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Lect 7 a enteroviruses-rmc

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Virology

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Lect 7 a enteroviruses-rmc

  1. 1. Enteroviruses An Overview
  2. 2. Enteroviruses  A genus of the picornavirus family  Naked ssRNA virus  Are stable in acidic pH  Enter the body mainly via ingestion  Primary site of replication is lymphoid tissue in the gut.  Spread to blood and into lumen of gut to be excreted in feces
  3. 3. Enterovirus Particles Courtesy of Linda M. Stannard, University of Cape Town, S.A.h
  4. 4.  At least 71 serotypes are known: divided into 5 groups  Polioviruses  Coxsackie A viruses  Coxsackie B viruses  Echoviruses  Enteroviruses Enteroviruses
  5. 5. Poliovirus  First identified in 1909  First grown in cell culture in 1949 which became the basis for vaccines.  3 serotypes of poliovirus (1, 2, and 3) but no common antigen.  Humans are the only susceptible hosts.  Polioviruses are distributed globally.  Immunization has eradicated poliovirus in most regions of the world except in the Indian Subcontinent and Africa.
  6. 6. Pathogenesis  Incubation period : 7 - 14 days.  After ingestion, the virus multiplies in the tonsils and Peyer's patches of the ileum  Transient viraemia occurs  In few cases, involves the CNS  Spreads along axons of peripheral nerves to involve anterior horn cells of spinal cord, intermediate grey ganglia and even posterior horn cells
  7. 7. Poliomyelitis: Flaccid Paralysis
  8. 8. Clinical Manifestations Subclinical infection (90 - 95%)  A minor influenza-like illness  Recovers within a few days  May be accompanied by aseptic meningitis Major illness (1 - 2%)  Signs of aseptic meningitis.  Infection of anterior horn cells: flaccid paralysis.  Infection of medulla: respiratory paralysis and death.
  9. 9. Laboratory Diagnosis  Virus Isolation  Mainstay of diagnosis  Can be readily isolated in cell culture from throat swabs, feces, rectal swabs & CSF.  Serology  Very rarely used
  10. 10. Support for Polio Patient
  11. 11. Prevention No specific antiviral therapy is available.  Intramuscular Poliovirus Vaccine (IPV)  Formalin inactivated virus of all 3 serotypes.  Oral Poliovirus Vaccine (OPV)  Consists of live attenuated virus of all 3 serotypes.  Produces local immunity through the induction of an IgA response as well as systemic immunity.
  12. 12. Prevention  The normal response rate to OPV is close to 100%.  OPV is used for the WHO poliovirus eradication campaign.  Poliovirus was targeted for eradication by the WHO by the end of year 2005  Eradicated from most regions of the world except the Indian subcontinent and sub-Saharan Africa.
  13. 13. Current Status of Wild Poliovirus Transmission
  14. 14. Properties of Enteroviruses CPE in cell cultures Monkey Human cell Pathology in Group Virus types kidney culture newborn mice Major disease associations Poliovirus 3 types + + - Paralytic poliomyelitis, aseptic (1 - 3) meningitis, febrile illness. Coxsackie 23 types - or E - or E + Aseptic meningitis, group A (A1-22, A24) febrile illness, conjunctivitis (A24), hand, foot and mouth disease. Coxsackie 6 types + + + Aseptic meningitis, severe neonatal group B (B1-6) disease, myopericarditis, encephalitis, febrile illness. Echovirus 31 types + E - Aseptic meningitis, rash, febrile (1-9, 11-27 illness, conjunctivitis, severe 29-33) generalized neonatal disease. Enterovirus 5 types + + - Polio-like illness, aseptic (68-72) meningitis, hand, foot and mouth (E71), epidemic conjunctivitis (E70) hepatitis A (E72)
  15. 15. Poliovirus Replication
  16. 16. Coxsackieviruses  Coxsackieviruses are distinguished from other enteroviruses by their pathogenicity for suckling rather than adult mice.  Two groups on the basis of the lesions in suckling mice.  Group A: diffuse myositis with acute inflammation and necrosis of fibers of voluntary muscles. Has 23 serotypes  Group B: focal areas of degeneration in the brain, necrosis in the skeletal muscles, and inflammatory changes in the dorsal fat pads, the pancreas and occasionally the myocardium. Have 6 serotypes
  17. 17. Echoviruses  Were accidentally discovered in human feces, unassociated with human disease during epidemiological studies of polioviruses. The viruses were named echoviruses (enteric, cytopathic, human, orphan viruses).  Altogether, There are 32 echoviruses (types 1-9, 11-27, 29-34
  18. 18. New Enteroviruses  Newly identified picornaviruses that are not polioviruses, coxsackie, and echovirus : 5 types (68 - 72).  Enterovirus 70 causes acute haemorrhagic conjunctivitis  Enterovirus 71 has been associated with epidemics of aseptic meningitis, encephalitis, paralytic poliomyelitis-like disease and hand-foot-mouth disease.
  19. 19. Diseases associated with Enteroviruses Syndrome Polio Cox A Cox B Echo Paralytic disease + + + + Meningitis-encephalitis + + + + Carditis + + + + Neonatal disease - - + + Pleurodynia - - + - Herpangina - + - - Rash disease - + + + Haemorr. conjunctivitis - + - - Respiratory infections + + + + Undifferentiated fever + + + + Diabetes/pancreatitis - - + -
  20. 20. Laboratory Diagnosis  Virus Isolation  Mainstay of diagnosis of enterovirus infection  Coxsackie B and Echoviruses can be readily grown in cell culture from throat swabs, feces, and rectal swabs. They can also be isolated from the CSF  Coxsackie A viruses cannot be easily isolated in cell culture. Can be isolated readily in suckling mice. Molecular techniques may provide a better alternative.  Serology  Very rarely used for diagnosis since cell culture is efficient.  Neutralization tests or EIAs
  21. 21. Cytopathic Effect (Virology Laboratory, New-Yale Haven Hospital)
  22. 22. Management and Prevention  No specific antiviral therapy available  IVIG in the treatment of neonatal infections or severe infections in immunocompromised individuals.  HNIG to prevent outbreaks of neonatal infection with good results.  No vaccine available

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