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The emergence of variant fowlpox viruses (FWPVs) and increasing field use of recombinants against avian influenza H5N1 emphasize the need to monitor vaccines and to distinguish them from field strains. Five commercial vaccines, two laboratory viruses and two European field isolates were characterized by PCR and sequencing at 18 loci differing between attenuated FP9 and its pathogenic progenitor. PCR failed to discriminate between the viruses and sequence determination revealed no significant differences at any locus, except for a polymorphic locus encompassed by deletion 24 (9.3 kbp) in FP9. Surprisingly, 'novel' previously unreported sequence (spanning 1.2 kbp) was found in both European field isolates and three of the vaccines. It was absent from the other two vaccines, removed by a 1.2 kbp deletion identical to that surprisingly also observed in the completely sequenced genome of FPV USDA. This locus (H9) adds a potentially useful tool for discriminating between FWPV field isolates and vaccines.

Original publication




Journal article


J gen virol

Publication Date





3545 - 3549


Amino Acid Sequence, DNA, Viral, Fowlpox virus, Molecular Sequence Data, Open Reading Frames, Polymerase Chain Reaction, Sequence Analysis, DNA, Vaccines, Synthetic, Viral Proteins, Viral Vaccines