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Flashcards in WK 4- Mosquito Borne Diseases Deck (44):
1

What is an arbovirus

virus spread by arthropods- ie. mosquitoes

2

What is an alphavirus- give examples

include RRV, BFV, Chikungunya

3

What are examples of flaviviruses

Dengue, Zika, MVE, JE, Kokobera, Kunjin, WNV, YFV

4

What is the family and genus of dengue and what mosquitoes transmit it

-Family: Flaviviridae
-Genus: Flavivirus
-Transmission:
Aedes aegypti = primary mosquito vector
Aedes albopictus= Asian tiger mosquito, not present in mainland Australia but in torres strait

5

What are the different serotypes of dengue

Dengue-1, Dengue-2, Dengue-3, Dengue-4

6

what is the epidemiology of dengue

most important vector-borne viral disease world-wide→ approx. 390 million infections/year→ less than <1% have severe dengue
--> have to notify public health

7

What are the symptoms of dengue- what is the incubation period

Symptoms are a spectrum-> Fever, Headache, Muscle & joint pains, Fine skin rash, Extreme fatigue→Most common in adults and older children
-IP 3-12 days

8

What are the symptoms of severe dengue

severe plasma leakage, bleeding and secondary organ involvement leading to dengue haemorrhagic fever (DHF) and dengue shock syndrome (DSS)--> if severe dengue occurs it is generally a secondary dengue infection

9

What are some factors influencing the severity of dengue

most differences are due to the difference in virulence of the dengue strain, host factors including age, prior dengue infection, gender, nutritional status, immune status, underlying disease and genetics

10

How does dengue cause DHF/DSS

1. Virus enters the mononuclear cell and replicates
2. Triggers production of Ab that cross react with endotheliocytes, plasmin and platelets, T cells
3. Cause apoptosis of endothelial cells, tissue macrophages, liver cells
4. Causes release of toxic products into the blood and inflamm cytokines-> causes increase of coag and consumption of platelets
5. Leads to endothelial dysfunction and development of a coagulation disorder

11

What is the antibody dependent hypothesis

1. After a person is infected with dengue, they develop an immune response to that dengue subtype → 2. The immune response produced specific antibodies to that subtype specific surface proteins that prevents the virus from binding to macrophage cells (the target cell that dengue viruses infect) and gaining entry→ 3. if another subtype of dengue virus infects the individual, the virus will activate the immune system to attack it as if it was the first subtype--> 4. The antibodies bind to the surface proteins but do not inactivate the virus. The immune response attracts numerous macrophages, which the virus proceeds to infect because it has not been inactivated--> 5. The body releases cytokines that cause the endothelial tissue to become permeable which results in Dengue Haemorrhagic Fever (DHF) and fluid loss from the blood vessels

12

What is NS1- when is it useful

nonstructural protein 1-Ag specific to dengue-> found in the blood and indicates presence of dengue virus

13

What mosquitoes carry the zika virus

Aedes aegypti, Aedes albopictus (only in TI)

14

What family does the zika virus belong to

flavivirus

15

Where is Zika most comon

Africa, The Americas, Asia, Pacific (tropical and subtropical regions)

16

What are the clinical presentations of zika- what occurs in the severe form

If symptomatic 2-7 days of: low grade fever, arthralgia, myalgia, headache, rash, conjunctivitis
-Severe disease is uncommon but can cause→ microcephaly, intracranial calcification and GBS (guillian barre syndrome) in adults

17

What lab diagnostic tests are used to test for zika

blood for PCR and serology, urine for PCR (can be detected in urine almost 2 weeks after the pt has been infected)

18

What genus is Ross River Virus and Barmah Forest Virus:

alphavirus

19

What countries are most affected by RRV/BRV

RRV: Australia, Indonesia, PNG & nearby Pacific Islands (highest rates in NT)- 5000 cases yearly
BFV: Australia only

20

What is the prevalence of RRV/BRV

varies according to location and season (large epidemics after large rain fall)

21

What mosquitoes spread the RRV/BFV

Aedes vigilax, Aedes camptorhynchus, Culex annulirostris

22

T or F- RRV/BFV have an animal-mosquito-animal cycle

true
1. Mosquitoes can infect birds and marsupials, creating a viral reservoir
2. The mosquito can then infect humans

23

What are the symptoms of RRV/BFV- what is the IP

70-90% asymptomatic but 10-30% develop; rash, fever, headache, fatigue, arthralgia (multiple joints), myalgia (key indicator)
-Duration of symptoms varies→ majority resolves within a month though some people can have a chronic infection)
IP= 3-11 days

