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Published Date: 2012-12-20 02:21:34
Subject: PRO/AH> Schmallenberg virus - Europe (76): virus RNA in bovine semen
Archive Number: 20121220.1460864

SCHMALLENBERG VIRUS - EUROPE (76): VIRUS RNA IN BOVINE SEMEN
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Date: Wed 19 Dec 2012
From: Martin Beer <Martin.Beer@fli.bund.de> [edited]

Detection of Schmallenberg virus RNA in semen samples
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In the framework of a study co-financed by the European Union, the Friedrich-Loeffler-Institut (FLI) analyzed the semen of bulls with a known SBV-antibody status for the presence of Schmallenberg virus (SBV) genome. All samples were investigated with an optimized RNA extraction method and a real-time RT-PCR (RT-qPCR) system developed and established at the FLI.

At present, 740 semen batches from 94 SBV-infected and seroconverting/seroconverted bulls have been analyzed. 26 semen batches from 11 bulls reacted positive in the RT-qPCR analyses with Cq-values from 26 to 37. In 3 of the 11 bulls with SBV-genome positive semen samples, also 1st SBV-antibodies could be detected. In 2 bulls SBV-genome could be detected for more than 40 days in 6 or 8 consecutive semen batches, respectively. Furthermore, in one bull a pattern of PCR-positive and PCR-negative consecutive semen batches was observed within 43 days (5 batches positive / 2 batches negative / 2 batches positive / 2 batches negative / 1 batch positive). This points to intermitting virus excretion in semen. However, it is currently unclear and topic of further studies, how long after seroconversion this situation may persist.

In addition, in vitro and in vivo studies about the infectivity of the SBV-positive semen samples are ongoing.

[Dr Martin Beer and Dr Bernd Hoffmann (Institute of Diagnostic Virology, Friedrich-Loeffler-Institut Insel Riems, Greifswald-Insel Riems, Germany)
Prof Dr Dr Thomas Mettenleiter (President Friedrich-Loeffler-Institut Insel Riems, Greifswald-Insel Riems, Germany)]

--
Dr Martin Beer
Head Institute of Diagnostic Virology
Friedrich-Loeffler-Institut
Am Suedufer 10
17493 Greifswald-Insel Riems
Germany
<Martin.Beer@fli.bund.de>

[The firsthand authoritative information above from the FLI, the German institute which first detected the emerging SBV in November 2011 and later developed a detection method (real-time RT-PCR) that has been made available to institutions elsewhere (see http://tinyurl.com/c66dsz2), is gratefully acknowledged.

The findings indicate that SBV behaves differently from Akabane virus, another teratogenic Simbu-group virus, in relation to semen contamination. According to Australian investigators (reference below), Akabane virus was not detected in the semen of artificially infected bulls even during their viraemic period. For the virus detection, inoculation of tissue cultures as well as subcutaneous injection of susceptible cattle were applied; the semen was found of a standard acceptable for artificial breeding. The authors concluded that Akabane virus infection of the bull would not affect reproduction.

The current findings, concerning SBV and bull semen, are obviously different. The risk posed by semen and embryos may not be regarded as "negligible" until further studies are accomplished. Results of the ongoing in vitro and in vivo studies, undertaken by the FLI investigators about the infectivity of the SBV-positive semen samples, are anticipated with interest.

As a precautionary measure, several countries, including Australia, Canada, and the USA have already applied restrictions on imports of bovine semen and embryos collected after 1 Jun 2011 from all EU countries. For their list and additional information, see ProMED-mail posting 20121218.1456595.

Reference
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Parsonson IM, Della-Porta AJ, Snowdon WA, and O'Halloran ML: Experimental infection of bulls with Akabane virus. Res Vet Sci. 1981 Sep; 31(2): 157-60 (abstract available at http://www.ncbi.nlm.nih.gov/pubmed/6798655). - Mod.AS]

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