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Arbovirus Flashcards

1
Q

What are the main arboviruses transmitted by Aedes Mosquitos?

A

Dengue Fever
Yellow Fever
Zika Virus
Chikungunya

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2
Q

Describe the vector Ecology of Aedes mosquitos

A

Well adapted to urban environements; will live in any containers with clean, still water (this includes tyres, bamboo and pots)

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3
Q

Describe the feeding habits of Aedes mosquitos?

A

Dat time feeders (diurnal, morning and night time are the most common)

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4
Q

What is the most common Arbovirus?

A

Dengue

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5
Q

What arbovirus family is dengue part of?

A

Flavivirus
4 serotypes - DEN-1, DENV-2, DENV-3, DENV-4

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6
Q

How is Dengue Transmitted?

A
  1. Mosquito: Aedes (Aegypto and Albopictus); 8-12 days before virus can replicate and pass on to the human
  2. Mosquito Transovarial transmission
  3. Vertical transimssion (rare but there are some reported cases)
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7
Q

What vectors are responsible for the transmission of Dengue?

A

Aedes Aegypti
Aedes Albopticus

There are NO animal hosts
Spread is: Mozzie –> human

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8
Q

What is the epidemiology of Dengue?

A
  • Most common Arbovirus
  • rapidly increasing globally (8 fold increase in the last 2 decades)
  • 390 million people affected globally, with 96 million having significant illness
  • suspect 1/2 of the world’s population is at risk of dengue
    -Classically affects from the tropic of cancer –> capricorn
  • 70% of the burden is in Asia and the South Pacific
  • Found on every continent
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9
Q

What is the incubation period of dengue?

A

4-10 days

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10
Q

How long do symptoms of Dengue typically last?

A

2-7 days

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11
Q

What is the presentation of (uncomplicated) Dengue? (i.e. no warning signs)

A
  1. Asymptomatic (majority of cases)
  2. FAR (Fever/Arthralgia/Rash)
    HIGH fever (>40C) + 2 of:
    - severe headache
    - pain behnd the eyes
    - muscle and joint pain (‘Breakbone fever’)
    - Nausea/vomiting
    - lymphadenopathy
    - rash (non specific)
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12
Q

What is the presentation of Severe Dengue (DHF/DSS)?

A

Leaky Vessel disease –> spontaneous bleeding, especially from mucous membranes, conjunctival injection (high haematocrit, low platelets)
hepatomegaly
Haematemesis/ haemtochezia
CNS involvement: Encephalopathy, encephalitis, GBS (uncommon), transverse myelitis

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13
Q

What is the pathophysiology of severe dengue?

A

patients who have had Dengue from a single serotype previously, have a partial immune protection against Dengue.
When they are bitten by a mosquito carrying a different serotype, they mount a PARTIAL immune response against the virus, which ends up leading to a massive inflammatory response, leading to endovascular leakage –> symptoms of severe dengue

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14
Q

How is dengue diagnosed?

A

Blood Tests: High haematocrit, low platelets, lecuopenia

PCR in early stage of disease
NS1 RDT
ELISA of IgM (recent) and IgG (chronic) antibodies

Other: Tourniquet Test

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15
Q

How is dengue managed?

A

Supportive management
Fever management with paracetamol

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16
Q

Which medication should be avoided in Dengue?

A

NSAIDs and Aspirin

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17
Q

How is can Dengue be prevented?

A

Prevention of Mosquito Breeding:
-disposing of waste appropriately
-emptying water, to reduce the presence of egg laying habitats
- insecticides into water containers
- Wolbachia
- Mesocyclops fish
Bacillus Thuninginesis bacteria (BTI)

Personal Protection
- window screen,
- indoor spraying (during outbreak)
- long sleeved clothing
- DEET
- ITNs for daytime sleepers

Community Engagement
- education and mobilisation for vector control

Active mosquito and virus surveillance

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18
Q

Is there a vaccine for dengue?

A

Yes, but only licensed for people living in endemic areas who have had a confirmed diagnosis of dengue at least once before

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19
Q

What is Chikungunya?

A

A flavivirus of the togavirus family, spread by mosquitos. It is associated with severe joint pain, joint disfigurement (name means ‘to be contorted’

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20
Q

What is the epidemiology of Chikungunya

A

Asia, Africa, Europe, Indian sub-continent, Americas

Associated with local Epidemics (e.g. Reunion Island, Kenya around Indian Ocean (hellllooo Lamu)

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21
Q

What are the vectors of Chikungunya?

A

Aedes Aegypti and Aedes Albopticus

Animals MAY (??primates) act as vectors but unknown for sure

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22
Q

What is the incubation of Chikungunya?

