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Epidemiology - MIDTERM 2 > Topic 46 - West nile fever, disease caused by Usutu virus and other mosquito-borne flaviviral diseases > Flashcards

Topic 46 - West nile fever, disease caused by Usutu virus and other mosquito-borne flaviviral diseases Flashcards

1
Q

Definition of West Nile fever:

A

A mosquito-transmitted, zoonotic disease with fever, general signs and sometimes meningo-encephalomyelitis and death for both animals and humans

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2
Q

Occurence of West Nile fever:

A

Worldwide

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3
Q

Where was the first isolation of West Nile fever ever found?

A

In Uganda, hence the name

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4
Q

First occurence of West Nile fever in Europe, when and where?

A

1960

France, Russia, Spain and Romania

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5
Q

First occurence of West Nile fever in USA:

A

1999

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6
Q

Maintaining host of West Nile fever:

A

Wild birds: goose, crow, pigeon

All birds are susceptible, but not all are maintaining hosts

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7
Q

Is there a cross-reaction between flavviviruses, and why?

A

Yes there is. They are all closely related, both genetically and antigenetically

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8
Q

West Nile fever is part of a serocomplex, what is it called and why is West Nile fever in it?

A

Japanese encephaitis serocomplex

In this complex we find several viruses that are antigenetically related, including West Nile fever

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9
Q

How many genetic lineages have West Nile fever?

A

9

But only two are pathogenic: Lineage 1 + 2 strains

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10
Q

Occurrence of lineage 1 strain of West Nile fever:

A

Worldwide

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11
Q

Occurrence of lineage 2 of West Nile fever:

A

Europe and Africa, all cases of Hungary since 2004

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12
Q

Host cycle of West Nile fever:

A

Wild birds - Mosquitos - Human and horses

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13
Q

If a bird becomes infected late/end of mosquito season, why could this be of importance of West Nile fever?

A

The viramia last for 20-100 days = 3 months prox

So if a bird is infected at the end of the season, they bird is infected for the whole winter and the bird is then the source of infection for the mosquitos the next season

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14
Q

Vector of West Nile fever:

A

Mosquito

Detected in more than 60 species

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15
Q

Principle vector of West Nile fever:

A

Culex pipiens

They are a breach vector, biological vector and transovarial transmission

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16
Q

What is a breach vector?

A

A vector feeding on two hosts, in West Nile fever case: Bird and mammals. They transport the virus for from birds to humans or mammals

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17
Q

Dead-end host of West Nile fever:

A

Humans
Horses

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18
Q

Pathogenesis of West Nile fever:

A

Infection –> multiplication –> Viraemia –> targets the brain –> inflammation of the brain

after infection we have a primary replication causing rash and skin lesions, then we have viraemia and the brain is targeted. The virus tarhets the neuron cells and replicates there and we see inflammation of the brain

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19
Q

Primary replication site of West Nile fever:

A

Endothel cells

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20
Q

In case of inflammation of the brain of West Nile fever, what can we see?

A
  1. Serous-lymphoid cell infiltration
  2. Neuron cell degeneration
  3. Inflammation of the peripheric nerves
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21
Q

How long after infection of West Nile fever does antibodies occur?

A

7-11 days

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22
Q

Is there a persisting infection of West Nile fever?

A

In mammals: rarely
In birds: frequent

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23
Q

susceptibility of West Nile fever:

A

Horse
Sheep
Dog and Cat
Geese
Wild birds

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24
Q

Clinical signs in horses infected with West Nile fever:

A

Mostly subclinical!!

If we see: mild clinical signs
1. anorexia
2. fever
3. depression
Are most characteristic

In less than 1% we see CNS signs

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25
Q

How many of the West Nile fever infected horses have a subclinical infection?

