Carrier status

Not all rabbits die after exposure to RHDV. Some are not affected by the virus and others survive infection.  It is a concern that rabbits that have recovered from RHDV could be infectious to other rabbits or whether asymptomatic vaccinated rabbits could carry the infection. At the present time, the answer to these questions is not clear because owners usually respond to an outbreak of RHD by vaccinating any surviving rabbits and ensuring that any new rabbits are already vaccinated.

A few laboratory studies have investigated the possibility of carrier status, but the results have conflicted. One investigation showed that the viral RNA from RHDV1 could be recovered after 15 weeks in vaccinated rabbits that were exposed to infection (Gall and Schirrmeier, 2006). A separate study by the same authors showed that three susceptible rabbits that were housed with five rabbits that had survived infection did not develop the disease. One susceptible rabbit was even challenged by inoculating it with RNA positive material from a rabbit that survived infection (Gall et al, 2007) but it still did not develop the disease.

Another investigation into RHDV2 demonstrated viral antigen in the faeces of exposed, but unaffected, rabbits up to 7 days after infection at which point they were sacrificed (Dalton et al. 2018).  A more recent study has shown that viral RHDV2 RNA was not present in the liver, spleen, lungs, kidneys, faeces or urine of vaccinated adults two weeks after infection (Le Minor et al. 2019).

Overall, it seems unlikely that carrier rabbits play an important part in the spread of RHD in domestic rabbits. Insect vectors, body fluids from carcases, faeces from scavengers or contaminated food are much more likely to be the source of infection.