''Enterovirus E'' (formerly bovine enterovirus (BEV)) is a

picornavirus Picornaviruses are a group of related Viral envelope, nonenveloped RNA viruses which infect vertebrates including fish, mammals, and birds. They are viruses that represent a large family of small, Positive-sense single-stranded RNA virus, positi ...

of the genus ''

Enterovirus ''Enterovirus'' is a genus of positive-sense single-stranded RNA viruses associated with several human and mammalian diseases. Enteroviruses are named by their transmission-route through the intestine ('enteric' meaning intestinal). Serologic ...

''. The virus may also be referred to as enteric cytopathic bovine orphan virus (ECBO). It is endemic in cattle populations worldwide, and although normally fairly nonpathogenic, it can cause reproductive, respiratory, or enteric disease – particularly when the animal is concurrently infected with another pathogen. The virus is spread horizontally by either the oral-fecal route or by the respiratory route. Viral shedding may occur for several months after initial infection. The virus has not been shown to transmit from animals to humans.

Virology

Structure and genome

In common with other picornaviruses, the capsid of BEV is composed of 60 copies of each of four structural proteins, VP1, VP2, VP3 and VP4, in icosahedral symmetry, at about 27 nm in diameter, and enclosing a single stranded positive sense RNA genome of about 7,500 bases. The capsid is not enveloped and roughly spherical with an outer radius of 159

Ångström The angstrom (; ) is a unit of length equal to m; that is, one ten-billionth of a metre, a hundred-millionth of a centimetre, 0.1 nanometre, or 100 picometres. The unit is named after the Swedish physicist Anders Jonas Ångström (1814–18 ...

s and an inner radius of 107 Å. The outer surface of BEV is smoother than the closely related

poliovirus Poliovirus, the causative agent of polio (also known as poliomyelitis), is a serotype of the species '' Enterovirus C'', in the family of '' Picornaviridae''. There are three poliovirus serotypes, numbered 1, 2, and 3. Poliovirus is composed ...

due to the truncation of surface protein loops in BEV. It is also smoother than the related human

rhinovirus The rhinovirus (from the "nose", , romanized: "of the nose", and the ) is a Positive-sense single stranded RNA virus, positive-sense, single-stranded RNA virus belonging to the genus ''Enterovirus'' in the family ''Picornaviridae''. Rhinoviru ...

due to the extension of a surface loop in BEV. The three antigenic sites of BEV all occur on a surface ridge at the junction between VP1, VP2, and VP3. BEV has a crater-like depression at the icosahedral 5-fold axis which descends into a cylindrical hole of 10 Å in diameter which runs almost to the inner surface of the capsid. A hydrophobic pocket contained within VP1 contains a

myristic acid Myristic acid (IUPAC name: tetradecanoic acid) is a common saturated fatty acid with the molecular formula . Its salts and esters are commonly referred to as myristates or tetradecanoates. The name of the acyl group derived from myristic acid is m ...

molecule, the removal of which appears to be a prerequisite for virus uncoating.

Replication

To replicate, BEV must attach to the host cell surface receptor, penetrate into the cell cytoplasm, and the genome must be uncoated. The host cell surface receptor for BEV has yet to be identified, but is sensitive to neuraminidase.

Genetic variability

BEVs were originally classified into seven serotypes, but are now accepted as falling into two serotypes, 1 and 2, which are further classified into subtypes. BEV strain VG-5-27 of serotype 1, subtype 1, is the most extensively studied. The tissue tropism of serotype 1 is extremely broad, including human, sheep, horse, dog, camel, and other mammalian hosts. BEV-like sequences have even been reported in shellfish from water contaminated with bovine faeces. Serotype 2 viruses are only found in domestic cattle.

Signs and symptoms

Most cattle show no clinical signs when infected with the virus. However

abortion Abortion is the early termination of a pregnancy by removal or expulsion of an embryo or fetus. Abortions that occur without intervention are known as miscarriages or "spontaneous abortions", and occur in roughly 30–40% of all pregnan ...

stillbirth Stillbirth is typically defined as fetus, fetal death at or after 20 or 28 weeks of pregnancy, depending on the source. It results in a baby born without vital signs, signs of life. A stillbirth can often result in the feeling of guilt (emotio ...

infertility In biology, infertility is the inability of a male and female organism to Sexual reproduction, reproduce. It is usually not the natural state of a healthy organism that has reached sexual maturity, so children who have not undergone puberty, whi ...

, and neonatal mortality can occur following infection of the reproductive tract. Enteric signs include

diarrhea Diarrhea (American English), also spelled diarrhoea or diarrhœa (British English), is the condition of having at least three loose, liquid, or watery bowel movements in a day. It often lasts for a few days and can result in dehydration d ...

and weight loss, and respiratory infection can produce a mucoid nasal discharge.

Diagnosis

As clinical signs are fairly nonspecific and bovine enterovirus is ubiquitous in cattle populations, other causes of disease must be ruled out before diagnosing enterovirus as the cause of disease.

Electron microscopy An electron microscope is a microscope that uses a beam of electrons as a source of illumination. It uses electron optics that are analogous to the glass lenses of an optical light microscope to control the electron beam, for instance focusing i ...

, PCR, complement fixation, antibody fluorescence, neutralization test, and haemagglutination can be used to identify the virus in tissues or secretions.

Treatment and control

Treatment is

symptomatic Signs and symptoms are diagnostic indications of an illness, injury, or condition. Signs are objective and externally observable; symptoms are a person's reported subjective experiences. A sign for example may be a higher or lower temperature ...

. Appropriate isolation and hygiene measures should be employed to minimise the spread of disease during an outbreak.

Research

The virus has been investigated for its antitumor capabilities, as it is capable of replicating within breast cancer cell lines and producing a

cytopathic effect Cytopathic effect (abbreviated CPE) refers to structural changes in host cells that are caused by viral invasion. The infecting virus causes lysis of the host cell or when the cell dies without lysis due to an inability to replicate. If a virus c ...

in human

monocyte Monocytes are a type of leukocyte or white blood cell. They are the largest type of leukocyte in blood and can differentiate into macrophages and monocyte-derived dendritic cells. As a part of the vertebrate innate immune system monocytes also ...