F. C.
MINETT
9
nized to be an enormous one and is even regarded
by some as insurmountable. It is not likely to be
a smaller problem in communities of young horses,
unless they are subjected to a good deal of res-
traint. Such restraint must be on epidemiological
lines, and aimed at promoting as effectively as
possible the dispersal of young stock from the
moment they are admitted. During recent years
the truth of this has been well recognized by the
veterinary officers concerned. We do not believe
that at the present time there is overcrowding of
the depot paddocks, or that it is practicable to
disperse stock more than is being done now. To
emphasize the point, however, we would refer to
the case of experimental epidemics in mice, from
which valuable lessons may be drawn. Topley
[1922, 1926] has shown that when mice, which
had been exposed to the risk of infection with
Bact. typhi-murium and among which an epidemic
was imminent, are dispersed into groups containing
19 to 25 mice, there is little effect on the mortality,
but when they are dispersed into smaller groups of
ten animals each, the mortality rate is greatly
reduced. Once the epidemic has started, however,
dispersal into still smaller groups of five mice
each had a much less marked effect. Topley,
therefore, suggests that, if at the first sign of an
outbreak animals are split into small groups
and after a certain interval are brought together
into groups of more manageable size, a severe
outbreak may be forestalled. The importance
of adequate spatial distribution of subjects at risk
is also admirably shown by the observations of
Glover [1918] on cerebrospinal fever in a military
unit. He found that the meningococcus
carrier rate provided an index of whether there
was overcrowding in the sleeping quarters. A
carrier rate reaching a certain figure, 20 per cent,
could be taken as a danger signal. In order to
reduce the rate and avert the danger of an outbreak
of cerebrospinal fever, it was merely necessary to
increase the distance between the beds.
Always to be borne in mind in the case of
strangles, as of other infectious diseases, is the
question of whether the movement and distri-
bution of young stock can be so changed as to
lessen the frequency of contact between them.
Admittedly, the question is more easily asked
than answered, but as Topley [1942] has said
'Any step that lessens the probability of effective
contact, direct or indirect, is a step in the right
direction. As we reduce the frequency of effective
contact, we reduce the mass of infective material
on which the probability of further diffusion in
part depends.'
The earlier in the purchasing season young
stock can be brought into the depots the better,
in this way a process of natural immunization
arising from intimate association in the paddocks
will have a longer time to develop before the
cold spell of winter. But since natural immuniza-
tion is largely an affair of chance, it i unlikely to
be so satisfactory as an efficient specific immuniza-
tion, so our hope for the future lies in the latter,
assisted by good dispersal and protection from
adverse weather conditions. As to the isolation
of declared cases of strangles in hospital, this is
not likely to do much good so far as the animals
which remain behind are concerned, especially if
we may assume that these include carriers and that
carriers and atypical cases have at least some im-
portance as spreaders. At the same time, any
systematic attempt at isolating infected animals
other than declared cases would be very difficult
under conditions at the depots. Finally, it may
be observed that one way of by-passing the
problem would be to replace young stock horses
largely by young stock mules, since these have
considerable inborn resistance to strangles.
As to the treatment of clinical cases, sulphanila-
mide therapy is worthy of more extended trial,
especially for cases in the very early stage
[Minett and Edwards,* 1945.]
SUMMARY
1. The article is concerned with strangles as it
has occurred in two large remount depots and on
certain horse-breeding farms in the Punjab. The
annual attack rates and mortality figures are given
for various periods between 1914 and 1942.
2. Some account is given of the methods or-
dinarily practised at these remount depots and
stud farms in dealing with young horse popula-
tons.
3. The principles involved in control of the
disease in remount depots are discussed.
ACKNOWLEDGEMENTS
Information on horse-breeding in India has
been kindly provided by the Director, Army
Remount Department. I am indebted to Bri-
gadier J. J. M. Soutar, C.B.E., Director of Army
Veterinary Services in India, for his interest and
support and to the officers named in the text for
their recorded opinions of which full use has been
made. Considerable help has also been obtained
from the officers in charge of the remount depots
and owners of the stud farms. Special mention is
to be made of the officer in command at Mona,
Colonel M. F. Keightley, A. R. D., of Veterinary
Officers at Mona and Sargodha in 1943 (Major
P. F. Woodland and Capt. G. McElligott, R. A.V.
C.); of Major W. P. S. Edwards, R. A. V. C., and
of Lieut. D. H. Witherington, R. A. V. C., acting
Veterinary Officer at Sargodha in 1943. Table I
is partly based on a chart prepared by Capt.
* In press.