Bluetongue Disease

BTV

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Changed on: 22.01.2019
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Bluetongue virus - elektronenmikroskopische Aufnahme, © CDC, J. Mast (Coda-Cerva, Belgium)
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Bluetongue virus - elektronenmikroskopische Aufnahme, © CDC, J. Mast (Coda-Cerva, Belgium)

Bluetongue Disease (BT) is a viral disease of cattle, sheep, goats, camelids and wild ruminants. In Austria Bluetongue Diseases a notifiable disease. Transmission occurs via biting midges. Bluetongue Disease first occurred in this country as serotype 8 on 07/11/2008; by 17/03/2011 Austria was once more declared free of Bluetongue Disease. On 17/11/2015 BTV serotype 4 was detected in Austria for the first time, thus Austria is no longer considered BT-free.

17/11/2015, Information from the Federal Ministry of Health

More information
Bluetongue virus - elektronenmikroskopische Aufnahme, © CDC, J. Mast (Coda-Cerva, Belgium)
caption
Bluetongue virus - elektronenmikroskopische Aufnahme, © CDC, J. Mast (Coda-Cerva, Belgium)

Bluetongue Disease (BT) is a viral disease of cattle, sheep, goats, camelids and wild ruminants. In Austria Bluetongue Diseases a notifiable disease. Transmission occurs via biting midges. Bluetongue Disease first occurred in this country as serotype 8 on 07/11/2008; by 17/03/2011 Austria was once more declared free of Bluetongue Disease. On 17/11/2015 BTV serotype 4 was detected in Austria for the first time, thus Austria is no longer considered BT-free.

17/11/2015, Information from the Federal Ministry of Health

More information

Occurrence

Occurrence

Bluetongue Disease was first identified in South Africa in 1934. The disease spread further with the export of merino sheep to many states in the African continent. Nowadays the Bluetongue Disease occurs virtually worldwide. On 17th August 2006 the first outbreak above the 50th parallel north was reported by authorities in the Netherlands. However, the serotype 8 (BTV 8) virus strain found in the Netherlands was not one of the strains native to southern Europe. An occurrence of a virus strain from serotype 6 (BTV 6) was also reported in Germany.
The first BTV case in a cow was reported in Upper Austria (Schärding district) on 07/11/2008. In total 28 BTV-positive animals were found. No further BTV cases have been detected since 06/03/2009. The spread of serotype 8 (BTV 8) was prevented by extensive vaccination measures.

YearSumViennaLower AustriaUpper AustriaSalzburgTyrolVorarlbergCarinthiaStyriaBurgenland
SerotypeBTV-8BTV-8BTV-8BTV-8
2008110010001000
2009170014102000
total280024103000

A variety of serotypes of the Bluetongue pathogen have been distributed in the Mediterranean region for years. Since 2014 it has been spreading very fast from the Black Sea coast. On 17/11/2015 Austria reported BTV, this time serotype 4, in the federal states of Styria and Burgenland.

Bluetongue in Austria

Bluetongue disease, Federal Agency for Food Safety and Veterinary Services (BVL), Switzerland

Blauzungenkrankheit, Friedrich Löffler Institut (FLI), Germany

Lower Saxony State Office for Consumer Protection and Food Safety, Germany

Blauzungenkrankheit, Federal Agentschap voor de veiligheid van de voedselketen, Belgium

OIE-World Organisation for Animal Health

EU Commission Homepage / Bluetongue

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Vorkommen von BTV-Serotypen in der EU (27.11.2015; © EU-Kommission)
Vorkommen von BTV-Serotypen in der EU (6.11.2015; © EU-Kommission)

Transmission

Transmission

The host range includes above all ruminants (e.g. cattle, sheep, goats), wild ruminants (e.g. deer, ibex, chamois) and camelids (e.g. alpaca). The most susceptible species is the sheep, although there are differences in susceptibility between different individual breeds. For humans there is no risk of infection. There is no risk of BLUETONGUE DISEASE spreading or being transmitted via meat or milk.
Infected animals have a low fatality rate and high morbidity.  Mortality (= the proportion of the susceptible animal population that dies of the disease) is reported as 1 % to 5 % in sheep, and up to 1.5 % in goats and cattle.

