NationalLibraryOfScotland/medical-history-of-british-india huggingface dataset:
18 THE INDIAN JOURNAL OF VETERINARY SCIENCE AND ANIMAL HUSBANDRY [ III, I
seems that the majority are capillaries or venules which have been abnormally
dilated but these may include occasional dilated lymph spaces. Apart from certain
large sized vessels which reveal a marked thinning and disruption of the muscular
coat, the most interesting lesions are presented by the endothelium of the smaller
vessels. The lesions consist of varying degrees of exudation into the endothelial
lining so that a sector of the vessel may become swollen to form a blunt finger-like
process filling a major portion of the lumen, whereas the endothelium of the other
sectors is very severely mutilated or are even actually shed (Plate VI, Fig. 2).
Where the vessel is seen to contain a plug of inflammatory exudate, portions of the
desquamated endothelium may be recognisable as forming a part of it. With regard
to the probable mechanism by which the bloating of the endothelium takes place,
one notices polymorphonuclear leucocytes and masses of eosinophiles inside the
stumpy finger-like process. The fact that the immediate vicinity of the vessel wall
at the affected sector is heavily crowded with eosinophile cells suggests that a factor
such as an excessive lowering of blood pressure may have determined the endothelial
disruption, particularly when the parasitic toxin had already affected the susceptible
intima. Fairley [1920] has failed to confirm the finding of an endophlebitis of the
mesenteric veins as described by Letulle [1905] in his comprehensive article on
intestinal bliharziosis. The other prominent lesion of the blood vessels is represented
by degrees of endarteritis obliterans.
Apart from the pathological changes in the blood vessels supplying the intes-
tine, which have been referred to above, it must be remembered that the majority
of the nodular lesions in the submucosa or the subserosa originate in the embolic
eggmasses which form in the vessels of the place (Plate V, Fig. 2). It may be
mentioned here that the writer has encountered more than once up to 20 ova in a
single embolic focus in the intestine but although hundreds of liver sections like-
wise have been examined, he has never been able to find more than one ovum
in an individual nodule in the liver. Another remarkable fact is that in the
equine intestine, the large majority of Schistosome ova have been seen to be wholly
restricted to the layers of tissue situated below the mucosa (Plate II, Fig. 2),
whereas in the histological sections prepared from the intestine of natural cases of
S. indicum infection in the sheep and in the bull of both the plains and hill breeds,
the ova have been found almost exclusively in the mucous membrane with practi-
cally no tendency to nodule formation, the actual lesion being more cellular than
fibrous and not calcareous at all. Montgomery [1906] states that the large intes-
tine of equines is the only organ where ova of S. indicum could be found present
in any numbers. He found the ova in the mucosa only and thought that they must
occupy the submucous tissue or the capillary at some time.
PLATE VI.
FIG. 1. (×105)
FIG. 2. (×166)
For explanation see page 27.
FIG. 3. (×21)
FIG. 4. (×32)
SCHISTOSOMA INDICUM, MONTGOMERY, IN EQUINES
19
Mesenteric and other lymphatic glands.—These glands react to schistosome
infection in very much the same way as noted in the foregoing description of tissue
changes, the differences depending upon their anatomical relationship and struc-
tural peculiarities. Examined with the naked eye, the glands are generally enlarg-
ed, œdematous and hæmorrhagic. The enlargement may take place in the region
of the hilus only or it may involve the whole gland, depending upon the severity of
the infection. Palpation of the affected region of the gland gives a hard
nodular feeling to the fingers, the healthy portions yielding normally to light
pressure. On incising an affected gland, pseudotubercles in varying stages of fibrosis
and calcareous degeneration are encountered throughout the gland. On micros-
copic examination the vessels and plexus of lypmhatics situated under the capsule
are found dilated. The lacunar system of lymph sinuses is infiltrated densely with
eosinophiles but the lymph-follicular tissue is practically unchanged excepting for
areas where it is directly squashed out due to the pressure exerted by the growing
nodular lesions, which latter have the same histological features, as those described
in connection with the liver. In advanced lesions, however, it is not possible to say
if the lymph follicles, the sinusoids or the vessels enclosed in the supporting strands
of trabeculæ had formed the initial seat for the developing lesions. The presence
of the typical Schistosome ova in the centre of the pseudotubercles establishes the
nature of the pathogenic agent. Further some glands may reveal only an endarteri-
tis obliterans, eosinophilia and a hæmorrhagic appearance. Whether the mesen-
teric, portal, mediastinal or the bronchial glands are involved, the predisposition to
the deposition of calcareous salts in the lesions is very marked. One portal gland
was encountered with such extensive calcification that the normal glandular struc-
ture was practically lost. The naked eye picture of the nodules was however very
typical.
