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Microbiology Part 2 > Lec 38 Vector-borne and zoonotic viral disease > Flashcards

Lec 38 Vector-borne and zoonotic viral disease Flashcards

1
Q

What are viral properties of arboviruses of alphaviruses? examples?

A

single strand pos sense RNA

examples: EEE, WEE, VEE

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2
Q

What are viral properties of flaviviruses? examples?

A

single strand pos sense RNA

examples: DENV, WNV, YF, SLE

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3
Q

What are viral propertiers of bunyaviruses? examples?

A

single strand neg sense RNA

examples: La Crosse, Hantaviruses

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4
Q

What is pathogenesis of alpha and flaviviruses?

A
  • 2-3 days : mild or asymptomatic
  • 3-7 days: prodrome viremia: mild systemic disease, fever, aches, chills, may infect macrophages, liver, spleen, lymph nodes
  • after that: viremia: sever or life threatening – encephalitis, yellow fever, hepatitis, hemorrhagic fever –> DHF/DSS [dengue]
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5
Q

Where is dengue virus [DV] normally found?

A

mainly in tropical and subtropical

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6
Q

What is the main vector of dengue?

A

aedes aegypti mosquito

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7
Q

What is the aedes aegypti mosquito? what does it look like? importance?

A
  • most common epidemic vector of dengue and yellow fever

- has white bands or scale patterns on legs and thorax

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8
Q

What is the importance of culex sp mosquito?

A

associated with transmission of WNV [west nile], SLE [st louis encephalisit], EEE [eastern equine], WEE [western equine], VEE [venezuelen equine]

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9
Q

How is dengue virus transmitted?

A
  • aedes aegypti mosquito [major vector]
  • aedes albopictus mosquito
  • no human to human transmission
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10
Q

How do the 4 serotypes of denV differ? is there cross immunity?

A
  • each serotype gives specific lifetime immunity and short-term cross immunity
  • all lead to severe and fatal disease
  • all types genetically distinct
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11
Q

What are markers present in serum with dengue infection?

A
  • see high levels of NS1 antigen during dengue infection
  • first antibody produced is IgM
  • if you get secondary infection of same virus type will get IgG
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12
Q

How do you detect dengue?

A
  • detect anti-DENV IgM in serum
  • PCR to detect DenV genome in serum/mosquitoes/tissue
  • detect NS1 with elisa
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13
Q

What are signs of dengue fever?

A
  • fever, muscle pain, rash, hepatitis, cytopenias

- biphasic course

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14
Q

what are signs of DHF [dengue hemorrhagic fever] and dengue shock syndrome [DSS]?

A
  • increased vascular permeability and plasma leakage, bleeding diathesis [from eyes, ears, etc]
  • develops during 2nd phase of illness
  • associated with 2ndary infection w/ different serotype
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15
Q

Who primarily gets DHF/DSS?

A

children, normally develops during second phase of biphasic DF and happens in secondary infection

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16
Q

What is antibody mediated immune enhancement [ADE]?

A
  • cross-reactive antibodies allow uptake of virus by macrophages/monocytes that have Fc receptor –> virus infects these cells and replicates = massive superinfection with increased viral load
  • get lots of cytokine release –> DHf/DSS

big problem = disease is caused by our own immune system

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17
Q

How do you prevent DENV?

A
  • minimize reduction of human-vector contact

- 3 vaccine trials ongoing

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18
Q

How do you control dengue vector?

A
  • eliminate egg-laying habitat [water/waste store/remove]
  • insecticides/barriers
  • sterilize male mosquitos [population control]
  • intriduce wolbachia pipientis into A aeypti = bacteria that blocks denv transmission
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19
Q

What are the concerns about DENV vaccines?

A
  • need to give protection against all 4 serotypes
  • need to be safe in already dengue immune pop
  • need protective antibody response and T cell immunity
  • need to be accessible and affordable
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20
Q

What happens with CYD vaccine?

A
  • only 30% efficacy, didn’t work against DENV-2

- need to go back to drawing board

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21
Q

Where is yellow fever endemic?

A

parts of south america and subsaharan africa

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22
Q

What is natural reservoir for yellow fever?

A

monkeys [humans can also act as source of infection]

23
Q

What is vector for yellow fever to humans?

A

aedes aegypti

24
Q

What are symptoms of yellow fever?

A

stage 1: fever, headache, leukopenia, can be asymptomatic

some people progress to stage 2: hepatitis, hemorrhagic diasthesis, multiorgan failure, mortality 50%

25
Q

What is vaccine for YF? side effect? who gets it?

A
  • live virus vaccine [17D]
  • side effect: rare YF-like illness
  • mandatory in some YF affected countries
  • one of most efficient vaccines available
26
Q

What are the viral agents of enceophalitis?

