Experimental infections of rabbits with rabbit haemorrhagic disease virus monitored by polymerase chain reaction.

Adult and 4-5-week-old rabbits were inoculated subcutaneously with rabbit haemorrhagic disease virus (RHDV). Samples were prepared from various tissues at intervals postinoculation (PI) for the detection of viral RNA and antigens. Using a haemagglutination test (HAT), viral antigens were detected in the liver, bile and spleen of the adult rabbits at and after 36 h PI. The reverse transcription-polymerase chain reaction (RT - PCR) showed that RHDVRNA was present in the liver, bile and spleen as early as 18 hours PI, whereas lung, kidney, thymus, mesenteric lymph node and buffy coat were found to be positive after more than 26 hours PI. In addition, viral RNA in urine and faeces showed a variable positivity at and after 36 hours PI. In the young rabbits, RT - PCR showed that RHDVRNA was present as early as 1 day PI in the liver, bile, spleen and buffy coat; whereas lung, kidney, thymus, mesenteric lymph node and faeces were found to be positive at and after 2 days PI. Bile and spleen were the only samples in which viral RNA was detected throughout the length of the experiment. Virus was not reactivated in six recovered virus-inoculated rabbits treated with dexamethasone or a classical swine fever virus vaccine. Using a haemagglutination inhibition test and an ELISA, antibody titres increased rapidly from one week PI onwards, peaked at approximately three weeks of age, and were maintained throughout the length of the experiment.