VIRAL ZOONOSES ZOONOTIC VIRUSES TRANSMISSIBLE FROM ANIMALS

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  • Virus causes productive infections of both vertebrate and invertebrate hosts – usually infects midgut of insect, then spreads and infects insect salivary glands – now poised to infect vertebrate host when insect feeds.
  • At least 150 species mosquito in US alone. ~3500 species worldwide
  • Human may have a low viremia and so be a dead end host; or human may be able to establish a human/insect cycle if the viremia is high enough – this human/insect cycle is called an urban cycle (see next slide)
  • Usually only used to refer to situations in which man plays and IMPORTANT role in the epidemiology of the virus.
  • WNV disease should be considered in any transplant recipient with unexplained fever and/or neurological symptoms during mosquito season This is true even for recipients who develop the infection long after their transplant.
  • 1999 Case Fatality Rate = 7/62 = 11.3% 2000 Case Fatality Rate = 2/21 = 9.5% 2001 Case Fatality Rate = 9/66 = 13.6% 2002 Case Fatality Rate = 284/4156 = 6.8% 2003 Case Fatality Rate = 264/9862 = 2.7% 2004 Case Fatality Rate = 100/2539 = 3.9% 2005 Case Fatality Rate = 119/3000 = 4.0% 2006 Case Fatality Rate = 177/4269 = 4.1% 2007 Case Fatality Rate = 124/3630 = 3.4% 2008 Case Fatality Rate = 43/1338 = 3.2%
  • Benjamin Rush (physician, a signer of the Declaration of Independence, friend of Benjamin Franklin and other founding fathers) probably made the first detailed clinical description of dengue during an epidemic in Philadelphia in 1780. Fever is often associated with the viremic phase.
  • CDC: Here we see a right lateral decubitus X-ray showing a large pleural effusion, typical of DHF the day after defervescence. When the chest X-ray is taken in this position, with the patient resting on the right side, the degree of plasma leakage may be quantified by means of the pleural effusion index. The pleural effusion index is calculated as 100 times the maximum width of the right pleural effusion, divided by the maximal width of the right hemithorax.
  • eg http://www.cdc.gov/mmwr/preview/mmwrhtml/mm5631a1.htm report August 2007: 2005 - Case of DHF in someone who apparently had first infection when living in Mexico or Texas, and then got a locally acquired second infection in Brownsville, Cameron County, South Texas. Investigations showed that from Aug-Nov there were at least 24 more cases of dengue fever in Cameron county – including some that were acquired in Texas. 64% of the Dengue fever cases met the criteria for DHF. Other pertinent facts for concern about DHF in South Texas 38% of residents of Brownsville, Texas had IgG antibodies to Dengue multiple serotypes of Dengue have been found in Brownsville since 1980 two mosquitoes that are excellent vectors for Dengue virus (Aedes aegypti and Aedes albopictus) are well established in South Texas
  • Serious epidemics have occurred on regular basis in US in many cities, including a major epidemic in Philadelphia in 1793, account of this by Benjamin Rush (see slide 39) was widely read. Last yellow fever epidemic in US was in New Orleans in 1905
  • check if figures are world wide or SE asia – article not explicit.
  • Richland county 3; Darlington county 1 (fatal, age >65); Charleston county 1
  • http://www.scdhec.net/health/lab/micro/medical_entomology/arbovirus_data.htm
  • http://www.scdhec.net/health/lab/micro/medical_entomology/arbovirus_data.htm
  • http://www.scdhec.net/health/lab/micro/medical_entomology/arbovirus_data.htm

Transcript

  • 1. VIRAL ZOONOSES
    • ZOONOTIC VIRUSES
      • TRANSMISSIBLE FROM ANIMALS
        • ARTHROPODS
          • often via a blood sucking arthropod
        • VERTEBRATES
          • bites, body fluids, inhalation etc
  • 2. VIRAL ZOONOSES PART I ARTHROPOD BORNE
  • 3. transmission
    • arthropod vectors (blood sucking)
    • Many arboviral diseases world wide (hundreds)
  • 4. VIGILANCE
  • 5.
    • ARBOVIRUSES
      • FEBRILE DISEASES
      • ENCEPHALITIS
      • HEMORRHAGIC FEVERS
  • 6. ARBOVIRUSES FAMILY ENVELOPE yes yes no SYMMETRY icosahedral helical icosahedral GENOME ssRNA (+ve) ssRNA (-ve) segmented dsRNA, segmented
  • 7. Birds Mammals Humans
  • 8.
    • ARTHROPOD
    • Habitat
    • Diurnal activity
    • Preferred host
    • Annual activity
    • Overwintering ability
    • Transovarial transmission
    • VERTEBRATE
    • Migratory activity
    • Persistence of viremia
    • Clinical consequences
    • Reservoir ?
    • Dead end host?
