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MICRO II > arboroviruses > Flashcards

arboroviruses Flashcards

1
Q

what is an arborovirus?

A

an arthropod born RNA virus that is spread from an insect to a vertebrate host

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2
Q

how are arboroviruses usually maintained?

A

by cycling between insect and vertebrate hosts

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3
Q

what are the only two arboroviruses for which the human is the major vertebrate host?

A

dengue and urban yellow fever

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4
Q

for most arboroviruses, who is the primary host?

A

birds or other animals. Man is only an incidental alternate host

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5
Q

what is the major arborovirus causing encephalitis?

A

West Nile Virus (WNV)

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6
Q

besides WNV, what 10 other arborovirses are encephalitis causing?

A
  1. Eastern Equine Encephalitis (EEE)
  2. Western Equine Encephalitis (WEE)
  3. St. Louis Encephalitis (SLE)
  4. Ca encephalitis viruses (North America)
  5. Powassan virus (North America)
  6. japanese encephalitis
  7. murray valley encephalitis (australia)
  8. venezuaelan equine encephalitis
  9. tick borne encephaliis (europe)
  10. Severe Fever with Thrombocytopenia Syndrome (SFTS) virus (china)
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7
Q

West Nile Virus (WNV) is a common cause of encephalitis where?

A

North and South america

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8
Q

most predominand mode of WNV transmission

A

WNV is transmitted in cycles involving a variety of Culex mosquito species and birds. Humans and domestic animals are incidental hosts

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9
Q

human to human spread of WNV occurs via (5)

A
  1. blood transfusions
  2. organ transplantation
  3. transplacental spread
  4. breast milk
  5. rarely from percutaneous occupational exposure
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10
Q

clinical manifestations of WNV

A

vast majority = asymptomatic
- only 25% get symptoms, usually characterized by: fever, headache, backache, muscle aches, vomitting, diarrhea and loss of appetite, transient macular rash —> this is called West Nile Fever

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11
Q

West Nile Fever

A

symptoms experienced by 25% of people with WNV.
characterized by: fever, headache, backache, muscle aches, vomitting, diarrhea and loss of appetite, transient macular rash

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12
Q

manifestations of neuroinvasive WNV (which happens in pprox 1% of cases)

A

meningitis, encephalitis, polio-like paralysis, death (death rate = 10%)

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13
Q

neuroinvasive forms of WNV are associated with populations:

A

> 50yo, immunodeficient (organ transplant, cancers)

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14
Q

How is WNV detected during acute disease?

A

specific IgM, IgG or RNA (by PCR), or IgM in serum

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15
Q

A diagnosis of WNV can be made retrospectively by

A

demonstrating a >4 fold rise in serum WNV IgG

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16
Q

txt for WNV

A

there is no known effective txt– you have to prevent it!

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17
Q

what is Eastern Equine Encephalitis (EEE) caused by?

A

caused by an alphavirus (EEEV) maintained in bird pops in fresh water swamps in the gulf of mexico

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18
Q

where is eastern equine encephalitis virus (EEEV) maintained and how is it transmitted to humans?

A

(EEEV) maintained in Cs. melanura and bird pops in fresh water swamps in the gulf of mexico and atlantic coasts and is transmitted to humans by different mosquito species

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19
Q

how many cases of encephalitis does EEEV cause a yr?

A

5-15 each summer/fall

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20
Q

populations most often affected by EEEV?

A

young children and elderly

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21
Q

death rate in those with EEEV and neurologic sequelae?

A

death rate: 50-70%. long term neuro sequelae in survivors might be seizures and mental retardation

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22
Q

daignostic procedures for EEEV, WEEV, WNV, and SLEV

A

similar to WNV: specific IgM, IgG or RNA (by PCR), or IgM in serum

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23
Q

prevention of EEEV, WNV, SLEV, WEEV?

A

reducing exposure (draining water from mosquito breeding sites), use of mosquito larvicides or mturation inhibitors, and mosquito repellants (10-50% DEET). Vaccines are in dvpmt

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24
Q

what is Western Equine Encephalitis (WEE) caused by?

