Virulence of Strains of Myxoma Virus and the Resistance of Wild Rabbits, Oryctolagus-Cuniculus (L), From Different Locations in Australasia

Abstract

Wild rabbits, Oryctolagus cuniculus (L.), caught at six locations in Australia and one in New Zealand in 1976-80, were bred in Canberra and their offspring (n=1392) challenged with seven strains of myxoma virus. Innate resistance varied between locations and was higher in rabbits from inland Australia. The virulence (lethality) of the myxoma strains in the rabbits from the different localities was not correlated with mean survival times. As the correlation between survival time and virulence has previously been the basis for the allocation of virulence grades by survival times, it is suggested that the virulence of field strains may be different from, and higher than, published results. On the basis of survival rates of unselected New Zealand wild rabbits the field strains collected in 1973-78 were allocated virulence grades of I and II.