A

4-8 days

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23
Q

What is Zika Virus?

A

Arbovirus spread by mosquitos.
Part of the Flavivirus family

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24
Q

What is the epidemiology of Zika?

A

South America inclu. Brazil
South Pacific
Africa
Asia

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25
Q

What is the transmission of Zika Virus?

A

Mosquito –> Human
Vertical
Sexual

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26
Q

What is the transmission of Zika Virus?

A

Mosquito –> Human
Vertical
Sexual

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27
Q

What are the vectors associated with Zika Virus?

What is the reservoir?

A

Aedes Mosquitos

Reservoir: Monkeys

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28
Q

What is the clinical presentation of Zika Virus?

A
  1. Asymptomatic
  2. CNS –> GBS!!!!
  3. Microcephaly in vertical transmission
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29
Q

What is the clinical presentation of Zika Virus?

A
  1. Asymptomatic
  2. CNS –> GBS!!!!
  3. Microcephaly in vertical transmission
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30
Q

What is the presentation of Zika Virus?

A

ASYMPTOMATIC

mild: fever , rash (very itchy!!), arthralgia, conjunctivitis

CNS complications: GBS (short but 27% require mechanical ventilation)

Symptoms last 2-7 days

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31
Q

What is the incubation period of Zika Virus?

A

3-14 days

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32
Q

What is the incubation period of Zika Virus?

A

3-14 days

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33
Q

What are the complications of Zika Virus?

A

Microcephaly in pregnancy
GBS

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34
Q

How is Zika diagnosed?

A

Usually test for Dangue and Zika at the same time!

PCR (NAT for ZIKV and DENV +/- NS1 for DENV) –> good for the first 7/7 of infection

ELISA (IgM/IgG)

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35
Q

How do you manage ZIka?

A

Symptomatic/Supportive management

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36
Q

What is Rift Valley Fever?

A

A Bunya Virus (Phlebovirus) which is spread by multiple species of mosquito and is primarily spread to humans via infected animals

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37
Q

Which vectors/reservoirs are associated with Rift Valley Fever?

A

Aedes Mosquito
Culex Mosquito

Farm animals

Humans are an accidental dead end host

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38
Q

What is the epidemiology of RVF?

A

Sub-Saharan Africa (literally places within the rift valley)

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39
Q

How is RVF transmitted to humans?

A

Mosquitos –> farm animals

Humans become sick from indirect or direct contact with the blood or organs of infected animals

Ingestion of unpasteurised milk of infected animals

no documented human - human transmission, but barrier nursing is recommended

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40
Q

Why is RVF important?

A
  1. Potential for global spread due to livestock trading
  2. Huge economic impact from livestock deaths
41
Q

What is the clinical Presentation of Rift Valley Fever?

A
  1. Asymptomatic
  2. Mild illness - fever, myalgia, joint pain, headache, conjunctivitis +/- meningism
  3. Severe (occurs in about 2% of cases)
    - Ocular –> retinal lesions; usually self limiting, but can cause blindness
    - Meningoencephalitis with long standing neurological deficit
    - Haemorrhagic Fever: hepatic failure, jaundice, spontaneous bleeding. 50% mortality rate

**Suspect RVF in any situation where livestock are having many spontaenous abortions

42
Q

How is RVF diagnosed?

A

PCR: looking for RVF reverse transcriptase

ELISA IgG and IgM

43
Q

How is RVF managed?

A

Supportive therapy

Consider Ribivirin

44
Q

Is there a vaccine for RVF?

A

Not licensed for human use.
There is a vaccine for livestock

45
Q

How is RVF prevented?

A

Animal Control
- Animal vaccination (ensure you change needles between animals)
- Animal health surveillance

Public health education
- improve animal husbandry
- pasturise milk in areas where it is endemic
- protection against mosquito bites

46
Q

What is Japanese Encephalitis

A

Arbovirus of the Flavivirus Family

47
Q

What are the vectors and reservoirs associated with JEV?

A

Vectors:
- Culex Mosquitoes

reservoirs:
- Birds (maintenance)
- Pigs (amplifiers)

48
Q

Explain the breeding, feeding and living habits of Culex Mosquitoes

A

Breeding: Eggs laid in rafts on stagnant (usually dirty) water
Feeding: Nighttime, Indoor and outdoor
Living: Standing water, rice fields, flooded areas, marshes, Dirty water

49
Q

What are the vector control measures for Culex Mosquitoes?

