Effect of inoculation route and ambient temperature on the survival time of rabbits, Oryctolagus cuniculus (L.), infected with Rabbit Haemorrhagic Disease Virus

A factorial experiment using survival time as a response variate was used to test the effects of inoculation route and ambient temperature on the pathogenesis of Rabbit Haemorrhagic Disease (RHD) in adult wild rabbits. Although ambient temperature had no effect on survival time, the route of inoculation was significant, with orally dosed rabbits dying about 21 h later than intramuscularly or intradermally dosed rabbits. Sex was a significant factor, with male rabbits dying 12 h later than females. Body weight (but not age) was also important because heavier rabbits died before lighter ones. The amount of virus detectable in the livers of cadavers decreased with increasing survival time; consequently, heavy rabbits, which died first, had the highest levels of virus. For future studies involving survival time as a response variate (e.g. testing the virulence of field strains of RHD in wild rabbits), it will be important to consider sex, body weight and route of inoculation as factors influencing survival time. Wild rabbits were highly susceptible to Czech (strain 351) virus that initially spread across Australia, with a mortality of over 90% being observed among the animals used in this experiment.