tests, although there was no clear indication of a distinct serotype. A monoclonal antibody, 4H4, against the Kakegawa strain belonging to group 1 lacked significant neutralizing activity for viruses of groups 2, 3, and 4. Therefore, we speculate that the genetic differences between these groups may have altered their antigenicity. Analysis of mutant viruses resistant to neutralization by 4H4 revealed that the antigenic site of the Kakegawa strain maps to amino acid position 284 of the S glycoprotein. This site is not homologous to a known antigenic site (aa 528) of the Quebec strain belonging to group 1, and it is not located in the conformational domain comprising domain I (aa 351–403) and domain II (aa 517–621). This amino acid constitutes a neutralization epitope of BCoV, which is distinct from aa 528 of the Quebec strain. These results indicate antigenic evolution of BCoV between the genetic groups circulating in Japan.

Development and application of one-step multiplex reverse transcription PCR for simultaneous detection of five diarrheal viruses in adult cattle

A one-step multiplex reverse transcription (RT)-PCR method was developed for the simultaneous detection of five viruses causing diarrhea in adult cattle: bovine group A rotavirus (GAR), bovine group B rotavirus (GBR), bovine group C rotavirus (GCR), bovine coronavirus (BCV), and bovine torovirus (BToV). The detection limit of the one-step multiplex RT-PCR for GAR, GCR, BCV, and BToV was 10², 10⁰, 10¹, and 10² TCID₅₀/ml, respectively, and that for GBR was 10⁶ copies/ml. The one-step multiplex RT-PCR with newly designed primers to detect GAR had higher sensitivity than a single RT-PCR with conventional primers, with no false-positive reactions observed for ten other kinds of bovine RNA viruses To assess its field applicability, 59 of 60 fecal samples containing one of these five viruses from all 25 epidemic diarrhea outbreaks in adult cattle were positive in the one-step multiplex RT-PCR assay. Furthermore, using four additional fecal samples containing two viruses (GBR and BCV or BToV), two amplified products of the expected sizes were obtained simultaneously. In contrast, all 80 fecal samples lacking the five target viruses from normal adult cattle were negative in the multiplex assay. Taken together, our results indicate that the one-step multiplex RT-PCR developed here for the detection of GAR, GBR, GCR, BCV, and BToV can be expected to be a useful tool for the rapid and cost-effective diagnosis and surveillance of viral diarrhea in adult cattle.

The detection and genetic characterization based on the S1 gene region of BCoVs from respiratory and enteric infections in Turkey

We investigated bovine coronavirus (BCoV) as an etiological agent in cattle with clinical respiratory and digestive signs using 147 feces and 199 nasal swab samples. A total of 18 test samples (16 feces and 2 nasal swap samples) were detected positive by ELISA and/or RT-PCR targeting the BCoV N gene. The partial S1 gene regions of BCoVs (An-4 and An-11) detected in feces samples from two herd-mate dairy calves were compared. Virological and serological results indicated that BCoVs are widespread in Turkey and are likely etiological agents in diarrhea cases in calves.

Genetic and antigenic characterization of newly isolated bovine toroviruses from Japanese cattle

Torovirus, a member of the Coronaviridae family, is a gastrointestinal infectious agent that has been identified in humans, cattle, pigs, and equines. Toroviruses, except equine torovirus, are difficult to propagate in cell culture; indeed, to date, only the Aichi/2004 strain of bovine torovirus (BToV) has been isolated among the human, bovine, and porcine toroviruses. In the present study, four cytopathogenic BToVs were isolated from diarrheal feces of the cattle using the HRT-18 cell line, and their genetic and antigenic properties were compared. The cytopathogenic features of BToV isolates in HRT-18 cells were similar to those of the Aichi/2004 strain. However, none of the isolates showed cytopathogenic effects in the HRT-18 cells of different origin, suggesting that one significant factor contributing to the cytopathogenicity of BToV depends on properties of the HRT-18 cells themselves. All BToVs isolated were able to agglutinate mouse, but not chicken, erythrocytes, while they lacked receptor-destroying enzyme activity. Analysis of the N terminus of the spike gene showed that three isolates, but not the Gifu-2007TI/E strain, were phylogenetically located in cluster 1 and its analogs and revealed high cross-reactivity with each other, as demonstrated by neutralization (NT) and hemagglutination inhibition (HI) assays. The Gifu-2007TI/E strain was classified close to cluster 2 and exhibited relatively low cross-reactivity with these viruses; however, the difference was not sufficient to classify BToVs into serotypes, suggesting that at least two subtypes distinguishable by the structure of the N terminus of the spike gene and that both NT and HI tests may be exist.

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.

Fatal winter dysentery with severe anemia in an adult cow

An adult dairy cow fatally affected with winter dysentery was investigated pathologically and virologically. The cow had severe anemia and diarrhea with massive blood. Pathologically, the loss of surface epithelial cells and necrosis of crypt epithelial cells in the large intestine were observed. Bovine coronavirus (BCV) antigen was observed in necrotic crypt epithelial cells of the large intestine. Virus particles were found in the necrotic epithelial cells of the large intestine. Virologically, BCV was isolated from the feces of the dead cow. The dead cow had no serum antibody against BCV although the co-habitants did. These suggest that severe infection of BCV in the cow without the BCV antibody accompanied by severe hemorrhagic anemia resulted in the cow's death.

