Dr KAMRAN AFZALAsst Prof Microbiology
Dengue Virus   Genus: Flavivirus   Family: Flaviviridae   Single-stranded RNA arbovirus   40–50 nm, spherical, lipid e...
Dengue Virus Particles
Aedes aegypti
Aedes Mosquito - CharacteristicsDistinct physical feature   Black and white stripes       on its body and legsFlying ti...
   Lays its eggs in clean, stagnant water      Pots, pans and utensils
Life cycle of Aedes aegypti                 4. Adult3. Pupae                      1. Eggs                2. Larvae
Did you know…   The female mosquito lays 30–150 eggs every 2-3 days   Only the female Aedes mosquitoes feed on blood    ...
Epidemiology   Endemic in more than 100 countries   A leading cause of hospitalization and death among    children in As...
Worldwide Prevalence
World at Risk
Worldwide Resurgence
Transmission Cycle   Transmission from human to human requires    the same female mosquito to bite a viremic    human and...
Pathogenesis of DHF - 1   Homologous Antibodies form non-infectious complexes
Pathogenesis of DHF - 2   Heterologous Antibodies form infectious complexes
Pathogenesis of DHF - 3   Heterologous complexes enter monocytes, where    virus replicates
Pathogenesis of DHF - 4   Infected monocytes → vasoactive    mediators → increased vascular    permeability and hemorrhag...
Pathology of DHF and DSS - 1DF Rash in DF show a lymphocytic vasculitis in the dermisDHF and DSS Most of the morphologic...
Pathology of DHF and DSS - 2   Liver and spleen are the target organs       DEN virus antigen detected in hepatocytes  ...
• Spleen - Enlarged and hemorrhagic
Dengue Clinical Syndromes   Classic dengue fever (DF)   Dengue hemorrhagic fever (DHF)   Dengue shock syndrome (DSS)   ...
Case Definition: Dengue Fever   An acute febrile viral disease frequently presenting with    headaches, bone or joint pai...
Case Definition: DHF4-Necessary Criteria (W.H.O.)   Fever, or recent history of acute fever   Hemorrhagic manifestations...
Case Definition: DSS   4-N criteria for DHF       +   Evidence of circulatory failure       Rapid and weak pulse      ...
Hemorrhagic Manifestations   Skin hemorrhages       Petechiae, purpura, ecchymoses   Gingival bleeding   Nasal bleedin...
Tourniquet Test   Inflate blood pressure cuff to    a point midway between    systolic and diastolic pressure    for 5 mi...
Differential Diagnosis   Influenza   Measles   Rubella   Malaria   Typhoid fever   Leptospirosis   Meningococcemia...
Common Misconceptions - DHF   Dengue fever + bleeding = DHF       Apply 4 WHO criteria and assess capillary permeability...
Treatment   Monitor blood pressure, hematocrit, platelet    count, level of consciousness and urine output   Fluids    ...
Laboratory Diagnosis   Non-specific lab tests       CBC - WBCs, platelets, hematocrit       Urine - check for microscop...
ELISA Test for Serologic Diagnosis
Virus Isolation: Cell Culture/ Fluorescent Antibody Test
Virus Isolation: Mosquito Inoculation
Prevention and Control
Mosquito Repellants   Insecticide sprays       Knock down and residual   Repellant oils   Repellant lotions   Electri...
Mosquito Barriers   Keep patient in screened sickroom or    under a mosquito net   To prevent Aedes aegypti mosquitoes  ...
Outdoor Fogging
Indoor Fogging
Aerial Spraying
Media Campaigns
Health Ministry Campaign
CDC Handout
CDC Investigation Report
Dengue Vaccine?   No licensed vaccine at present   Effective vaccine must be ‘tetravalent’   Clinical trials of an atte...
Role of Pak Army in Dengue
Role of Pak Army in Dengue
Future Outlook   Continued vigilance and surveillance is very important   True and active community participation is the...
