Phylogenetic analysis of rabbit haemorrhagic disease and European brown hare syndrome viruses by comparison of sequences from the capsid protein gene

A 398 bp fragment of the capsid protein (VP60) gene of 39 clinical samples of rabbit haemorrhagic disease virus (RHDV) and 17 of European brown hare syndrome virus (EBHSV), collected between 1981 and 1995 from 17 countries, was amplified by PCR and directly sequenced. The alignment of the nucleotide sequences and the subsequently constructed phylogenetic tree clearly separated RHDV from EBHSV as phylogenetic entities. The nucleotide homology rates between the RHDV and EBHSV groups ranged between 52.6% and 60.0%. The homology rates within the groups were much higher, 89.4% to 100%, for the RHDV samples, and 89.4% to 100% for the EBHSV specimens. No intermediate viruses were found. Despite the high homology, three main branches could be identified in the phylogenetic tree of the RHDV samples, corresponding to the epizootiological data, while the EBHSV dendrogram did not show such well defined branches. The present results support the classification of RHDV and EBHSV as two distinct members of the Caliciviridae family. Nevertheless, a comparison with previously determined sequences of other caliciviruses shows that RHDV and EBHSV are more closely related to each other than to any other calicivirus.