NationalLibraryOfScotland/medical-history-of-british-india huggingface dataset:
THE ETIOLOGY OF BURSATI.
221
the surface. When the surface is shed, the sore is smooth, but as granulations
start, an irregular worm-eaten picture is presented. The degenerative lesion is
seen to be active at more than one focus, the healing of the first sore being followed
by the appearance of fresh ones at the same site or elsewhere. It seems obvious
from this that the supply of the infective agent is continuously maintained
throughout the Bursati season and this has been repeatedly confirmed in micros-
copic sections. In an equine already affected or showing what has been called a
Bursati diathesis [ Collins, 1874 ], an accidental wound may assume the typical
clinical features, but it is very doubtful if ordinary wounds on non-infected cases
ever develop into the genuine sores of Bursati. Pruritus may be intense at the com-
mencement, but if the sores are protected from flies, the affected animal does not
show much evidence of discomfort, once the disease has become established.
The clinical features of Bursati sores are typical, but the most distinctive of
all is the presence of what have been called kunkurs. These are yellowish bodies,
globular and of the size of a millet seed or a pea, or elongated and about the size
of a rice grain, found in varying numbers embedded in little pockets or fistulae in
the limited patches of the diseased tissues. The kunkurs are soft and contain
granular flesh coloured material when young but are hard and fibrous or even
calcareous when old. Deposition of calcareous salts is generally inappreciable but
occasionally it may be very pronounced. When pressed between glass slides, well-
formed kunkurs behave as a hard elastic body. They have a smooth surface and
can be easily shelled out on pressure, leaving pockets of variable dimensions in the
mother tissue. If an incision be made into the tumefied tumour, the underlying
disease process is found to extend well beyond the limits of the superficial sore and
more numerous kunkurs are seen in the subcutaneous tissue. Most writers have
described caseous and calcareous degeneration in kunkurs but there seems to be no
resemblance of these to tuberculous changes. The commonest predilection seats
of the lesions are provided by the angles of the mouth, the fetlock and pasterns,
the prepuce and the face just below the eyes, but occasionally the lesions may occur
in any other situation liable to persistent and mild abrasions.
The occurrence of Bursati kunkurs in internal organs such as the liver, lung,
kidney, etc., has been reported by several workers [ Burke, Meyrick, Steel, 1881,
Lingard 1905, and others ]; but it has been shown in another article by Datta
[1933] that the conditions of '' perihepatitis and small filarial nodules" of
Lingard [ 1905 ], "calcific diathesis " of Meyrick [ 1878 ], and " Calcareous de-
generations in the horse " of Smith [ 1885 ], are due to infection with Schistosoma
indicum. It has to be conceded, however, that at least one internal organ—the
lung—is sometimes affected with genuine lesions of Bursati. Meyrick [ 1878 ]
222 THE INDIAN JOURNAL OF VETERINARY SCIENCE AND ANIMAL HUSBANDRY [III, III.
and Burke [ 1884 ] found Bursati horses showing lung lesions, and Hodgkins [ 1910 ]
describes a case of lung affection in which the organ in stated to have been the
subject of an intensive Bursati invasion, being crammed with nodules of varying
sizes, and the pleura covered with whitish yellow patches beneath which were
pieces of kunkur ranging in size from a hazel nut to a pin's head. These appear
to be the only recorded cases in India which may be considered as cases of pul-
monary habronemiasis in addition to the following. From a severe case of Bursati,
mule No. 738 of the L. A. T. T. Coy., Lahore Cantt., destroyed on humane grounds,
a specimen of lung showing kunkurs, portions of skin lesions, and a sample of
worms, collected from the stomach, were obtained through the kindness of Major
V. C. Leckie, R.A.V.C. Histological examination of the skin and the lung revealed
the presence of actual habronema larvae and the typical lesions in both the organs.
This Bursati case is of considerable interest, as it is the first definite case of so-called
internal Bursati and pulmonary habronemiasis to be proved in this country. It
should be noted in passing that the stomach worms collected from this case were
identified as Habronema muscae.