  • 9. PREVENTION
    • SURVEILLANCE
    • VECTOR CONTROL
    • REPELLENTS
    • CLOTHING
    • TIMING OF ACTIVITY (OR CANCELLATION)
    • VACCINE
  • 10. SYLVATIC (JUNGLE) CYCLE arthropod arthropod vertebrate human vertebrate
  • 11. URBAN CYCLE human cycle note: viruses which have a human cycle may also have a sylvatic/jungle cycle arthropod arthropod human human
  • 12. OUTBREAKS
    • TEND TO BE SUMMER/EARLY FALL
    • SPORADIC
    • UNPREDICTABLE
  • 13. ARBOVIRAL DISEASE
    • MANY DIFFERENT ARBOVIRUSES CAUSE DISEASE
    • OFTEN SUB-CLINICAL
  • 14. ARBOVIRAL DISEASE
    • INITIAL VIRAL REPLICATION
      • endothelial cells
      • macrophages/monocyte lineage
    • INTERFERON (RNA VIRUSES)
      • headache, fever, myalgia
    • VIREMIA
      • spread to target tissues, depending on tropism of virus
  • 15. RECOVERY
    • INTERFERON
    • CELL-MEDIATED IMMUNITY
    • ANTIBODY MAY PLAY A ROLE IN PREVENTING SPREAD DURING VIREMIC PHASE
  • 16. DIAGNOSIS
      • Immunological techniques
      • RT-PCR for viral RNA
  • 17. RESISTANCE
    • IgG
  • 18. ARBOVIRUSES – ENCEPHALITIS North America California serogroup (La Crosse etc)   BUNYAVIRIDAE West US, Canada, Mexico, Brazil Western equine encephalitis East US, Canada Eastern equine encephalitis   TOGAVIRIDAE North America St Louis encephalitis North America, parts of Europe, parts of Africa West Nile virus encephalitis   FLAVIVIRIDAE DISTRIBUTION FAMILY
  • 19. ARBOVIRUS ENCEPHALITIS
    • SPORADIC
    • LOW % INFECTIONS -> CLINICAL CASES
    • NOT ALL CASES -> MAJOR DISEASE
    • PROBABLY UNDERDIAGNOSED
  • 20. WEST NILE VIRUS
    • Reservoir: birds
    • Vector: mosquito
    • human, horse
      • dead end hosts
    http://www.cdc.gov/ncidod/dvbid/westnile/cycle.htm flavivirus
  • 21. flavivirus West Nile virus
  • 22. flavivirus West Nile virus Final 2008 West Nile Virus activity in the United States
  • 23. WEST NILE VIRUS
    • Symptoms:
      • Fever
      • Meningitis
      • Encephalitis
      • More rarely:
      • Acute flaccid paralysis
        • West Nile polio-like paralysis
          • poliomyelitis - inflammation spinal cord
    http://www.cdc.gov/ncidod/dvbid/westnile/cycle.htm flavivirus
  • 24. West Nile Virus
    • For every ~150 people infected
      • ~30 mild symptoms
        • mild fever, headache, body ache, maybe rash
          • may never see physician, even if do, may not be diagnosed
      • ~1 severe illness
        • e.g. encephalitis, meningitis, high fever, stiff neck, stupor, disorientation, coma, tremors, convulsions, muscle weakness
          • frequency of flaccid paralysis unknown, but much less than frequency of encephalitis
    flavivirus
  • 25.
    • Case fatality ratio:
    • Seen in all age groups but higher in the elderly
      • the majority of cases of neuroinvasive diseases and fatalities are over 50 yrs age
    • Transplant recipients may be at higher risk
      • increased incidence of clinical disease
      • increased risk of severe disease
    WEST NILE VIRUS flavivirus
  • 26. http://www.cdc.gov/ncidod/dvbid/westnile/resources/wnv_transplant%20brochure6_12_07.pdf
  • 27. WEST NILE VIRUS
    • transmission:
    • Mosquito (vast majority of cases)
    • Blood transfusion (blood supply is now screened)
    • Organ donation
    flavivirus
  • 28. Reported Human WNV Disease Cases, US 1999 62 2000 21 2001 66 2002 4156 2003 9862 2004 2539 2005 3000 2006 4269 2007 3630 2008 1338 2009 515 (as of 10-20-09) 2008 Case Fatality Rate = 44/1356 = 3.2% flavivirus
  • 29. ST. LOUIS ENCEPHALITIS
    • Second commonest mosquito borne disease in US
    • Reservoir: birds
      • Man is usually a dead end host
    • Vector: mosquito
    • <1% infections clinical
    • Elderly at higher risk
    • CFR 3-25%
    • ~100 cases/year av.
    flavivirus
  • 30. EASTERN EQUINE ENCEPHALITIS
    • Reservoir: birds
    • Vector: mosquito
    • Sentinels
      • horse,quail, turkey
    • Under 15yrs, over 50yrs at higher risk
    • CFR ~35%
    • ~5 cases/year av.
