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Epidemiology - MIDTERM 2 > Topic 42 - Equine encephalomyelitis caused by togaviruses > Flashcards

Topic 42 - Equine encephalomyelitis caused by togaviruses Flashcards

1
Q

Name the different types of equine encephalomyelitis:

A
  1. Eastern Equine Encephalomyelitis
  2. Western Equine Encephalomyelitis
  3. Venezuelan Equine Encephalomyelitis
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2
Q

Causative agent of equine encephalomyelitis:

A

Alphavirus genus, under togavirus

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3
Q

Definition of Eastern, western and Venezuelan Equine Encephalomyelitis?

A

It is an acute neurological disease in horses, which is present only in America

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4
Q

How is Eastern, western and Venezuelan Equine Encephalomyelitis transmitted?

A

By vectors = mosquitos

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5
Q

Can Eastern, western and Venezuelan Equine Encephalomyelitis affect other species?

A

YES
including humans = notifiable diseases!!

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6
Q

Occurence of Eastern Equine Encephalomyelitis:

A

From Canada, through USAs east coast to the Central America

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7
Q

Occurence of Western Equine Encephalomyelitis:

A

From Canada, through the USAs west coast and Mexico, down to south America

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8
Q

Occurence of Venezuelan Equine Encephalomyelitis:

A

USA southern states, Central and south America

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9
Q

Are togaviruses enveloped or non-enveloped?

A

Enveloped = weak resistance - Very sensitive

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10
Q

Are togaviruses stenoxen or euryxen?

A

Euryxen, wide host range

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11
Q

Transmission type in case of Eastern, western and Venezuelan Equine Encephalomyelitis

A

indirect

Also transovarial transmission of mosquitos, and they are biological vectors

Need a vector = mosquitos

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12
Q

Maintaining host of Eastern Equine Encephalomyelitis

A

Bird

The mosquito feeds on the bird, gets the virus and spread it by feeding on other species

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13
Q

Maintaining host of Western Equine Encephalomyelitis:

A

Bird and rodents

Mosquito feed on the bird and rodents, gets the virus and spread is by feeding on other species

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14
Q

Maintaning host of Venezuelan Equine Encephalomyelitis

A

Rodents

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15
Q

Are Eastern, western and Venezuelan Equine Encephalomyelitis spread whole year around?

A

No, they are seasonal epidemics: Late spring, summer and early autumn season - Depending on the weather conditions

the outbreak also depends on the number of mosquitos

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16
Q

Dead-end host of Eastern Equine Encephalomyelitis

A

Horse and humans

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17
Q

Dead-end host of Western Equine Encephalomyelitis

A

Horse and humans

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18
Q

Dead-end host of Venezuelan Equine Encephalomyelitis

A

Human only, the horse is part of the transmission cycle

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19
Q

What is the transmission cycle of Eastern Equine Encephalomyelitis

A

Bird to mosquito

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20
Q

What is the transmission cycle of Western Equine Encephalomyelitis

A

Bird-Mosquito-Rodent

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21
Q

What is the transmission cycle of Venezuelan Equine Encephalomyelitis

A

Rodents-Mosquito and horses-Mosquito

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22
Q

Pathogenesis of Eastern, western and Venezuelan Equine Encephalomyelitis:

A

Mosquito - infecion - endothel cells - regional lymph nodes - viraemia - visceral organs

Mosquito bite. the virus gets into the blood vessels, and the first cells infected are the endothel cells covering the vessels from the inside. The first replication happens here. With the blood the virus gets to the REGIONAL LYMPH NODES and we have a virus replication and then we will have the FIRST VIRAEMIA where the virus spread all over the body, especially to the visceral organs

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23
Q

Pathogenesis: What happens in case of Eastern, western and Venezuelan Equine Encephalomyelitis, after the virus reaches the visceral organs?

A

We will have a SECOND VIRAEMIA, where we will see characterisitc clinical signs and CNS problems.

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24
Q

In case of Eastern, western and Venezuelan Equine Encephalomyelitis, why can we see CNS problems?

A

The virus will reach the brain, by crossing the blood-brain-barrier. It damages the brain cells, the neuron cells, by replicating in the neuron cells and we will see the CNS symptoms

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25
Q

which clinical signs in the different fever stages in case of Eastern, western and Venezuelan Equine Encephalomyelitis can we observe?

A

1st stage = depression
2nd stage = CNS symptoms

Different fever stages due to there being two viraemia

26
Q

Mortality rate in case of Eastern Equine Encephalomyelitis

A

Most severe!

75-98%

27
Q

Mortality rate in case of Western Equine Encephalomyelitis

A

The mildest

10-50%

28
Q

Mortality rate in case of Venezuelan Equine Encephalomyelitis

A

32-86%

29
Q

What does the mortality depend on?

A

The virulence variants.

Very virulent = severe disease

30
Q

What happens if there is a recovery in case of Eastern, western and Venezuelan Equine Encephalomyelitis:

A

There will be a LIFE-LONG IMMUNITY, but we might see movement problems due to the CNS damages

31
Q

Incubation time of Eastern, western and Venezuelan Equine Encephalomyelitis:

A

Long.
1-3 weeks

32
Q

Clinical signs in peracute form in case of Eastern, western and Venezuelan Equine Encephalomyelitis:

A

Fever and shock, might have death within 12 hours if the strain is very virulent

33
Q

Clinical signs in acute form in case of Eastern, western and Venezuelan Equine Encephalomyelitis:

A

Slower course of action.

