Green's distemper vaccine virus has been propagated 30 generations in developing hen eggs.
Injections were made onto the chorio-allantoic membranes of eggs that had received a preliminary incubation of 8 days. Re-incubation was done at 35°C., and passage of the membranes was made at approximately 4 day intervals.
The egg-adapted strain produced markedly oedematous changes with some necrosis in the membranes, but only occasionally killed the embryo. The titre of infected chorio-allantoic membranes, measured by ferret injection was between 10⁻³ and 10⁻⁵. That of the embryos and extra-enbryonic fluids of the same eggs was 10⁻³.
The reactions produced by the egg-adapted strain when injected into
ferrets were similar to those produced by the parent strain.
Five c.c. of anti-distemper serum neutralized the egg-cultured virus.
Thirteen dogs were inoculated with suspensions of chorio-allantoic membranes.
In nine there was no reaction. In one there was a slight reaction,
but in three the reactions were very severe and one died after showing
typical distemper symptoms.
The egg-adapted virus did not agglutinate chicken or guinea pig red
cells and failed to infect mice when instilled intra-nasally.
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