Molecular characterization of Marek's disease virus genomes isolated from white-fronted geese

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To characterize the genomes of Marek's disease virus serotype 1 (MDV 1) isolated from wild geese, feather tips and blood samples were collected from 200 pintails in Hokkaido, 63 bean geese (Anser fabalis), 15 canada geese (Branta canadensis), and 50 white-fronted geese (Anser Albifrons) in the fareast area of Russia during 2003-2005. Samples were also collected from 147 white-fronted geese at Hokkaido during 2003-2005. Total cellular DNAs were extracted from these samples, and the meq gene-specific nested PCR was performed to detect the MDV 1 genome. The MDV genome was not detected from pintails, but 25-30% of samples from thses geese were positive for the meq gene. These results showed that MDV 1 is present in wild goose populations though no clinical signs were observed in these geese.In the next experiment, nucleotide sequence analysis of the MDV1 genomes obtained from white-fronted geese was done to estimate the pathogenicities of the MDV1 strains. The nucleotide sequences of the meq genes of the MDV1 strains were very similar to those of very virulent MDV1 reported previously. In addition, a deletion in the glycoprotein (g) L gene, which was reported in the very virulent MDV1, was also found in the MDV1 strains from white-fronted geese. These results suggested that the MDV1 strains detected in white-fronted geese are very virulent. However, nucleotide sequence of the gB gene of goose-derived MDV1 was slightly different from that of very virulent MDV1 isolated from chickens in the Hokkaido area, showing that the MDV1 transmission between chickens and geese is not so frequent at the present time. It should be noted that the meq gene of one MDV1 strain was very similar to that of very virulent MDV1 isolated from chickens in the Hokkaido area, and it will be necessary to study larger numbers of samples from goose populations.