Bluetongue disease

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Bluetongue virus

The bluetongue (syn. Bluetongue , mouth disease , Catarrhal fever of sheep ) is a viral infectious disease of ruminants such. B. Sheep , cattle and goats . Its name is derived from the blue color ( cyanosis ) of the tongue, one of the leading symptoms when the disease breaks out. The disease is a notifiable animal disease . There is no risk of infection for humans, which is why meat and dairy products can be consumed without hesitation.

Pathogens

The pathogen that causes the disease is the bluetongue virus (BTV for short), an orbivirus from the Reoviridae family . It therefore belongs to the non-enveloped double-stranded RNA viruses . At least 24 different serotypes are known of this virus, each with a different virulence . The pathogen that has been found in central and northern Europe since 2006 is serotype 8, or BTV-8 for short. Serotype 1, or BTV-1 for short, has also been spreading northwards in south-west France since 2008. In October 2008, BTV-6 was detected in the Netherlands.

transmission

The bluetongue virus is the genus mosquitoes Culicoides from the family of midges transmitted. Of the more than 5000 species in Central Europe, around a dozen are held responsible as vectors , especially insects of the Culicoides obsoletus group and Culicoides dewulfi . Furthermore, the species C. actoni , C. brevitarsis , C. fulvus , C. imicola , C. insignis , C. nubeculosus and C. variipennis have been proven to be pathogens.

The midges ingest the virus circulating in the blood of an infected animal during the act of suckling. After a cycle of reproduction in the insect, during which the virus also gets into the salivary gland, it transfers this to another animal the next time it is suckled. The reproduction cycle in the insect takes place at a temperature of 25 ° C in 10 to 15 days. This period is also known as the “extrinsic incubation period” (EIP). Once infected, midges will remain infected with the virus for the rest of their life. Purely mechanical transmission is also possible through other blood-sucking arthropods (e.g. mosquitoes , ticks or sheep lice ), but little is known about the frequency and efficiency of this transmission path. Other possibilities include transmission via the semen of infected bulls, which contains the virus during viraemia , and via contaminated syringes as part of veterinary activities. It is not known to be transmitted through smear infection among animals or to humans.

The susceptibility to this infectious disease is greatest in sheep , especially in lambs, but unevenly distributed among the various breeds of sheep. Goats and other domestic animals get sick less often and more severely. The main pathogen or reservoir hosts are cattle , which themselves rarely become seriously ill, as well as wild ruminants ( antelopes , deer ) and African wild rodents.

When winter weather sets in, no new infections are to be expected, since the midges are no longer active as carriers.

Symptoms and course of the disease

sheep

After an incubation period of 2 to 15 days, fever and hyperemia of the mucous membranes of the head develop for 6 to 8 days . Edema also occurs on the lips, eyelids and ears, as well as blue-red coloration (cyanosis) in the mouth area and especially on the tongue. As a result mucosa develop in these areas erosions and - ulcers . Often there is also foamy salivation, nasal discharge (possibly purulent) and breathing difficulties. Inflammation on the claw edge and in the skeletal muscles lead to lameness. Pregnant animals sometimes have abortions or give birth to malformed lambs.

Beef

After an incubation period of five to twelve days, the disease progresses to different degrees depending on the type of virus. The more common mild forms are accompanied by a temporary fever, decreased appetite, increased salivation and possibly a clammy gait. Affected animals recover relatively quickly, but even without visible signs of illness, abortions, fertility disorders , fetal malformations and increased calf mortality can occur. The rarer serious illnesses are initially characterized by high fever, apathy , tachypnea , increased salivation and hyperemia of the head mucous membranes. The oral mucosa, the lips and especially the tongue initially develop cyanosis and swellings, and later erosions and ulcerations. Inflammatory changes occur on the coronet and teats, especially in unpigmented areas. Inflammations in the muscles and claws lead to reluctance to move and lameness.

Diagnosis and differential diagnoses

To confirm the suspected diagnosis, the serological detection of BTV antibodies is possible with a competitive ELISA . Furthermore, a virological examination of the virus culture and the virus detection by means of an immunofluorescence test can be carried out. Genome detection is carried out using RT-PCR . Blood or plasma, as well as spleen, lymph nodes or heart blood from the dead animal are used as sample material.

Depending on the animal species, differential diagnostics u. a. Foot and mouth disease , vesicular stomatitis , BVD / MD , malignant catarrhal fever , lip rash , mustache , smallpox disease in sheep and goats and acute haemonchosis are possible.