Aedes aegypti Thank you
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Dengue

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Dengue

  1. 1. Dr KAMRAN AFZALAsst Prof Microbiology
  2. 2. Dengue Virus Genus: Flavivirus Family: Flaviviridae Single-stranded RNA arbovirus 40–50 nm, spherical, lipid env Genome is approximately 11 Kb 4 serotypes:  DEN-1, DEN-2, DEN-3 and DEN-4  Infection with one dengue serotype provides lifelong immunity to that serotype, but there is no cross-protective immunity to the other serotypes
  3. 3. Dengue Virus Particles
  4. 4. Aedes aegypti
  5. 5. Aedes Mosquito - CharacteristicsDistinct physical feature Black and white stripes on its body and legsFlying time: dusk to dawnBites during the dayShort flight: house to houseImperceptible bite
  6. 6.  Lays its eggs in clean, stagnant water  Pots, pans and utensils
  7. 7. Life cycle of Aedes aegypti 4. Adult3. Pupae 1. Eggs 2. Larvae
  8. 8. Did you know… The female mosquito lays 30–150 eggs every 2-3 days Only the female Aedes mosquitoes feed on blood  Female mosquitoes need the protein found in blood to produce eggs  Human blood is preferred with the ankle area as a favored feeding site Male mosquitoes feed on plant and fruit nectar After 8-12 days of acquiring the virus, mosquitoes become infective, remain so for whole life span (1-3 months) The eggs of A. aegypti can resist desiccation for up to 1 yr
  9. 9. Epidemiology Endemic in more than 100 countries A leading cause of hospitalization and death among children in Asia 2.5 billion people or two fifths of the world population are now at risk 50 million cases of DF worldwide every year 0.5 million cases of DHF require hospitalization each year, a very large proportion of whom are children, ~ 5% die Without proper treatment, DHF fatality rates can exceed 20%
  10. 10. Worldwide Prevalence
  11. 11. World at Risk
  12. 12. Worldwide Resurgence
  13. 13. Transmission Cycle Transmission from human to human requires the same female mosquito to bite a viremic human and then bite a susceptible human at an interval of around 8-12 days
  14. 14. Pathogenesis of DHF - 1 Homologous Antibodies form non-infectious complexes
  15. 15. Pathogenesis of DHF - 2 Heterologous Antibodies form infectious complexes
  16. 16. Pathogenesis of DHF - 3 Heterologous complexes enter monocytes, where virus replicates
  17. 17. Pathogenesis of DHF - 4 Infected monocytes → vasoactive mediators → increased vascular permeability and hemorrhagic manifestations (DHF and DSS) Activation of memory T cells → Inflammatory cytokines, including TNF-α and interleukins (IL-2, IL-6, and IL-8) → Increased vascular endothelial permeability or trigger death of target cells through apoptosis
  18. 18. Pathology of DHF and DSS - 1DF Rash in DF show a lymphocytic vasculitis in the dermisDHF and DSS Most of the morphologic abnormalities result from DIC and shock Hemorrhage and congestion are seen in many organs Hemorrhagic effusions in the pleural, pericardial and abdominal cavities
  19. 19. Pathology of DHF and DSS - 2 Liver and spleen are the target organs  DEN virus antigen detected in hepatocytes Liver - Variable morphology  Severe, diffuse hepatitis with mid-zonal necrosis  Focal areas of necrosis  No PMN cells, and no lymphocytes in the liver lesions  Kupffer cells destroyed in cases of focal or severe necrosis  Councilman hyaline body is present as an apoptotic cell
  20. 20. • Spleen - Enlarged and hemorrhagic
  21. 21. Dengue Clinical Syndromes Classic dengue fever (DF) Dengue hemorrhagic fever (DHF) Dengue shock syndrome (DSS)  DSS is actually a severe form of DHF
  22. 22. Case Definition: Dengue Fever An acute febrile viral disease frequently presenting with headaches, bone or joint pain, muscular pains, rash and thrombocytopenia (Breakbone fever) Incubation period  3-7 days (range 2-15 days) Temperature  Bimodal peak (saddle-back form) Rash  Maculo-papular, lasts for 3-4 days
