Schmallenberg virus

Schmallenberg virus
Virus classification
Group: Group V ((−)ssRNA)
Order: Unassigned
Family: Bunyaviridae
Genus: Orthobunyavirus
Species: Schmallenberg virus
Distribution of Schmallenberg virus by country in Europe
Schmallenberg virus

Schmallenberg virus is the informal name given to a recently isolated orthobunyavirus, which has not been given a formal name as of January 2013, initially reported in October 2011[1] to cause congenital malformations and stillbirths in cattle, sheep, goats, and possibly alpaca.[2][3] It appears to be transmitted by midges (Culicoides spp.) which are likely to have been most active in causing the infection in the northern hemisphere summer and autumn of 2011, with animals subsequently giving birth from late 2011.[2] Schmallenberg virus falls in the Simbu serogroup of Orthobunyaviruses; as of January 2013, it is considered to be most closely related to the Sathuperi and Douglas viruses.[4]

The virus is named after Schmallenberg, in North Rhine-Westphalia, Germany, from where the first definitive sample was derived.[2] After Germany, it has also been detected in the Netherlands, Belgium, France, Luxembourg, Italy, Spain, the United Kingdom,[5] Switzerland,[6] Ireland,[7] Finland,[8] Denmark,[9] Sweden,[10] Austria,[11] Norway,[11] Poland[11] and Estonia.[11]

The virus has been recognised by the European Commission's Standing Committee on the Food Chain and Animal Health[2] and the Friedrich-Loeffler-Institut (German Research Institute for Animal Health).[11] A risk assessment in December 2011 did not consider it likely to be a threat to human health,[12] as other comparable viruses are not zoonotic.[11]

Immunity can possibly be acquired naturally against SBV. It is possible that the seasonality of the infection cycle would not entail a second epidemic circulation next year, due to the shortness of the viraemic period (about 4 to 6 days post exposure, longer in affected foetuses). Vaccination is a possible option for controlling the disease as a vaccine exists for the similar Akabane virus.[13] In March 2012, scientists of the Friedrich-Loeffler-Institut first succeeded in producing an electron microscope image of the Schmallenberg virus.[14]

Molecular biology

(A) Phylogenetic relationship between Schmallenberg virus and orthobunyaviruses of the Simbu, Bunyamwera, and California serogroups. (B) Detection of Schmallenberg virus genome in the blood of experimentally infected calves.

The genetic structure of Schmallenberg virus is typical for Bunyaviridae viruses, which are a family of enveloped negative-sense single stranded RNA viruses with a genome split into three parts - Small (S), Medium (M) and Large (L). The L RNA segment encodes an RNA-dependent RNA polymerase (L protein), the M RNA segment encodes two surface glycoproteins (Gc and Gn) and a nonstructural protein (NSm), while the S RNA segment encodes a nucleocapsid protein (N) and, in an alternative overlapping reading frame, a second nonstructural protein (NSs).[15] The genomic RNA segments are encapsidated by copies of the N protein in the form of ribonucleoprotein (RNP) complexes.[16] The N protein is the most abundant protein in virus particles and infected cells and, therefore, the main target in many serological and molecular diagnostics.[17][18]

Signs of disease

(A) Phylogenetic relationship between Schmallenberg virus and orthobunyaviruses of the Simbu, Bunyamwera, and California serogroups. (B) Detection of Schmallenberg virus genome in the blood of experimentally infected calves.

The virus causes two different profiles of Schmallenberg:

These disease signs have occurred during the period when the disease vectors (mosquitos, sandflies, midges) are active, during the summer and autumn of 2011, mainly affecting cattle.

Congenital malformations in newborn sheep, goats and calves are the most obvious symptoms. In many cases, the dam apparently has not presented signs of illness. These cases have occurred from December 2011, especially in sheep. The major malformations observed were: scoliosis, hydrocephalus, arthrogryposis, hypoplasia of the cerebellum and an enlarged thymus.[19]

Diagnosis

Blood samples from live animals with suspicious symptoms are taken for analysis. Dead or aborted fetuses suspected of having the virus are sampled by taking a piece of the brain or spleen for analysis. The samples are tested with the RT-PCR for Schmallenberg virus that has been developed by the Friedrich-Loeffler Institute in Germany.[19] A commercial kit is now available from AdiaVet[20] which targets the L region of the tripartite ssRNA genome of the virus.[21]

Cases in the United Kingdom

The disease was confirmed as present in the UK on 22 January 2012, on being formally identified in four sheep farms in Norfolk, Suffolk and East Sussex.[5] By 27 February 2012, the disease was reported in other counties in the south of England including the Isle of Wight, Wiltshire, West Berkshire, Gloucestershire, Hampshire and Cornwall.[22] It is likely that it was carried to Eastern England by midges from mainland Europe,[5] a possibility previously identified as a risk by Defra.[5]

Import bans

Russia, Ukraine, Kazakhstan, Egypt and Mexico have all suspended imports of live cattle and sheep, along with embryos and semen from affected countries.[23]

United States ban import of bovine germplasm collected in EU countries after June 1, 2011.[24]

