Reoviridae: Definition, Classification and Laboratory Diagnosis

In this article we will discuss about Reoviridae:- 1. Definition of Reoviridae 2. Classification of Reoviridae 3. Pathogenesis 4. Laboratory Diagnosis 5. Epidemiology.

Contents:

1. Definition of Reoviridae
2. Classification of Reoviridae
3. Pathogenesis of Reoviridae
4. Laboratory Diagnosis of Reoviridae
5. Epidemiology of Reoviridae

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1. Definition of Reoviridae:

The name Reo is derived from “Respiratory Enteric Orphan” virus because of their frequent occurrence in respiratory tract and enteric tract. Since its pathogenicity was not known, it was called Orphan. Reo viruses show wide range of hosts (man, birds, plant and insects). The RNA genome is double stranded and divided into two segments.

2. Classification of Reoviridae:

The family Reoviridae contains two genera:

A. Orthoreo Virus:

There are three serotypes (1, 2, 3) of mammalian reo viruses found mostly in animals and sometimes in man. Although reo viruses are found in fever, respiratory tract illness and diarrhoea in children, it has not been well established that it produces human disease. Amongst the reo viruses, Rota virus is recognised as important cause of gastroenteritis throughout the world.

B. Rota Virus:

Rota virus causes gastroenteritis in mammals and birds.

Rota virus (Rota, Latin wheel) virus is similar to Reo virus with a double walled icosahedral capsid resembling a wheel. Its genome consists of double stranded segmented RNA. Electron microscopy shows two types of Rota viruses, complete (65-70 nm in diam.) and incomplete particles.

3. Pathogenesis of Reoviridae:

There are 4 serotypes of Rota viruses. They are now recognised as common cause of infantile diarrhoea and also diarrhoea in calf and infant mice. The virus multiplies in cyto­plasm of epithelial cells of small intestine and are excreted in the stool during the first few days of diarrhoea.

4. Laboratory Diagnosis of Reoviridae:

1. Virus in the stool can be demonstrated by immune electron microscopy—ELISA Immuno diffusion test.

2. Antibody titre can be measured by ELISA and CFT.

5. Epidemiology of Reoviridae:

Infection occurs by faecal-oral route; nosocomial infection is common. Rota virus diarrhoea is common in children of 6 months to 2 years. Antibodies appear in serum of 60-90% children of 6 years of age.

In addition to Rota viruses and adenoviruses, there are other viruses which are also associated with gastroenteritis in man. More than 60% of diarrhoeal diseases are due to viral infection, whereas 30% diarrhoeal cases are caused by bacterial and parasitic agents.

Diarrhoea in calves, piglets and dogs is cause by Corona viruses which are recognised pathogens. Their role is still uncertain in diarrhoea in man, though they are detected in human diarrheic stools. Several small round (20-30 nm) unclassified viruses have been detected in stools of acute diarrhoea of children.