  23. 23. Case Definition: DHF4-Necessary Criteria (W.H.O.) Fever, or recent history of acute fever Hemorrhagic manifestations Low platelet count (100,000/mm3 or less) Objective evidence of “leaky capillaries”:  Elevated hematocrit (20% or more over baseline)  A positive ‘Tourniquet Test’  Pleural or other effusions
  24. 24. Case Definition: DSS 4-N criteria for DHF + Evidence of circulatory failure  Rapid and weak pulse  Narrow pulse pressure (< 20 mm Hg) OR hypotension for age  Cold, clammy skin and altered mental status Frank shock is direct evidence of circulatory failure DEN-2 Mortality rate 1-10% (up to 40%)
  25. 25. Hemorrhagic Manifestations Skin hemorrhages  Petechiae, purpura, ecchymoses Gingival bleeding Nasal bleeding Gastrointestinal bleeding  Hematemesis, melena Hematuria Increased menstrual flow
  26. 26. Tourniquet Test Inflate blood pressure cuff to a point midway between systolic and diastolic pressure for 5 minutes Positive test:  20 or more petechiae per 1 inch² (6.25 cm²)
  27. 27. Differential Diagnosis Influenza Measles Rubella Malaria Typhoid fever Leptospirosis Meningococcemia Rickettsial infections Bacterial sepsis Other viral hemorrhagic fevers
  28. 28. Common Misconceptions - DHF Dengue fever + bleeding = DHF  Apply 4 WHO criteria and assess capillary permeability DHF kills only by haemorrhage  Patient dies as a result of shock Poor management turns dengue into DHF  Poorly managed dengue can be more severe, but DHF is a distinct condition, which even well-treated patients may develop Positive tourniquet test = DHF  Tourniquet test is a nonspecific indicator of capillary fragility
  29. 29. Treatment Monitor blood pressure, hematocrit, platelet count, level of consciousness and urine output Fluids  The volume of fluid needed is similar to the treatment of diarrhea with mild to moderate isotonic dehydration Antipyretics  Avoid aspirin and NSAIDS Blood and components therapy Continue monitoring after defervescence  Patients develop DHF after defervescence
  30. 30. Laboratory Diagnosis Non-specific lab tests  CBC - WBCs, platelets, hematocrit  Urine - check for microscopic hematuria Dengue-specific lab tests  Serology  IgM ELISA / ICT  IgG ELISA / ICT  NS1 Antigen ELISA / ICT  Virus isolation  PCR to determine serotype  Cell culture  Mosquito Inoculation
  31. 31. ELISA Test for Serologic Diagnosis
  32. 32. Virus Isolation: Cell Culture/ Fluorescent Antibody Test
  33. 33. Virus Isolation: Mosquito Inoculation
  34. 34. Prevention and Control
  35. 35. Mosquito Repellants Insecticide sprays  Knock down and residual Repellant oils Repellant lotions Electric lamps Mats Coils High frequency sound Use a larvicide  Temephos
  36. 36. Mosquito Barriers Keep patient in screened sickroom or under a mosquito net To prevent Aedes aegypti mosquitoes from biting infected patients and acquiring the virus
  37. 37. Outdoor Fogging
  38. 38. Indoor Fogging
  39. 39. Aerial Spraying
  40. 40. Media Campaigns
  41. 41. Health Ministry Campaign
  42. 42. CDC Handout
  43. 43. CDC Investigation Report
  44. 44. Dengue Vaccine? No licensed vaccine at present Effective vaccine must be ‘tetravalent’ Clinical trials of an attenuated tetravalent vaccine currently underway Effective, safe and affordable vaccine will not be available in the immediate future
  45. 45. Role of Pak Army in Dengue
  46. 46. Role of Pak Army in Dengue
  47. 47. Future Outlook Continued vigilance and surveillance is very important True and active community participation is the key It is likely to be few years before the vaccine can be considered for widespread use in populations in endemic areas The only control method is: ‘ Efficient vector control ’
  48. 48. Aedes aegypti Thank you

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