24

What causes australian encephalitis- what mosquito is involved

-Caused by Murray Valley Encephalitis virus (MVEV), and less commonly Kunjin virus (KUNV)--> spread by Culex annulirostris

25

What is the natural host of the Murray Valley Encephalitis virus (MVEV)- where is it most common

water birds--> mainly occurs in the north

26

What are the symptoms of MVE (murray valley encephalitis)- What is the IP- what occurs in the severe form

IP 7-28 days
-Most cases asymptomatic but disease can be mild to severe & fatal
-Approx. 1/1000 cases symptomatic but pt can develop; Fever, anorexia, headache +/- nausea, diarrhoea, dizziness
-Encephalitic syndrome may lead to coma and death or permanent neurological dysfunction

27

What mosquito transmits JEV (japanese encephalitis virus)- where does JEV mainly occur

Aedes albopictus→ Mosquito-pig-mosquito cycle
-Mainly occurs in Asia, PNG (the mosquito that transmits it isn’t on the Australian mainland)

28

What are the symptoms and IP of japanese encephalitis virus

-IP 5-15 days
-Most cases asymptomatic
-Small % cases severe
-Headache, fever, convulsions, coma
-1/3 cases fatal, 1/3 recover with long-term neurological sequela

29

What mosquito transmits chikungunya virus

Alphavirus transmitted by Aedes albopictus mosquitoes (don’t have this mosquito on our mainland)

30

Where is chikungunya virus present

Has re-emerged in Africa, Asia & Indian Ocean islands due to vector spread & human travel

31

What are the symptoms of chikungunya virus

fever, myalgia, rash, arthralgia
-Can be fatal

32

How do you diagnose arbovirus- why is it important to use laboratory diagnosis

Signs and symptoms of a variety of viral infections may be similar, important to use lab tests to get definite diagnosis
-Diagnosis can be through: PCR/antigen tests, detection of immune response to viral infection (IgM), NS1 for dengue--> important to test for Ab and the virus as Ab take time to develop

33

What is the ELISA test used for in arbovirus diagnosis

Detection of virus-specific IgM antibodies
-Suitable for testing large numbers of samples
-Well established sensitivity, but some specificity issues (can detect if the Ag is there (so has high sensitivity) but difficult to determine the type of Ag (lower specificity)

34

What does a thick slide show and what does a thin slide show

Thick= determines whether there is a viral infection
Thin= allows you to see individual RBC and determine the type of virus by looking at the morphology

35

What are the treatments available for arbovirus

-No specific anti-viral agents available
-Most cases require rest & supportive therapy, i.e. manage the symptoms

36

What are some preventative activities for Mosquito-Borne Disease

-avoid mosquito bites
-public education programs (personal protection, reduction of mosquito breeding sites, biological control of vectors)
-Vaccines- JE (japanese encephalitis), YFV (yellow fever)
-Public health surveillance

37

What mosquito transmits malaria

Anopheles mosquito

38

What are the 5 types of malaria parasites

Plasmodium falciparum, Plasmodium ovale, Plasmodium vivax, Plasmodium malariae, Plasmodium knowlesi

39

What areas are mainly affected by malaria

South-west Pacific (Solomon Islands, PNG, Vanuatu), Asia (Thailand, Myanmar, Vietnam, India), Africa
-Australia is malaria free

40

What are the symptoms of malaria

-fever, headache, backache, nausea, vomiting, muscle and joint pains, dry cough, splenomegaly

41

What tests are used to test for malaria

-Blood in EDTA tube
-Thick and thin films
-Malaria PCR and rapid test card

42

What is the tx of malaria

Early malaria easily treated, however late, severe or complicated malaria can be a life-threatening emergency
-Have to use antimalarial drugs in combination--> artemisinin combination therapy is used for p.falciparum to prevent resistance

43

How do you prevent and control malaria

Prevention
-Travel advice re. antimalarial drugs
-Avoidance of mosquito bites
-Vaccine
-Control
-Public health efforts
-Public health notification & follow-up of cases
Prevention & Control of Malaria

44

Given that West Nile Virus (WNV) is almost identical to Kunjin virus both genetically and immunologically discuss whether WNV is a serious threat to Australia.

-West Nile virus is almost identical genetically and immunologically to Kunjin virus → Unlike West Nile virus, Kunjin virus usually causes no symptoms.
-If West Nile virus were introduced it would have to compete with Kunjin virus for vertebrate hosts and vectors. -Because antibodies to Kunjin virus neutralise West Nile virus (and vice versa), it may prove more difficult for West Nile
virus to become established or spread rapidly