Lungs.—Helminthic nodules in the equine lungs have received a considerable
attention due to their importance in the differential diagnosis of glanders, and
the work of Angeloff [1907], Olt [1910] and Theiler [1918] in this connection are
noteworthy. In the case of the latter worker, it is unfortunate that no particular
attempt was made to prove the presence of worms in cases where eosinophilia
was noted. Although a cysticercus or a nematode was suspected Theiler states
that in the majority of lesions no parasites were found. In the figures presented
by Theiler [1918] and by Knowles and Slocock [1931], nodules in the lungs are
more frequent than those in the liver, whereas the present investigation has
brought out the greater frequency of nodules in the latter organ and this agrees
with Lingard's [1905] experience too. Nematodes have been suspected by the
workers in South Africa and Egypt and the frequency of: liver lesions in India is to
be expected from a knowledge of the other forms of intestinal schistosomiasis. It
SCHISTOSOMA INDICUM, MONTGOMERY, IN EQUINES
21
There may be little or no bronchial or peribronchial reaction. In order to explain
why the bilharzial lesions in the lung are not more numerous, it seems justifiable to
presume that some of the developing lesions abort prematurely due to the rupture
of the interalveolar septa which are structurally very fragile. Nematode lesions
again do not appear to be so predisposed to the deposition of calcareous salts.
But the most easily recognisable difference in the character of the two types of
lesions is the very definite and abrupt margin which invariably encircles the indi-
vidual lesion of bilharzial origin, whereas the boundary of a nematode lesion can
scarely be deciphered by the naked eye since there is a very gradual transition from
the obviously diseased to the suspiciously healthy zones. A rare nematode lesion
may resemble one of bilharzial origin, but the latter is so definite that a microscopic
examination is seldom necessary for the purpose of distinguishing it from the former
(Plate II, Fig. 3). This remark holds true for lesions in any organ.
Spleen.—A moderate enlargement and hyperæmia may be the only lesions in
this organ and they are due to portal stasis. As a result of diffusion of toxic pro¬
ducts, there may be an increase in the supporting tissue. Areas of infarction are
frequent and they may be as small as a silver two-anna coin. Actual nodules are
occasionally seen and in extreme cases the organ may be permeated with them.
Brown granules of blood pigment and eosinophiles may be seen here and there.
Peritoneal cavity.—Evidence of ascitic fluid may or may not be present. In cases
where it is present, it may be a serous flocculent fluid or a fluid streaked with blood.
DIAGNOSIS.
The problem of arriving at a correct dignosis of this condition in life is beset with
certain difficulties. Information on its geographical distribution and the clinical
history of a case are useful adjuncts but an assured diagnosis rests upon the discovery
of the specific ova in the fæces. As the ova may not appear with regularity in the
fæces until the case is advanced, fæcal examination on more than one occasion should
be carried out. Generally it is the flecks of mucus, which may or may not be blood
stained, that contain the ova, singly or in clusters. Since Schistosome ova are heavy
and settle down either on standing or on the fæces being centrifuged, the sugar floation
methods of diagnosis are not suitable. The sample of fæces therefore, is diluted
with 10 to 20 times its volumes of water and the solution passed through a fine
sieve to eliminate the coarse grains and fibres of vegetable matter. The filtrate is
then centrifuged or allowed to settle for 24 hours. Coverslip preparations of fresh
smears made from the sediment can be examined directly under the low power of
22 THE INDIAN JOURNAL OF VETERINARY SCIENCE AND ANIMAL HUSBANDRY [ III, I
the miscroscope or if the smear shows a considerable amount of animal matter, a
couple of drops of 5 per cent. caustic potash may be added to the smear to facili-
tate examination. A microphotograph of ova of S. indicum is to be found in Plate
II, Fig. 4 and this has been taken from a coverslip preparation obtained from
a sample of bovine fæces.
