Erbovirus
Encyclopedia
Erbovirus is a viral
genus
of the Picornaviridae family. Viruses belonging to the Erbovirus genus have been isolated in horses with acute upper febrile respiratory disease. The structure of the erbovirus virion is icosahedral, having a diameter of 27-30 nm.
and is able to infect cultured cells from a broad range of mammals including rabbit kidney (RK13), African green monkey kidney (Vero), equine foetal kidney (EFK), and is able to infect humans.
The RNA
genome of the virion is inside the capsid that is composed by twelve capsomers, which are cup-shaped pentamers.
The erbovirus particles are non-enveloped and the molecular mass of the virions is around 8-9 x 106 Daltons. They are resistant to inactivation by non-ionic detergent treatment.
Erbovirus, as a typical picornavirus, has a single-stranded positive-sense RNA genome. A feature of the picornavirus genome is the virus protein that is linked at the 5’ end of the genome, known as "VPg" (Virus-Protein-attached-to-the-Genome). In addition, the 3’ end of the genome has a poly-A tail. The transcription of the erbovirus genome gives rise to a polyprotein which is further more processed and cleaved to give the mature viral proteins, in order from 5' to 3' : L ("Leader"), VP4, VP2, VP3, VP1, 2A, 2B, 2C, 3A (Vpg), 3B, 3Cpro, 3Dpol.
The type (and only) species of the Erbovirus genus is Equine rhinitis B virus which was recently found to have three phylogenetically distinct serotypes, equine rhinitis B virus (ERBV)-1, ERBV-2 and ERBV-3. One such phylogenetic group was found to mostly comprise of "acid stable" virus isolates, surviving pH 3.6 for 1 hour at room temperature.
that is not a foot-and-mouth disease
virus (FMDV), and appears to only infect horses once they begin training for racing (approx. 2 years old). ERAV enters the blood and elicits a very high serum antibody response that seems to then limit the spread of the virus by herd immunity
, given that only approximately 40% of horses have detectable ERAV antibody. The low serum antibody response of ERBV appears to allow the continual, seasonal re-infection of horses. Horses are also known to shed ERBV for up to two years, possibly more.
Virus
A virus is a small infectious agent that can replicate only inside the living cells of organisms. Viruses infect all types of organisms, from animals and plants to bacteria and archaea...
genus
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
of the Picornaviridae family. Viruses belonging to the Erbovirus genus have been isolated in horses with acute upper febrile respiratory disease. The structure of the erbovirus virion is icosahedral, having a diameter of 27-30 nm.
Physical characteristics
The virion essentially is a nucleocapsid that is visible under an electron microscopeElectron microscope
An electron microscope is a type of microscope that uses a beam of electrons to illuminate the specimen and produce a magnified image. Electron microscopes have a greater resolving power than a light-powered optical microscope, because electrons have wavelengths about 100,000 times shorter than...
and is able to infect cultured cells from a broad range of mammals including rabbit kidney (RK13), African green monkey kidney (Vero), equine foetal kidney (EFK), and is able to infect humans.
The RNA
RNA
Ribonucleic acid , or RNA, is one of the three major macromolecules that are essential for all known forms of life....
genome of the virion is inside the capsid that is composed by twelve capsomers, which are cup-shaped pentamers.
The erbovirus particles are non-enveloped and the molecular mass of the virions is around 8-9 x 106 Daltons. They are resistant to inactivation by non-ionic detergent treatment.
Erbovirus, as a typical picornavirus, has a single-stranded positive-sense RNA genome. A feature of the picornavirus genome is the virus protein that is linked at the 5’ end of the genome, known as "VPg" (Virus-Protein-attached-to-the-Genome). In addition, the 3’ end of the genome has a poly-A tail. The transcription of the erbovirus genome gives rise to a polyprotein which is further more processed and cleaved to give the mature viral proteins, in order from 5' to 3' : L ("Leader"), VP4, VP2, VP3, VP1, 2A, 2B, 2C, 3A (Vpg), 3B, 3Cpro, 3Dpol.
The type (and only) species of the Erbovirus genus is Equine rhinitis B virus which was recently found to have three phylogenetically distinct serotypes, equine rhinitis B virus (ERBV)-1, ERBV-2 and ERBV-3. One such phylogenetic group was found to mostly comprise of "acid stable" virus isolates, surviving pH 3.6 for 1 hour at room temperature.
Epidemiology
ERBV's appear to infect most foals and weanlings, eliciting a low serum antibody response in stark contrast to equine rhinitis A virus (ERAV), which is the only species of the genus AphthovirusAphthovirus
Aphthovirus is a viral genus of the family Picornaviridae. Aphthoviruses infect vertebrates, and include the causative agent of foot-and-mouth disease. Foot-and-mouth disease virus is the prototypic member of the genus Aphthovirus...
that is not a foot-and-mouth disease
Foot-and-mouth disease
Foot-and-mouth disease or hoof-and-mouth disease is an infectious and sometimes fatal viral disease that affects cloven-hoofed animals, including domestic and wild bovids...
virus (FMDV), and appears to only infect horses once they begin training for racing (approx. 2 years old). ERAV enters the blood and elicits a very high serum antibody response that seems to then limit the spread of the virus by herd immunity
Herd immunity
Herd immunity describes a form of immunity that occurs when the vaccination of a significant portion of a population provides a measure of protection for individuals who have not developed immunity...
, given that only approximately 40% of horses have detectable ERAV antibody. The low serum antibody response of ERBV appears to allow the continual, seasonal re-infection of horses. Horses are also known to shed ERBV for up to two years, possibly more.