The diversity of Porcine Reproductive and Respiratory Syndrome Virus Type 1 and 2 in Denmark

Lise Kirstine Kvisgaard, Charlotte Kristiane Hjulsager, Charlotte Sonne Kristensen, Manreetpal Singh Brar, Frederick Chi-Ching Leung, Lars Erik Larsen

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    Abstract

    Both Type 1 and Type 2 PRRS viruses are circulating among Danish pigs. The first appearance of Type 1 PRRSV in Denmark was in 1992 whereas the Type 2 PRRSV was introduced in 1996 after the use of a live attenuated vaccine that reverted to virulence. Since then, vaccination to control the disease for both PRRSV genotypes has been widely used in Denmark and it is therefore highly relevant to monitor the diversity of currently circulating PRRSV strains. Only subtype 1 of the Type 1 PRRSV strains and vaccine-like Type 2 PRRSV strains were previously detected in Denmark, however, only few Danish PRRSV strains were sequenced. Denmark exports more than 50.000 living pigs each month. A portion of these pigs inevitably harbor PRRSV. Thus, the diversity of PRRSV in Denmark is of interest to other countries besides Denmark. The main objective of the present study was to close the gap in knowledge on the genetic diversity of currently circulating PRRSV stains in Danish pigs by sequencing ORF5 and ORF7 of approximately 41 Type 1 and 50 Type 2 strains isolated between 2003 and 2013. Furthermore, full genome analysis was performed on nine Type 1 and nine Type 2 selected strains. The preliminary assessment of the results showed that the Type 1 strains all belonged to subtype 1. Based on the ORF5 sequences, the Danish Type 1 viruses clustered into two groups. These two groups shared 84 % to 92 % and 94 % to 99% nucleotide identity to the Lelystad virus, respectively. The sequenced Type 2 viruses showed a significant higher level of identity in that the ORF5 sequences were 94 - >99 % identical at the nucleotide level. Most of the Type 2 viruses, shared high level of identity to the VR2332 vaccine strain (Ingelvac MLV), but a few more diverse isolates were also identified, including strains with interesting deletions in NSP2 and other genes. The full genome sequences of Danish strains showed an overall nucleotide identity of 88-98% (Type 1) and 94 % to >99 % (Type 2). The impact of these results will be discussed.
    Original languageEnglish
    Publication date2013
    Number of pages1
    Publication statusPublished - 2013
    EventInternational Porcine Reproductive and Respiratory Syndrome Symposium (PRRS 2013) - Beijing, China
    Duration: 20 May 201322 May 2013
    http://www.prrssymposium.org/

    Conference

    ConferenceInternational Porcine Reproductive and Respiratory Syndrome Symposium (PRRS 2013)
    CountryChina
    CityBeijing
    Period20/05/201322/05/2013
    Internet address

    Bibliographical note

    Poster presentation.

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