Bovine Enterovirus

By Uriel Blas Machado, DVM, PhD, DACVP

Bovine enterovirus (BEV) belongs to the family Picornaviridae (picornaviruses), which consists of small (18–30 nm), nonenveloped viruses with an icosahedral capsid that encloses a single copy of positive-sense RNA genome. Bovine enterovirus is in the genus Enterovirus, along with poliovirus, human enterovirus, coxsackieviruses, swine vesicular disease virus, echovirus 11, and others. Originally classified into several serotypes, only two serotypes, BEV-1 and BEV-2 are now recognized.Because of the unavailability of type specific antisera or a commercially available diagnostic test, a genotypic classification, which supports previous recognized serological distinctions has been proposed. Despite the large volume of information available on other enteroviruses very little documentation exists on the pathogenesis of BEV infections in cattle or on its prevalence in North America. Several case reports in the 1950s and 1970s document the isolation of BEV from feces and various tissues from apparently healthy animals or from animals with clinical signs that ranged from mild to moderate diarrhea to reproductive disease. However, these older reports are difficult to interpret as they relied solely on serological assays or had identified more than one infectious agent. Recently in the first report of BEV in more than 20 years, BEV-1 was isolated from a 2-year-old pregnant Aberdeen Angus in Oklahoma with fatal enteric disease. This heifer was 7.5 months pregnant, from a herd of 100 apparently healthy cows, and died within 10 hours of hospitalization. At necropsy, the mucosa of the spiral colon and cecum had multiple foci of hemorrhage and ulceration. Virus isolation from intestinal lesions followed by electron microscopy yielded an approximately 27 nm, nonenveloped, cytopathic, virus. Further characterization by molecular and phylogenetic analyses classified the virus isolate as bovine enterovirus type 1 (BEV-1). At the time of this writing, reports that describe animals experimentally infected with virulent BEV-1, the lesions associated with infection and disease, or its pathogenesis in cattle do not exist. Faculty members at the Athens Veterinary Diagnostic Laboratory are conducting research on this virus isolate. Obtaining information about the susceptibility of cattle to challenge, the pathology associated with infection, and the prevalence of BEV-1 infection in herds would be essential to the understanding of infection and disease in cattle.

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