The appearances to be expected at post-mortem examination have already been
referred to, and for those who have not the opportunity of studying microtome
sections, the following methods of obtaining confirmation of a Schistosome infection
may be adopted :—
(a) Ferguson's [1911 ]—Digestion method. The ova can be conveniently
demonstrated in the tissues by digesting selected portions in 3 per cent.
or 4 per cent. caustic potash solution.
(b) Fairley's [ 1920 ] direct method. Large areas of the intestinal mucosa
can be examined directly under the microscope by fixing compara-
tively large portions of the intestinal wall between two glass slides,
which are kept in position by means of rubber bands. This method
is not suitable for highly thickened intestinal wall.
(c) Collection of the worms in copula or singly, from the portal blood or
by careful dissection of the smallar branches of the vessels of the
rectal mesentery, which is the most frequent site.
METHODS OF CONTROL.
Since the parasites are located in the vascular system, ordinary anthelminthics
do not reach them. Specific treatment with intravenous administration of tartar
emetic, emetin and antimosan is indicated. As treated animals are likely to be
reinfected, it is necessary to take steps for the prevention of infection. Attempts
should be made to destroy the parasite in some stage of its life cycle. Snail-
infested land should be treated with lime or dilute copper sulphate. Thorough
hygienic disposal of the excreta of schistosome-infected goats, sheep, bulls or
equines should be carried out, and in this connection it should be noted that
Montgomery discovered S. indicum in horses, donkeys and sheep at Muktesar,
Baldrey [ 1906 ] found similar ova in sheep at Lahore, and Fairley and his
coworkers [1930] found S. indicum infection in goats. Recently Mr. V. R.
Rajagopalan, one of the writer's assistants, has collected the same parasite from
(1) a hill bull at Muktesar, (2) a specimen of sheep's intestine from Sind, and (3)
the intestine of a plains bull, suspected of Johne's disease at Mona.
SCHISTOSOMA INDICUM, MONTGOMERY, IN EQUINES
23
DISCUSSION.
It will be noticed that in considering the morbid lesions of this form of equine
Schistosomiasis precedence has been given to the liver. The extreme form of
hypertrophy which the organ undergoes under action of the disease and its easily
recognisable gross changes have been noted. The condition has been designated
as a nodulated portal cirrhosis since those are the typical histological features of
the lesions. From the strict scientific standpoint, however, the disease is an
intestinal schistosomiasis, since it is by the involvement of the bowels only that the
parasite is enabled to attain the fulfilment of its life-history. In regard to the
liver lesions, it is of interest to note that Manson [ 1902 ] records the occasional
presence of small numbers of schistosome ova in the liver of men., but refers to no
pathological lesions caused by them, and Scheube [ 1903 ] records the finding of ova
in a man's liver with slight cirrhosis. Credit is due to Symmers [ 1903 ] for being
the first to record the finding of china-white nodules of sizes varying from a pin-
point to a split pea, periportal fibrosis and for describing extensive lesions of
" claypipe stem " cirrhosis of the liver. Miliary tubercle-like nodules were encoun-
tered by Katsurada [1905] and since then the specific liver lesions of schistosomiasis
have received considerable attention in the publications of Wooley [ 1906 ],
Phalen and Nichols [ 1908 ], Letulle and Nattan-Larrier [ 1909 ], Houghton [ 1910],
Jouveau-Dubreil [ 1913 ], Lampe [ 1925 ] and others. Reference must also be
made to Montgomery [ 1906 ] who obtained the majority of his collection of
S. indicum from the equine liver after its removal from the body, from the pancrea-
tic veins in two cases and from the mesenteric vessels of all the eight cases examined.
Although he noticed the liver to be enlarged and, in nearly all instances, to be studded
with small pearl-like calcareous nodules, sometimes as large as a pea, well defined by
a fibrous capsule and easily enucleated, he considered them to be different from
those described by Symmers [ 1903 ] but possibly of the same origin as Mazzanti's
filarial lesions, referred to by Lingard [1905]. With regard to "pipe stem"
cirrhosis, Montgomery went on to say that '' in equines this does not appear to be
present, though in one case a similar naked eye condition existed, but in the lesions
ova could not be found." An explanation of the persistent failure of the writer to
find adult schistosomes in the histological sections (excepting a single notable case
mentioned already) would seem to be that the worms inhabit the larger branches
of the portal trunk whereas the nodules were situated in the finer ramifica-
tions only and further that the worms may have escaped with the portal
blood during post-mortem examination. As regards the consistent failure of
Montgomery to record any definite lesions, in spite of the presence of numbers of
the parasite, his own view that the animals examined had but recently become
24 THE INDIAN JOURNAL OF VETERINARY SCIENCE AND ANIMAL HUSBANDRY [ III, I
affected is probably partly true, and in other cases there may have been some
resistance on the part of the host.
