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Bluetongue, BTV-8 Trans-Placental Transmission

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  • Bluetongue, BTV-8 Trans-Placental Transmission

    [Note for the thread Editor(s): if you want, this post could be moved into another sub-forum after some hours. IOH]

    D1 - Animal Health and Standing Commitees -

    Short Report
    Working Group on bluetongue transmission and surveillance - Brussels 30April 2008
    Participants: P. Heinen (BE), J. Hooyberghs (BE), P.Mortier (BE), K. De Clercq (BE) S. Ralchev (BG), J. Lacina (CZ), S. Mellegard (DK), H. Weinandy (DE), N. Rehm (DE),C. Staubach (DE), A. Raie (EE), S. Gaynor (IE), O. Mangana (EL), V. Almansa (ES), L. Romero (ES), A. Pacquet (FR), M. Drouet (FR), N. Ferrarini (IT), D. Daukste (LV), R. Serbavicius (LT), C. Dahm (LU), V. Palfi (HU), ), W. Pelgrim (NL), C. Posthumus Meyjes (NL), P. Van Rijn (NL), G. Seiwald (AT), Zmudzinski (PL), R. Amador (PT), A. Ionescu (RO), A. Hari (SI), M. Mojzis, (SK), K. Levonene ( FI), K. Mieziewska (SE), S. Sternberg Lewerin (SE), S. Hall (UK), A. Calyton (UK), P. Have (EFSA), P Calistri (BT-Net), C. Oura (CRL), P. Mellor (CRL), K. Darpel (CRL), F. Reviriego Gordejo (SANCO-D1).

    Outcome of the meeting

    1. Trans-placental route of transmission:
    ? CRL presented the preliminary results of BBSRC to investigate trans-placental and persistent infection with BTV.
    Apart from the incident in Northern Ireland data on 54 calves in 20 farms show that 1/3 of the calves were trans-placentally infected.
    The preliminary conclusions indicate that trans-placental transmission ob BTV-8 occurs and it does so frequently but it has to be confirmed if this is the major means of over-wintering in Northern Europe.

    ? The conclusions of the report presented by Belgium indicate that trans-placental transmission in cattle is proven for BTV-8 but so far no proof yet of trans-placental transmission in sheep. Immune-competent and immune-tolerant calves are born from infected dams.

    ? Data from the Netherlands confirm that BTV-8 in found in newborn calves indicating trans-placental transmission.

    ? The preliminary results of the Spanish investigations under the trans-placental transmission protocol prepared by the CRL data from 17 farms and 88 dams and 93 calves in the seasonally free period of a highly BTV-1 infected zone did not identify any case of trans-placental transmission.

    ? Slovakia reported on one case of trans-placental transmission of BTV-8 in a heifer imported into SK from NL.

    ? Similar events indicating trans-placental transmission in cattle have been found in 4 MSs for BTV-8 but not for BTV-1

    2. Surveillance
    ? The current surveillance activities based on the minimum requirements for monitoring and surveillance programmes laid down in Annex I to Regulation (EC) No 1266/2007 were discussed.

    ? Major drawbacks identified were:
    i. Difficulties to find adequate sentinel animals
    ii. Mass vaccination policy being implemented without a DIVA test available
    iii. Divergent views on the relative usefulness of the passive clinical surveillance and sentinels.

    ? Further reflection is needed on the objectives to be achieved by monitoring and surveillance and consequently a rationalization of the measures in place could be necessary

    3. Conlusions:
    ? Trans-placental transmission of BTV occurs at least for BTV-8. The protective measures recently in force (Regulation (EC) No 384/2008) appear to be necessary and proportionate. An amendment simplifying the provisions as regards the safety of vaccinated animals independently of the type of vaccine used (MLV or inactivated) could be needed.

    ? An amendment of Annex I to Regulation (EC) No 1266/2007 could be needed once the objectives of the surveillance/monitoring, the surveillance tools (passive, active, sentinels, serological/virological/entomological) and the intensity of surveillance is further developed.
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