References

  1. ↑ Dongyou Liu: Molecular Detection of Animal Viral Pathogens, Schmallenberg virus, S. 563, CRC Press, 2016, ISBN 9781498700368
  2. 1 2 3 4 Kai Kupferschmidt (13 January 2012). "New animal virus takes northern Europe by surprise". Science. Retrieved 16 January 2012.
  3. ↑ Richard Black (7 August 2012). "Schmallenberg virus 'may spread across UK'". BBC News. Retrieved 7 August 2012.
  4. ↑ "Schmallenberg virus (SBV)" (PDF). Friedrich-Loeffler-Institut. 31 January 2013. Retrieved 5 February 2013.
  5. 1 2 3 4 Damian Carrington (23 January 2012). "Schmallenberg virus confirmed on farms in the UK". The Guardian. Retrieved 23 January 2012.
  6. ↑ Regula Kennel (20 July 2012). "Schmallenbergvirus auch in der Schweiz" [Schmallenberg virus also in Switzerland] (in German). Schweizerische Eidgenossenschaft. Retrieved 5 December 2013.
  7. ↑ "Schmallenberg virus confirmed in a bovine foetus in County Cork". Department of Agriculture, Food & the Marine. 30 October 2012. Retrieved 5 December 2013.
  8. ↑ Ulla Rikula (15 January 2013). "Schmallenberg virus found in deformed lambs". Finnish Food Safety Authority Evira. Retrieved 5 December 2013.
  9. ↑ Mette Buck Jensen (7 June 2012). "Schmallenberg virus påvist i danske husdyr for første gang". Danmarks Tekniske Universitet. Retrieved 5 December 2013.
  10. ↑ Erika Chenais (27 November 2012). "Nytt virus hos får och nötkreatur i Sverige". Statens veterinärmedicinska anstalt. Retrieved 5 December 2013.
  11. 1 2 3 4 5 6 Schmallenberg virus: new Orthobunyavirus in cattle, updated 10 January 2012, accessed 16 January 2012
  12. ↑ Risk assessment: New Orthobunyavirus isolated from infected cattle and small livestock ─ potential implications for human health, European Centre for Disease Prevention and Control, 22 December 2011, accessed 17 January 2012
  13. ↑ SMC(UK) Fact Sheet on Schmallenberg virus
  14. ↑ FLI: First visualization of Schmallenberg virus
  15. ↑ Alexander., Plyusnin,; M., Elliott, Richard (2011-01-01). Bunyaviridae : molecular and cellular biology. Caister Academic Press. ISBN 9781904455905. OCLC 711044654.
  16. ↑ Ariza, A.; Tanner, S. J.; Walter, C. T.; Dent, K. C.; Shepherd, D. A.; Wu, W.; Matthews, S. V.; Hiscox, J. A.; Green, T. J. (2013-06-01). "Nucleocapsid protein structures from orthobunyaviruses reveal insight into ribonucleoprotein architecture and RNA polymerization". Nucleic Acids Research. 41 (11): 5912–5926. ISSN 0305-1048. PMC 3675483 Freely accessible. PMID 23595147. doi:10.1093/nar/gkt268.
  17. ↑ Bilk, S.; Schulze, C.; Fischer, M.; Beer, M.; Hlinak, A.; Hoffmann, B. (2012-09-14). "Organ distribution of Schmallenberg virus RNA in malformed newborns". Veterinary Microbiology. 159 (1–2): 236–238. doi:10.1016/j.vetmic.2012.03.035.
  18. ↑ Bréard, Emmanuel; Lara, Estelle; Comtet, Loïc; Viarouge, Cyril; Doceul, Virginie; Desprat, Alexandra; Vitour, Damien; Pozzi, Nathalie; Cay, Ann Brigitte (2013-01-15). "Validation of a Commercially Available Indirect Elisa Using a Nucleocapside Recombinant Protein for Detection of Schmallenberg Virus Antibodies". PLOS ONE. 8 (1): e53446. ISSN 1932-6203. PMC 3546048 Freely accessible. PMID 23335964. doi:10.1371/journal.pone.0053446.
  19. 1 2 "Programa nacional de vigilancia epidemiológica frente al virus de Schmallenberg" (PDF). Ministerio de Agricultura Alimentación y Medio Ambiente. 2 February 2012. Retrieved 8 February 2012.
  20. ↑ SBV - Schmallenberg Virus PCR Detectction Kit
  21. ↑ Genbank: Schmallenberg virus RdRp gene for RNA-dependent RNA polymerase, segment L, genomic RNA, isolate BH80/11-4
  22. ↑ "Schmallenberg livestock virus hits 74 farms in England". BBC News. 27 February 2012. Retrieved 5 December 2013.
  23. ↑ "Turkish cattle demand key amid Schmallenberg bans". Agra Informa. 9 March 2012. Retrieved 5 December 2013.
  24. ↑ "Schmallenberg Virus Restrictions for Imported Bovine Germplasm from the European Union (EU), or Countries Following EU Legislation". Animal and Plant Health Inspection Service. 12 September 2013. Retrieved 5 December 2013.
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