F. C. MINETT
7
the efficacy of curative measures may be gauged in
part by the case mortality. He has pointed out
that factors having a bearing on the result of
preventive efforts would be the total number of
young stock admitted during the season, the
accommodation available for them, and the
number infected before admission. As regards
curative measures, the mortality rate should not
be the sole criterion and account should also be
be taken of the duration of illness as determining
the setback to normal development. Judged by
these criteria, he concludes that up to 1932 the
measures adopted at Mona and Sargodha have
been unsuccessful.
On the question of control we may record the
following more important recommendations in a
report dated 1923 by Major H. Allen:
(1) the Veterinary Officer should be in absolute
charge of segregation;
(2) young stock should be bought and admitted
as early in the season as possible and in large
batches. Batches of young stock admitted should
be separated as far as feasible from previous
batches;
(3) young stock should not be purchased while
showing symptoms;
(4) when strangles appears in animals of a
particular block, fill up with young stock mules;
(5) never overcrowd the paddocks or the segrega-
tion area. Not more than 12 to 15 animals should
be accommodated in each paddock. Paddocks
should also be well isolated from one another;
(6) do not attempt to 'classify' stock while in
segregation, as this means altering the constitu-
tion of groups;
(7) catarrh cases may be treated in their pad-
docks, but typical strangles cases should be
immediately removed to strangles paddocks and
severe cases to strangles hospitals;
(8) keep young stock in segregation for not less
than three or four months;
(9) provide for a convalescent paddock in the
segregation area;
(10) after passing through segregation, stock
should be accommodated for a month in 'semi-
segregation';
(11) stock should be protected from chills; and
(12) cleanliness and disinfection are important.
Manure should not accumulate. Soiled fodder
and litter should be burnt. Disinfection of
buckets, water troughs, twitches, and the hands
of attendants.
Fig. 1 suggests that the whole of recommenda-
tion No. 2 has not been observed, but with the
possible further exception of No. 11, all other
recommendations, we believe, are being satisfied.
We would, however, add, as recommendation
No. 13, a satisfactory food and water supply.
Epizootiology of strangles. As a problem in
epizootiology, that of strangles at the remount
depots appears to be a fairly straightforward one
and can be dealt with on lines which are
familiar to students of the subject. The rise in the
incidence of strangles when young horses are
brought together somewhat resembles the epide-
mic rise of naso-pharyngeal infections which fol-
low the reaggregation of children shortly after the
commencement of the school terms. It may be a
useful lesson to try to visualize for a moment
what may really be happening when a batch of
30-60 young horses is brought in and then split
up into smaller groups of say 12 to 15 each. At
the time of arrival, the animals are certainly not
normal in the sense that all are free from the
streptococci which cause strangles nor as pos-
sessing a uniform susceptibility to these strep-
tococci, should they chance to meet them. We
may assume that some, perhaps many of them,
although apparently in good health, will be
harbouring the specific streptococci in some part
of the upper respiratory tract (healthy carriers or
latent cases), a few may be suffering from atypical
strangles in the form of nasal catarrh, and the rest
will be really healthy. It may next be noted (a)
that the status of many animals of the group, in
respect of their bodily resistance and of any
pathogenic streptococci they may harbour, has
changed since their earlier days in the breeding
areas, because they are now older, may already
have experienced strangles, have mixed with new
companions, and have just undergone the fatigue
of a journey to the depot; and (b) that their
status is destined to change still more profoundly
under the new conditions they will experience at
the depot. Thus it may be expected that, as a
result of the unusually close contact before and
during the journey as well as of the new grouping
at the depot, the carrier rate will rise, and in
due course clinical cases of strangles will be liable
to appear, in which case increasing amounts of
infective material will become available to other
animals of the group. The closer the contact
the more rapidly will spread take place and the
larger the dosage of infective material likely to be
absorbed. The final result will be that all the
animals will quickly become infected and react in
various ways, with the possible exception of those
which have secured a substantial measure of
immunity from attacks of strangles in the breeding
areas. Thus, towards the close of the purchasing
season a horse population will be established
having a level of naturally acquired immunity
which is fairly high on the average and which is
not likely to be disturbed by the specific stre-
ptococci still existent among them or by any
further happenings. Unfortunately, in the past