A

80-90%

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26
Q

CNS signs in West Nile fever:

A
  1. skin oversensitivity
  2. weakness of the hindlims (strange movement, strange walk)
  3. Teeth grinding
  4. convulsions
  5. Partial parlysis
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27
Q

Lethality rate of West Nile fever:

A

9-90%

If CNS problems are seen = 100%

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28
Q

Clinical signs in sheep infected with West Nile fever

A

1.Teeth grinding
2. Ataxia
3. Movement problems

All CNS problems

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29
Q

Clinical signs in dogs and cats infected with West Nile fever

A

they have asymptomatic seroconversion

We rarely see fever and CNS signs

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30
Q

Age susceptibility of geese infected with West Nile fever:

A

3-12 weeks of age

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31
Q

Clinical signs in geese infected with West Nile fever:

A
  1. Abnormal head position
  2. Wing parslysis
  3. Ruffled feathers
  4. Ataxia
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32
Q

Lethality in geese infected with West Nile fever:

A

14-40 %

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33
Q

Susceptible wild birds of West Nile fever:

A

Stork
Birds of prey
Crow
Magpie
Sparrow
Seagull
Blackbird
Penguin

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34
Q

Name wild birds that are sensitive to West Nile fever, and what does it mean that they are sensitive?

A

Crow, birds of prey, goose

They might die from the infection

35
Q

Name wild birds that are not so sensitive to West Nile fever, and what does it mean that they are not so sensitive?

A

Stork, pigeon

They can fly bigger distances with the virus

36
Q

Clinical signs of wild birds infected with West Nile fever:

A

Most of them are asymptomatic, but some might die from the infection

37
Q

Outcome of asymptomatic infection of West Nile fever in wild birds:

A

asymptomatic seroconversion

38
Q

Outcome if the wild bird is showing clinical signs in case of West Nile fever, and which clinical signs do they show?

A

Sudden death

They show:
1. Seizures
2. Ataxia
3. Paralysis

39
Q

Pathological lesions in case of West Nile fever:

A

Seen in birds and horses, not very obvious signs

fluid accumulation in the epicardium

40
Q

Histopathological lesions in case of West Nile fever:

A

Much more obvious, also seen in birds and horses

  1. Inflammation in the brain
  2. Haemorrhages
  3. Neuron cell degeneration
  4. Glia cell proliferations
  5. serous-cellular infiltration of myocardium
  6. Cell degeneration and apoptosis of myocardium
41
Q

How to diagnose West Nile fever:

A
  1. Clinical signs
  2. Lab tests
  3. Pathological + histopathological
42
Q

Differential diagnosis of West Nile fever:

A

Febrile illnesses with CNS signs

  1. Rabies
  2. Toxicosis
43
Q

How can we differentiate West Nile fever from other diseases:

A
  1. It is seasonal
  2. CNS signs - ALWAYS notify incase it could be West Nile fever
44
Q

Laboratory diagnosis of West Nile fever:

A

We can do:
1. RT-PCR
2. Virus isolation
3. Immunochemistry
4. Serology

But these are not very good, and mostly done if there is enough time - as in research

45
Q

Laboratory work to diagnose West Nile fever:

A

In acute cases we do blood work and do RT-PCR, but we cannot really detect the virus from the blood, so we do coagluated blood instead and detect IgM

46
Q

Why can we detect IgM in the blood after West Nile fever infection, or any other infection?

A

After infection IgM are produced immediately, so in acute phases IgM can be seen in the blood

47
Q

Why can also detecting IgM be a problem in case of West Nile fever?

A

IgM detection ca be negative, if the animal previously have been vaccinated - but not properly to protect from infection

We can detect IgG instead if IgM in this case, which can be seen in the blood

48
Q

Prevention and control for West Nile fever:

A
  1. Mosquito control
  2. Use of repellents against mosquito
  3. Vaccinations, but only for horses
49
Q

Vaccination type in case of West Nile fever:

A

Recombinant inactivated vaccine

2x basic immunisation, then yearly BEFORE mosquito

50
Q

Public health aspects of West Nile fever:

A

ZOONOTIC!!