Lingard is the only worker in India, who has described calcareous nodules on
the membrana nictitans, and further he has furnished a picture of the same, which
bears some resemblance to the conjunctival lesions described by the Australian
workers, Lewis and Seddon [ 1918 ]. When bursati lesions occur on the limbs,
they present a circular contour of variable diameter with an even raised margin.
The sores present irregularly elevated granulations, and on the slightest manipula-
tion, they bleed readily. The slow inflammatory processes progress by contiguity
of tissue, often receding in one place and advancing in another. There may be a
thin, brownish scab formation or a blood-streaked serum may be discharged. Pus
formation is seen but rarely, and that after secondary infection. When healing
takes place, which process is very slow, the superficial skin becomes thickened,
depigmented and shows sparse hair growth. The experience of the present writer,
which he has confirmed histologically, shows that the organised or partly organised
lesions persist under the apparently wholly cicatrised wound and show considerable
predisposition to attacks in the following year, and this is in conformity with the
experience of "Max " [ 1876 ]. Lesions in fresh and also very distant sites occur
quite frequently in an affected subject. The lesions below the eye follow very
ciosely the tract that lachrymal secretion or tears keep moist, and present an elon-
gated, excoriated form with irregular edges and multiple surface erosions. Due to
structural peculiarities of the prepuce, the lesions there show a marked tendency
towards extension and calcification and the individual kunkurs are generally of a
large size. Paraphymosis is often met with as a complication in stallions.
THE ETIOLOGY OF BURSATI.
223
Apart from the local lesions, there is scarcely any systemic disturbance, and
bursati does not impair an animal much from its serviceable qualities unless the
disease has assumed a very extensive form, or has affected the penis, the seat of
saddle or the angle of the mouth. The disease generally occurs in old animals but
young animals are also affected. As a rule, there is only a single case in a stable,
and the disease has not been observed to spread by direct or indirect contagion to
other equine subjects, housed in the same or in an adjoining stable. Removal
of a diseased animal, in the height of the Bursati season, to particular places, e.g.,
Jhansi, or to the hills, has been observed by more than one worker [ Burke, 1881,
Holmes, 1914 ] to exercise a very salutary effect on the course of the disease. It is
said that cases of Bursati are not so frequent now-a-days as compared with what
they were a generation ago, and this may probably be explained as being due partly
to the better hygienic conditions now obtainable for our animals, and partly to a
diminution of the number of horses in the country.
PATHOLOGICAL HISTOLOGY.
Unlike other aspects of Bursati, its pathological histology has been dealt with
by remarkably few workers. Even in Holmes' description, superseding as it does
the earlier and more imperfect attempts, a consideration of it has been dismissed
in about twenty lines. Credit, however, is due to him for having described for the
first time certain essential features of Bursati, e.g., the presence of a marked eosi-
nophile infiltration and what he terms, empty spaces of varying sizes. From the
foregoing remarks it is clear that a fuller and, at the same time, a more correct
description of the histological features of these growths is certainly indicated at this
juncture. Again, for the successful elucidation of further problems regarding the
mode of infection and efficient methods of diagnosis and control, the definite and
significant histological findings recorded below, should serve as helpful indications.
Materials for the present studies were provided by a valuable collection of 26
samples of preserved growths, received at this Institute from time to time since 1922
to date, from different parts of India. Of these a few were neoplastic or merely
inflammatory in nature; and although some samples were in a bad state of preserva-
tion it is satisfactory to record that the same helminthic incitant was consistently
demonstrated in 17 samples, obtained from such distant parts as Assam, United
Provinces, Hyderabad-Deccan, the Punjab and North-West Frontier Province.
Further, in these positive cases and in 5 other samples from the same collection
typical microscopic lesions, which in the light of present experience may be consi-
dered as of more value in diagnosis than even the worm larvae, have been persis¬
224 THE INDIAN JOURNAL OF VETERINARY SCIENCE AND ANIMAL HUSBANDRY [III, III.
tently detected (Plate XVII, fig. 1). Experience has repeatedly shown that the
demonstration of the actual parasite, once the typical lesions had been seen, depended
upon the examination of a sufficient number of serial sections, although the growths
in a majority of cases were excised only at a late stage of the disease, when one
might have expected that the most interesting stages of the disease process had
passed off.
