R. L. CORNELL AND RATANA OONYWONGSE 3
In tropical Africa Daubney [1937, 1] has examined the method and records
a mortality of approximately 18 per cent when the Mukteswar virus is
inoculated into grade and native cattle alone. Reactions and mortality
are, however, easily controlled by a small simultaneous dose of serum or a
previous dose of vaccine. In his own series of passages for the attenuation
of the virus he concludes that there was a gradual suppression of symptoms
from the 85th passage. Subsequently [Daubney, 1937, 2] the same author
describes how at the 160th passage the Kabete virus appeared to have reached
a degree of attenuation for cattle similar to that of the Mukteswar strain
which has been passaged in goats since 1929. Some uncertainty with regard
to the reliability of the resultant immunity exists from these Kenya trials
especially when serum has been combined with the method. It is further
recorded from Kenya [Veterinary Department, Kenya, 1939] that a most
important feature of the method is that the mild disease due to goat virus
does not appear to be contagious either to cattle or to goats and there is
thus less danger of the creation of foci of infection from immunisation. It
is also stated that, like all methods of conferring an active immunity, goat
virus must produce a reaction to produce a result.
It is apparent from a perusal of the records of the employment of goat
virus for immunisation that the inherent resistance to the disease of the
animals to be immunised is a prime factor with regard to the safety of the
procedure and it behoves all who contemplate its employment on a large
scale to make every endeavour to assess this factor. Increasing experience
of rinderpest and its control impresses on one the wide variations of such
resistance that occur among susceptible species, breeds and races.
THE VIRUS EMPLOYED
The virus was obtained from the veterinary laboratory, Insein, Burma
but had originated at Mukteswar. The exact number of passages since
its first adaptation to goats could not be ascertained but the number must
total many hundreds (290 passages had taken place in Burma before we
obtained possession). We have maintained it by subcutaneous inoculation
into locally procured goats and no special attempt has been made to pro-
long the passage series to obtain greater attenuation. Infective spleens have
been stored in the refrigerator and goats inoculated when fresh virus was
required or to ensure survival and viability of the virus. Passage injec-
tions have been carried out on an average once a month. On this account
few goats have been left to recover or die and we cannot accordingly make
adequate comparisons of mortality with series carried out elsewhere. Tem-
perature reactions have been fairly constant up to a peak of 105°F (morning
temperature) but other characteristic symptoms have not been striking.
Dullness, falling off of appetite, a marked staring coat and a tendency to stand
with legs tucked in and an arched back presenting an appearance of malaise
and discomfort are apparent from the time that the temperature rises and
for about a week afterwards. Diarrhœa frequently follows but definite
pneumonia has been encountered but rarely. Among goats that survive
loss of condition often amounting to emaciation has been rather noticeable.