Rotavirus

• Family: Reoviridae
• Genus: Rotavirus

Classification of Rotavirus:

• Classified into seven distinct groups (A to G) based on structural antigen VP6.
• Group A, B, and C Rotaviruses are found in Human infection as well as animal infection
• Group A Rotaviruses are most frequent Human pathogen

Structure, composition and properties of Rotavirus

1. Structure:

Figure: Structure of Rotavirus

• Characteristics ”wheel” like appearance (Rota-means wheel)
• Size: 65nm-100nm in diameter
• Shape: Spherical shape
• Symmetry: Icosahedral

2. Genome composition:

• Genome: 11 segments of double stranded RNA (ds RNA )
• Protein: 6 structural protein (VP) and 6 Non-structural protein (NSP)
• Envelope: Absent
• Nucleic acid is surrounded by two layer of capsid- inner capsid (VP6) and outer capsid (VP7)
• VP4 is the spike protein, it is a cell surface receptor                          Figure: 11 segments of genome of Rotavirus

3. Other properties

• Replication: Occurs in cytoplasm of infected cell.
• Rota virus contain an RNA-dependent RNA polymerase and other enzymes capable of producing capped RNA transcripts
• Rota virus do not grow in cell line culture

Rotaviruses are inactivated by-

• Heating to 100°C
• Treatment with acid (pH<3),
• Glutaraldehyde (3%),
• Phenol,
• Formalin,
• Chlorine
• Alcohol (70%),

Replication of Rota virus:

1. Attachment: by VP4 on cell surface receptor
2. Penetration: receptor mediated endocytosis
3. Un-coating in lysosome
4. Transcription is mediated by endogenous virus dependent RNA polymerase (transcriptase)
5. Translation to produce viral structural protein
6. Synthesis of full length transcript
7. Some of the full length transcript are encapsidate
8. Synthesis of –ve sense RNA strand with capsid to form ds RNA
9. Formation of inner capsid
10. Morphogenesis: budding of single shelled virus into RER acquiring pseudo envelope
11. Removal of pseudo envelope and replaced by outer capsid in RER
12. Maturation
13. Cell lysis and Release

Figure: Replication cycle of Rotavirus

Mode of Transmission:

• Ingestion of contaminated food and water
• Directly from faeces contaminated fingers
• Occasionally by droplet infection
• Children below 5 years are mostly affected
• Adults are infected by contact with pediatric cases

Incubation period: 2-3 days

Pathogenesis:

• Rota virus replicates in enterocyte near the tip of villi destroying enterocytes
• Viral encoded toxin: early profuse, secretory diarrhea is caused by enterotoxin, NSP4.
• Disruption of intestinal epithelium due to virus replication
• Histologic changes of enterocytes that triggers enteric nervous system, intestinal secretion and immune response
• The acute infection and diarrhoea normally resolves within 7 days in immunocompetent hosts.

Clinical symptoms:

1. Local infection:

• Acute Gastroenteritis, severe in case of infants aged 6-24 months.
• Infected Infants are unable to digest milk due to lactase deficiency caused by destruction of enterocytes
• Diarrhoea, nausea and vomiting
• Malabsorption of Na+, water, and disaccharides
• Symptoms of Dehydration: decrease in urination, dry mouth and throat and feeling dizzy when standing up.

2. Systemic infection:

• High grade Fever
• Lymphocytosis and transient neutropenia.

3. Complication:

• Febrile Convulsion in small children
• Severe dehydration, hypotonia and shock

Laboratory diagnosis:

Specimen: faeces in early infection,

• Viral antigen detection: solid phase agglutination, ELISA
• Electron microscopy
• EIA (enzyme immune assay): it is sensitive to detect virus in stool
• Dip stick/ rapid test
• PCR: For genotyping of Rotavirus
• Virus culture: No cell line culture

Treatment:

• Oral rehydration
• Other supportive rehydration therapy to control loss of water and electrolytes
• Vaccine: Two Oral rotavirus vaccines are currently licensed for use in infants
  1. RotaTeq® (RV5) is given in 3 doses at ages 2 months, 4 months, and 6 months
  2. Rotarix® (RV1) is given in 2 doses at ages 2 months and 4 months

Prevention and control:

• Sanitation
• Waste water treatment
• Health professional should wash their hands with soap and water before and after patient contact.

References

1. https://medlineplus.gov/rotavirusinfections.html
2. www.immune.org.nz/diseases/rotavirus
3. http://www.mayoclinic.org/diseases-conditions/rotavirus/symptoms-causes/dxc-20186931
4. http://www.webmd.com/children/vaccines/tc/rotavirus-topic-overview#1
5. https://en.wikipedia.org/wiki/Rotavirus
6. http://www.medicinenet.com/rotavirus/article.htm
7. https://www.cdc.gov/rotavirus/about/treatment.html
8. https://researchspace.auckland.ac.nz/handle/2292/1286
9. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC372748/
10. http://www.fbae.org/2009/FBAE/website/special-topics_general_issues_rotaviruses.html

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