VIRAL ZOONOSES

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
1999
West Nile virus
6
2000
West Nile virus
7
2001
West Nile virus
8
2002
West Nile virus
9
2003
West Nile virus
10
2004
West Nile virus
11
2005
West Nile virus
12
2006
West Nile virus
13

• ARBOVIRUSES
• ENCEPHALITIS
• FEBRILE DISEASES
• HEMORRHAGIC FEVERS

14
ARBOVIRUSES
FAMILY
ENVELOPE yes yes no
SYMMETRY icosahedral helical icosahedral
GENOME ssRNA (ve) ssRNA (-ve) segmented dsR
NA, segmented
15
(No Transcript)
16

• ARTHROPOD
• Habitat
• Diurnal activity
• Preferred host
• Annual activity
• Overwintering ability
• Transovarial transmission

• VERTEBRATE
• Migratory activity
• Persistence of viremia
• Clinical consequences
• Reservoir ?
• Dead end host?

17
PREVENTION

• SURVEILLANCE
• VECTOR CONTROL
• REPELLENTS
• CLOTHING
• TIMING OF ACTIVITY (OR CANCELLATION)
• VACCINE

18
SYLVATIC (JUNGLE) CYCLE
19
URBAN CYCLE
human cycle
20
OUTBREAKS

• TEND TO BE SUMMER/EARLY FALL
• SPORADIC
• UNPREDICTABLE

21
ARBOVIRAL DISEASE

• MANY DIFFERENT ARBOVIRUSES CAUSE DISEASE
• OFTEN SUB-CLINICAL
• INITIAL VIRAL REPLICATION
• ENDOTHELIAL CELLS
• MACROPHAGES/MONOCYTE LINEAGE
• INTERFERON (RNA VIRUSES)
• VIREMIA

22
RECOVERY

• INTERFERON
• CELL-MEDIATED IMMUNITY
• ANTIBODY MAY PLAY A ROLE DURING VIREMIC PHASE

23
DIAGNOSIS

• Immunological techniques
• PCR for viral RNA

24
RESISTANCE

• IgG

25
ARBOVIRUSES ENCEPHALITIS
FAMILY TOGAVIRIDAE Eastern equine
encephalitis Western equine encephalitis Venezuela
n equine encephalitis FLAVIVIRIDAE West Nile
virus encephalitis St Louis encephalitis BUNYAVI
RIDAE California serogroup (La Crosse etc)
DISTRIBUTION East US, Canada West US, Canada,
Mexico, Brazil Central and S America, Texas,
Florida North America, parts of Europe, parts
of Africa North America North America
26
ARBOVIRUS ENCEPHALITIS

• SPORADIC
• LOW INFECTIONS - CLINICAL CASES
• NOT ALL CASES - MAJOR DISEASE
• PROBABLY UNDERDIAGNOSED

27
EASTERN EQUINE ENCEPALITIS

• Reservoir birds
• Vector mosquito
• Sentinels
• horse,quail, turkey
• Under 15yrs, over 50yrs at higher risk
• CFR 35
• 5 cases/year av.

CDC
togavirus
28
EASTERN EQUINE ENCEPALITIS
CDC
togavirus
29
WESTERN EQUINE ENCEPALITIS

• Reservoir birds
• Vector mosquito
• Sentinels
• horse,quail, turkey
• Children at higher risk
• CFR 3-5
• No human cases recently

togavirus
30
WEST NILE VIRUS

• Reservoir birds
• Vector mosquito

flavivirus
http//www.cdc.gov/ncidod/dvbid/westnile/cycle.htm
31
flavivirus
West Nile virus
32
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
33
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. encepalitis, 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
34
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
35
http//www.cdc.gov/ncidod/dvbid/westnile/resources
/wnv_transplant20brochure6_12_07.pdf
36
WEST NILE VIRUS

• transmission
• Mosquito (vast majority of cases)
• Blood transfusion (blood supply is now screened)
• Organ donation

flavivirus
37
flavivirus

• Reported Human WNV Disease Cases, US
• 1999 62
• 2000 21
• 2001 66
• 2002 4156
• 2003 9862
• 2004 2539
• 2005 3000
• 2006 4269
• 2007 (Oct 31) 3195

2007 Case Fatality Rate 87/3195 2.7
38
ST. LOUIS ENCEPHALITIS

• Second commonest mosquito borne disease in US
• Reservoir birds
• Man is usually a dead end host
• Vector mosquito
• Elderly at higher risk
• CFR 3-25
• 120 cases/year av.

flavivirus
39
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
40
bunyavirus
2000 - 2 cases in SC, Charleston area
La Crosse life cycle
41
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
42
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
43
(No Transcript)
44
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

45
http//news.bbc.co.uk/2/hi/americas/6422319.stm pa
tients being treated for Dengue fever in a
Paraguayan hospital
46
DENGUE FEVER

• Fever (overlaps with viremic phase)
• headache
• retro-orbital pain
• myalgia, arthralgia
• bone-ache breakbone fever
• sometimes rash
• may look like flu, measles, rubella
• more rarely encephalitis

47
DENGUE HEMORRHAGIC FEVER/DENGUE SHOCK SYNDROME

• hemorrhages
• plasma leakage
• hemoconcentration
• hypotension
• circulatory failure
• shock

48
CDC
DHF - petechiae
49
Dengue hemorrhagic fever - pleural effusion
CDC
Vaughn DW et al. J Infect Dis 1997 176322-30.
50
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

51
DENGUE HEMORRHAGIC FEVER

• Immune enhancement hypothesis
• more mononuclear cells infected
• infected monocytes release vasoactive
  mediators
• increased vascular permeability
• hemorrhagic symptoms

52
DENGUE HEMORRHAGIC FEVER

• children more severe disease
• do not give aspirin
• because of anticoagulant affect
• CFR depends on rapid response
• can be as low as 1

53
(No Transcript)
54
YELLOW FEVER

• jungle and urban cycles
• hemorrhages
• degeneration liver, kidney, heart
• CFR 50
• Vaccine
• important to consider in travel to areas with
  yellow fever

CDC
55
The end
56
(No Transcript)
57
WEST NILE VIRUS
flavivirus
http//www.cdc.gov/ncidod/dvbid/westnile/clinician
s/epi.htm
58
WEST NILE VIRUS
flavivirus
59
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

SC - 2005
flavivirus
http//westnilemaps.usgs.gov/sc_human.html