Topic 57 - Bluetongue Flashcards
Causative agent of bluetongue
Orbivirus genus, under sedoreoviridae family - reovirus
Definition of bluetongue disease
Disease transmitted by insect vector, we can see endothel-damages in sheep and cattle
Which species is most sensitive to bluetongue disease?
sheep
Cattle is less sensitive, but still show clinical signs
Occurence of bluetongue disease:
Worldwide distribution, mostly in warmer regions
When was bluetongue disease introduced to Europe?
1998
When did bluetongue disease arrive to Hungary?
2007
How many serotypes of bluetongue disease:
29
Protection of serotypes of bluetongue disease:
The vaccine should contain the serotypes which actually causes the problems at the certain geographical areas
Host susceptibility of bluetongue disease:
sheep
cattle
goat - more resistance, rarely see clinical signs
is bluetongue notifiable or not?
it is notifiable
Which season is it most common to get infected with bluetongue disease?
In mosquito season: late spring, summer and early autumn
How can bluetongue disease be spread?
- with the wind = 50-250km distance
- Transport of infected ruminants.
- with semen
- Transplacental infection
How long can sheep carry bluetongue disease?
2 months
How long can cattle carry bluetongue disease?
asymptomatic carriers
Outcome of transplacental infection of bluetongue disease:
immunotolerance = They dont produce antibodies against the virus
We also see:
1. Abortions due to placental vessel damage
2. developmental problems, mostly the brain is affected
Pathogenesis of bluetongue disease:
There is a mosquito bite, the virus is injected into the blood and we have a small replication there. We have a primary multiplication and a viraemia, and a second replication in the endothel cells which will cause oedemas and haemorrhages
Primary replication site of bluetongue disease:
Lymphatic tissue
At what day of infection of bluetongue disease does viraemia occur?
day 5-11
Incubation time of bluetongue disease
3-7 days
Clinical signs in sheep infected with bluetongue disease:
- Fever, depression and dyspnoea (first signs)
- conjunctivits
- eyelid-oedema
- Lacrimation
- Oedema under the skin, on ears, head, chin and neck
- muscle damages = movement problems
- enteritis in lambs
- loss of wool
9 abortion
mortality in sheep infected with bluetongue disease:
10%, mostly young or weak animals
Clinical signs in cattle infected with bluetongue disease:
Usually subclinical infections - no clinical signs, therefore hard to recognize
If clinical signs:
1. nasal discharge
2. reduced milk production
3. oedema
4. muzzle erosions
5. ulcerations
6. abortions
Clinical signs in goats infected with bluetongue disease:
subclinical carriers
How to diagnose bluetongue disease:
- seasonlatiy
- clinical signs
- pathology
These will give a good suspicion, but we also have to do virus detection and serology
Virus detection method of bluetongue disease:
RT-PCR
Since the bluetongue disease is notifiable, virus identification is important for the diagnosis
Serology method for bluetongue disease:
ELISA and virus neutralisation
We can detect of the animal was vaccinated or not
Why is virus neutralisation needed in case of bluetongue disease?
Due to cross-reactions. To determine the antibody specificity, to see which serotype that was the cause of the infection - for vaccines
Differential diagnosis of bluetongue disease, viral diseases:
Everythign with mucous membrance damages, oedema, haemorrhages, cyanosis, endothel cel damages
- FMD
- Sheep pox
- IBR
- BVD
- Malignant catarrhal fever
Prevention and control in bluetongue disease free countries:
- Restrictions
- Slaughter of affected animals
- Vector control
- prevention of introduction, quarantine
- Separation of seropositive pregnant animals
Prevention and control in bluetongue disease endemic countries:
(mostly Africa)
Use attenuated vaccines
What can happen if the vaccine is by a live strain?
It can shed, there is an infection of mosquitos and there is a risk of reversion. This is because it is a RNA virus, it can regain its virulence