Transmission of the pathogen takes place via biting midges (Culicoides spp.), meaning there is no direct transmission path from mammal to mammal. Since midges are involved in the proliferation of the viruses, the disease is seasonally bound to the activity of Culicoides midges. Cases of the disease occur seasonally, mostly in late summer and autumn. In Austria too, the occurrence of insect vectors in large numbers was detected as part of the “Bluetongue Monitoring 2007-2010” project. The Culicoides midge ingests blood containing the BT virus when sucking the blood of the infected animal. The BLUETONGUE VIRUS (BTV) first reaches the intestine of the Culicoides midge and from there enters the salivary glands. The next time blood is sucked, saliva containing the BT virus is introduced into the bloodstream of the mammal (ruminant). There the BT virus replicates and spreads to all organs. The mammal then produces an immune response (formation of anti-bodies) to counter the pathogen. The BT virus can be detected in midges for up to approximately 28 days, in sheep for up to approximately 60 days and in cattle for up to approximately 150 days.

Symptoms

Symptoms

Bluetongue is a cyclical disease. The incubation period is 10 days. Being bitten by an infected midge leads to viraemia in the susceptible host with fever and clinical symptoms. The clinical picture in cattle is similar to FMD, while in sheep lameness is usually the most noticeable symptom.

The most frequent form of the disease is the unapparent one. Different forms of the disease have been observed in sick animals: acute, subacute and abortive, all beginning with a raised temperature.

The symptoms are:

  • Fever (40-42 °C)
  • Hyperaemia of the oral and nasal mucous membranes
  • Lip oedema
  • Hoof inflammation: hyperaemia of the coronary band area
  • Spontaneous abortions
  • Changes in the skeletal musculature

In terms of differential diagnosis, FMD, MCF, BHV1, BVD, PI3, VS (vesicular stomatitis), EHD, ORF, circulatory disorders of other genesis etc. come into consideration.

Control / Prevention

Control / Prevention

Bluetongue Disease is a notifiable disease according to Austria’s Animal Diseases Act.
Monitoring of the Austrian animal population concentrates on identifying BTV-positive animals and on control of animal movement:

  • exhaustive examination of susceptible animals 
  • BTV 8 vaccination in cattle, sheep and goats

A monitoring programme has been in operation in Austria since 2007 in accordance with a sampling plan drawn up by AGES. After Austria was declared BT-free, annual, seasonally-bound BT monitoring was tested for BLUETONGUE DISEASE starting from September to December in 4 regions with 301 cattle in each. Following the occurrence of BT in the Balkans, a fifth region (risk area, dark green) was introduced on the Hungarian border in April 2015. Samples are taken quarterly in regions 1-4 and monthly in region 5. All the animals are tested for BT antibodies and must therefore never have been vaccinated with a BTV vaccine. The aim is to detect BTV infection in an area early by using these sentinel animals, so that possible outbreaks of Bluetongue Disease are detected as soon as possible and control measures can be implemented early - Austrian Federal Ministry of Health: information on the monitoring programme.

BLUETONGUE reports Austria 2007, 2008, 2009, 2010

When an animal tests positive for BTV in Austria, control measures in accordance with BLUETONGUE control regulations come into force (see statutory provisions on the Austrian Federal Ministry of Health homepage).

Vaccination

There are serotype-specific vaccines for BLUETONGUE DISEASE. An inactivated BTV 8 vaccine has been approved by EMEA for cattle and small ruminants since 01/08/2008. Currently no official vaccination programme against BT is being implemented in Austria. Vaccination against serotype 4 of BLUETONGUE DISEASE is permitted, whereby vaccination can take place on a voluntary basis at the request (and own costs) of the animal owner. But as BLUETONGUE DISEASE is a notifiable disease under Austria’s Animal Diseases Act, certain general conditions must be observed when doing so - - for more information visit the Austrian Federal Ministry of Health Homepage.

EU Commission homepage/Bluetongue

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BT monitoring 2015 - risk area dark green
BT monitoring 2015 - risk area dark green
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BT monitoring 2014
BT monitoring 2014
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BT monitoring 2013
BT monitoring 2013
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BT monitoring 2012
BT monitoring 2012

Diagnosis

Diagnosis

Suitable sample materials are:

  • Blood (EDTA/serum)
  • Milk
  • Organs
  • Midges

Verification of BTV from the above-mentioned materials is possible with the following procedures:

  • Serological test procedures for antibody detection: ELISA (serum and milk) and serum neutralisation test (serum)
  • Molecular biological identification (EDTA blood, organs and midges)
  • BT virus replication (EDTA blood, organs, possibly midges)

Information on the testing laboratories:

AGES-Institute for veterinary Disease Control, Mödling
Nationales Referenzlabor

Contact: Dr. Angelika Loitsch, angelika.loitschno@Spam@agesno.Spam.at

Other AGES testing laboratories:
AGES Institute for Veterinary Disease Control, Linz
AGES Institute for Veterinary Disease Control, Innsbruck

 

 


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