First we see: Excitement, increased sensitivity

Later we see: Loss of appetite, icterus due to the infection of liver and apathy

34
Q

Clinical signs in acute form, 2nd stage of fever, in case of Eastern, western and Venezuelan Equine Encephalomyelitis:

A

Encephalitis: Visual disturbances, head convulsions, paralysis

Myelitis (infection of spinal cord): Lameness, convulsions, paralysis

35
Q

Extra clinical signs in case of venezuelan equine encephalomyelitis:

A

Colic and enteric problems such as diarrhoea

36
Q

Clinical signs in case of mild virulence in Eastern, western and Venezuelan Equine Encephalomyelitis:

A

Chronic form.

This is very rare, and last for 1-2 weeks

37
Q

Pathological lesions in case of Eastern, western and Venezuelan Equine Encephalomyelitis:

A

We can not see any lesions macroscopically, only through histopathology

38
Q

Histopathological lesions in case of Eastern, western and Venezuelan Equine Encephalomyelitis:

A
  1. Encephalitis and myelitis
  2. Grey and white matter is affected
  3. We can see lymphatic, neutrophil granulocytes
  4. We can see thrombosis
39
Q

Histopathological lesions, chronic form, in case of Eastern, western and Venezuelan Equine Encephalomyelitis:

A

Degenerative and reparative processes

40
Q

How can we diagnose Eastern, western and Venezuelan Equine Encephalomyelitis:

A

Based on:
1. clinical signs
2. Seasonality
3. Geopgraphic origin
We should have a good idea of disease

We should notify authority if we suspect!

41
Q

Which laboratory investigations can we do in case of Eastern, western and Venezuelan Equine Encephalomyelitis:

A

In case of dead animals, we do SAMPLING

To detect the VIRUS, we use RT-PCR

42
Q

Differential diagnosis of Eastern, western and Venezuelan Equine Encephalomyelitis:

A

Every disease which affects the brain!!

  1. Rabies
  2. West Nile fever
  3. Getah virus
  4. Listeriosis
  5. Botulism
  6. Metal poisining
  7. Plant poisining
43
Q

Treatment in enzootic countries of Eastern, western and Venezuelan Equine Encephalomyelitis:

A

Supportive treatment

44
Q

Prevention in enzootic countries of Eastern, western and Venezuelan Equine Encephalomyelitis:

A

vaccination and mosquito control

45
Q

Vaccine type in enzootic countries of Eastern, western and Venezuelan Equine Encephalomyelitis:

A

Inactivated, trivalent vaccine. Vaccinate against all 3 at once, and repeated every year

46
Q

Vaccination time/amount in enzootic countries of Eastern, western and Venezuelan Equine Encephalomyelitis:

A

2 x basic immunity and then yearly repetitions

47
Q

In case of Venezuelan equine encephalomyelitis there is used a vaccine only for prevention of outbreak, what is it called?

A

Strain TC83, an attenuated vaccine

48
Q

In Eastern, western and Venezuelan Equine Encephalomyelitis free countries, which prevention measures are to be done?

A
  1. Avoid introduction
  2. Repeated serological investigations during quarantine, of the animal comes from an infected area
49
Q

3 reasons why Eastern, western and Venezuelan Equine Encephalomyelitis is notifiable:

A
  1. Present only in America, we don`t want it to appear somehwere else
  2. High mortality, almost 100%
  3. Zoonotic
50
Q

Name some public health concerns regarding Eastern, western and Venezuelan Equine Encephalomyelitis:

A
  1. Infection of pregnant humans in 2nd-3rd trimester can cause abortions or newborn cerebral necrosis
  2. Children are more sensitive, frequent CNS symptoms
  3. Permanent defects after recovery: dementia, movement problems
  4. Human vaccine is available
51
Q

Clinical signs in humans in case of Eastern, western and Venezuelan Equine Encephalomyelitis:

A
  1. Fever
  2. Headache
  3. Nausea
  4. Vomiting
52
Q

Name other disease caused by “alphaviruses”:

A
  1. Chikungunya
  2. O`nyong-nyong
  3. Ross River fever
  4. Getah virus infection
  5. Sindbis virus infections
  6. Semliki forest virus infection
53
Q

Why is the disease called Chikungunya?

A

It means “What bends you”, because there are so severe joint pains and muscle pains that the patient cannot stand straight

54
Q

Occurrence of Chikungunya disease:

A

Tropical countries

55
Q

Host and clinical signs in case of Chikungunya disease:

A

Humans

Joint pains, fever, rash, haemorrhages

56
Q

Vector in case of Chikungunya disease:

A

Mosquito

57
Q

Host and clinical signs in case of O`nyong-nyong disease:

A

Human

Fever and rash

58
Q

Host and clinical signs in case of Ross River fever disease:

A

Human

Fever, arhrithis and rash

59
Q

Host and clinical signs in case of Getah virus:

A

Pigs, horses, pandas and other mammalians

Most importantly: horse encephalitis

60
Q

Host and clinical signs in case of Sindbis virus infection:

A

Human

Fever, muscle and joint-pain and rash

61
Q

Host and clinical signs in case of Semliki forest virus infection:

A

Rodents and humans

Rodent: encephalitis
Humans: mild or no symptoms

62
Q

What is special with Semliki forest virus infection?

A

Genetically modified virus can be used for brain tumour therapy

Epidemiology - MIDTERM 2 (35 decks)

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