Abstract
BackgroundThe genus pestivirus within the family Flaviviridae includes bovine viral diarrhoea virus (BVDV) types 1 and 2, border disease virus (BDV) and classical swine fever virus. The two recognised genotypes of BVDV are divided into subtypes based on phylogenetic analysis, namely a-p for BVDV-1 and a-c for BVDV-2.MethodsThree studies were conducted to investigate the phylogenetic diversity of pestiviruses present in Northern Ireland. Firstly, pestiviruses in 152 serum samples that had previously tested positive for BVDV between 1999 and 2008 were genotyped with a RT-PCR assay. Secondly, the genetic heterogeneity of pestiviruses from 91 serum samples collected between 2008 and 2011 was investigated by phylogenetic analysis of a 288 base pair portion of the 5’ untranslated region (UTR). Finally, blood samples from 839 bovine and 4,437 ovine animals imported in 2010 and 2011 were tested for pestiviral RNA. Analysis of animal movement data alongside the phylogenetic analysis of the strains was carried out to identify any links between isolates and animal movement.ResultsNo BVDV-2 strains were detected. All of the 152 samples in the first study were genotyped as BVDV-1. Phylogenetic analysis indicated that the predominant subtype circulating was BVDV-1a (86 samples out of 91). The remaining five samples clustered close to reference strains in subtype BVDV-1b. Out of the imported animals, 18 bovine samples tested positive and 8 inconclusive (Ct ≥36), while all ovine samples were negative. Eight sequences were obtained and were defined as BVDV-1b. Analysis of movement data between herds failed to find links between herds where BVDV-1b was detected.ConclusionGiven that only BVDV-1a was detected in samples collected between 1968 and 1999, this study suggests that at least one new subtype has been introduced to Northern Ireland between 1999 and 2011 and highlights the potential for importation of cattle to introduce new strains.
Highlights
The genus pestivirus within the family Flaviviridae includes bovine viral diarrhoea virus (BVDV) types 1 and 2, border disease virus (BDV) and classical swine fever virus
A new species of atypical bovine pestivirus, Hobi virus, (BVDV-3) consisting of viral strains first detected in foetal calf serum (FCS) has been proposed [10]
Panel I One hundred fifty two serum samples submitted from 152 different herds to the Veterinary Sciences Division of the Agri-Food and Biosciences Institute (AFBI-VSD) between 1999 and December 2008 were selected from an archive for determination of viral species by real time RT-PCR
Summary
The genus pestivirus within the family Flaviviridae includes bovine viral diarrhoea virus (BVDV) types 1 and 2, border disease virus (BDV) and classical swine fever virus. Two genotypes of bovine viral diarrhoea virus (BVDV) referred to as BVDV types 1 and 2 (BVDV-1, BVDV-2), are currently recognised. A new species of atypical bovine pestivirus, Hobi virus, (BVDV-3) consisting of viral strains first detected in foetal calf serum (FCS) has been proposed [10]. The batch of FCS from which Hobi virus was identified was produced in South America and commercialised in European countries [11] and the same viral strain was subsequently detected in a buffalo from Brazil [12], in a calf in Thailand [13], in calves in Italy [14] and in dairy cattle in India [15]
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