Re-emergence of a genetic outlier strain of equine arteritis virus: Impact on phylogeny

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Re-emergence of a “historical” EAV strain.

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An updated EAV phylogeny scheme.

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Measures to improve EAV phylogenetic analysis through harmonization.

Equine arteritis virus (EAV) is the causative agent of equine viral arteritis (EVA), a respiratory and reproductive disease of equids, which is notifiable in some countries including the Great Britain (GB) and to the OIE. Herein, we present the case of a persistently infected stallion and the phylogenetic tracing of the virus strain isolated. Discussing EAV occurrence and phylogenetic analysis we review features, which may aid to harmonise and enhance the classification of EAV.

Genome sequence analysis of 10 Dutch porcine circovirus type 2 (PCV-2) isolates from a PMWS case-control study

The factors responsible for the emergence of post-weaning multisystemic wasting syndrome (PMWS) as an epidemic disease with significant impact upon the pig industry are not all known. Porcine circovirus type 2 (PCV-2) has been shown to be necessary but not sufficient for the expression of PMWS. Retrospective serological and molecular surveys have shown that PCV-2 was widespread and was maintained with only occasional reports of sporadic PMWS in the 30 year period prior to the recent emergence of the epidemic form of the syndrome. However, the recent spread of the disease in Europe and elsewhere has pointed to the transmission of a novel pathogen. One explanation to reconcile this paradox is that PWMS is caused by a unique PCV-2 variant that is being spread through pig populations. To test this hypothesis, complete genomes (1767 bp) of 10 Dutch PCV-2 isolates from 4 PMWS affected premises and 6 farms without PMWS were sequenced. Phylogenetic analysis showed that these sequences were grouped together although they differed on 77 nucleotide positions relative to each other (95.6-100% identity between the 10 isolates). None of these nucleotide changes identified impacted upon transcriptional elements or other important recognised features of the genome of the PCV-2. Amino acid changes were recorded on 4 positions in ORF1 and on 16 positions in ORF2 but, importantly, no consistent pattern was evident between PCV-2 isolates from affected and control pigs. These data provide further evidence to suggest that factor(s) in addition to PCV-2 are necessary in the development of PMWS.

Detection and genetic typing of type 2 porcine circoviruses in archived pig tissues from the UK

Porcine circovirus 2 (PCV-2) is implicated as the causative agent of post-weaning multisystemic wasting syndrome (PMWS) and is also associated with porcine dermatitis and nephropathy syndrome (PDNS). The recent emergence of epidemic PMWS in the United Kingdom was predated by sporadic cases of PDNS dating back to the early 1980's. The aim of this study was to investigate whether PCV-2 DNA was present in archival tissues, and if so, to investigate the relatedness of these viruses with contemporary strains of PCV-2. DNA extracted from paraffin wax-embedded tissue blocks ( n = 68), was subjected to a TaqMan polymerase chain reaction (PCR) targeting a fragment of ORF1 of PCV-2. Positive results were obtained from 41% (9/22), 31% (4/13) and 32% (8/25) of submissions from the 1990's, 1980's and 1970's respectively. The presence of PCV-2 antigen in some of these tissues was confirmed by immunohistochemistry (IHC). A PCR targeting ORF2 was used to obtain sequence data for phylogenetic analysis. Sequences from 5 archival tissues were unique but showed high genetic identity to PCV-2 sequence obtained from a 2000 PDNS case. These data demonstrate that similar isolates of PCV-2 have been present in the UK pig population for more than 30 years.

Evidence for the presence of hepatitis E virus in pigs in the United Kingdom

Samples of serum, tissue and faeces from two pig herds in England were examined for hepatitis E virus by reverse-transcriptase PCR (RT-PCR), and a virus strain from each herd was partially sequenced. Eleven of 42 faecal samples and 16 of 21 tissue samples from two pigs were positive for the virus by RT-PCR. Analysis of two unique but closely related nucleotide sequences obtained from the two herds showed that the viruses clustered in genotype III (6) with a human strain of the virus from an autochthonously acquired case of acute hepatitis in the UK. An ELISA based on recombinant open reading frame 2 (ORF-2) was used to detect antibodies to hepatitis E virus in 256 pig sera from the UK; 85.5 per cent of the samples were positive, compared with 58 per cent of similar samples from Swedish pigs and 23.5 per cent of samples from Dutch pigs.