M. K. SREENIVASAN AND S. K.
CHAUDHURY
231
showed short chains of streptococci.
By cul-
tural examination it was proved that five of
the seven cases were associated with haemo-
lytic streptococci which fermented salicin and
trehalose, but not lactose and mannitol, thus
resembling Edwards' Type B1 or Bazeley's
Type 4.
TRANSMISSION EXPERIMENTS
1. With blood
Blood drawn at the height of temperature
from three cases, Nos. 5, 6 and 7 of the series,
two of which subsequently had parotid abs-
cesses, were injected subcutaneously
into a
foal, No. 499, aged four months. Apart from
a sudden and transient rise of temperature (to
103.4°F.) 14 days after the first injection, there
were no symptoms.
Blood transmission was also carried out from
the experimentally-infected foal with negative
results, the blood at this time showing no bac-
teria in culture.
2. With culture
A 24-hour broth culture of streptococci,
isolated during this outbreak, was sprayed into
the nostrils of foal 499, 21 days after the last
blood injection. Four days later, there was a
definite rise in temperature associated with
nasal discharge and swelling of the submaxil-
lary region.
This swelling was hard and
painful and gradually spread over the face,
especially on the left side. Metastatic abscesses
then
appeared
over
the
submaxillary,
parotid and pharyngeal regious, abscess forma-
tion being fully developed within nine days,
when the temperature rose to 105.6° F. The
abscesses were opened on that day and dressed
antiseptically.
It took
nearly four weeks
before the animal was declared cured.
IMMUNITY TEST
For this purpose cases 5, 6 and 7 and the
artificially infected foal 499 were used.
A 24-
hour culture of streptococci, isolated during
the outbreak was sprayed into the nostrils, a
healthy foal No. 512 being included as control.
During an observation period of three weeks,
there was no sign of the disease in the recover-
ed animals, while the control foal developed
from the 3rd day a temperature which gradu-
ally rose to 104.6° F. on the 7th day and per-
sisted for a week, when thick creamy discharge
from the right nostril was present.
This dis-
charge on microscopical and cultural examina-
tion yielded haemolytic streptococci. The
control foal was left untreated but developed
no further symptoms.
From the above observations, it is seen that
the incubation period in the two artificially -
infected animals (foals 499 and 512) was three
to four days.
The immunity test revealed
that animals which had once suffered from the
disease, naturally or artificially
acquired,
attained a strong immunity lasting for at least
four months. To test the duration of immunity,
the same strains of streptococci maintained for
a year in culture media were used on healthy
as well as on recovered ponies. None of these
animals got the disease, indicating that the
bacteria had lost its virulence.
An attempt
at exalting the virulence by rabbit passage was
unsuccessful.
DISCUSSION
In this small outbreak only adult animals
were at risk, but in three of the seven affected
the lesions were those of typical strangles. In
this connection it may be noted that the ponies
had lived a relatively isolated existence in the
Kumaun hills and had only rarely been
in close contact with other equines.
Their
susceptibility would therefore be high. Experi-
mentally, it is interesting to note that a clinical
attack of strangles was readily set up in foais
by means of a streptococcus culture.
Bazeley
[1943] found that positive results could only
be obtained with certainty by using a very
young (4½ hr.) culture, but in this work there
was no difficulty in setting up the disease in
young foals with a 24-hour culture of an early
generation.
SUMMARY
1. An account is given of a small outbreak
of strangles in adult ponies, associated with
haemolytic streptococci of Edwards' type B 1
or Bazeley's equine type 4.
2. Blood of affected animals taken at the
height of fever was non-infective, but strangles
in its typical form was easily set up experi-
mentally in foals by nasal installation of a 24-
hour brooth culture of the streptococcus.
3. Naturally and experimentally infected
animals were proved to be immune.
ACKNOWLEDGEMENT
The authors acknowledge their thanks to Mr.
J. R. Haddow for encouragement and to Mr.
V. R. Rajagopalan, for assistance on the bacte-
riological side.
REFERENCE
Bazeley, P.L . (1943). Aust. vet. J. 19, 62