Mosquitoes & Zoonoses Flashcards

1
Q

What is the “extrinsic incubation period” in regards to mosquito zoonoses?

A

The amount of time it takes for a pathogen to become infectious within a mosquito after the blood meal

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2
Q

T/F: Mosquitoes are the most important vectors of human disease worldwide

A

TRUE

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3
Q

What are the 3 equine encephalitis viruses? What family are they from?

A

Western (WEEV), Eastern (EEEV), and Venezuelan (VEEV)

Togaviridae, genus Alphavirus

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4
Q

What pathogenicity is seen in equids with VEEV, EEEV, and WEEV?

A

VEEV: up to 80% fatality
EEV: 90+% fatal
WEEV: ~ 20-40% case fatality rate

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5
Q

Who are the natural reservoirs for WEEV, VEEV, and EEEV?

A

WEEV: birds
VEEV: rodents - enzootic reservoir and horses - epizootic reservoir
EEV: birds

*epizootics occur periodically

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6
Q

What cause epizootics (of EEEV, WEEV), and where do they being?

A

They begin in nature - increased transmission of virus between mosquitoes and birds and then spills over to incidental hosts

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7
Q

T/F: Incidental hosts are usually dead-end hosts (cannot infect mosquitoes)

A

TRUE

but there are some exceptions

**BOTH horses and humans with VEEV are NOT dead end hosts

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8
Q

What is the mosquito vector involved in the enzootic reservoir cycle (wild birds and mosquitoes) of Eastern Equine Encephalitis Virus

A

Culiseta species

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9
Q

What is the “bridge” mosquito spps that is a part of the epizootic cycle between birds and the incidental hosts of EEEV?

A

Aedes species

Incidental hosts: horses, humans, swine etc
**these are DEAD END hosts

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10
Q

What is the most virulent Equine Encephalitis virus?

A

Easter EEV

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11
Q

How soon before human infections of EEEV would you note infections in horses?

A

Usually about two weeks before human infections

*begin with fever, decreased appetite, and lethargy —-> neuro –> fatal cases have ~5-10day course

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12
Q

What are risk factors for humans getting EEEV?

A

Outdoor activities in an area with EEEV infected mosquitoes

*incubation period if 3-10 days

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13
Q

What symptoms are seen in humans with EEEV?

A

Some people are asymptomatic (90+%)
Symptoms range from flu-like illness to encephalitis, coma, and death
*many survivors will have mild to severe permanent neuro damage

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14
Q

What is the species of mosquito involved in the natural cycle of WEEV?

A

Culex tarsalis

*bridge mosquito is the same as EEEV - Aedes species

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15
Q

What clinical signs are seen in horses with WEEV and humans with WEEV?

A

Horses: infections are rare - being with fever, anorexia, lethargy and can progress to neuro signs and end in coma/fatality in severe cases in about 5-10 days

Humans: symptoms range from flu like illness to encephalitis, coma, and death (much less than EEEV) Mild to severe neuro deficits are seen in survivors

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16
Q

Are EEEV and/or WEEV titers in symptomatic horses high or low?

A

LOW (both in blood and CSF)

17
Q

If you are working on a horse infected with EEEV, and you see him get bit by a mosquito, then that mosquito tries to bite you… Are you scared for your life??

A

No - that mosquito will not be infectious immediately.

The population of mosquitoes that infected this horse are of more concern

18
Q

What EEV is foreign to the US?

A

VEEV

19
Q

What species of mosquito and animals are involved in the sylvatic or enzootic cycle of VEEV?

A

Rodents and Culex species

20
Q

What species of mosquitoes are involved in epizootic transmission of VEEV?

A

Psorophora and Aedes species

21
Q

For which one of these equine dz can a horse be a reservoir and not just a dead end host?

Eastern EEV
Western EEV
Venezuelan EEV
West Nile Virus
None
A

Venezuelan EEV

22
Q

What clinical signs will you see in equids with VEEV?

A

Present either as febrile or encephalitic dz

Peracute death may occur with no previous signs

23
Q

What symptoms will you see in humans infected with VEEV? Are they ever asymptomatic?

A

Almost 100% of cases are symptomatic

Typically febrile illness with neuro symptoms in less an 1% of adults and fatality in about 10% of those cases (higher in children)

24
Q

How do you prevent VEEV?

A

It’s a reportable foreign animal dz in the USA
Mosquito/rodent control
Sentinel surveillance using pheasants

25
Q

West Nile Virus is in the genus ________. It is maintained in a mosquito - ________ - mosquito cycle

A

Flavivirus
Bird

**primarily transmitted via culex species of mosquitoes

26
Q

How long do birds maintain viremia post exposure?

A

1-4 days

*mosts bird survive

27
Q

What clinical signs will you see in horses with WNV?

A

Neurological: ataxia, hypermetria, weakness, peri or tetraparesis, recumbency, and death

28
Q

What symptoms will you see in a person infected with WNV?

A

about 80% of people will be asymptomatic
about 20% develop mild febrile illness
1 in 150 will develop neuroinvasive disease (old people are at highest risk)

29
Q

Who are the dead end hosts of WNV?

A

Humans and Horses

30
Q

After infection, what kind of immunity to WNV will form?

A

Life long

31
Q

How does secondary infection of WNV occur?

A

bloodborne infection
laboratory exposure
breast milk