  1. Usually asymptomatic, but in some cases humans show clinical signs and even CNS problems
  2. No vaccine available
51
Q

Clinical signs of humans in case of West Nile fever:

A
  1. Fever
  2. Discomfort
  3. Loss of appetite
  4. swelling of lymph nodes
52
Q

Lethality of humans in case of West Nile fever:

A

Recovery in 3-6 days

53
Q

Susceptibility of more severe signs of West Nile fever:

A

Humans over the age of 60, usually with other diseases in the background such as: diabetes, blood pressure etc. The virus crosses the blood-brain-barrier and we see CNS problems

54
Q

Clinical signs in more severe cases in humans for West Nile fever:

A
  1. Coma
  2. Convulsions
  3. Paralysis
  4. disorientation
  5. muscle weakness
55
Q

Recovery from severe signs of West Nile fever:

A

Can recover, but permanent damages may remain, such as: weakness of the limbs, milder dementia

56
Q

Name other mosquito-borne flaviviruses that causes infection:

A
  1. Japanese encephalitis
  2. St.Louis encephalitis
  3. Murray-valley encephalitis
  4. Wesselsbron disease
  5. Turkey meningoencephalitis
  6. Usutu
  7. Duck egg-drop syndrome
  8. Dengue fever
  9. Yellow fever
  10. Zika virus infection
57
Q

Occurece of Japanese encephalitis

A

Asian countries: Japan, Korea

58
Q

Susceptible species of Japanese encephalitis:

A

horse, swine, other mammals and birds

59
Q

Reservoir host of Japanese encephalitis:

A

swine + water birds

60
Q

Occurence of St.Louis encephalitis:

A

America

61
Q

Susceptible species of St.Louis encephalitis:

A

Horse, human, bird

62
Q

Reservoir host of St.Louis encephalitis:

A

wild birds

63
Q

Occurence of Murray-valley encephalitis:

A

Australia, NEw-guinea

64
Q

Susceptible species of Murray-valley encephalitis:

A

humans, children more than adults
mammals

65
Q

Reservoir of Murray-valley encephalitis:

A

wild birds

66
Q

Occurence of Wesselsbron disease:

A

Sub-saharan Africa

67
Q

Susceptibility of Wesselsbron disease:

A

Sheeo
Other mammals
humans - Subclinical

68
Q

Occurence of Turkey meningoencephalitits

A

Isreal
South Africa
Turkey

69
Q

Clinical signs of Turkey meningoencephalitits:

A
  1. CNS signs
  2. Reduced egg production
  3. Mortality increased

Attenuated vaccine in endemic countries

70
Q

Occurence of Usutu?

A

Africa and central-Europe

71
Q

Susceptibility of Usutu:

A

Wild birds
Horses
Humans - ZOONOTIC

72
Q

Occurence of duck egg-drop syndrome

A

China

73
Q

Occurence of dengue fever

A

World wide

74
Q

Susceptible species of dengue fever:

A

humans

Mokeys too, and they are also reservoir host

75
Q

How many types of dengue fever is there?

A

4

First we get infected with the 1st type, then the 2nd, then the 3rd and if we get infected for a 4th time it is most severe

76
Q

Clinical signs of the 4 types of dengue fever:

A

1: antibody-dependendt enhancement
2: Dengue-fever
3. Dengue haemorrhagic fever
4. Dengue shock syndrom - can lead to death

77
Q

Occurence of yellow fever:

A

Worldwide

78
Q

Why the name yellow fever?

A

Causes liver damage - yellow discoloration of the skin

79
Q

Vaccination from yellow fever?

A

yes, necessary before travel to endemic areas

80
Q

Occurence of Zika virus:

A

Africa

81
Q

Reservoir host of Zika virus:

A

Monkeys

82
Q

Susceptible species of Zika virus:

A

Humans

83
Q

Transmission route of Zika virus:

A

Mosquitos

Epidemiology - MIDTERM 2 (35 decks)

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