Biological and genetic analysis of a bovine-like coronavirus isolated from water buffalo (Bubalus bubalis) calves

We describe the isolation, biological and genetic characterization of a host-range variant of bovine coronavirus (BCoV) detected in water buffalo (Bubalus bubalis). By conventional and real-time RT-PCR assays, the virus was demonstrated in the intestinal contents of two 20-day-old buffalo calves dead of a severe form of enteritis and in the feces of additional 17 buffalo calves with diarrhea. Virus isolation, hemagglutination and receptor-destroying enzyme activity showed that the buffalo coronavirus (BuCoV) is closely related to BCoV but possesses some different biological properties. Sequence and phylogenetic analyses of the 3' end (9.6 kb) of the BuCoV RNA revealed a genomic organization typical of group 2 coronaviruses. Moreover, the genetic distance between BuCoV and BCoV was proven to be the same or even higher than the distance between other ruminant coronaviruses and BCoV. In conclusion, our data support the existence of a host-range variant of BCoV associated with enteritis in buffaloes.

Severe outbreak of bovine coronavirus infection in dairy cattle during the warmer season

A severe outbreak of enteric and respiratory disease associated with bovine coronavirus (BCoV) infection is described. The outbreak occurred in a dairy herd of southern Italy in the first decade of September 2006, when summer temperatures were still recorded, affecting calves, heifers and adult cows, with a marked decrease in milk production. By virus isolation and RT-PCR targeting the S gene, BCoV was identified as the etiological agent of the outbreak, whereas bacteriological, parasitological and toxicological investigations failed to detect other causes of disease. BCoV strains with 99–100% nucleotide identity in the S gene were isolated from nasal, ocular and rectal swabs, thus proving the absence of separate clusters of virus on the basis of tissue tropism. Sequence analysis of the haemagglutination-esterase and spike proteins of the strain detected in one rectal sample (339/06) showed a high genetic relatedness with recent BCoV isolates (98–99% amino acid identity), with several unique amino acid substitutions in the S protein. The BCoV outbreak described in this paper presents interesting aspects: (i) the occurrence of a severe form of disease in the warmer season; (ii) the simultaneous presence of respiratory and enteric disease; (iii) the involvement of young as well as adult cattle.

Detection and characterization of bovine coronaviruses in fecal specimens of adult cattle with diarrhea during the warmer seasons

Bovine coronavirus (BCoV) is an etiological agent associated with winter dysentery (WD), prevalent in adult cattle during the winter. Although we previously detected, isolated, and characterized BCoV strains from adult cattle with WD (WD-BCoV strains) during the winter in South Korea, the precise epidemiology, as well as the causative agent of diarrhea in adult cattle in the warmer seasons, has not been examined. We examined 184 diarrheic fecal specimens collected from 75 herds of adult cattle from seven provinces during the spring (warm), autumn (warm), and summer (hot) seasons. Bovine coronavirus-positive reactions were detected for 107 (58.2%) diarrheic fecal samples (in 47/75 herds). Of these 107 positive samples, 90 fecal samples from 33 herds tested positive for BCoV alone and 17 fecal samples from 14 herds also tested positive for other pathogens. Biological comparisons between the 9 BCoV strains isolated in this study and the 10 previously isolated WD-BCoV strains revealed that there was no receptor-destroying enzyme (RDE) activity against mouse erythrocytes in the 9 BCoV strains but the 10 WD-BCoV strains had high RDE activity. Phylogenetic analysis of the spike (S) and hemagglutinin/esterase (HE) proteins revealed that all the Korean BCoVs clustered together regardless of season and were distinct from the other known BCoVs, suggesting a distinct evolutionary pathway for the Korean BCoVs. These and previous results revealed a high prevalence and widespread geographical distribution of BCoV, suggesting that this virus is endemic in adult cattle with diarrhea in all seasons in South Korea.

[Severe acute respiratory syndrome]

In the Fall of 2002 a report from Guangdong Province in China showed the occurrence of an outbreak of atypical pneumonia. This outbreak rapidly progressed from China to Hong Kong, Singapore, Toronto, and the USA, to more than 25 countries worldwide and almost 3500 cases to date in april 2003. The clinical features associate a fever with mild respiratory symptoms which can progress to a typical acute respiratory distress syndrome requiring intensive care unit admission. Enteric forms with diarrhea were recently described in Hong Kong. The medical community responded very rapidly and united in front of this major health crisis. In a couple weeks, the agent, a new Coronavirus was isolated, therapeutic guidelines were proposed and measures to limit the outbreak diffusion were started worldwide. We summarize here the history of the outbreak, the clinical, laboratory and radiological features of SARS. April 2003 therapeutic guidelines are also reported.

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.

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

OBJECTIVE

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.

ANIMALS

56 crossbred steers.

PROCEDURES

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.

RESULTS

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.

CONCLUSIONS AND CLINICAL IMPLICATIONS

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.