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Flashcards in arboroviruses Deck (107):
1

what is an arborovirus?

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

2

how are arboroviruses usually maintained?

by cycling between insect and vertebrate hosts

3

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

dengue and urban yellow fever

4

for most arboroviruses, who is the primary host?

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

5

what is the major arborovirus causing encephalitis?

West Nile Virus (WNV)

6

besides WNV, what 10 other arborovirses are encephalitis causing?

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)

7

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

North and South america

8

most predominand mode of WNV transmission

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

9

human to human spread of WNV occurs via (5)

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

10

clinical manifestations of WNV

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

11

West Nile Fever

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

12

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

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

13

neuroinvasive forms of WNV are associated with populations:

> 50yo, immunodeficient (organ transplant, cancers)

14

How is WNV detected during acute disease?

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

15

A diagnosis of WNV can be made retrospectively by

demonstrating a >4 fold rise in serum WNV IgG

16

txt for WNV

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

17

what is Eastern Equine Encephalitis (EEE) caused by?

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

18

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

(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

19

how many cases of encephalitis does EEEV cause a yr?

5-15 each summer/fall

20

populations most often affected by EEEV?

young children and elderly

21

death rate in those with EEEV and neurologic sequelae?

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

22

daignostic procedures for EEEV, WEEV, WNV, and SLEV

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

23

prevention of EEEV, WNV, SLEV, WEEV?

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

24

what is Western Equine Encephalitis (WEE) caused by?

an alphavirus- WEEV

25

where is WEEV distributed?

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

26

life cycle of WEEV is similar to...

EEEV

27

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

WEEV

28

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

nope-- you have to prevent it!

29

St. Louis Encephalitis is caused by a

flavavirus (SLEV) widely distributed throughout the western hemisphere

30

the primary transmission cycle of St. Louis Encephalitis involves...

Culex mosquitos and wild birds

31

severity of ifxn with St. Louis Encephalitis increases with...

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

32

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

WEE/EEE: alpha virus
SLE: flavavirus

33

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

flavivirus with 4 serotypes

34

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

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

35

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

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

36

DHF

Dengue hemorrhagic fever-- 500,000 cases annually

37

which mosquitoes carry dengue?

Aedes mosquitoes

38

the infectious cycle of dengue

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

39

what has caused the increase of Dengue cases?

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

40

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

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

41

pathogenesis of dengue

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)

42

symptoms of dengue correlate with...

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

43

Dengue Shock Syndrome (DSS) can occur after

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

44

Dengue Shock Syndrome (DSS) is associated with

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

45

DSS occurs most commonly

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

46

most common clinical manifestations of dengue

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

47

break-bone fever is associated with which virus?

dengue-- severe muscle aches and fever

48

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

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

most rapid diagnosis of dengue virus (DENV)?

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

txt for DENV

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

major prevention of DENV?

mosquito control

52

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

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

53

Yellow Fever Virus (YFV) is localized to

tropical areas of sub-saharan african and SA

54

how was yellow fever brought to the americas?

aboard slave trade ships

55

the primary transmission cycle for Yellow Fever (YF) involves

nonhuman primates and Aedes monsquitos

56

annual YF cases and death rate

200,000 annually with fatality of 20-50%

57

clinical features of YF

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

diagnosis of YFV

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

59

treatment for YF

surrportive-- no YF specific antiviral agents avb

60

is YF preventable?

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

61

pitfalls of YF vaccine

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

62

travelers going where should get YF vaccine once every 10 yrs

at risk areas in african and SA

63

YF prevention can be done via:

1. vaccine
2. mosquito control

64

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

alphavirus genus of the togavirus family

65

what does chikungunya mean and why was the name given

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

66

where is chikugunya virus (CKV) common?

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

67

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

from A. aegypti to A albopictus

68

clinical features of chikugunya viruse (CKV)

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

69

diagnosis of CKV

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

70

txt of CKV

supportive-- no specific antivirals or vaccine

71

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

YF

72

representative flaviviruses of Japanese encephalitis virus group (4)

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

73

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

a mosquito and a bird

74

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

1. horses
2. people

75

the spread of WNV continues because most people are...

asymptomatic

76

WNF lasts how long?

approx 1 week, may be followed by persistent fatigue

77

two togaviridae viruses

1. EEEV and WEEV

78

4 flaviviridae viruses

1. SLEV
2. JEV
3. WNV
4. DENV

79

1 Bunyaviridae virus

California encephalitis virus (CEV)

80

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

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

81

WNV meningitis manifestations

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

82

clinical manifestation of WNV encephalitis

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

risk factors for neuroinvasive meningitis:

risk increases 1.5 x/decade
immunodeficiency (organ transplant >40x risk), genetic CCR5 deficiency (increased severity/death)

84

long term clinical outcomes of WNV encephalitis

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

85

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

old men (esp 80-90 yo)

86

WNV poliomyelitis

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

87

EEEV ifxn is symptomatic in? asymp in?

symp: humans and horses
asymp: in birds

88

when does EEE happen?

summer

89

EEEV
family:
genus:
stranded:
north american isolate:
south american isolate:

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

what is the most neuropathogenic arbovirus in USA?

EEEV

91

clinical manifestations of EEEV

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

92

long term sequelae of EEEV

seizures, spastic paralysis, personality changes, mental retardation

93

lab findings for EEE

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

94

diagnosis of EEE

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

WEEV commonly found

west of mississippi in US and western canada

96

SLEV found

throughout americas, except northeast

97

culture of CSF with SLEV is usually

negative

98

SLEV manifestations

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

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

1. lacrosse
2. janestown canyon

100

animal reservoir for CA encephalitis viruses

sylvan mammals maintained in northeast and central forests

101

clinical manifestations of CA encephalitis viruses

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

102

what greatly increased the spread of arboviruses?

travel

103

japanese encephalitis is common in

india, nepal, northern south east asia

104

important non-encephalitis arbovirus?

DENV

105

DENV is-
family:
stranded:
serotypes:

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

106

what is unique about Aedes aegypti, which transmits DENV?

primarily a daytime feeder

107

replications/transmission of DENV

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...