A

an alphavirus- WEEV

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25
Q

where is WEEV distributed?

A

in the western plains and valleys of the US, Canada and SA

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26
Q

life cycle of WEEV is similar to…

A

EEEV

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27
Q

which generally causes a more mild disease with a lower death rate, EEEV or WEEV?

A

WEEV

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28
Q

is there txt or a vaccine for WNV, EEEV, WEEV or SLEV?

A

nope– you have to prevent it!

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29
Q

St. Louis Encephalitis is caused by a

A

flavavirus (SLEV) widely distributed throughout the western hemisphere

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30
Q

the primary transmission cycle of St. Louis Encephalitis involves…

A

Culex mosquitos and wild birds

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31
Q

severity of ifxn with St. Louis Encephalitis increases with…

A

age (> 60 has highest incidence of encephalitis and fatality rate of 22%)

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32
Q

WEE and EEE are both caused by a ____ virus, whereas SLE is caused by a ____

A

WEE/EEE: alpha virus

SLE: flavavirus

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33
Q

Dengue virus is what type of virus and has how many serotypes?

A

flavivirus with 4 serotypes

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34
Q

each serotype of dengue provides what type of immunity? what does this mean about infection?

A

specific lifetime immunity and short-term cross immunity, so each ind can be infected up to 4 times

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35
Q

what is the most common cause of arbovirus disease in the world today?

A

dengue– 100 million ifxns annually, 500,000 of which have dengue hemorrhagic fever (DHF)

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36
Q

DHF

A

Dengue hemorrhagic fever– 500,000 cases annually

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37
Q

which mosquitoes carry dengue?

A

Aedes mosquitoes

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38
Q

the infectious cycle of dengue

A

involves aedes mosquitoes, primarily in tropical areas of Asia, Africa and the americas

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39
Q

what has caused the increase of Dengue cases?

A
  1. lack of proper vector control
  2. increased urbanization
  3. climatic changes
  4. international travel
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40
Q

epidemics of dengue usually involve how many people? and where has dengue reemerged in the states?

A

thousands of people. outbreaks have reemerged in the US, primarily in texas and florida due to travel

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41
Q

pathogenesis of dengue

A
  1. mosquito bite
  2. DENV replicates locally and in lymph nodes
  3. w/in 2-3 days spreads via blood to various tissues including skin (multiple tissues/organs can be involved– liver, skin, rarely the brain)
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42
Q

symptoms of dengue correlate with…

A
  1. viremia
  2. replication in certain tissue (eg muscle)
  3. cytokine release
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43
Q

Dengue Shock Syndrome (DSS) can occur after

A

sudden extravasation of plasma into extravascular sites including pleural and abdo cavities

44
Q

Dengue Shock Syndrome (DSS) is associated with

A

intense immune activation and the formaion of immune complexes and activation of the complement system

45
Q

DSS occurs most commonly

A

in secondary ifxns amongst those with pre-existing partial anti-dengue immunity– heterologous antibodies may enhance viral uptake/replication

46
Q

most common clinical manifestations of dengue

A

febrile illness similar to influenza, but often with SEVERE muscle aches (“break-bone fever”), together with a rash, headache and mild hepatitis

47
Q

break-bone fever is associated with which virus?

A

dengue– severe muscle aches and fever

48
Q

clinical manifestations of the most severe form of Dengue– Dengue Hemorrhagic fever (DHF)

A 
bleeding from skin, gums, nasal passages, gi tarct and gu tract.
blood platelets= low (thrombocytopenia)
evidence of leaky capillaries
low BP
rapid/weak pulse
skin = cold and clammy
altered mental status
death
49
Q

most rapid diagnosis of dengue virus (DENV)?