A

Improve water drainage
Improve latrines
Polystyrene beads in pit latrines
Impregnated bed nets
Bacillus thuringiesis (BTI)
DEET
ITNs
Protective clothing

50
Q

How is JEV transmitted?

A

Culex spp. of mosquitoes bite humans **within humans the viraema is too low to pass on to mosquitoes again - in this way we are an accidental dead end host for the JEV

51
Q

What is the epidemiology of JEV?

A

South East Asia, Western Pacific
3 billion people at risk of infection
70000 cases per year
It is the most important cause of viral encephalitis in SEA
Children > Adults
Associated with epidemics in the rainy season
Rural and Peri-urban settings (where people come into contact with birds and pigs)

52
Q

Who is most at risk of JEV?

A

Children in areas where there is much rice farming
Epidemics in displaced people

53
Q

What is the presentation of JEV?

A

Most cases are ASYMPTOMATIC (1 in 300)

MILD (Fever + Headache), gastro pain, vomiting

SEVERE
- High fever
- Coma
- Seizure
- Spastic paralysis and parkinsonism
- Raised ICP
- Polio-like illness, with destruction of the anterior horn cells

54
Q

What is the incubation period of JEV?

A

4-14 days

55
Q

What is the mortality rate of JEV?

A

30% of people with Severe JEV will die
20-30% of the survivors will suffer from permanent intellectual disability

56
Q

How is JEV diagnosed?

A

PCR in acute infection

ELISA - IgM for JEV (CSF > Serum)

57
Q

How is JEV managed?

A

Supportive treatment only. There is no other available management

58
Q

How is JEV prevented?

A
  1. Vaccination of humans is the top priority (4 vaccines are currently available; 2 active and 2 inactive)
    - Live attenuated SA14-14-2 from China is the most commonly used vaccine due to cost
    - Expensive
  2. PPE
59
Q

What is Yellow Fever?

A

Arbovirus (Flavivirus family) spread by Aedes and Hemogogus mosquitos, which is particularly prone to causing epidemics of disease

60
Q

What are the transmission cycles of Yellow Fever?

A
  1. Sylvatic (Jungle): Monkeys –> mosquito –> monkeys +/- humans (accidental host)
  2. Sylvatic/Urban Cycle: Monkeys/humans –> mosquitos –> monkeys/humans
  3. Urban: human –> mosquito –> human
    Occurs in epidemics of areas where people are unvaccinated and not previously exposed to YF
61
Q

What is the epidemiology of Yellow Fever?

A
  1. Americas: infrequent infections, usually sylvatic transmission, significant morbidity and mortality
    Haemogogus > Aedes
  2. Africa: frequent infections, usually rural-urban or epidemic spread, with lower levels of morbidity and mortaltiy (although still up to 25%!)
    Aedes > Hemogogus

**NO YF currently in Asia –> primed as high risk for epidemic!!!
30 000 deaths annually
Increasing

62
Q

What is the incubation of yellow fever?

A

3-6 days

63
Q

What is the presentation of Yellow Fever?

A
  1. Asymptomatic is the most common
    **Can present like dengue, and often occurs in the same areas AND is hard to diagnose
  2. Fever: usually biphasic and mild, mylagia, headache
  3. VHF = Toxic phase –> occurs 24-48h after initial FAR phase
    - Multi organ failure, ESP. fulminant hepatic failure
    - UGI Bleeds
    - Faget’s sign
    - Hepatomegaly and jaundice
    - spontaneous bleeding
    - 50% of patients who enter into the toxic phase die within 7-10 days
64
Q

How is YF diagnosed?

A
  1. PCR (acute)
  2. ELISA (IgM acute, IgG chronic)
  3. Autopsy: Councilman bodies in tissues (also seen in RVF and CCHF)
65
Q

What is the differential diagnosis for severe yellow fever?

A

Leptospirosis
Severe malaria
Viral hepatitis
Other haemorrhagic fevers
Other flaviviruses

66
Q

How is Yellow Fever managed?

A

Supportive management only

67
Q

How is Yellow Fever prevented?

A
  1. 17D Vaccination (avoid in >60), live attenuated
    - Caution in elderly, HIV +ve and pregnant women in the middle of an epidemic, where risk of current infection is high
  2. Vector control
    - Larvicides
  3. Vector surveillance (helps to predict epidemics)
  4. PPE
  5. Endemic preparedness and response
68
Q

What is the EYE?

A

WHO plan: Elimination of Yellow Fever Epidemics
- improved vaccination
- control outbreaks rapidly
- prevent international/ cross country spread

69
Q

What are the vectors and reservoirs associated with Yellow Fever

A
  • Aedes Aegypti
  • Aedes Albopticus
  • Hemogogus spp.
  • Sabethes spp. (rare)
70
Q

Discuss the importance of Aedes Albopictus as a vector in disese?

