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Epidemiology - MIDTERM 2 > Topic 59 - African horse sickness, equine encephalosis > Flashcards

Topic 59 - African horse sickness, equine encephalosis Flashcards

1
Q

Definition of African horse sickness:

A

A vector transmitted disease of equines with acute, febrile signs. Causes endothelial damages, oedemas, haemorrhages, pulmonary and cardiac disease and have a high mortality

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2
Q

Occurence of African horse sickness:

A

Africa mainly, but found also in spain, portugal, turkey

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3
Q

Causative agent of African horse sickness:

A

Orbivirus genus, reovirus family

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4
Q

How many serotypes is there of African horse sickness?

A

at least 9, the virulence differs

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5
Q

Susceptible species of African horse sickness:

A

Horse
Donkey
Zebra

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6
Q

Is African horse sickness notifiable?

A

yes

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7
Q

The host of African horse sickness

A

Horse

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8
Q

Which of the susceptible species are resistant to African horse sickness?

A

Zebra

They get infected, but we rarely see clinical signs - But they can still carry the infection

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9
Q

How long will the viraemia last in African horse sickness in horses?

A

4-8 days, but even as long as 18 days

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10
Q

How long will the viraemia last in African horse sickness in zebras?

A

28 days

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11
Q

How is African horse sickness shed in horses?

A

Through:
- Semen
- Urine
- Discharges

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12
Q

How can a carnivore be infected with African horse sickness?

A

By consumption of infected horse meat, blood or organs

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13
Q

Pathogenesis of African horse sickness:

A

Infection by a vector. We have a primary virus replication, then we have viraemia which will cause lymphatic and blood vessel endothel damage. Due to endothel damage we see oedema and haemoerrhages

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14
Q

Site of primary replication in African horse sickness:

A

Lymphatic tissue

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15
Q

Mortality rate in horses if infected with African horse sickness

A

70-96% (up to 100%)

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16
Q

Mortality rate in mules if infected with African horse sickness

A

50%

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17
Q

Mortality rate in donkeys if infected with African horse sickness

A

10%

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18
Q

Mortality rate in zebras if infected with African horse sickness

A

Most of them survive, close to 0%

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19
Q

Incubation time of African horse sickness:

A

5-7, but can 2-14 days

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20
Q

Clinical signs in peracute form of African horse sickness:

A

Starts with fever, causing general weakness, sweating and red conjunciva
Then we have dyspnoea, coughing

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21
Q

Very characteristic clinical sign in peracute form of African horse sickness:

A

Foamy nasal discharge

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22
Q

Peracute phase of African horse sickness, death within how long?

A

within 24 hours. They suffocate

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23
Q

Another name of peracute form of African horse sickness:

A

Pulmonary form

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24
Q

Clinical signs of acute form of African horse sickness:

A

Similar to peracute form, only longer

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25
Q

Acute form of African horse sickness, death within how long?

A

one week

26
Q

Clinical sign in subacute form of African horse sickness:

A
  1. Fever at the beginning
  2. Oedema due to vessel damage (around: lips, head, tongue, throat, eyes and later on neck we can also see chest oedema
27
Q

Which clinical sign can we see in the final stage of subacute form of African horse sickness:

A

Haemorrhages in the conjunctiva and on the ventral surface of the tongue

28
Q

Subacute form of African horse sickness, death within how long?

A

4-8 days after onset of signs, due do cardiac dysfunction

29
Q

What causes cardiac dysfunction in subacute form of African horse sickness?

A

The heart tries to push the blood through the oedematic tissue and fails, causing a dysfunction

30
Q

Another name of the subacute phase of African horse sickness:

A

Cardiac and oedematic form

31
Q

Which of the differtent phases/forms of African horse sickness, is most commonly seen?

A

The sunacute form

32
Q

What do we call the clinical sign of African horse sickness, where we see oedema around the eyes, lips, head, tongue and throat?

A

Hippo head

33
Q

If survival from subacute form of African horse sickness, how long until the oedeama dissapears?

