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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
What is the transmission of Zika Virus?
Mosquito --> Human Vertical Sexual
26
What is the transmission of Zika Virus?
Mosquito --> Human Vertical Sexual
27
What are the vectors associated with Zika Virus? What is the reservoir?
Aedes Mosquitos Reservoir: Monkeys
28
What is the clinical presentation of Zika Virus?
1. Asymptomatic 2. CNS --> GBS!!!! 3. Microcephaly in vertical transmission
29
What is the clinical presentation of Zika Virus?
1. Asymptomatic 2. CNS --> GBS!!!! 3. Microcephaly in vertical transmission
30
What is the presentation of Zika Virus?
ASYMPTOMATIC mild: fever , rash (very itchy!!), arthralgia, conjunctivitis CNS complications: GBS (short but 27% require mechanical ventilation) Symptoms last 2-7 days
31
What is the incubation period of Zika Virus?
3-14 days
32
What is the incubation period of Zika Virus?
3-14 days
33
What are the complications of Zika Virus?
Microcephaly in pregnancy GBS
34
How is Zika diagnosed?
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)
35
How do you manage ZIka?
Symptomatic/Supportive management
36
What is Rift Valley Fever?
A Bunya Virus (Phlebovirus) which is spread by multiple species of mosquito and is primarily spread to humans via infected animals
37
Which vectors/reservoirs are associated with Rift Valley Fever?
Aedes Mosquito Culex Mosquito Farm animals Humans are an accidental dead end host
38
What is the epidemiology of RVF?
Sub-Saharan Africa (literally places within the rift valley)
39
How is RVF transmitted to humans?
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
40
Why is RVF important?
1. Potential for global spread due to livestock trading 2. Huge economic impact from livestock deaths
41
What is the clinical Presentation of Rift Valley Fever?
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
How is RVF diagnosed?
PCR: looking for RVF reverse transcriptase ELISA IgG and IgM
43
How is RVF managed?
Supportive therapy Consider Ribivirin
44
Is there a vaccine for RVF?
Not licensed for human use. There is a vaccine for livestock
45
How is RVF prevented?
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
What is Japanese Encephalitis
Arbovirus of the Flavivirus Family
47
What are the vectors and reservoirs associated with JEV?
Vectors: - Culex Mosquitoes reservoirs: - Birds (maintenance) - Pigs (amplifiers)
48
Explain the breeding, feeding and living habits of Culex Mosquitoes
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
What are the vector control measures for Culex Mosquitoes?
Improve water drainage Improve latrines Polystyrene beads in pit latrines Impregnated bed nets Bacillus thuringiesis (BTI) DEET ITNs Protective clothing
50
How is JEV transmitted?
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
What is the epidemiology of JEV?
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
Who is most at risk of JEV?
Children in areas where there is much rice farming Epidemics in displaced people
53
What is the presentation of JEV?
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
What is the incubation period of JEV?
4-14 days
55
What is the mortality rate of JEV?
30% of people with Severe JEV will die 20-30% of the survivors will suffer from permanent intellectual disability
56
How is JEV diagnosed?
PCR in acute infection ELISA - IgM for JEV (CSF > Serum)
57
How is JEV managed?
Supportive treatment only. There is no other available management
58
How is JEV prevented?
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
What is Yellow Fever?
Arbovirus (Flavivirus family) spread by Aedes and Hemogogus mosquitos, which is particularly prone to causing epidemics of disease
60
What are the transmission cycles of Yellow Fever?
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
What is the epidemiology of Yellow Fever?
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
What is the incubation of yellow fever?
3-6 days
63
What is the presentation of Yellow Fever?
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
How is YF diagnosed?
1. PCR (acute) 2. ELISA (IgM acute, IgG chronic) 3. Autopsy: Councilman bodies in tissues (also seen in RVF and CCHF)
65
What is the differential diagnosis for severe yellow fever?
Leptospirosis Severe malaria Viral hepatitis Other haemorrhagic fevers Other flaviviruses
66
How is Yellow Fever managed?
Supportive management only
67
How is Yellow Fever prevented?
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
What is the EYE?
WHO plan: Elimination of Yellow Fever Epidemics - improved vaccination - control outbreaks rapidly - prevent international/ cross country spread
69
What are the vectors and reservoirs associated with Yellow Fever
- Aedes Aegypti - Aedes Albopticus - Hemogogus spp. - Sabethes spp. (rare)
70
Discuss the importance of Aedes Albopictus as a vector in disese?
- 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
What is the presentation of Chikungunya?
**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
What is the differential of Chikungunya?
Dengue Zika
73
How is Chikungunya diagnosed?
PCR ELISA Some RDT availability
74
How is Chikungunya managed?
Supportive management only Avoid NSAIDs in case of concurrent Dengue infection
75
Is there a vaccine against Chikungunya? How is it prevention?
No Prevention as the same for other Aedes Mosquito illnesses
76
What is the classification of West Nile Fever?
Arbovirus Flavivirus CNS infection Has similar antigenetic complexes to Japanese Encephalitis
77
What is the epidemiology of West Nile Fever?
More or less global, except not classically seen in South America Classically: Africa, Middle East, South Europe and North America
78
What are the vectors and reservoirs of West Nile Virus?
Culex Mosquito spp, esp. Culex Pipens. (can have transovarial spread) Reservoirs: Birds Farm Animals and humans are accidental 'dead-end' hosts
79
What can predict outbreaks/cause global outbreaks of WNV?
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
How is WNV transmitted?
Mosquito Bites Blood/Organ transplant
81
What is the presentation of WNV?
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
Who is most at risk for developing severe WNV?
Elderly Immunocompromised people
83
What is the incubation period of WNV?
3-14 days
84
How is WNV diagnosed?
1. Serum or CSF ELISA (IgG/IgM) 2. RT-PCR
85
What is the management of WNV?
Supportive
86
Is there an available vaccine for WNV?
Not for humans There is an available horse vaccine
87
How is WNV prevented?
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
What is O'Nyong Nyong?
Arbovirus Togavirus family
89
What is the vector of O'Nyong Nyong?
Anopheles This is the only arbovirus spread by anopheles
90
What is the epidemiology of O Nyong Nyong
Africa - classically Uganda
91
What is the clinical presentation of ONN?
Fever, Arthralgia, Rash
92
What is Ross River Virus?
Arbovirus Togavirus family
93
What is the epidemiology of Ross River?
Exclusively found in Australia
94
What is the presentation of Ross River Virus?
FAR **epidemic polyarthritis
95
What are the vectors of Ross River Virus? Reservoirs?
Aedes Culex Reservoirs: Wallabies, Kangaroos (probably)
96
Name 3 Warning Signs of Dengue?
* 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
What is the presentation of JEV?
1. Asymptomatic 2. Fever 3. Gi Symptoms 4. Neuro Symptoms - Encephalitis - Tonic clonic seizures - Flaccid Paralysis - Parkinsonism
98
What part of the brain does JEV involve?
Basal Ganglia Midbrain Pons Thalamus
99
How do you diagnose JEV?
Serlogy: IgM (X-reactivity with West Nile Virus) MRI Brain (high resource only)

DTM&H (29 decks)

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