The usual picture of Bursati consists of an inflammatory granulation tissue in-
volving the skin and the subcutaneous tissue, characterised by a profound eosino-
philia and the presence of well-defined areas of degeneration. These areas represent
sections of the so-called kunkurs (Plate XVII, Fig. 1), which have been known since
the earliest times to form a typical clinical feature of these growths, and in the
centre of these, sharply margined empty spaces are frequently seen. Since the
causal parasites are very fragile and soon lose their distinguishing features, it is
often difficult to detect them without great perseverance. Only odd parasites are
found actually lying free in the supporting matrix of the growth. The large
majority of the larvæ are found enclosed in what appear to be capillary vessels,
the majority of which are probably venules (Plate XIV, fig. 2 and Plate XV, fig.
2), since in the centre of the kunkurs one often observes a delicate-walled structure
with a well-defined lumen and containing eosinophile cells or blood pigment. In
the earliest stage of an individual lesion, the worm larvæ are found invariably to
form the nucleus of the commencing degenerative changes (Plate XV, fig. 1); and
concentration of toxic products appears to be much higher in the immediate sur-
roundings of the worm than at the periphery, where the degenerative process gradu-
ally subsides into the healthy tissue. Since the toxin diffuses for the same distance
in all directions, the degeneration area is often seen to have a round or oval contour
(Plate XVII, fig. 1). In early lesions around the parasite the cellular constituents
predominate, the earliest picture being represented by an accumulation of lympho-
cytes in foci, supported by scanty, thin, fibrillary strands of connective tissue,
disposed in a loose and circular manner. In the centre of these, a blood vessel with
the enclosed larva is almost invariably to be seen as forming the nucleus for the
nodule (Plate XVIII, fig. 1). In a few sections, however, the typical early lympho-
cytic reaction has been seen around an unoccupied capillary. In others the usual
appearance of diffusive degenerative changes around a vessel, containing eosinophile
leucocytes mainly, but no worm or its remnants, has been seen. The reactions are
obviously due to the parasite in both these types of sections, it having been missed
as a result of the sectioning knife passing at a different level. Around the indivi-
dual nodular lesions an attempt at delimiting the parasitic action is manifested by
the formation at most of two or three concentric rings of connective tissue, but the
THE ETIOLOGY OF BURSATI.
225
process of ringed fibrosis has never been seen to have advanced to any great degree
compared with, what one finds in Schistosomiasis indicum in the horse, for instance.
The connective tissue strands of old growths may be very dense and appear to be
almost cartilaginous in texture.
The sequence of events in the formation of kunkurs would appear to be as
follows. The earliest tissue reaction against the parasite is represented by the
lymphocytic infiltration, followed by an aggregation of plasma cells, neutrophile
leucocytes and eosinophiles. Plate XIV, fig. 1, shows a typical habronemic
abscess in the skin, consisting practically wholly of lymphocyte cells arranged in a
nodular form around the worm larvæ, as one usually finds in the gastric lesions due
to H. megastoma and no eosinophiles or fibrosis are seen at this stage. Necrosis
and karyorrhexis of the nuclei of eosinophiles and other cells then takes place.
While necrosis is in progress around the parasites, one finds at the periphery of the
necrotic mass, young fibrous tissue cells massing together with giant cells. The
supporting matrix between the kunkurs is provided by typical granulation tissue in
various stages of development, generally with a dense accumulation of eosinophiles
in lymph channels and proliferation of endothelial cells and fibroblasts. In a
growth of very recent formation the superficial covering is composed of unaltered
epithelium with extreme dilatation and engorgement of subcutaneous capillaries,
which generally run perpendicular to the surface epithelium. Plate XIV, fig. 2,
shows a section through the periphery of a kunkur, which presumably was formed
in the course of one of these perpendicular capillaries. Exudation into the epithe-
lial covering and consequently a hazy appearance of individual cells is later seen,
leading eventually to superficial breaches or ulceration. Generally the hair folli-
cles are unaffected in the early stage, excepting for a tendency towards a collection
of the exudate in them, but sometimes a few hair follicles are seen to form sites of
actual degenerative lesions as in Plate XVII, fig. 2. The surface epithelium is
ulcerated more or less extensively in the active stages, and an attempt at repair by
an ingrowth of the surface epithelium is seen now and again. It is a noteworthy
fact that, generally in the commencing disease, a more pronounced reaction than
could be expected from a surface infection, has been seen in the deeper parts of the
subcutis. Contrarily, Plate XVI, fig. 1, however, is the picture of an exceptional
section in which the superficial epithelium shows a degenerative involvement, but
careful examination failed to reveal the presence of any parasitic incitant and the
subcutis appeared to be normal except for the presence of some eosinophiles here
and there. An idea of the marked degenerative power possessed by the parasite
can be gathered from a study of sections, and from this, it appears improbable that
penetration of the surface skin by the larva, without leaving any trace of the track