A

3-8 days

34
Q

Clinical signs of chronic form of African horse sickness:

A
  1. Recurrent fever, higher in the afternoons - VERY CHARACTERISTIC
  2. Rarely other signs
35
Q

Another name of the chronic form of African horse sickness:

A

Febrile form

36
Q

In which species mainly can we see the chronic form of African horse sickness?

A

Donkeys, zebras and immune horses

37
Q

There is a mixed form of African horse sickness, what are the clinical signs?

A
  1. Fever
  2. Mild respiratory signs
  3. Oedemas
  4. Lower mortality - but some animals do die
38
Q

Another name of the mixed form of African horse sickness:

A

Respiratory and cardiac form

It has a slower development, but a longer virulence strain

39
Q

Pathological lesions in case of African horse sickness:

A
  1. Pulmonary oedema
  2. haermorrhages in the mucosa
  3. Oedema under the skin
  4. Fibrinous exudate in the thoracic cavity
  5. Epi- and endocardial haemorrhages
  6. VESSEL DAMAGE!!
40
Q

How can we diagnose African horse sickness?

A
  1. Clinical signs
  2. Pathology
  3. Epizootiology

These 3 will raise the suspicion, but because it is notifiable we do lab samples as well

41
Q

Which laboratory methods do we do in case of African horse sickness?

A

RT-PCR or AG-ELISA to detect virus, and ELISA for serology

42
Q

Differential diagnosis of African horse sickness:

A

Everything with endothel damage

  1. Equine viral arteritis
  2. Babesiosis
  3. Anthrax
  4. Equine infectious anaemia
43
Q

Prevention in African horse sickness endemic countries:

A

Immunisation, horses should be vaccinated

44
Q

Type of vaccine used in African horse sickness endemic countries and for how long does it last?

A

Attenuated, polyvalent vaccine

Lasts for a few years

45
Q

What is a polyvalent vaccine?

A

Several serotypes are induced by the vaccine

46
Q

Prevention in African horse sickness free countries to avoid the disease:

A
  1. Restriction on importation from endemic countries
  2. Quarantine for min 30(!) days
  3. Insecticide treatment against ectoparasite, as a vector control
47
Q

Prevention in African horse sickness free countries if there is an outbreak:

A
  1. Slaughtering of affected animals
  2. insect control
  3. Long term surveillance and monitoring
  4. Vaccinations in the safety zone
48
Q

Which type of vaccine is used in the safety zone in case of an outbreak of African horse sickness in free countries:

A

Inactivated, type-sepcific vaccine x2

49
Q

Causative agent of equine encephalosis

A

Orbivirus genus, reovirus family

50
Q

Occurence of equine encephalosis:

A

South-Africa, rarely seen in other countries

51
Q

Susceptible species of equine encephalosis

A

Equines

52
Q

Pathogenesis of equine encephalosis

A

Similar to African horse sickness.
We see blood vessel damage and the clinical signs are consequences of the damages.

53
Q

Incubation time for equine encephalosis:

A

3-10 days

54
Q

Clinical signs of equine encephalosis in donkey and mule:

A

Frequently asymptomatic

55
Q

Clinical signs of horses if infected with equine encephalosis:

A

Also asymptomatic, but if clinical signs are seen:
1. Fever for 1-5 days and loss of appetite
2. Consequences of the blood vessel damages:
- Oedema of the lips and eyelids
- Elevated pulse
- CNS sign
- Abortion, due to blood vessel damage of the placenta
- Enteritis

56
Q

Mortality rate of equine encephalosis:

A

close to 0%

57
Q

Recovery time of equine encephalosis:

A

1-3 weeks

58
Q

Laboratory methods to diagnose equine encephalosis:

A

Virus isolation
PCR
Serology: ELISA can be used to screen and see if the animal have been affected or not

59
Q

Prevention of equine encephalosis:

A

Only epidemiological measures

60
Q

Is there a vaccine for equine encephalosis?

A

no

Epidemiology - MIDTERM 2 (35 decks)

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