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Lect 7 b diarrhoea viruses-rmc

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Lect 7 b diarrhoea viruses-rmc

  1. 1. Diarrheal Viruses
  2. 2. Viral Gastroenteritis  Viruses probably cause upto 3/4 of all infective diarrheas.  The second most common viral illness after upper respiratory tract infection.  In developing countries, a major killer of undernourished infants.  Rotaviruses cause of half a million deaths per year.  Only some gut-asociated viruses cause gastroenteritis.
  3. 3. Gastroenteritis Viruses • Rotaviruses • Adenoviruses •Astroviruses • Calciviruses
  4. 4. Rotavirus Particle
  5. 5. Rotaviruses  Naked ds RNA viruses, 80 nm in diameter.  50-80% of all cases of viral gastroenteritis.  Severe symptoms in neonates and young children.  Up to 30% mortality rate in malnourished children, responsible for up to half a million deaths per year.  Symptomatic infections again common in people over 60.
  6. 6. Rotavirus Pathogenesis
  7. 7. Rotaviruses  Faecal-oral spread  Incubation period 24-48 hr  Abrupt onset of vomiting and diarrhoea, a low grade fever may be present  Live attenuated vaccines now available for use in children
  8. 8. Rotaviruses Replication
  9. 9. Global Distribution of Rotavirus Gastroenteritis
  10. 10. Diagnosis of Rotavirus Infection  Rapid antigen testing of the stool, either by ELISA (>98% sensitivity and specificity)  Anti-rotavirus antibodies (IgM and IgA) are excreted in the stool after the first day of illness  Antibodies remain positive for 10 days after primary infection and longer after re-infection  80% of the population have antibody against rotavirus by the age of 3  Electron microscopy
  11. 11. Enteric Adenoviruses  Naked DNA viruses, 75 nm in diameter.  Types 40 and 41are associated with gastroenteritis.  Possibly the second most common viral cause of gastroenteritis (7-15% of all endemic cases).  Most people have antibodies against enteric adenoviruses by the age of 3.  Diagnosed by electron microscopy or by the detection of adenovirus antigens in faeces by ELISA