Toroviruses

Scientific Classification
Kingdom	Virus
Order	Nidovirales
Family	Coronaviridae
Genus	Torovirus
Species	Toroviruses

Also known as: Torovirus —Torovirus infections — Berne virus— BEV — Breda virus— BRV— Bovine torovirus— BoTV— diarrhea in calves— Equine torovirus—ETV—Prototype Berne virus— Porcine torovirus—

Introduction

Toroviruses are relatively new viruses belonging to the family Coronaviridae. The viruses are enveloped positive sense single-stranded RNA (ssRNA) viruses that are pleomorphic, 120-140 nm in diameter and are relatively stable in acid or alkaline environment between pH 2.5-10. Toroviruses have been isolated from horses (Equine torovirus, ETV, prototype Berne virus) and calves with diarrhoea (bovine torovirus, BoTV, prototype Breda virus).

Signalment

Host include cattle, zebu, goats, horses, sheep, pigs, lagomorphs, rodents, domestic cats and humans.

Clinical Signs

The disease causes diarrhoea, pyrexia, dehydration, lethargy and depression in all ages of cattle. In calves it causes anorexia, mucoid faeces and the following neurological signs; generalised weakness, paralysis, inability to stand, trembling and sudden death. It can also cause respiratory problems such as laryngitis, tracheitis and pneumonia. Young, colostrum-deprived calves are particularly at risk. In cats, diarrhoea and protruding nictating membranes have been associated with feline torovirus infections.

Epidemiology

Toroviruses are found in many species but little is known about the transmission or interspecies transmission of the virus. It is presumed that it is spread via the faecal-oral route and spread through subclinical or chronically infected cattle . The Berne virus(BEV) has been found in horses; whereas the Breda virus (BRV) is found in cattle of which there are two serotypes; BRV 1 and 2. Breda virus in cattle can be detected in the dome epithelium and enterocytes of the intestines and differentiate within the epithelial cells of the villi; interrupting the cattles absorptive capacity, although not as dramatically as the rotavirus. Pigs can shed the torovirus without showing any symptoms of disease (Kroneman et al., 1998). Kroneman A, Cornelissen LAHM, Horzinek MC, Groot RJde, Egberink HF, 1998. Identification and characterization of a porcine torovirus. Journal of Virology, 72(5):3507-3511; 35 ref.

Distribution

Worldwide in cattle and horses.

Diagnosis

Berne virus P138/72 is the only torovirus isolate to date (Cornelissen et al., 1998). Cornelissen LAHM, Woensel PAMvan, Groot RJde, Horzinek MC, Visser N, Egberink HF, 1998. Cell culture-grown putative bovine respiratory torovirus identified as a coronavirus. Veterinary Record, 142(25):683-686; 38 ref. The diagnostic methods include a combination of electron microscopy, immuno-electron microscopy (IEM), haemagglutination inhibition or ELISA. Toroviruses can be differentiated from coronaviruses by using IEM (Woode, 1987). Woode GN, 1987. Breda and Breda-like viruses: diagnosis, pathology and epidemiology. Novel diarrhoea viruses., 175-191; [Ciba Foundation Symposium 128]; 23 ref.

Villus fusion and atrophy and thinning of intestinal wall can be seen on post-mortem.

Treatment

There is no specific treatment. Animals can be supported with fluids to prevent dehydration as a result of the episodes of diarrhoea. Secondary bacterial infections can be treated with antibiotics. Culture and sensitivity recommended.

Control

Isolation of infected animals and good hygiene and sanitary measures may help reduce the spread of the disease.

References

Toroviruses Learning Resources
Flashcards Test your knowledge using flashcard type questions	Blue Eye Disease Flashcard

Toroviruses Learning Resources
Flashcards Test your knowledge using flashcard type questions	Toroviruses Flashcards