A

HEMP AIR

H = herpes virus [HSV-1]
E = equine encephalitis [eastern + western +  venezuelen + other arboviruses -- west nnile, st lous, la crosse]
M = measles/mumps
P = polio and other enteroviruses
A = Adenovirus
I = Influenza
R = rabies
27
Q

What is port of entry for measle/mumps/varicella zoster viruses causing encephalitis?

A

respiratory tract

28
Q

What is port of entry for polio + other enteroviruses causing encephalitis?

A

GI tract

29
Q

What is port of entry for HSV causing encephalitis?

A

genital tract and oral mucosa

30
Q

What is port of entry for arboviruses causing encephalitis?

A

subcutaneous tissue

31
Q

When does encephalitis primarily occur and by what viruses?

A

primarily ocurs in summer [may-oct/nov] due to mostly enteroviruses and some tick/mosquito borne arboviruses

32
Q

What is genus of west nile virus?

A

flavivirus

33
Q

What are properites of west nile? host? vector?

A

host: mammals and bird
vector: mosquitors
properties: single strand RNA

34
Q

What are signs of west nile infection?

A

~60-80% are asymptomatic or subclinical

  • of the symptomatic:
  • – west nile fever
  • – neuroinvasive disease [meningitis, encephalitis]
35
Q

What are risk factors for human WNV disease?

A
  • increased age
  • immunosuppression
  • CCR5 deletion is risk factor for WNV
36
Q

How is west nile virus transmitted?

A
  • via mosquito

- also alternatively can get human –> human by: transfusion, transplantation, transplacental, breast milk

37
Q

What is the primary pathologic feature of WNV in CNS?

A

multifocal encephalitis

38
Q

How are hantaviruses transmitted?

A

by inhalation of virus-contaminated aerosols of rodent excretions

39
Q

What is sin nombre virus [SN]? vector? disease? where?

A
  • type of hantavirus
  • causes HPS [hantavirus pulm syndrome]
  • in US/Canada
  • vector = deer mouse
40
Q

What is New York virus [NY]? vector? disease? where?

A
  • type of hantavirus
  • causes HPS [hantavirus pulm syndrome]
  • in US
  • vector = white footed mouse
41
Q

What is hantaan virus [HTN]? vector? disease? where?

A
  • type of hantavirus
  • causes HFRS [hemorrhagic fever with renal syndrome]
  • in Russia/China/Korea
  • vector = striped field mouse
42
Q

What is structure of rhabdovirus?

A
  • single stranded
  • neg sense
  • RNA
  • has envelope
  • covered by trimers of glycoproteins
  • core has N, NS, and L proteins
43
Q

What is post exposure prophylaxis for rabes?

A
  • one dose of human rabies Ig pHRIG] and five doses of rabies vaccine given in month
44
Q

What is function of rhabdovirus G protein?

A
  • facilitates attachment, assembly, budding

- elicits neutralizing antibodies –> used in PEP

45
Q

What is the function of the rhabdovirus M matrix protein?

A

facilitates assembly and budding

46
Q

What is life cycle of rabies infection?

A
  • cells most infected are neurons [with ganglioside and CD56 receptors] and muscles [with nicotinic receptor]
  • attaches cell, fuses
  • replicates in cytoplasm –> vRNA is template for mRNA and cRNA
  • assembles/buds at cell surface
47
Q

What are the receptors that rabies binds to? on which cells?

A

gangliosides and CD56 on neurons

nicotinic receptors on muscle

48
Q

Where in cell does rhabdovirus replicate?

A

in cytoplasm

49
Q

what is the pathogenesis of rhabdovirus infection?

A
  • animal bites you
  • virus enters through break in skin, mucosal surface or respiratory tract
  • infects and replicates in muscle cells
  • infects and replicates in nerve that innervates muscle spindle
  • travels through axons and spreads to CNS
  • travels to multiple organs through peripheral nerves
  • becomes highly concentrated in saliva
  • antibody response develops late
50
Q

What are negri bodies?

A
  • viral neucleocapsids
  • eosinophilic pockets of rabies virus
  • contained in cytoplasm of hyppocampal pyramidal cells, purkinje cells, cortical neurons
  • pathologic sign of rabies infection
51
Q

What is mech of injury of rhabdorvirus?

A
  • minimal/no neuronal necrosis
  • may interfere with neurotransmission
  • induces apoptosis of T lymphocytes
52
Q

What are clinical features of rabies?

A
  • incubation period usually < 90 days but may be years
  • have few days of viral prodrome
  • symptomatic: personality change, parasehtesis, pain at site of exposure, other neuro symptoms
  • comma in 2-4 days
  • death in 18 days
53
Q

How do you diagnose rabies?

A
  • biopsy DFA of nape of neck

- PCR CSF/saliva/tissue

54
Q

How do you prevent rabies?

A
  • immunize animals
  • targeted pre-exposure vaccination
  • wound care, vaccination and rabies Ig after exposure

Microbiology Part 2 (30 decks)

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