Rinderpest immunity in calves was investigated by
a study of neutralizing antibodies.
In young calves aged from 1 day to 2 months, the
progeny of rinderpest susceptible dams, the serological response to viable lapinised rinderpest virus, as
measured by the serum titres 21 days after inoculation,
did not differ from those of adult susceptible cattle.
Maternally- derived rinderpest antibodies were found
to be transferred from the Cam to the calf via the colostrum, No antibodies were detected in the sera of calves
before suckling. The colostra of immune dams contained
rinderpest antibodies to a higher titre than that of the
dams' sera; 30-40 hours after the ingestion of such
colostra, newborn calves possessed high antibody levels
in their sera, levels greater than those of their dams'
sera, approaching but less than those of the colostra
ingested. Thereafter the antibody levels in the calves'
sera declined linearly. The mean half -life of maternally derived rinderpest antibody in calves was 36.7 days and the
extinction point 10.9 months (the extinction point was the
thane calculated for, the titre to fall to 100.0, 1 month
being equal to 30 days).
Two young calves, from susceptible dams, which each . ingested daily for 5 weeks 1 gallon of milk containing
rinderpest antibodies failed to show evidence of their
absorption from the intestinal tract.
In calves which were the progeny of rinderpest-immune
dams the serological response to viable caprinized rinderpest virus depended upon the level of maternally-derived
passive immunity at the time of inoculation. All calves
aged & months or more at the time of inoculation produced
antibodies, whereas no calves aged 3 months or less do so.
Some calves aged between 4 and 7 months were, and others
were not, actively immunized. Two critical levels of
maternally-derived antibodies occurred, one below which all
calves produced antibodies and another above which no calf
produced antibodies. The response in calves with preinoculation titres between these two levels varied. There
was a significant relationship between the level of maternally - derived antibody at the ti :e of inoculation of vaccine and
the amount of antibody produced during the following 3 weeks,
the greater the preinoculation titre the smaller the amount
of antibody produced. Similarly there was also a significant relationship between the preinoculation titre and the
1 year post -inoculation titre. Also, where calves possessed
a high level of antibody before inoculation, but were actively
immunized, antibody was produced at a slower rate than in
those calves possessing little or no maternally- derived antibody.
The development of an active immunity to rinderpest by
those calves possessing maternally-derived antibody was not
necessarily associated with a clinical reaction. When
passively immune calves failed to produce antibodies following caprinized rinderpest virus inoculation, sensitization of the antibody-forming mechanism did not occur
as was demonstrated by failure to show an anamnestic
response following later exposure to rinderpest antigen.