Detection of RNA of rabbit haemorrhagic disease virus from New Zealand wild rabbits

Rabbit numbers have returned to high levels in some areas of New Zealand following the initial spread of rabbit haemorrhagic disease virus (RHDV). We undertook to determine whether possible infection with an RHDV-related virus was interfering with the initiation of new outbreaks of rabbit haemorrhagic disease (RHD). RHDV RNA was detected by polymerase chain reaction with reverse transcription (RT-PCR) using RHDV-specific primers from tissue samples of wild rabbits that had been shot in the field. RHDV RNA was detected in 11 of 19 rabbits from an area of Otago where the rabbit population had greatly expanded and in 2 of 8 rabbits from the West Coast where outbreaks of RHD had not been previously reported. Among the 13 rabbits positive for RHDV RNA, 10 had detectable antibodies against RHDV. The nucleotide sequences of the isolates - a segment of the RHDV capsid gene - shared about 99% identity with that of the Czech strain V351 and that of a 1997 New Zealand wild isolate, but shared only about 84% identity with that of a European benign rabbit calicivirus. These results provide evidence for persistent infection of RHDV in rabbits.