The emergence of rabbit haemorrhagic disease virus: will a non-pathogenic strain protect the UK?

Rabbit haemorrhagic disease virus emerged in China in 1984, and has killed hundreds of millions of wild rabbits in Australia and Europe. In the UK the re appears to be an endemic non-pathogenic strain, with high levels of sero prevalence being recorded, in the absence of associated mortality. Using a seasonal, age-structured model we examine the hypothesis that differences i n rabbit population demography differentially affect the basic reproductive rates (RO) of the pathogenic and lion-pathogenic strains, leading to each dominating in some populations and not others. The strain with the higher R -0 excluded the other, with the dynamics depending upon the ratio of the tw o R-0 values. When the non-pathogenic strain dominated, the pathogenic stra in caused only transient mortality, although this could be significant when the two R-0 values were similar. When the pathogenic strain dominated, rep eated epidemics led to host eradication. Seroprevalence data suggest that t he non-pathogenic strain may be protecting some, but not all UK populations , with half being 'at risk' from invasion by the pathogenic strain and a fi fth prone to significant transient mortality. We identify key questions for empirical research to test this prediction.