ABSTRACT
The objective of this study was to identify and partially characterize 3 equid herpesviruses that were isolated postmortem from zebras in Ontario, Canada in 1989, 2002, and 2007. These 3 virus isolates were characterized by plaque morphology, restriction fragment length polymorphism (RFLP) of their genomic deoxyribonucleic acid (DNA), real-time polymerase chain reaction (PCR) assay, and sequence analyses of the full length of the glycoprotein G (gG) gene (ORF70) and a portion of the DNA polymerase gene (ORF30). The isolates were also compared to 3 reference strains of equid herpesvirus 1 (EHV-1). Using rabbit kidney cells, the plaques for the isolates from the zebras were found to be much larger in size than the EHV-1 reference strains. The RFLP patterns of the zebra viruses differed among each other and from those of the EHV-1 reference strains. Real-time PCR and sequence analysis of a portion of the DNA polymerase gene determined that the herpesvirus isolates from the zebras contained a G at nucleotide 2254 and a corresponding N at amino acid position 752, which suggested that they could be neuropathogenic EHV-1 strains. However, subsequent phylogenetic analysis of the gG gene suggested that they were EHV-9 and not EHV-1.
L'objectif de la présente étude était d'identifier et de caractériser partiellement trois herpesvirus équins isolés de zèbres décédés en Ontario, Canada en 1989, 2002, et 2007. Ces trois isolats viraux furent caractérisés par morphologie des plages de lyse, par polymorphisme de taille des fragments de restriction (RFLP) de leur ADN génomique, par épreuve de réaction d'amplification en chaîne par la polymérase (PCR) en temps réel, et analyse de la séquence de la toute la longueur du gène de la glycoprotéine G (gG) (ORF70) et une portion du gène de la polymérase de l'ADN (ORF30). Les isolats furent également comparés à trois souches de référence d'herpesvirus équin de type 1 (EHV-1). L'examen de la culture des virus sur des cellules rénales de lapin a permis de constater que les plages de lyse causées par les isolats provenant des zèbres étaient beaucoup plus grandes que celles causées par les souches de référence d'EHV-1. Les patrons de RFLP des virus de zèbres différaient entre eux ainsi que des souches de référence d'EHV-1. Les analyses par PCR en temps réel et l'analyse de séquence d'une portion du gène de la polymérase de l'ADN ont permis de déterminer que les isolats d'herpesvirus provenant de zèbres avaient un G comme nucléotide à la position 2254 et un acide aminé N correspondant à la position 752, ce qui suggère qu'il pourrait s'agir de souches neuropathogènes d'EHV-1. Toutefois, des analyses phylogénétiques subséquentes du gène gG suggèrent qu'il s'agirait plutôt d'EHV-9 et non d'EHV-1.(Traduit par Docteur Serge Messier).
Subject(s)
Equidae , Herpesviridae Infections/veterinary , Herpesviridae/classification , Herpesviridae/isolation & purification , Animals , Animals, Zoo , Female , Herpesviridae/genetics , Herpesviridae Infections/epidemiology , Herpesviridae Infections/virology , Male , Ontario/epidemiology , PhylogenyABSTRACT
Five cases of infectious laryngotracheitis (ILT) occurred in the fall of 2004 in the Niagara Peninsula, in Southern Ontario. At about the same time two more cases occurred in Eastern Ontario and one case in South-Western Ontario. We examined, at a molecular level, 10 Ontario ILT virus field isolates from 2004 and early 2005 as well as four ILT vaccine viruses by polymerase chain reaction-restriction fragment length polymorphism analyses of ICP4 and glycoprotein E genes, and partial sequencing of UL47 and glycoprotein G genes. We determined that the five Niagara Peninsula ILT viruses were identical among themselves. They represented an independent cluster of ILT cases and were not related to other cases that occurred during 2004 and early 2005. Viruses isolated during the outbreaks in Eastern and South-Western Ontario could not be differentiated from chicken embryo origin ILT vaccine viruses. Niagara Peninsula isolates were different, at a molecular level, from all four vaccine viruses that were examined and from ILT viruses that had been previously analysed and reported in the literature. Taken together our data indicate that both "wild-type" and vaccine-derived viruses are involved in ILT cases in Ontario.
