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VIRAL ZOONOSES

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  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. vertebrate arthropod arthropod vertebrate human SYLVATIC (JUNGLE) CYCLE

  11. human arthropod arthropod human URBAN CYCLE human cycle note: viruses which have a human cycle may also have a sylvatic/jungle cycle

  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

  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 flavivirus http://www.cdc.gov/ncidod/dvbid/westnile/cycle.htm

  21. flavivirus West Nile virus

  22. Final 2008 West Nile Virus activity in the United States flavivirus West Nile virus

  23. WEST NILE VIRUS • Symptoms: • Fever • Meningitis • Encephalitis More rarely: • Acute flaccid paralysis • West Nile polio-like paralysis • poliomyelitis - inflammation spinal cord flavivirus http://www.cdc.gov/ncidod/dvbid/westnile/cycle.htm

  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. WEST NILE VIRUS 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 flavivirus

  26. http://www.cdc.gov/ncidod/dvbid/westnile/resources/wnv_transplant%20brochure6_12_07.pdfhttp://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. flavivirus 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%

  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 USA: last confirmed human case 1999 togavirus

  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. bunyavirus 2000 - 2 cases in SC, Charleston area La Crosse life cycle

  35. ARBOVIRUSES – FEVER AND HEMORRHAGIC FEVER FAMILY FLAVIVIRIDAE Dengue Yellow fever REOVIRIDAE Colorado tick fever MAIN DISEASES fever, hemorrhagic fever hemorrhagic fever fever DISTRIBUTION World wide, especially tropics Africa, S. and C. America North America

  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. flavivirus 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

  39. flavivirus http://news.bbc.co.uk/2/hi/americas/6422319.stm patients being treated for Dengue fever in a Paraguayan hospital

  40. flavivirus 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

  41. flavivirus DENGUE HEMORRHAGIC FEVER/DENGUE SHOCK SYNDROME • hemorrhages • plasma leakage • hemoconcentration • hypotension • circulatory failure • shock

  42. flavivirus CDC DHF - petechiae

  43. Dengue hemorrhagic fever - pleural effusion CDC Vaughn DW et al. J Infect Dis 1997; 176:322-30.

  44. flavivirus 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

  45. flavivirus DENGUE HEMORRHAGIC FEVER • Immune enhancement hypothesis • more mononuclear cells infected • infected monocytes release vasoactive mediators • increased vascular permeability • hemorrhagic symptoms

  46. flavivirus 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%

  47. flavivirus

  48. flavivirus 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

  49. The end

  50. (Time Dec 2007)