6
Problem of Equine Strangles in India
Fig. 3 shows that at the depots the proportion
of fatal cases rises as the strangles season advances,
which conforms to the suggestion that attacks
later in the season are more severe. At the stud
farms the rates do not appear to differ greatly
throughout the year.
As to the ages at death, figures for 27 animals
are available for Coleyana.
Age in months .
Number dying .
3
0
6
1
9
4
12
8
15
8
18
3
Over 18
3
Deaths are, therefore, most frequent in yearlings.
Mules. The mortality in mules (Table II) is
much less than in horses, being about 1.0 per cent.
There is no significant difference as between
Mona and Sargodha, nor in mortality rates over
years.
AGES OF ANIMALS AT ADMISSION
The following figures for 543 cases at Coleyana
over the period 1930-43 show the age groups of the
animals on admission for strangles.
Age (months) .
Number . .
Per cent
3
11
6
83
9
86
12
123
15
5
— 81.6—
8
50 21
21
24
15
(years) . .
.
3
23
4
22
—18.4—
5
18
Over 5
Over 37
The proportion of older animals admitted is
perhaps surprisingly high. Of the younger ones,
the largest proportion fall in the age groups 10-12
months, the next largest proportions being four
to six and seven to nine months. A study of the
outbreaks coming within the period shows that
the bulk of the earliest clinical attacks appears in
younger animals, though it is of course possible
that infection may have been acquired in the first
instance from adult carriers.
DISCUSSION
Opinions and experiences of earlier observers on
strangles. Many years' experience has taught
veterinary officers that strangles cannot be pre-
vented from appearing in Army Remount Depots,
and many believe that the main object should be
to produce a mild form of the disease in early life,
which will leave a long and serviceable immunity.
Unfortunately, while strangles is always of most
importance during the first season the young stock
are in the depot, the disease is said to vary greatly
in its incidence and severity from one season to
another and from one outbreak to another; and
this has not only caused difficulties in attempts at
natural immunization but has also made it
difficult to judge the efficacy of methods of pre-
vention. It has been noted, however, that at the
depots during any one season the prevalence and
severity of the disease increase with the passage
of time to reach its highest intensity in March and
April, irrespective of the date of onset. Capt.
G. W. Short [1939] has also remarked that the
first cases in a season are mild and succeeding
ones tend to be progressively more severe. It
has, therefore, been recommended that young
stock should be purchased as early in the season
as possible and never later than March. On the
question of immunity, mules have a considerable
natural resistance, and in them strangles is mild
and death rare. In horses, while second attacks
are comparatively rare, there are numbers of
reports [e.g. Langley, 1938; Short, 1939] of a
second attack in the same animal one to eight
months later, the first attack haying sometime
occurred before admission to the depot. As to
the time elapsing between exposure and appear-
ance of symptoms, while some young horses may
show symptoms within a few days of arriving
at the depot, Edwards [1926] has commented on
the fact that many cases crop up some time
after admission.
As to the phase of maximal infectivity of cases
the belief has been expressed that animals are
most dangerous spreaders during the early stages
of the attack, while on the question of spread
from recovered animals opinion is divided. As
to the influence of weather conditions, a subject
to be dealt with in another paper—it has been
remarked that heavy rains are liable to be followed
by a number of cases, while in mild weather the
disease tends to be less severe.
Efforts at control. A great deal of attention has
been paid to this problem at Mona and Sargodha,
but without striking success. Reports of this
work are given by J. T. Edwards [1923-25, 1925]
and Arnold [1932]. The measures tried, apart
from those designed to inhibit the spread of in-
fection, have included the use of streptococcus
vaccines of various kinds (dead cultures; living
cultures of low or high virulence; sensitized,
formalinized or 'extracted' cultures; 'pyovac-
cine'), convalescent serum with exposure to
natural infection, serum combined with the nasal
application of infective material, as well as
various proprietary preparations. As curative
agents, such drugs as tryparsamide, sulphonamide
P, prontosil, etc., have been tried. During the
past ten years the tendency has been to recognize
that useful results were not to be expected from
such methods and to rely on measures for pre-
venting the spread of the disease or producing
mild attacks. Means which may be adopted
with this end in view may now be considered.
Brigadier A. J. Williams [1932] considered that a
fair test of the efficacy of preventive measures
would be the percentage of young stock admitted
during the year which develop the disease, while