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Bovine enterovirus (BEV) is a small, non-enveloped RNA virus belonging to the family Picornaviridae and the genus Enterovirus. For decades, BEV was considered a relatively innocuous agent, frequently isolated from the feces of healthy cattle and often termed an "orphan" virus without a clear disease association. However, a growing body of evidence over recent years has challenged this perception, linking BEV to outbreaks of respiratory, gastrointestinal, and reproductive disease in cattle populations worldwide. As an emerging and re-emerging pathogen, understanding the biology, epidemiology, and clinical impact of bovine enterovirus is increasingly important for veterinarians and the cattle industry.
Figure 1. Bovine enterovirus and associated disease. (Greening G E,et al.2016)
Bovine enteroviruses are classified within the enterovirus genus, which includes nine enterovirus species (A–J) and three rhinovirus species (A–C). BEV specifically falls under Enterovirus species E (EV-E) and Enterovirus species F (EV-F). This classification has evolved from earlier serological groupings, which originally recognized several serotypes but have now been consolidated with genotypic analysis providing more precise distinctions. Structurally, BEV particles are minute, measuring approximately 20–30 nanometers in diameter, with an icosahedral capsid and no lipid envelope. This non-enveloped nature contributes to their remarkable environmental stability. The genome consists of a single-stranded, positive-sense RNA molecule approximately 7.5 kilobases in length. This genome encodes a single open reading frame (ORF) that produces a large polyprotein precursor, which undergoes proteolytic cleavage to yield four structural proteins—VP1, VP2, VP3, and VP4—that form the viral capsid, and seven non-structural proteins involved in viral replication.
Bovine enteroviruses are distributed worldwide and are considered ubiquitous among cattle populations globally. Seroprevalence studies indicate that exposure is common, with many animals acquiring infection early in life. The virus has been isolated from various hosts, including cattle, buffalo, sheep, goats, and deer, though serotype 2 viruses appear to be more restricted to domestic cattle. Transmission occurs primarily through the fecal-oral route, with the virus shed in high concentrations in the feces of infected animals. Respiratory transmission via aerosolized nasal secretions is also possible. Once introduced into a herd, BEV spreads rapidly, particularly among young animals. Infected cattle can disseminate the virus continually through feces and nasal discharge for more than three months after apparent clinical recovery, serving as persistent sources of infection for herdmates.
The clinical significance of BEV has been a subject of evolving understanding. Historically considered an apathogenic commensal, BEV is now recognized as a causative agent associated with three main clinical syndromes:
| Key Molecular Targets | Details |
| Gastrointestinal Disease | Diarrhea is the most commonly reported clinical sign associated with BEV infection. Affected animals may exhibit loose, watery, or mucoid feces, often dark in color. Outbreaks of acute gastroenteritis in cattle herds have been increasingly linked to BEV, with affected animals showing significant diarrheal symptoms, sometimes accompanied by slight fever and loss of appetite. The virus replicates in the intestinal epithelium, causing cell damage and subsequent malabsorption. |
| Respiratory Disease | Respiratory signs are also frequently observed, either alone or in conjunction with enteric disease. Infected cattle may develop mucoid nasal discharge, coughing, and mild respiratory distress. Experimental inoculation studies have provided insights into BEV's respiratory pathogenesis. In one study, calves inoculated intranasally with BEV developed fever, depression, and significant pulmonary lesions, including purulent bronchitis, interstitial pneumonia, and peribronchial lymphoid hyperplasia. These findings suggest that BEV can trigger pulmonary immune responses and create conditions conducive to secondary bacterial infections, potentially contributing to shipping fever complex. |
| Reproductive Disease | Reproductive manifestations are among the most economically significant consequences of BEV infection. These include abortion, stillbirths, infertility, and neonatal deaths. The virus has been isolated from placental tissues, fetal materials, and reproductive tract secretions, confirming its ability to localize in reproductive organs. A fatal case of BEV-1 infection in a pregnant heifer documented at the University of Georgia illustrates the potential severity: the animal died within 10 hours of hospitalization, with necropsy revealing hemorrhagic and ulcerative lesions in the spiral colon and cecum. |
Diagnosis of BEV infection is challenging due to the similarity of its clinical signs to other cattle pathogens, such as bovine viral diarrhea virus (BVDV), rotavirus, coronavirus, and Salmonella. Laboratory diagnosis relies on two main approaches: detecting viral RNA in feces, blood, or tissue samples using reverse transcription-polymerase chain reaction (RT-PCR) during the acute phase of infection, and detecting specific antibodies (IgM and IgG) using serological tests such as enzyme-linked immunosorbent assay (ELISA) during the convalescent phase. Prevention and control of BEV are primarily focused on biosecurity measures, herd management, and supportive care. Biosecurity measures include strict quarantine of new animals, disinfection of equipment and facilities, proper waste management to reduce fecal contamination, and control of rodent and insect populations, which can act as mechanical vectors. Providing clean, uncontaminated feed and water is also critical for preventing fecal-oral transmission.
Bovine enterovirus has transitioned from an obscure "orphan" virus to a recognized pathogen with significant implications for cattle health and productivity. Its ability to cause gastrointestinal, respiratory, and reproductive disease, coupled with its environmental stability, widespread distribution, and genetic diversity, positions BEV as an important agent in the complex landscape of bovine infectious diseases. While historically underappreciated, the increasing recognition of BEV's pathogenic potential underscores the importance of accurate diagnosis, surveillance, and ultimately, the development of effective control measures including vaccines. As research continues to unravel the molecular epidemiology and pathogenesis of this ubiquitous virus, veterinarians and producers must remain vigilant to its presence and impact.
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