PriProET based melting point analyses on PRRSV positive field samples

Assessment of listing and categorisation of animal diseases within the framework of the Animal Health Law (Regulation (EU) No 2016/429): porcine reproductive and respiratory syndrome (PRRS)

Porcine reproductive and respiratory syndrome (PRRS) has been assessed according to the criteria of the Animal Health Law (AHL), in particular criteria of Article 7 on disease profile and impacts, Article 5 on the eligibility of PRRS to be listed, Article 9 for the categorisation of PRRS according to disease prevention and control rules as in Annex IV and Article 8 on the list of animal species related to PRRS. The assessment has been performed following a methodology composed of information collection and compilation, expert judgement on each criterion at individual and, if no consensus was reached before, also at collective level. The output is composed of the categorical answer, and for the questions where no consensus was reached, the different supporting views are reported. Details on the methodology used for this assessment are explained in a separate opinion. According to the assessment performed, PRRS can be considered eligible to be listed for Union intervention as laid down in Article 5(3) of the AHL. The disease would comply with the criteria as in Sections 4 and 5 of Annex IV of the AHL, for the application of the disease prevention and control rules referred to in points (d) and (e) of Article 9(1). The animal species to be listed for PRRS according to Article 8(3) criteria are domestic pigs and wild boar.

Emergence of a virulent porcine reproductive and respiratory syndrome virus (PRRSV) 1 strain in Lower Austria

BACKGROUND

In spring 2015, an outbreak of porcine reproductive and respiratory syndrome (PRRS) struck Lower Austria caused by a PRRS virus (PRRSV) strain spreading rapidly among both previously PRRSV negative and vaccinated pig herds. This case report describes the first well-documented emergence of the PRRSV strain responsible for this outbreak.

CASE PRESENTATION

A PRRSV seronegative piglet-producing farm in Lower Austria encountered losses in foetuses and suckling piglets of up to 90 %; clinical signs in sows and nursery piglets included fever and reduced feed intake. Additionally, high percentages of repeat breeders and losses of up to 40 % in nursery piglets occurred. An infection with PRRSV was suggested by the detection of antibodies by enzyme linked immunosorbent assay and confirmed by quantitative real time PCR. The underlying PRRSV strain, termed AUT15-33, was isolated by passage on porcine alveolar macrophages, partially sequenced (ORF2-7) and grouped as PRRSV-1, subtype 1. In phylogenetic analysis of the genome region coding for the structural proteins, ORF2-7, AUT15-33 clustered with Belgian strains but identities were as low as 88 %. In contrast, analysis of ORF7 sequences revealed a close relationship to Croatian strains from 2012 with an identity of 94 - 95 %.

CONCLUSIONS

In the year following the outbreak, the same PRRSV strain was identified repeatedly in different regions of Austria. It can be speculated that the new strain has novel advantageous properties.

Characterization of two Austrian porcine reproductive and respiratory syndrome virus (PRRSV) field isolates reveals relationship to East Asian strains

Porcine reproductive and respiratory syndrome virus (PRRSV) causes major problems for the swine industry worldwide. Due to Austria's central location in Europe, a large number of animals are transported through the country. However, little is known about current PRRSV strains and epidemiology. We determined full-length genome sequences of two Austrian field isolates (AUT13-883 and AUT14-440) from recent PRRSV outbreaks and of a related German isolate (GER09-613). Phylogenetic analysis revealed that the strains belong to European genotype 1 subtype 1 and form a cluster together with a South Korean strain. Remarkably, AUT14-440 infected the simian cell line MARC-145 without prior adaptation. In addition, this isolate showed exceptional deletions in nonstructural protein 2, in the overlapping region of glycoprotein 3 and 4 and in the 3' untranslated region. Both Austrian isolates caused similar lung lesions but only pigs infected with AUT14-440 developed clear clinical signs of infection. Taken together, the genetic and biological characterization of two novel Austrian PRRSV field isolates revealed similarities to East Asian strains. This stresses the necessity for a more detailed analysis of current PRRSV strains in Europe beyond the determination of short ORF5 and ORF7 sequences.

Development of a primer-probe energy transfer based real-time PCR for the detection of Swine influenza virus

Swine influenza virus (SIV) causes a contagious and requiring official notification disease of pigs and humans. In this study, a real-time reverse transcription-polymerase chain reaction (RT-PCR) assay based on primer-probe energy transfer (PriProET) for the detection of SIV RNA was developed. The assay uses matrix gene-specific primers and an Oregon Green-labeled fluorescent probe and was employed for the detection of SIV in clinical samples to identify outbreaks and to monitor the prevalence of disease. The PriProET technology was used to obtain a probe melting profile for confirmation of the specific product amplification. The assay is specific for influenza virus with a sensitivity of detection limit of approximately 10 copies of RNA by PCR. Based on serial dilutions of SIV, the detection limit of the assay was approximately 0.003 TCID(50)/ml for H1N1 A/Swine/Poland/KPR9/2004 virus. The PriProET RT-PCR was suitable for the detection of SIV RNA isolated directly from clinical samples. The assay detected SIV RNA in pre-clinical swab samples as early as 2 days post-infection (dpi). The PriProET RT-PCR assay is an alternative to the existing diagnostic assays and could have enhanced applicability for clinical diagnosis.

Identification of a genetically diverse sequence of porcine reproductive and respiratory syndrome virus in Slovenia and the impact on the sensitivity of four molecular tests

A total 91 serum samples and 51 pig tissue samples were collected between October 2009 and June 2010 from 30 herds, where a clinical picture of infection or/and porcine reproductive and respiratory syndrome (PRRS) antibody-positive pigs were detected. Of the 142 samples tested, 65 (45.8%) were identified as porcine reproductive and respiratory syndrome virus (PRRSV) positive by a one-step reverse transcription and polymerase chain reaction (RT-PCR). The sequencing results of 258 nucleotides in ORF7 from 30 herds with PRRSV-positive samples revealed the circulation of six genetically different strains of PRRSV, all belonging to the Subtype 1 (Type I). Twenty-three (76.6%) of the thirty positive herds were infected with a genetically identical cluster, with 98.9-100% nucleotide identity between the herds, representing the detection of a new strain of PRRSV in Europe, not published previously. From these 23 herds, positive PRRSV samples were detected with gel-based RT-PCR, but all gave false-negative results with two commercial real-time kits. When using a third commercial real-time kit, 28 (93.3%) of 30 positive samples in gel-based RT-PCR were detected as the Type I, confirming that the sensitivity of this real-time kit is much greater than the sensitivity of the previous two. The influence of new genetic variants of PRRSV circulating in Slovenia on molecular diagnosis and the control of the infection is discussed.