Torovirus is a genus of viruses within the Coronaviridae

Coronaviridae

Coronaviruses are enveloped, single-stranded, positive-sense RNA viruses with club-shaped surface about 120-160 nm in diameter that resemble a “corona”.-Virology:...

 family that primarily infect vertebrates. They cause gastroenteritis

Gastroenteritis

Gastroenteritis is marked by severe inflammation of the gastrointestinal tract involving both the stomach and small intestine resulting in acute diarrhea and vomiting. It can be transferred by contact with contaminated food and water...

 in mammals, including humans but rarely. Torovirus particles share characteristics with other members of the coronavirus family; they are round, pleomorphic, enveloped virus

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...

es about 120 to 140 nm in diameter. The virus particle has surface spikes proteins that are club-shaped and are evenly dispersed over the surface. A nucleocapsid that is doughnut-shaped with helical symmetry is present.

Transmission is thought to be via the faecal-oral route.

Genome

Toroviruses are class IV viruses, and have a single piece of single-stranded, positive-sense RNA

RNA

Ribonucleic acid , or RNA, is one of the three major macromolecules that are essential for all known forms of life....

. The total length of this is about 28,000 nucleotides and, like all members of the Coronaviridae

Coronaviridae

Coronaviruses are enveloped, single-stranded, positive-sense RNA viruses with club-shaped surface about 120-160 nm in diameter that resemble a “corona”.-Virology:...

, toroviruses have a complex replication systems that includes the use of subgenomic mRNA

Subgenomic mRNA

Subgenomic mRNAs are essentially smaller sections of the original transcribed template strand. During transcription, the original template strand is usually read from the 3' to the 5' end from beginning to end...

, ribosomal frameshifting, and polymerase stuttering

Polymerase stuttering

Polymerase stuttering is the process by which a polymerase transcribes a nucleotide several times without progressing further on the mRNA chain. It is often used in addition of poly A tails or capping mRNA chains by less complex organisms such as viruses....

.

Species

Well-studied species within this genus include:

• Bovine torovirus
• Equine torovirus
• Human torovirus
• Porcine torovirus

Clinical signs and diagnosis

In cattle, the disease causes diarrhoea and systemic signs such as pyrexia, lethargy and anorexia. In calves, it may cause neurological signs and lead to death.

Pigs can be infected without showing any signs.

Diagnosis of the viral infection involves electron microscopy, ELISA

ELISA

Enzyme-linked immunosorbent assay , is a popular format of a "wet-lab" type analytic biochemistry assay that uses one sub-type of heterogeneous, solid-phase enzyme immunoassay to detect the presence of a substance in a liquid sample."Wet lab" analytic biochemistry assays involves detection of an...

 or haemagglutination

Hemagglutination assay

The hemagglutination assay is a method of quantification for viruses or bacteria by hemagglutination...

 inhibition.

Treatment and control

Supportive treatment may be given to prevent dehydration

Dehydration

In physiology and medicine, dehydration is defined as the excessive loss of body fluid. It is literally the removal of water from an object; however, in physiological terms, it entails a deficiency of fluid within an organism...

 and secondary infections.

Control relies on good biosecurity

Biosecurity

Biosecurity is a set of preventive measures designed to reduce the risk of transmission of infectious diseases, quarantined pests, invasive alien species, living modified organisms...

 measures including prompt isolation

Isolation (health care)

In health care, isolation refers to various measures taken to prevent contagious diseases from being spread from a patient to other patients, health care workers, and visitors, or from others to a particular patient...

 and disinfection

Disinfection

Disinfectants are substances that are applied to non-living objects to destroy microorganisms that are living on the objects. Disinfection does not necessarily kill all microorganisms, especially nonresistant bacterial spores; it is less effective than sterilisation, which is an extreme physical...

of premises.

History

In 1972, a virus was isolated from a horse in Berne, Switzerland. The virus did not react with antisera against known equine viruses and was shown to have a unique morphology and substructure. In 1982 a similar, unclassified virus was isolated from calves in Breda, Iowa. In 1984 particles resembling these viruses were discovered in the faeces of humans. On the basis of the available information on these viruses, the establishment of a new family of viruses—Toroviridae—was proposed at the 6th International Congress on the Taxonomy of Viruses at Sendai, Japan, but the genus was later assigned to the Coronaviridae.

External links

• Toroviruses reviewed and published by Wikivet, accessed 08/10/2011
• Viralzone: Torovirus
• Virus Pathogen Database and Analysis Resource (ViPR): Coronaviridae