Disease Information (5) (Provided by Emerging Exotic Diseases Lab, Foreign Animal Diseases Division) ( 07/05/11 ) | |||||
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Part | Charger | leeyh | date | 07/05/11 | |
□ BLUETONGUE
1. Definition
- Vector (Culicodies spp) borne viral disease in Ruminants
2. Aetiology
- Virus family Reoviridae, genus Orbivirus. 24 serotypes have been identified.
3. Host range
- Sheep: disease; variation in breed susceptibility
- Cattle, goats, dromedaries, wild ruminants: generally inapparent infection
4. Geographical distribution
- The virus is present in a broad band of countries extending appriximately between 50°N and 35°S. The bluetongue virus has been shown by serology to be present in regions where the Culicoides vector is present (e.g. Africa, the Americas, Australia and some countries of southern Asia and Oceania). However, clinical disease with confirmation by virus isolation has been observed in a few countries only.
- For detailed information on occurrence, see recent issues of World Animal Health and the OIE Bulletin
5. Transmission
- Biological vectors: Culicoides spp.
- Sources of virus
Infected Culicoides
Blood
Semen
6. Incubation period
- Incubation period is 5-20 days
7. Gross lesions
- Congestion, oedema, haemorrhages and ulcerations of digestive and respiratory mucosae (mouth, oesophagus, stomach, intestine, pituitary mucosa, tracheal mucosa)
- Congestion of hoof laminae and coronary band
- Hypertrophy of lymph nodes and splenomegaly
- Severe bilateral broncholobular pneumonia (when complications occur)
8. Diagnosis
- Clinical diagnosis
Acute form (sheep and some species of deer)
Pyrexia up to 42°C, depression
Inflammation, ulceration, erosion and necrosis of the mucosae of the mouth
Swollen and sometimes cyanotic tongue
Lameness due to coronitis or pododermatitis and myositis
Abortion
Complications of pneumonia
Emaciation
Either death within 8-10 days or long recovery with alopecia, sterility and growth delay
Inapparent infection
Frequent in cattle and other species (cf. epidemiology)
- Laboratory diagnosis
Isolation of the agent
Inoculation of sheep
Intravascular inoculation in 10-12-day-old embryonated chicken eggs
Identification of the agent
Plaque reduction serum neutralisation (for serotyping - many cross-reactions)
Serological test
Competitive ELISA (prescribed tests in the Manual))
Agar gel immunodiffusion
Virus neutralisation
Complement fixation
Samples
Isolation and identification of the agent
Living animals: blood in heparin
Freshly dead animals: spleen, liver, red bone marrow, heart blood, lymphnodes
Aborted and congenitally infected newborn animals: precolostrum serum plus same samples as for freshly dead animals
All samples have to be preserved at 4°C, and not frozen
Serological tests : Paired sample sera
9. Control and eradication
- Disease-free areas : quarantine and serological survey, vector control, especially in aircraft
- Infected areas : vector control
10. Public health aspects
- There is no risk to human health
11. Further infomation : http://www.oie.int/eng/maladies/en_fiches.htm?e1d7
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