The occurrence of a severe intractable debility as a prominent symptom in
this equine schistosomiasis has been emphasised earlier in this paper. Hodgkins
[1920], Sewell [1921], Allen [1923] and Steevenson [1924 and 1930] have
recorded certain experimental data obtained by them in their attempt to elucidate
the problem of persistent debility amongst army horses in India and there is
little doubt that a number of these cases are due to habronemiasis or strongylosis,
but on the other hand, it has been shown above that on further investigation a
number of such cases occurring amongst army horses are in reality a schistosomia-
sis. It is not possible to say with certainty at this stage what proportion of the
cases of persistent debility are due to each of these three causes, but a preliminary
survey of the samples of outside specimens collected at Muktesar since 1921 has
revealed only but half a dozen cases of lesions in the liver and lungs which can be
ascribed to nematode larvæ, as compared with a large number of cases now proved
to be bilharzial. With regard to gastric habronemiasis. however, the worms and
the stomach lesions caused by them are so commonly found in equine subjects in
India that probably it would not be wrong to state that as many as 95 per cent.
of animals harbour these parasites, but it is probable that in the majority of those
cases without stomach lesions little harm results. This statement would seem
warranted in view of the findings in Egpyt by Knowles and Slocock [ 1931 ] that
86 per cent. of animals infected with Habronema were in good or fair condition.
On the whole, therefore, it appears that the conditions described in this paper, due
to infection with S. indicum, apart from malnutrition, are the most important
factor in the causation of persistent debility of equines in India.
ACKNOWLEDGMENTS.
The author's thanks are due to Mr. G. D. Bhalerao, M. Sc., Helminthologist,
for confirming the specific identity of the worm ova ; to Mr. J. Sunder Rao, Artist,
for the prompt execution of the photographic illustrations. Further the author is
greatly indebted to his chief Mr. F. Ware, F.R.C.V.S., I.V.S., for evincing keen
interest and for granting every facility for the present investigation.
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DESCRIPTION OF ILLUSTRATIONS.
Plate I.—Macroscopic lesions three-fourths the natural size.
Liver.—Specimen No. 1532 shows a number of the specific pseudotubercles through the trans-
parent capsule. The majority of the nodules are discrete but a few are coalesced.
Specimen No. 562 iii.—Liver capsule shows ' miliary ' pseudotubercles.
Specimen No. 750-B.—A conglomeration of calcareous, pea-sized nodules has produced an
elevation of the hepatic surface.
Specimen No. 1558.—Section through the liver parenchyma shows numerous pearl-white nodules.
Section on the right shows degrees of perihepatitis.
Specimen No. 993 shows hard indurated nodules on the capsule.
Intestine.—Specimen Nos. 562, ii & 1931 (left).—Peritoneal surface of the intestine shows
distinct nodular excrescences.
Specimen Nos. 1931 (right) & 909 show the intestinal mucosa with the typical minute ulcers
characterised by black hæmorrhagic surface.
Lungs.—Specimen Nos. 1481 & 750-A show the lung pleura, the former affected with a
single discrete nodule and the latter with an accumulation of more or less distinct pseudo-
tubercles.
Specimen No. 1562—Lung parenchyma shows discrete and coalesced nodules.
Plate II.—Fig. 1. Low power microphotograph of a portion of diseased liver showing how
the organ is packed with nodules in various stages. One or more circular rings can be
seen in the central pith of each nodule. Empty spaces due to the central degenerated area
having fallen out are seen also.
Fig.2.—Low power microphotograph of a portion of affected intestine. Varying sizes of the
nodular lesions are seen involving all the coats with a preponderance of lesions in the sub-
mucosa and subserosa. The mucosa appears to be more or less intact.