R. L CORNELL AND RATANA OONYWONGSE 7
clear cut, the test buffalo which received 40 c.c. nasal washings from this
calf showed no temperature rise until the fourteenth day when symptoms
and fever developed simultaneously and the animal died on the eighteenth
day following injection. Both symptoms and post mortem were indicative
of rinderpest. We have experienced irregular reactions with a prolonged
incubation period with other buffaloes employed for goat virus tests but
have always realised that cross infection with buffalo virus subsequent to
experimental inoculation cannot be ruled out with certainty when animals
are maintained at a serum and vaccine institute where virus is perpetuated.
Our conclusions are, however, that virus was present in the nasal secretion
of calf XX and that it was probably present in the nasal secretion of calf
XXI in a minimal amount. We have not deemed it necessary to test for
the presence of virus in the copious nasal secretion or in faeces mixed with
blood from animals which develop the severe and acute reactions so often
resulting in death and we cannot but believe, that such animals are infective
to other susceptible animals.
Contact experiments in rinderpest infection may be so inconclusive
that a long series of negative results would be unconvincing. We have,
however, carried out a small controlled test in the nature of a field trial which
we will record as well as some field experiences. Three buffaloes were tied
up in close proximity to cattle which had been injected with goat virus
and all used the same small stream for drinking. Temperatures were recorded
and no infection resulted. This observation is of course entirely inconclusive
and we merely record it.
FIELD TRIAL
In a district which was free from rinderpest and which, according to
records, had been free for three years, all bovines employed for transport,
carting or packing operations (pack bullocks are extensively employed in
this region) involving movement about the area were injected with goat virus.
The vaccinated animals were put out of work for fourteen days but strict
control of movement was not and could not be enforced. The work was
carried out from village to village and in all 2,870 bovines were vaccinated.
The area about which we are speaking had provided trial bullocks for testing
and the indications were that the stock was about fifty per cent susceptible.
Buffaloes, female bovines and calves were not inoculated at this stage and
contact between these and the vaccinated animals which used common
grazings and water supply was fairly close, although the custom of the country
to tether animals rather than to permit more extensive ranging does curtail
contact to some extent. The whole district was carefully watched for two
months and there was never any indication that any in contact animal had
contracted infection. Among the 2,870 animals injected, two deaths were
reported and fourteen reactions were more severe than desirable.
It appears therefore, from all the evidence available, that animals
infected with goat virus and which show little or very mild reactions are
definitely less infective than animals infected with a more virulent virus
(the experimental evidence of the absence of virus in the urine in two tests
also supports such a contention). In view of the serious nature of the re-