226 THE INDIAN JOURNAL OF VETERINARY SCIENCE AND ANIMAL HUSBANDRY [III, III.
followed by it, can really take place, since a single larva in the subcutaneous situa-
tion has been seen to produce quite large areas of degenerative foci, probably due
in part to the burrowing nature of the exudative fluid. In a number of these large
degenerative areas, one can make out only a few interlacing strands of adult con-
nective tissue and an occasional capillary in an otherwise homogeneously
eosinophile mass. In places, organisation is seen to have taken place, either whole
or in part; in others, it has scarcely started. Any parasitic debris which is not
removed by phagocytosis, is soon made innocuous by the deposition of lime salts.
Lesions in the prepuce show a very marked predisposition to calcification and to
extension, but these features have been seen occasionally in the lesions in other
situations.
The most outstanding and fundamental changes, however, concern the blood
capillaries. When the degenerative changes in the endothelium of the capillary
have not gone very far, a thin layer of a delicate endothelium can be recognised
without much difficulty (Plate XVIII, fig. 2). Certain vessels show varying degrees
of endarteritis with partial or total obliteration of the lumen by the replacing
connective tissue and also an increase in the amount of elastic tissue at places.
The commencing inflammatory changes in the vessel wall are represented by a
tendency to diffuse staining (Plate XV, fig. 2). More severe inflammations are
manifested by a marked dilatation of the wall due to infiltration with exudative
cells. The degree of exudation apparently determines whether only the endothe-
lium is to be proliferated or shed, or the vessel wall is to undergo necrosis, calcifi-
cation or total disruption. The desquammated endothelial cells can be seen lying
scattered in the periphery of the thrombus mass formed in an affected vessel, or
where the wall has given way, the endothelial cells may be wandering free in the
matrix of the growth.
It is important to note here that apparently healthy worms in cross — or lon-
gitudinal sections have been seen lying quite free in the more or less dilated lumen
of capillary vessels (Plate XIX, fig. 1) with varying degrees of degenerative change
in the vessel wall (Plate XV, fig. 2). On measurement, larvæ are seen to vary in
size within certain limits and from this, one presumes them to be in slightly
different stages of development. Usually the larvæ are seen lying straight and
singly but occasionally a single worm in a coiled form (Plate XV, fig. 1) or several
worms may be encountered in a larger sized capillary. A central intestinal canal
and a number of cuticular ridges at regular intervals can be seen in cross-sections,
(Plate XV, fig. 2) or if the parasite has been cut longitudinally, the characteristic
striations, both longitudinal and transverse (Plate XVIII, fig. 1), can be made out
in the worm structure inside the vessel. Expert helminthological opinion was
THE ETIOLOGY OF BURSATI.
227
obtained from Mr. G. D. Bhalerao, M.Sc., who identified the larvae, as those of
Habronema spp. In certain sections, little, if any, degenerative changes in the
parasite can be discerned; in other sections an empty, ovoid or spiral space, which
was also seen by Holmes [1914], containing a granular debris, apparently an impress
of an escaping or a degenerated parasite fallen out in sectioning, is to be noticed.
