''Bornaviridae'' is a family of
negative-strand RNA virus
Negative-strand RNA viruses (−ssRNA viruses) are a group of related viruses that have negative-sense, single-stranded genomes made of ribonucleic acid. They have genomes that act as complementary strands from which messenger RNA (mRNA) is sy ...
es in the order ''
Mononegavirales
''Mononegavirales'' is an order of negative-strand RNA viruses which have nonsegmented genomes. Some common members of the order are Ebola virus, human respiratory syncytial virus, measles virus, mumps virus, Nipah virus, and rabies virus. All of ...
''. Horses, sheep, cattle, rodents, birds, reptiles, and humans serve as natural hosts. Diseases associated with bornaviruses include
Borna disease
Borna disease, also known as sad horse disease, is an infectious neurological syndrome of warm-blooded animals, caused by Borna disease viruses 1 and 2 (BoDV-1/2). BoDV-1/2 are neurotropic viruses of the species ''Mammalian 1 orthobornavirus,'' ...
, a fatal neurologic disease of mammals restricted to central Europe; and
proventricular dilatation disease (PDD) in birds. Bornaviruses may cause encephalitis in mammals like horses or sheep. The family includes 11 species assigned to three genera.
History
Borna disease was first identified in 1926 and its genome was isolated in 1990. The ICTV proposed the creation in 1996 of the family ''Bornaviridae'' along with the genus ''Bornaviru''s (today ''Orthobornavirus''). The viral family is named after the city of
Borna in
Saxony, Germany
Saxony (german: Sachsen ; Upper Saxon: ''Saggsn''; hsb, Sakska), officially the Free State of Saxony (german: Freistaat Sachsen, links=no ; Upper Saxon: ''Freischdaad Saggsn''; hsb, Swobodny stat Sakska, links=no), is a landlocked state o ...
, which is where many animals were lost to the sporadic encephalopathy caused by the viral disease.
Structure
Orthobornavirions are enveloped, with spherical geometries and helical capsids. The diameter is around 70 to 130 nm. Genomes are made of negative-sense single-stranded RNA. They are linear, monopartite and around 8.9 kbp in length. The genome codes for nine proteins.
Proteins of orthobornaviruses that have been characterized:
Life cycle
In the ''Mononegavirales'' order, ''Bornaviridae'' is one of only two families with viruses that replicate in the nucleus. Entry into the host cell is achieved by attachment of the viral GP glycoproteins to host receptors, which mediates clathrin-mediated endocytosis. Replication follows the negative stranded RNA virus replication model. Negative stranded RNA virus transcription, using polymerase stuttering, with some alternative splicing mechanism, is the method of transcription. The virus exits the host cell by nuclear pore export. This virus usually has a highly variable incubation period of around a few weeks to several months. Horses, sheep, cattle, rodents, birds, and humans serve as the natural hosts. Transmission routes are
fomite
A fomite () or fomes () is any inanimate object that, when contaminated with or exposed to infectious agents (such as pathogenic bacteria, viruses or fungi), can transfer disease to a new host.
Transfer of pathogens by fomites
A fomite is any ina ...
s, contact, urine, feces, and saliva.
Pathogenicity
Between 2011 and 2013, three German breeders of
variegated squirrel
The variegated squirrel (''Sciurus variegatoides'') is a tree squirrel in the genus ''Sciurus'' found in Costa Rica, El Salvador, Guatemala, Honduras, southern Mexico, Nicaragua, and Panama. Fifteen subspecies are recognised. It is a common s ...
s (''Sciurus variegatoides'') had encephalitis with similar clinical signs and died 2 to 4 months after onset of the clinical symptoms. Genomic analysis found a previously unknown orthobornavirus in a contact squirrel and in brain tissue from the three men, the researchers reported, and it is the "likely causative agent" in their deaths. Prior to this, bornaviruses were not thought to be responsible for human diseases. More VSBV-1 infected squirrels from the subfamilies
Sciurinae
Sciurinae is a subfamily of squirrels (in the family Sciuridae), uniting the flying squirrels with certain related tree squirrels. Older sources place the flying squirrels in a separate subfamily (Pteromyinae) and unite all remaining sciurids into ...
and
Callosciurinae
The Callosciurinae are an Asiatic subfamily of squirrels containing over 60 species (mostly found in South East Asia) named after the genus ''Callosciurus'', which means "beautiful squirrels".
Classification
*Family SciuridaeThorington, R. W. Jr ...
were also confirmed to be present not only in Germany but in the Netherlands. Zero VSBV-1 positive squirrels showed clinical signs of infection. Since behavioral disease has been studied in BoDV-1 infected animals like
rhesus monkeys
The rhesus macaque (''Macaca mulatta''), colloquially rhesus monkey, is a species of Old World monkey. There are between six and nine recognised subspecies that are split between two groups, the Chinese-derived and the Indian-derived. Generally b ...
,
tree shrews
The treeshrews (or tree shrews or banxrings) are small mammals native to the tropical forests of South and Southeast Asia. They make up the entire order Scandentia, which split into two families: the Tupaiidae (19 species, "ordinary" treeshrews) ...
, and rats, BoDV-1 has also been hypothesized to be associated with humans psychiatric conditions such as schizophrenia and affective psychoses. In several studies with large sample sizes, there has been an association with increased presence of BoDV-1 antibodies in hospitalized psychiatric patients and a higher
seroprevalence
Seroprevalence is the number of persons in a population who test positive for a specific disease based on serology (blood serum) specimens; often presented as a percent of the total specimens tested or as a proportion per 100,000 persons tested. As ...
rate among the psychiatric patients when compared to the control groups.
[Milad Azami, Farid Azizi Jalilian, Ali Khorshidi, Younes Mohammadi, Zeinab Tardeh,
The association between Borna Disease Virus and schizophrenia: A systematic review and meta-analysis,
Asian Journal of Psychiatry, Volume 34, 2018,Pages 67-73, ISSN 1876-2018, https://doi.org/10.1016/j.ajp.2017.11.026.]
Taxonomy
References
External links
Viralzone: BornaviridaeICTVBorna: Bornaviridae
{{Authority control
Mononegavirales
Virus families