48
REPORT OF THE IMPERIAL INSTITUTE OF VETERINARY RESEARCH,
It is known that it is very difficult to intervene successfully against streptococcal
infections by the inoculations of" vaccines " made up according to the common methods
employed; for example, in the form of joint-ill in foals due to streptococci it would seem
that no benefit is conferred by this means. However, if, as seems indicated by the
laboratory tests and such human reasoning as one can apply to the circumstances in the
present state of our knowledge, the " aggressin" issued to the Depôts was capable of
evoking a response on the part of the animal organism towards streptococcic invasion,
then one cannot but turn to the view that natural strangles is not initiated as an invasion
with this type of organism. The streptococci, according to this view, must be regarded
as secondary invaders, of similar significance to the organisms found readily by ordinary
bacteriological examination in the evolution of swine fever. The belief has already been
expressed by certain workers that the disease is set up by an " ultra-visible virus " as
the initial causal agent, with streptococci as mere secondary invaders. It might be
argued that such agents as were employed in attempting to set up an immunity were
not specifically capable of bringing about a response against all the types of virulent
streptococci capable of producing strangles. This argument, however, cannot be sub-
stantiated, for if it were true, horses would throughout their lives be susceptible to
recurrent attacks of strangles through exposure to different types of streptococci capable
of producing the disease; this is not what is well known to occur.
The indications seem therefore that attempts should be made to combat strangles
by resorting to other means than streptococcic products. Whether the morbid products
of the disease can be suitably treated and still retain a " specific factor " capable of
evoking an immunity response,or intervention similar to that employed in certain diseases
due to ultra-visible viruses can be adopted with success remains to be examined. In
undertaking immunization by the latter procedure the possibility comes to mind that
a method of sero-vaccination could be readily tested, by inoculating susceptible animals
with what may be a good anti-serum, obtained about seven days after the commence-
ment of apyrexia from other animals that have sustained a mild but decided febrile attack
of the natural or artificially communicated disease, and artificially infecting them simul-
taneously with the " virus," in the manner that was carried out as explained above in
the case of foals at the Ahmednagar stud.
A note of appreciation must be recorded here of the splendid collaboration given in
these investigations by Major G. W. Williamson, R.A.V.C., Stud Farm, Ahmednagar,
Capt. J. Bell, R.A.V.C., Remount Depôt, Sargodha, and Capt. R. E. Bond, R.A.V.C.,
Remount Depôt, Mona. It is hoped that the privilege may be retained of enjoying their
experienced clinical co-operation in endeavouring to discover a solution of the disease
problem.
(n) Treatment of worm infections. Hookworm disease in dogs in India appears to
have a significance comparable to that of the infection in the human subject, and owing
to the habits of life of canine subjects is probably even more widespread, and is un-
doubtedly one of the chief factors in the causation of the anæmia and wasting prevailing
commonly in this species in the country. Numerous laboratory examinations of fæces
by means of one of the new floatation methods (SHEATHER' S) for the detection of worm ova
have revealed an almost universal infection of dogs, particularly of pariah dogs, with anky¬
lostomes, and in young dogs affected with emaciation the numbers of eggs discoverable are
sometimes enormous. It was therefore thought that an investigation of the possibilities
of treatment along the lines which have been the subject of intensive study by HALL
in America and have been productive of striking success in his hands might enable the
laboratory to tender reassuring advice to dog-owners in India. The procedure adopted
by HALL for estimating what is termed the anthelmintic efficacy of a drug is a simple one:
the number of worms passed in the fæces after treatment are counted, the subject then
destroyed, the number of worms remaining in the bowel counted, and the ratio between
the number of worms passed and the number originally present in the bowel represents
the anthelmintic efficacy. In the tests carried out at the laboratory a modified procedure
was adopted, so that more information could be obtained from single affected subjects :
a considerable number of pariah dogs were obtained from Bareilly and samples of fæces
from each of them were examined systematically daily. It is known that isolated exami-
nations may not give precise indications as to the degree of infection, but nevertheless
it is believed that daily examination of fæces from a dog carried on in approximately
the same manner for several months gives a " curve" which furnishes what may be
called good practical information as to the state of infection in the bowels. After the
curve had been under observation for some time in a dog showing distinct worm infection,
a system of treatment was applied (after 24 hours' fasting), and the curve then watched
for three weeks or longer, when the same or another system was applied if evidence of
infection was again distinct.