A

most rapid: PCR amplification from acute serum
other: IgM capture assays, but serologic diagnosis may be problematic bc of extensive cross-reactivity among DENV serotypes with other flaviviruses

50
Q

txt for DENV

A

intensive care and monitoring of extremely ill pt with DHF-DSS with anticipitory supportive care, but no specific anti-DENV therapy or vaccine avb

51
Q

major prevention of DENV?

A

mosquito control

52
Q

Yellow Fever Virus (YFV) are what type of virus?

A

flaviviruses with differing genotypes that have been called East Africa, West African and New World

53
Q

Yellow Fever Virus (YFV) is localized to

A

tropical areas of sub-saharan african and SA

54
Q

how was yellow fever brought to the americas?

A

aboard slave trade ships

55
Q

the primary transmission cycle for Yellow Fever (YF) involves

A

nonhuman primates and Aedes monsquitos

56
Q

annual YF cases and death rate

A

200,000 annually with fatality of 20-50%

57
Q

clinical features of YF

A

asymptomatic or flu-like symp
severe disease: hepatitis/jaundice and hemorrhagic diatheses with bleeding episodes as described for dengue hemorrhagic fever
multi organ involvement may lead to shock, heart failure, renal failure, coma and death

58
Q

diagnosis of YFV

A

PCR detection of virus in clinical specimens or by serology (early virus specific IgM, later IgG abs)

59
Q

treatment for YF

A

surrportive– no YF specific antiviral agents avb

60
Q

is YF preventable?

A

yes, with an attenuated (17D) vaccine that produces immunity in 95% of recipients with single dose

61
Q

pitfalls of YF vaccine

A

rarely assoc with neuro comp (encephalitis) or death, esp in elderly

62
Q

travelers going where should get YF vaccine once every 10 yrs

A

at risk areas in african and SA

63
Q

YF prevention can be done via:

A
  1. vaccine

2. mosquito control

64
Q

Chikungunya viruses (CKV) belongs to what genus/family?

A

alphavirus genus of the togavirus family

65
Q

what does chikungunya mean and why was the name given

A

it means “that which binds up” and is referring to the stooped posture from virus induced arthritis

66
Q

where is chikugunya virus (CKV) common?

A

Africa, and recently spread to Indian subcontinent and elsewhere in asia

67
Q

the chikugunya virus (CKV) mutation allowed it to boraden it’s mosquito host from ____ to ____

A

from A. aegypti to A albopictus

68
Q

clinical features of chikugunya viruse (CKV)

A

fever characterized by influenza-like symp, fevers and joint pain. GI symp, rash, lymphocytopenia and hypocalcemia

69
Q

diagnosis of CKV

A

detection of viral RNA or infectious virus from blood, or by detection of IgM and or IgG ab in serum

70
Q

txt of CKV

A

supportive– no specific antivirals or vaccine

71
Q

what is the only arbovirus we studied that has a vaccine?

A

YF

72
Q

representative flaviviruses of Japanese encephalitis virus group (4)

A
  1. japanese encephalitis virus
  2. murray valley encephalitis virus
  3. st. louis encephalitis virus
  4. west nile virus
73
Q

the enzootic (maintenance/amplification) cycle of WNV is between

A

a mosquito and a bird

74
Q

the epizootic spread of WNV is to? the epidemic spread is to?

A
  1. horses

2. people

75
Q

the spread of WNV continues because most people are…

A

asymptomatic

76
Q

WNF lasts how long?

A

approx 1 week, may be followed by persistent fatigue

77
Q

two togaviridae viruses

A
  1. EEEV and WEEV
78
Q

4 flaviviridae viruses

A
  1. SLEV
  2. JEV
  3. WNV
  4. DENV
79
Q

1 Bunyaviridae virus

A

California encephalitis virus (CEV)

80
Q

the macular rash of WNV usually arises… and is more frequent in… than…

A

upon clinical improvement, and is more frequent in persons with WNF than with neuroinvasive disease

81
Q

WNV meningitis manifestations

A

similar to other viral meningitis:
fever, headache, stiff neck, photophobia. CSF pleocytosis; generally lymphocytic, but may be neutrophilic, severe headache, dehydration

