This virus showed greater genetic and antigenic diversity than RHDVa compared with classic RHDV, with [approximately equal to]82% nucleotide sequence similarity in VP60 between wild-type RHDV2 and RHDV (11,18,19).
Until 2014, only the benign rabbit calicivirus Australia-1 (RCV-A1) and the RHDV biocontrol strain CAPM V-351 (and its descendants) were circulating in Australia (7,31).
Strikingly, the third isolate (BlMt-1) was most closely related to an RHDV2 variant generated by recombination of the RHDV2 capsid gene (Figure, panel B) and the RHDV genogroup 1 nonstructural genes (Figure, panel A), which has recently been reported to be circulating in Portugal and the Azores (8,9).
In 1991, CSIRO imported the Czech351 strain of RHDV to assess its potential as a biocontrol tool for controlling the European rabbit, which causes massive economic and ecologic damage and is declared a pest species in Australia.
K5 is a naturally occurring overseas strain of rabbit calicivirus that Australian rabbits dont have resistance toand the government, together with industry, research organisations and state and territory governments, has invested in its development and proposed roll out.
On the other hand, the number of lynxes killed on roads doubled in 2013 (n = 14) in relation to 2012 (n = 7), and this has been linked to increased lynx displacements related to rabbit scarcity potentially associated with the impact of the new variant of RHDV (http://www.
It also highlights the importance of using wildlife monitoring schemes as detection tools for monitoring the impact of stochastic factors, such as the variant RHDV, on wildlife populations.
Before the new variant of RHDV emerged and, on the basis of phylogenetic relationships, RHDV strains had been divided into 6 genogroups (G1-G6) (1), with strains of G6, or RHDVa, having a distinct antigenic profile (6).
We analyzed the samples for RHDV by reverse transcription PCR.
The identification of rabbit caliciviruses (RCVs) (5,6), nonpathogenic viruses antigenetically similar to RHDV
, and recent descriptions of a pathogenic RCV (7), an RHDV
variant grouping with RCV viruses in phylogenetic analysis (8), and nonpathogenic RHDV
(9) raise questions about the origins, classification, and nomenclature of these viruses.
After blocking with milk diluted in phosphate-buffered saline, RHDV
strains isolated from whole liver extracts of infected animals were incubated on coated plates at dilutions corresponding to 1 x [10.
GenBank accession numbers for complete and partial rabbit caliciviral nucleotide sequences used for phylogenetic analysis are as follows: RHDV
strains USA IA00 (AF258618), USA UT01 (EU003582), USA NY01 (EU003581), USA IN05 (EU003579), JX China 97 (DQ205345), China CD (AY523410), China WHNRH (DQ280493), Italy 90 (EU003580), Germany FRG (NC001543), China WX84 (AF402614), Mexico 89 (AF295785), Spain AST89 (Z49271), Ireland 18 (DQ367359), Italy BS89(X87607), EBHSV (NC002615), RCV (X96868), MRCV (GQ166866).