Therapy and prevention

If the disease progresses mildly, it is also possible for cattle to heal themselves independently. In addition to measures to alleviate local symptoms, it is recommended not to expose sick animals to sunlight, which can worsen the symptoms.

Disease prevention includes regular insect control, stabling of endangered animal populations during the night and vaccinations (active immunization) in contaminated or suspected countries. To reduce the bite infestation, pyrethroids such as deltamethrin or cyfluthrin can be used.

Due to transport restrictions, e.g. B. virological and serological tests when animals are transported from the 150 km zone (observation area) to the “free” area, the spread of the disease should be prevented.

For Germany, the federal states under the leadership of Hesse ordered 20,989,550 vaccination doses with a total order value of around 16,900,000 euros from three manufacturers in 2008. On April 25, 2008, the Federal Council also approved an ordinance of the BMELV that provided for mandatory vaccination for sheep, goats and cattle with certain exceptions. The EU co-financed the vaccination in 2008 as an emergency measure. In addition, the European Commission approved a vaccination and monitoring program for 2009 in November 2008 and made more than 61 million euros available for the purchase of vaccines and the cost of diagnostic tests. Of the approximately 18 million vaccinations up to November 1, 2008, 650 undesirable side effects were reported. In rare cases there have been deaths or miscarriages . In most cases, however, no direct connection between vaccine and side effects has been demonstrated; a not inconsiderable part could have been caused by the stress associated with mass vaccination. It is estimated that an undesirable side effect occurred in a maximum of one case per 30,000 vaccinations, which indicates that the vaccines used are very well tolerated.

Occurrence and Distribution

The disease was first described in South Africa in 1905 , and from there it was transported to other parts of Africa with merino sheep . It has also advanced from Africa across the Mediterranean to southern Europe. Bluetongue is also clinically present in the Middle East, on the Indian subcontinent, in China , the USA and Mexico , where mosquitos are active year-round as vectors. Virus strains without a typical clinical picture have been detected in Southeast Asia , northern South America , northern Australia and Papua New Guinea .

In August 2006, the disease first appeared in sheep in the Dutch province of Limburg , in the Belgian province of Liège, as well as in eight cattle herds and a flock of sheep in the Aachen region in North Rhine-Westphalia . Then in 2006 a total of 885 cases nationwide, in 2007 approx. 20,500 cases and in 2008 5,125 cases were officially detected, with North Rhine-Westphalia and, since 2008, Lower Saxony being most severely affected. The Federal Ministry of Food, Agriculture and Consumer Protection (BMELV) provides current figures on the occurrence of bluetongue in Germany .

Until the end of 2007, the European countries Belgium, Denmark, Germany, France, Luxembourg, the Netherlands, Switzerland, the Czech Republic and the United Kingdom were affected by the BTV-8 serotype. In 2008, BTV-8 was also detected for the first time in Italy and Spain - other serotypes were found there up until then. Cases have recently become known in the Balkan countries.

Infected mosquitoes can be moved up to 200 kilometers by winds and then spread the pathogen in the new location. Animal movements, semen and the trade of infected animals on the one hand, and the spreading of insects by airplanes and strong winds on the other hand can bring the pathogen to other free regions at any time. However, it is only able to survive there if suitable vectors and a susceptible host population are available.

The BTV-8 found in Central Europe is not the same one found in Southern Europe. Scientists therefore rule out climatic reasons as the reason for the spread to Northern Europe. Serotype 8 originally only occurred south of the Sahara and the Caribbean , possibly also in India or Pakistan . How the virus got to the Netherlands is still unclear.

In October 2008, virus type 6 (BTV 6), which was previously not widespread in Europe , was found in the eastern Netherlands on the border with North Rhine-Westphalia and Lower Saxony . Four farms were affected, around which a 20 km exclusion zone was established. No vaccine is yet available for the new type of virus, which is normally only found in Central America and Africa. The virus found is also used in a live vaccine from South Africa, so vaccination of the affected animals with a live vaccine that is not approved in the EU is obvious.

In November 2008, serotype 6 (BTV-6) was found in eight cattle farms in the immediate vicinity of the border in the Grafschaft Bentheim district .

With effect from February 15, 2012, the BMELV officially declared Germany free from bluetongue. However, it appeared again for the first time in mid-December 2018 in a cattle farm in Ottersweier in the Rastatt district (Baden-Württemberg). As a result, a restricted zone of 150 kilometers was established, which includes Baden-Württemberg and Saarland in full, as well as southern parts of Rhineland-Palatinate and Hesse. The Enzkreis announced that the measures there would last for two years. In general, reference was made to the reporting requirement for all farm animals.