82
Q

clinical manifestation of WNV encephalitis

A

alterations of mental status and/or focal neuro findings (+/- meningitis)
severity ranges from mild confusion to coma/death
more frequent in elderly/immunosuppressed
assoc. neur manifestations: movement disorders, cranial nerve palsies)

83
Q

risk factors for neuroinvasive meningitis:

A

risk increases 1.5 x/decade

immunodeficiency (organ transplant >40x risk), genetic CCR5 deficiency (increased severity/death)

84
Q

long term clinical outcomes of WNV encephalitis

A

persistent difficulties, parkinson like tremors that diminish over time, cognitive complaints… but 70% have at least some functional recovery

85
Q

is WNV encephalitis more common in men or women? young or elderly?

A

old men (esp 80-90 yo)

86
Q

WNV poliomyelitis

A

anterior horn cells– acute, asymmetric paralysis (but generally no sensory loss), asymmetric weakness, monoplegia, and persistend functional impairment

87
Q

EEEV ifxn is symptomatic in? asymp in?

A

symp: humans and horses
asymp: in birds

88
Q

when does EEE happen?

A

summer

89
Q 
EEEV
family:
genus:
stranded:
north american isolate:
south american isolate:
A

family: togaviridae
genus: alphavirus
stranded: single stranded RNA
north american isolate: 1 variant- most neuropthogenic arbovirus in the USA
south american isolate: 3 variants, less virulent

90
Q

what is the most neuropathogenic arbovirus in USA?

A

EEEV

91
Q

clinical manifestations of EEEV

A

headache, fever, vomiting, malaise, progressing in 24-48 hours to disorientation and somnolence. Mortality is 50-70%

92
Q

long term sequelae of EEEV

A

seizures, spastic paralysis, personality changes, mental retardation

93
Q

lab findings for EEE

A

spinal fluid pleocytocis (600-2000/mm3), PMN predom. early, later lymph; increased prot; glucose = normal

94
Q

diagnosis of EEE

A

most commonly serological, demonstration of rise in Ab titer btwn acute and convalescent serum. virus can be isolated from brain biopsy and sometimes CSF

95
Q

WEEV commonly found

A

west of mississippi in US and western canada

96
Q

SLEV found

A

throughout americas, except northeast

97
Q

culture of CSF with SLEV is usually

A

negative

98
Q

SLEV manifestations

A

fever/headache, meningitis or encephalitis.
encephalitis: altered reflexes, CNS changes 20-30%, seizures (10%)– associated w/poor prognosis, ataxia

fatality is 2 (young) -22 (elderly)%, sequelae = infrequent

99
Q

California encephalitis refers to a grp of related viruses including (2)

A
  1. lacrosse

2. janestown canyon

100
Q

animal reservoir for CA encephalitis viruses

A

sylvan mammals maintained in northeast and central forests

101
Q

clinical manifestations of CA encephalitis viruses

A

most = asymp
enceph = most common in <15 yo
mortality: 1%, long term morbidity includes seizures and personality changes

102
Q

what greatly increased the spread of arboviruses?

A

travel

103
Q

japanese encephalitis is common in

A

india, nepal, northern south east asia

104
Q

important non-encephalitis arbovirus?

A

DENV

105
Q

DENV is-
family:
stranded:
serotypes:

A

DENV is-

family: flavivirus
stranded: ss RNA
serotypes: 4 (DENV 1,2,3,4)

106
Q

what is unique about Aedes aegypti, which transmits DENV?

A

primarily a daytime feeder

107
Q

replications/transmission of DENV

A
  1. virus transmitted to human by fm Aedes mosquito
  2. virus replicates in target organ
  3. virus infects WBC and lymph tissue
  4. virus released and circs in blood
  5. second mosq ingests virus in blood
  6. virus replicates in mosq midgut and other orgs/infects salivary glands
  7. virus replicates i salivary glands
  8. mosq transmits virus…

MICRO II (8 decks)

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