A
  • Survives well in cold climates
  • Rapidly spreading from Asia –> Europe, Africa, Americas
  • More hardy than aegypti; needs less water, is less picky about its habitat
71
Q

What is the presentation of Chikungunya?

A

**Majority of people are SYMPTOMATIC

FAR
- Abrupt onset fever, debilitating joint pain, which can last for YEARS

Opthalmological and CNS complications (conjunctivitis)

Serious complications are UNCOMMON

72
Q

What is the differential of Chikungunya?

A

Dengue
Zika

73
Q

How is Chikungunya diagnosed?

A

PCR
ELISA
Some RDT availability

74
Q

How is Chikungunya managed?

A

Supportive management only
Avoid NSAIDs in case of concurrent Dengue infection

75
Q

Is there a vaccine against Chikungunya?

How is it prevention?

A

No

Prevention as the same for other Aedes Mosquito illnesses

76
Q

What is the classification of West Nile Fever?

A

Arbovirus
Flavivirus
CNS infection
Has similar antigenetic complexes to Japanese Encephalitis

77
Q

What is the epidemiology of West Nile Fever?

A

More or less global, except not classically seen in South America

Classically: Africa, Middle East, South Europe and North America

78
Q

What are the vectors and reservoirs of West Nile Virus?

A

Culex Mosquito spp, esp. Culex Pipens. (can have transovarial spread)

Reservoirs: Birds
Farm Animals and humans are accidental ‘dead-end’ hosts

79
Q

What can predict outbreaks/cause global outbreaks of WNV?

A

Bird migratory patterns

Sudden increase in mass deaths of birds can predict a future outbreak (but only NA birds; in other areas birds have a relative protection against WNV)

80
Q

How is WNV transmitted?

A

Mosquito Bites
Blood/Organ transplant

81
Q

What is the presentation of WNV?

A

Asymptomatic (80%)

Mild Illness: Headache, fever, myalgia, lymphadenopathy, rash (trunk)

Severe: West Nile Encephalitis/Meningitis/Poliomyelitis
Occurs in 1:150 people infected with WNV

82
Q

Who is most at risk for developing severe WNV?

A

Elderly
Immunocompromised people

83
Q

What is the incubation period of WNV?

A

3-14 days

84
Q

How is WNV diagnosed?

A
  1. Serum or CSF ELISA (IgG/IgM)
  2. RT-PCR
85
Q

What is the management of WNV?

A

Supportive

86
Q

Is there an available vaccine for WNV?

A

Not for humans
There is an available horse vaccine

87
Q

How is WNV prevented?

A
  1. Accurate monitoring of animal deaths; horse encephalitis and bird deaths can give a clue that WNV could spread throughout the population
  2. PPE against mosquito bites
  3. Vector control
88
Q

What is O’Nyong Nyong?

A

Arbovirus
Togavirus family

89
Q

What is the vector of O’Nyong Nyong?

A

Anopheles

This is the only arbovirus spread by anopheles

90
Q

What is the epidemiology of O Nyong Nyong

A

Africa - classically Uganda

91
Q

What is the clinical presentation of ONN?

A

Fever, Arthralgia, Rash

92
Q

What is Ross River Virus?

A

Arbovirus
Togavirus family

93
Q

What is the epidemiology of Ross River?

A

Exclusively found in Australia

94
Q

What is the presentation of Ross River Virus?

A

FAR
**epidemic polyarthritis

95
Q

What are the vectors of Ross River Virus?

Reservoirs?

A

Aedes
Culex

Reservoirs:
Wallabies, Kangaroos (probably)

96
Q

Name 3 Warning Signs of Dengue?

A
  • Abdominal pain or tenderness
  • Persistent vomiting
  • Clinical fluid accumulation
  • Mucosal bleed
  • Lethargy or restlessness
  • Liver enlargement > 2 cm
  • Laboratory finding of increasing HCT concurrent with rapid decrease
    in platelet count
97
Q

What is the presentation of JEV?

A
  1. Asymptomatic
  2. Fever
  3. Gi Symptoms
  4. Neuro Symptoms
    - Encephalitis
    - Tonic clonic seizures
    - Flaccid Paralysis
    - Parkinsonism
98
Q

What part of the brain does JEV involve?

A

Basal Ganglia
Midbrain
Pons
Thalamus

99
Q

How do you diagnose JEV?

A

Serlogy: IgM (X-reactivity with West Nile Virus)
MRI Brain (high resource only)

DTM&H (29 decks)

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