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Lect 4 - Varicella-zoster virus (vzv), cmv, ebv

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Varicella

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Lect 4 - Varicella-zoster virus (vzv), cmv, ebv

  1. 1. Varicella-Zoster Virus (VZV)
  2. 2. Properties  ds DNA enveloped virus  One antigenic serotype only  Causes two major diseases: • Chickenpox (Varicella), usually in childhood. Is a primary infection • Shingles (Zoster), later in life. Is a reactivation of an earlier varicella infection
  3. 3. Entry of virus via respiratory tract Lymphoid system Viremia Epithelium at different sites After 14 days reaches the main Target: the skin Becomes latent in the cerebral or posterior root ganglia Reactivation Pathogenesis
  4. 4. Replication of VZV
  5. 5. Varicella (Chickenpox) • Is a primary infection • Incubation period: 14-21 days • Highest prevalence in the 4 - 10 years old age group • Presents with fever, lymphadenopathy, a widespread vesicular rash. • Is highly communicable, with an attack rate of 90% in close contacts.
  6. 6. Rashes of Chickenpox
  7. 7. • Is a reactivation of an earlier varicella infection • Mainly affects a single dermatome of the skin • Any age but majority >50 years of age • Characteristic vesicles often accompanied by intense pain which may last for months (postherpetic neuralgia) Herpes Zoster (Shingles)
  8. 8. Herpes Zoster (Shingles) • Herpes zoster affecting the eye and face may pose great problems • Complications include encephalitis and disseminated herpes zoster.
  9. 9. Management Varicella • Uncomplicated varicella is a self limiting disease • Acyclovir Herpes Zoster • Acyclovir • The main problem is post herpetic neuralgia
  10. 10. Prevention • For urgent protection passive immunization with Zoster immunoglobulin (ZIG)
  11. 11. Cytomegalovirus (CMV)
  12. 12. Properties • ds DNA enveloped virus • Named so as it can form multinucleated cells (syncytia) with characteristically staining inclusions
  13. 13. Epidemiology: Transmission • Can be vertical or horizontal • May occur in utero, perinatally or postnatally. • Sexual contact • Blood and blood products • Transplanted organ • Life long carrier state • Reactivation
  14. 14. Clinical Manifestations • Congenital infection – cytomegalic inclusion disease • Perinatal & Postnatal infection - usually asymptomatic
  15. 15. Congenital Infection • Defined as the isolation of CMV from the saliva or urine within 3 weeks of birth. • Commonest congenital viral infection; affects 0.3 - 1% of all live births. • The second most common cause of mental handicap after Down's syndrome • Responsible for more cases of congenital damage than rubella
  16. 16. Characterized by: • Involvement of CNS: Significant defects within 2 years of life Severe hearing loss Ocular abnormalities Mental retardation Congenital Infection
  17. 17. Management Congenital infections • Not usually possible to detect Perinatal and postnatal infection • Usually not necessary to treat
  18. 18. Epstein-Barr Virus (EBV)
  19. 19. Epidemiology • In developing countries, by the age of two, 90% of children are seropositive. • The virus is transmitted by contact with saliva, in particular through kissing.
  20. 20. Disease Association 1. Infectious Mononucleosis 3. Burkitt's lymphoma 4. Nasopharyngeal carcinoma 5. Oral leukoplakia in AIDS patients 6. Chronic interstitial pneumonitis in AIDS patients
  21. 21. Infectious Mononuclosis (IM) • Features include: Fever Lymphadenopathy Splenomegaly Usually a self-limiting disease • Jaundice (in some patients)
  22. 22. • Diagnosis of IM Detection of EBV IgM Atypical lymphocytes are present in the blood • There is no specific treatment Infectious Mononuclosis (IM)
  23. 23. Burkitt’s Lymphoma (BL) • Endemic in parts of Africa (where it is the commonest childhood tumor) • Usually in age 3-14 years • Responds well to chemotherapy • It is restricted to areas with malaria: may be a cofactor. • In theory BL can be controlled by the eradication of malaria (as has happened in Papua New Guinea) or vaccination against EBV
  24. 24. Nasopharyngeal Carcinoma (NPC) • It is very prevalent in S. China, where it is the commonest tumor in men and the second commonest in women. • Prognosis is poor.
  25. 25. Diagnosis • Acute EBV infection The heterophile antibody test Detection of anti-EBV IgM • Burkitt’s lymphoma: Histology • NPC Histology The determination of the titre of anti-EBV IgA in screening for early lesions of NPC
  26. 26. Immunocompromised Patients • Transplant recipients e.g. renal – Associated with lymphoproliferative disease and lymphoma • AIDS patients – Associated with oral leukoplakia and with various Non-Hodgekin’s lymphoma • Ducan X-linked lymphoproliferative syndrome – This condition occurs exclusively in males who had inherited a defective gene in the X-chromosome
  27. 27. Vaccination • A vaccine against EBV which prevents primary EBV infection should be able to control both BL and NPC • Must be given early in life to: – Seronegative organ transplant recipients – Those developing severe IM • This vaccine is being tried in Africa.

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