4
Rinderpest Immunisation with Goat Virus
TESTS OF VIRULENCE OF THE VIRUS CATTLE
Class I. Cattle have been obtained for testing purposes from areas which
are subject to frequently recurring outbreaks of rinderpest, their suscepti-
bility is therefore unknown but if enquiries are made with regard to past
history one can generally rely on young animals being susceptible.
Class II. Animals from a part of the country which, from its situation
and local stock contacts, has always enjoyed long periods of freedom from
the disease and which is known to have been completely free for the last five
years. Bovines from this district can be relied on to be at least 90 per cent
susceptible.
Class III. An area intermediate between Class I and Class II. It enjoys
freedom from infection for variable periods and at the time that a test was
carried out no outbreak had been reported for three years.
Ten young bovines obtained from an area of Class I were injected with
1 c.c. of a 0.5 per cent saline suspension of fresh spleen from a reacting goat.
Only one animal showed anything suggestive of a definite temperature re-
action and in this case the peak temperature was only 102.8°F (fourth day).
Another showed slight looseness of the bowels on the ninth day and a dis-
inclination to feed on the eleventh day. None of the other animals showed
any appreciable departure from the normal. Blood was drawn from two
animals, neither of which had shown any definite reaction, on the seventh
day following the injection of the goat virus and each sample was injected
into two susceptible buffaloes in doses of 5 c.c. Infection occurred in every
case, two of the test animals died of acute rinderpest and two recovered after
severe clinical attacks. The ten young bovines were retested twenty-one
days later with virulent buffalo blood and appeared to be completely im-
mune.
The experiment shows that at least four of the ten animals were sus-
ceptible to rinderpest in the sense that they were not solidly immune as a
result of previous infection and recovery.
A second experiment was carried out with ten adult cattle from an area
described as Class II, i.e. the most susceptible stock available in the country.
Five were injected with 1 c.c. of citrated blood and five with 1 c.c. of 0.5 per
cent saline spleen suspension of a reacting goat. All gave a typical tempera-
ture curve, four showed some evidence of malaise and a little diarrhœa or
softening of the faeces but the departure from the normal was transient,
while one animal died on the tenth day after exhibiting symptoms of only
moderate severity. It was an old, thin and weak animal and death did not
appear to be attributable solely to the reaction.
With animals obtained from an area of Class III, a test on eleven cattle
of ages varying from about two-and-a-half years old to very aged animals
produced four definite temperature reactions with slight indisposition for,
two or three days, two indications of malaise with no temperature, while
five animals, all aged ones, showed no appreciable effects whatsoever and were
probably immune from a previous attack.
These tests show therefore that goat virus is safe for use without serum
on cattle throughout this country and that the degree of attenuation might
be said to approach the ideal. Details of these tests are set out in Table I.