After several cases with serotype 4 had been reported from Hungary since September 2015, three confirmed cases also occurred in Austria ( Burgenland and Styria ) in November 2015. This is the first evidence of the BTV in Austria since 2008.

literature

  • Franz J. Conraths et al .: Bluetongue Disease in Germany: Clinic, Diagnostics and Epidemiology. In: The practical veterinarian. 88 (Suppl. 2), 2007, ISSN  0032-681X , pp. 9-15.
  • Gerrit Dirksen: Bluetongue Disease . In: Gerrit Dirksen et al. (Ed.): Internal medicine and surgery of the cattle. 4th edition. Verlag Parey, Berlin 2002, ISBN 3-8263-3181-8 , pp. 366-368.
  • Dieter Ebner: Bluetongue disease. In: Heinrich Behrens u. a .: Textbook of Sheep Diseases. 4th edition. Verlag Parey, Berlin 2001, ISBN 3-8263-3186-9 , pp. 159-162.

Individual evidence

  1. ^ P. Roy: Molecular Dissection of Bluetongue Virus. In: TC Mettenleiter u. F. Sobrino (Ed.): Animal Viruses Molecular Biology. Caister Academic Press UK, Chapter 7
  2. ↑ http://www.promedmail.org/pls/otn/f?p=2400:1001:2945550523171103::NO::F2400_P1001_BACK_PAGE,F2400_P1001_PUB_MAIL_ID:1000,74505
  3. ↑ World Organization for Animal Health discovers carriers of bluetongue disease - CordisNachrichten of October 25, 2006, last checked on June 15, 2008
  4. ↑ Mellor, PS, 1990, The replication of bluetongue virus in Culicoides vectors, Current Topics in Microbiology and Immunology, 162
  5. ↑ Wittmann, EJ, Baylis, M., 2000, Climate Change: Effects on Culicoides-TransmittedViruses and Implications for the UK, The Veterinary Journal, 160 (2)
  6. ↑ International Society for Infectious Diseases Promed Mailing List: BLUETONGUE - EUROPE (26): BTV-8, FRANCE, NETHERLANDS, 23 August 2007
  7. ↑ FLI: Bluetongue Disease - Recommendations for the Protection of Ruminants from Infestation with Midges. Sept. 2007 ( pdf )
  8. ↑ Press release of the state government of Hesse dated March 31, 2008: The Hessian state government's tendering process for ordering the vaccine doses against bluetongue has been completed
  9. ↑ Press release: "Commission approves additional funds to combat bluetongue and scrum disease" of July 22, 2009 [1]
  10. ↑ Andreas Hoffmann: Vaccination campaign to combat bluetongue. In: Dt. TAB. 57 (2009), pp. 166-186.
  11. ↑ BMELV press release No. 076 of April 30, 2009 ( Memento of November 10, 2014 in the Internet Archive )
  12. ↑ ProMED-mail: Bluetongue - Europe (61): BTV-8, Czech Republic, OIE . ProMED-mail 2007; Nov 29: 20071129.3856, [2] .
  13. ↑ ProMED-mail: Bluetongue - Europe (03): BTV-8, Spain, OIE . ProMED-mail 2008; 19 Jan: 20080119.0233, [3]
  14. ↑ Disease timelines of the OIE
  15. ↑ www.umweltruf.de: New bluetongue virus type appeared published on October 27, 2008
  16. ↑ http://www.animal-health-online.de/gross/2008/10/28/niederlandisches-agrarministerium-bestatigt-blauzungen-typ-6-impfvirus/10398/#more-10398
  17. ↑ Communication from the BMELV to the OIE of November 28, 2008
  18. ↑ Declaration by the BMELV ( memo of November 2, 2012 in the Internet Archive ) published on February 22, 2012, last checked on February 27, 2012
  19. ↑ Bluetongue outbreak in Germany. December 18, 2018, accessed December 28, 2018 .
  20. ↑ Large exclusion zone around Rastatt after the outbreak of bluetongue. In: the new wave. December 13, 2018, accessed December 28, 2018 (German).
  21. ↑ Bluetongue: Enzkreis remains restricted area for two years - news from the Enzkreis and the district of Calw | PZ-news.de - Pforzheimer Zeitung. Retrieved December 28, 2018 .
  22. ↑ BMG press release of November 17, 2015

Web links

 Wikinews: Bluetongue  - In The News

Regulations

Additional information