REOVIRUS -ROTAVIRUS

R.Varidianto Yudo T., dr.,MKes.Lab. Mikrobiologi

Fakultas Kedokteran Universitas Hang Tuah

• Reoviruses are medium-sized viruses with a double-stranded, segmented RNA genome.

• The family includes human rotaviruses, the most important cause of infantile gastroenteritis around the world

• Acute gastroenteritis is a very common disease with significant public health impact.

Rotaviruses

• Rotaviruses are a major cause of diarrheal illness in human infants and young animals, including calves and piglets.

• Infections in adult humans and animals are also common.

• Rotavirus is transmitted by Fecal-Oral route

Characteristic• Virion: Icosahedral, 60–80 nm in diameter, double

capsid shell • Genome: Double-stranded RNA, linear, segmented

(10–12 segments); total genome size 16–27 kbp • Proteins: Nine structural proteins; core contains

several enzymes. Main enzym is RNA-dependent RNA polymerase

• Envelope: None (transient pseudoenvelope is present during rotavirus particle morphogenesis)

• Replication: Cytoplasm. Virions not completely uncoated. Release by lysis of the cell not by budding.

Classification & Antigenic Properties

• Rotaviruses have been classified into five species (A–E), plus two tentative species (F and G), based on antigenic epitopes on the internal structural protein VP6.

• These can be detected by immunofluorescence, ELISA, and immune electron microscopy (IEM).

• Group A rotaviruses are the most frequent human pathogens.

• Outer capsid proteins VP4 and VP7 carry epitopes important in neutralizing activity, with VP7 glycoprotein being the predominant antigen.

• These type-specific antigens differentiate among rotaviruses and are demonstrable by Nt tests.

• Multiple serotypes have been identified among human and animal rotaviruses.

• Some animal and human rotaviruses share serotype specificity.

Pathogenesis• Rotaviruses infect cells in the villi of the small

intestine (gastric and colonic mucosa are spared). • They multiply in the cytoplasm of enterocytes and

damage their transport mechanisms. • One of the rotavirus-encoded proteins, NSP4, is a

viral enterotoxin and induces secretion by triggering a signal transduction pathway.

• Damaged cells may slough into the lumen of the intestine and release large quantities of virus, which appear in the stool (up to 1010 particles per gram of feces).

• Viral excretion usually lasts 2–12 days in otherwise healthy patients but may be prolonged in those with poor nutrition.

• Diarrhea caused by rotaviruses may be due to impaired sodium and glucose absorption as damaged cells on villi are replaced by nonabsorbing immature crypt cells.

• It may take 3–8 weeks for normal function to be restored.

Treatment & Control• Treatment of gastroenteritis is supportive, to correct the loss

of water and electrolytes that may lead to dehydration, acidosis, shock, and death. Management consists of replacement of fluids and restoration of electrolyte balance either intravenously or orally, as feasible. The infrequent mortality from infantile diarrhea in developed countries is due to routine use of effective replacement therapy.

• In view of the fecal-oral route of transmission, wastewater treatment and sanitation are significant control measures.

• An oral bovine-based rotavirus vaccine was licensed in the United States. A safe and effective vaccine remains the best hope for reducing the worldwide burden of rotavirus disease.