Passive immunity in myxomatosis of the european rabbit (Oryctolagus cuniculus): the protection conferred on kittens born by immune does

Abstract

1. The existence of passive immunity to myxomatosis was demonstrated by the inoculation of normal young rabbits with either myxoma-immune serum or saline, and their subsequent inoculation with the standard laboratory strain of myxoma virus. All the passively immunized animals lived longer than the control animals and a few survived.2. Passive immunity could also be demonstrated in the offspring of myxoma-immune mothers. When these were challenged by mosquito bite inoculation with the standard laboratory strain of myxoma virus they either failed to become infected, or survived infection for several days longer than the progeny of normal does. When challenged by the intradermal inoculation of a slightly attenuated strain of myxoma virus 25 % of the progeny of immune does survived the infection, whereas none of the normal kittens survived.3. The survival times of young rabbits in both the normal and passively immunized groups was influenced by their age, very young animals dying several days earlier than rabbits 4 and 6 weeks old.4. The possible epidemiological consequences of passive immunity in the behaviour of myxomatosis in populations of wild rabbits are discussed.