    • horses and humans dead end hosts
    CDC togavirus
  • 31. EASTERN EQUINE ENCEPHALITIS CDC togavirus
  • 32. WESTERN EQUINE ENCEPALITIS
    • Reservoir: birds
    • Vector: mosquito
    • Sentinels
      • horse,quail, turkey
    • Children at higher risk
    • CFR 3-5%
    • humans and horses dead end hosts
    togavirus USA: last confirmed human case 1999
  • 33. CALIFORNIA SEROGROUP ENCEPHALITIS (includes La Crosse virus)
    • Recently commoner in eastern US
    • Reservoir: small mammals
    • Vector: mosquitos
    • Children at higher risk
    • Low CFR
    • ~80 cases/year av.
    bunyavirus
  • 34. La Crosse life cycle 2000 - 2 cases in SC, Charleston area bunyavirus
  • 35. ARBOVIRUSES – FEVER AND HEMORRHAGIC FEVER FAMILY FLAVIVIRIDAE Dengue Yellow fever REOVIRIDAE Colorado tick fever DISTRIBUTION World wide, especially tropics Africa, S. and C. America North America MAIN DISEASES fever, hemorrhagic fever hemorrhagic fever fever
  • 36. COLORADO TICK FEVER - coltivirus
    • Vector: tick
    • Mild disease in man
    • Fever, rash, arthralgia
    • RMSF important consideration in differential diagnosis
    • Probably common, rarely reported
    Reovirus family
  • 37. flavivirus
  • 38. DENGUE FEVER
    • jungle cycle (monkeys-mosquitoes)
    • urban cycle (man-mosquitoes)
    • rapidly increasing disease in tropics
    • approx. 100-200 cases/yr in US due to import
      • occasional indigenous transmission
    • 50-100 million cases per year worldwide
      • ~900,000 cases in Central and S. America in 2007
    flavivirus
  • 39. http://news.bbc.co.uk/2/hi/americas/6422319.stm patients being treated for Dengue fever in a Paraguayan hospital flavivirus
  • 40. DENGUE FEVER
    • Fever (overlaps with viremic phase)
    • headache
    • retro-orbital pain
    • myalgia, arthralgia
    • severe joint and muscle pain ‘breakbone fever’
    • sometimes rash
    • may look like flu, measles, rubella
    • more rarely encephalitis
    flavivirus
  • 41. DENGUE HEMORRHAGIC FEVER/DENGUE SHOCK SYNDROME
    • hemorrhages
    • plasma leakage
    • hemoconcentration
    • hypotension
    • circulatory failure
    • shock
    flavivirus
  • 42. DHF - petechiae CDC flavivirus
  • 43. Dengue hemorrhagic fever - pleural effusion CDC Vaughn DW et al. J Infect Dis 1997; 176:322-30.
  • 44. DENGUE HEMORRHAGIC FEVER
    • immunopathological
    • 4 serotypes (1, 2, 3, 4)
      • increase in areas in which all 4 circulate has led to more cases DHF fever in South and Central America
      • Entomologic, serologic and virologic conditions are now such that locally acquired DHF can occur in South Texas
    • maternal antibody
    flavivirus
  • 45. DENGUE HEMORRHAGIC FEVER
    • Immune enhancement hypothesis
      • more mononuclear cells infected
      • infected monocytes release vasoactive mediators
      • increased vascular permeability
      • hemorrhagic symptoms
    flavivirus
  • 46. DENGUE HEMORRHAGIC FEVER
    • do not give aspirin, ibuprofen
      • because of anticoagulant affects
      • (acetaminophen OK)
    • children more severe disease
    • CFR depends on rapid response
      • can be as low as 1%
    flavivirus
  • 47. flavivirus
  • 48. YELLOW FEVER
    • jungle and urban cycles
    • hemorrhages
    • degeneration liver, kidney, heart
    • CFR 50%
    • Vaccine (live attenuated)
      • important to consider in travel to areas with yellow fever
      • egg grown
      • contraindicated in immune suppression
    CDC last yellow fever epidemic in US - 1905 flavivirus
  • 49. The end
  • 50. (Time Dec 2007)
  • 51.  
  • 52. Aedes albopictus is a species of mosquito which is a good vector for Dengue
  • 53.  
  • 54. WEST NILE VIRUS flavivirus http://www.cdc.gov/ncidod/dvbid/westnile/clinicians/epi.htm Table. Median age (in years) of development of West Nile illness following infection Year* Fever Meningitis Encephalitis (with or without associated meningitis) Death** 2002 49 46 64 78 2003 45 46 62 80 **Most deaths were among encephalitis patients.
  • 55. WEST NILE VIRUS flavivirus
  • 56. WEST NILE VIRUS
    • Case fatality ratio:
    • Higher in elderly
        • The 1 fatality in SC in 2005 was over 65 years old
    • Peaks about Aug-Sept
    flavivirus SC - 2005 http://westnilemaps.usgs.gov/sc_human.html SC
  • 57. 1999 West Nile virus
  • 58. 2000 West Nile virus
  • 59. 2001 West Nile virus
  • 60. 2002 West Nile virus
  • 61. 2003 West Nile virus
  • 62. 2004 West Nile virus
  • 63. 2005 West Nile virus
  • 64. 2006 West Nile virus
  • 65.  
  • 66.  
  • 67.  
  • 68.