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Published Date: 2012-05-22 09:39:42
Subject: PRO/AH/EDR> Schmallenberg virus - Europe (42): genetic reassortment
Archive Number: 20120522.1140819

SCHMALLENBERG VIRUS - EUROPE (42): GENETIC REASSORTMENT
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Date: Tue 22 May 2012
Source: Archives of Virology 2012, DOI: 10.1007/s00705-012-1341-8O, Rapid Communication [summarised, edited]
http://www.springerlink.com/content/87q6wk20x3kx5241/ (subscription)

[Received: 16 Feb 2012; Accepted: 9 Apr 2012; Available on-line: 16 May 2012]

Genetic reassortment between Sathuperi and Shamonda viruses of the genus _Orthobunyavirus_ in nature: implications for their genetic relationship to Schmallenberg virus
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Abstract:

The recent outbreak of malformations in ruminants in Northern Europe caused by Schmallenberg virus [SBV] induced us to analyze the genetic properties of the related orthobunyaviruses and clarify their relationship.

The sequencing of 3 genomic RNA segments of Sathuperi, Shamonda and Douglas viruses (SATV, SHAV and DOUV) revealed that the M RNA segment of SATV and DOUV had a high degree of sequence identity with that of SBV, but the S and L RNA segments closely matched those of SHAV. Phylogenetic analysis of the 3 genomic RNA segments indicated that SBV is a reassortant, with the M RNA segment from SATV and the S and L RNA segments from SHAV.

[Byline: Tohru Yanase, Tomoko Kato, Maki Aizawa, Yozo Shuto, Hiroaki Shirafuji, Makoto Yamakawa and Tomoyuki Tsuda]

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Communicated by:
Sabine Zentis
Gut Laach
52385 Nideggen, Germany
<CVLonghorns@aol.com>

[The following concluding passage from the full article includes useful background data (references omitted):

"SATV and SHAV have similar geographic distributions in Africa and Asia and use the same arthropod vectors (_Culicoides_ biting midges) and vertebrate hosts (ruminants), suggesting that the ancestor of SBV was generated by co-infection with both viruses in the past. The Japanese SATV strains are genetically stable but are slightly diverged from SBV in the M RNA segment, suggesting that their evolution had occurred independently in geographically separated regions. It is uncertain whether or not the high pathogenicity of SBV is the result of re-assortment. In the affected areas [Europe], an increase in the number of deformed calves and lambs due to infection with SBV was observed. DOUV is spread widely throughout northern and eastern Australia, but it has not yet been associated with any diseases. Three cases of malformation in calves that were seropositive for SHAV but negative for other teratogenic pathogens, such as Akabane virus (AKAV) and Aino virus (AINOV), were reported in Japan in 2003. Also, in 2008, 2 calves had deformities that were suspected to be caused by SATV infection (unpublished data). However, the number of reported cases of abortion and malformation in cattle did not clearly increase in the areas of virus isolation, unlike in the areas where outbreaks of AKAV and AINOV infections occurred. Sheep likely have higher susceptibility to SBV than do cattle in northern Europe. Therefore, the pathogenicity of SATV and SHAV in the ovine fetus should also be assessed.

The sequence data determined herein will contribute to the development of diagnostic tools for better understanding of the incidence and distribution of these viruses. Unfortunately, the Indian and African strains of SATV were not available in this study, but their analysis will be necessary to clarify the geographical source of SBV in detail. Further genetic characterization of orthobunyaviruses, including characterization of members of the same species with different geographical origins, will be essential for understanding their molecular epidemiology and evolution".

The incidence of clinical SBV cases (Arthrogryposis and/or hydranencephaly) has been decreasing in May [2012]. The last case in the UK was recorded on 14 May [2012] (as stated on 18 May [2012]). It was predicted that the appearance of cases will be discontinuing during June 2012 (7 months after the termination of the 2011 vector season).

So far, Sathuperi virus has been demonstrated in India and Japan and Shamonda virus in Nigeria and Japan. Unravelling the origin of SBV and its route(s) of introduction into northwestern Europe is needed for the prevention of future penetrations of arboviral diseases."

Decisions on measures to control or prevent further SBV-related losses in Europe deserve to be preceded by a serosurvey addressing the ruminant populations in the affected as well as the unaffected parts of Europe. - Mod.AS]

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