The anterior and posterior ends of the causative larva have been seen in more
than one section (Plate XIX, figs. 2 and 3). As the anterior ends, which
were seen in two cases, appeared to be more typical than the posterior, they were
submitted to a careful examination. The vestibule was found to be cylindrical
in both the cases and to measure 36.5μ and 39.0μ. in length, the measurements
corresponding very closely to those of H. muscæ ; and from this, it would appear
that the larvæ, in all probability belong to this species. As a suggestion has been
made by a worker that different species of Habronema may be responsible for
growths in different parts of the horses' body, it may be noted that one of the
above two specimens was obtained from the prepuce of a horse and the other from
the neck of another subject.
It is interesting to add here that the histological features of Bursati have been
studied, side by side, with those of a definite case of cutaneous habronemiasis
of the horse, as it occurs in Greece. The tissues from the latter were obtained
through the courtesy of Messrs. Pheloukis and Knithakis of the Veterinary Research
Laboratory of the Ministry of War at Athens. As a result of these studies, the
Grecian condition was found to be identical in histological features and in the
characters of the parasitic larvae with Bursati, as it occurs in India.
DISCUSSION.
The statement of such a distinguished man as Railliet (1915) that " In India
one still confuses, under the name of Bursati, cutaneous lesions caused by moulds
and by nematodes " appears to be partly responsible for having kept alive the
general impression in India, Egypt and elsewhere that at least two distinct disease
entities, mycotic and helminthic, are included under the term in this country.
Apart from this confusion, doubts, regarding the probability of a habronemic
origin of this condition, have been expressed in rather emphatic terms by Freeborn,
Hart and Howell [1927], who hold that the infestation of Bursati by Habronema
is accidental and does not constitute the etiological factor. Among others disin-
clined to accept the habronemic origin, is Baylis [1929], who states: " It seems
conceivable however that the sores may be produced first by some other agency
and the worms be deposited in them by flies."
228 THE INDIAN JOURNAL OF VETERINARY SCIENCE AND ANIMAL HUSBANDRY [III, III.
Although the invariable association of Habronema larvae with Bursati lesions
has been shown in the present histological studies, it is to be admitted that the
mere presence of worms is by itself not enough for the purpose of casually
connecting them with the growth until the disease has actually been reproduced
under artificial conditions. Again, the failure on the part of several workers [Van
Saceghem, 1919, and Hill, 1920] to induce the Habronema worm to penetrate the
intact skin would seem to provide enough room for the presumptive view,
advanced by Roubaud and Descazeau [1921], that the presence of pre-existing
abrasions or broken cutis is essential for the production of so-called Summer
Sores, and the obvious method of proving this would be to create the disease ex-
perimentally by introducing into wounds Habronema larvae actually derived from
the proboscis of flies. If a more reasonable explanation regarding the production
of natural cases of the disease were not forthcoming, parenthetically it may be
said that one such is available and is given below, the invading Habronema larvae
would be reduced to the status of mere secondary organisms ; and the condition,
etiologically, would present some analogy to myiasis, which in a great majority of
cases is caused by fly larvae deposited in previously existing wounds. On the
other hand, it is noteworthy that while in myiasis the invading larvae duly grow
to maturity, Habronema larvae encountered in Summer Sores and Bursati represent
only erratic forms, which, after wriggling about for a while in the resulting
inflammatory granuloma, die and lie embedded in degenerated areas, the kunkurs,
as observed upon histological examination of diseased tissues. The question
therefore arises if cutaneous habronemiasis represents an accidental secondary
condition, or whether it can be brought into the category of a normal disease
entity, such as one finds in gastric habronemiasis, where the stomach of the equine
represents the normal habitat for the developing worms. The death and degenera-
tion of the worm in the kunkurs cannot be a feature necessary for the fulfilment
of its life-history, and it seems certain that their death is due to some accident or
misfit in the host-parasite relationship, which they cannot help. In describing
certain noteworthy histological findings, it has been stated above that the most
outstanding and fundamental changes in Bursati concern the blood capillaries, and
that in the centre of early kunkurs, a blood vessel with the enclosed larva is
almost invariably to be seen as forming the nucleus for the individual nodule-for-
mation. Again healthy worms have also been seen inside apparently healthy
vessels (Plate XVIII, fig. 2). These findings bring out significantly the close
analogy of Bursati to human filariasis, due to Filaria bancrofti, where the worms
accidentally get held up in the capillaries producing the characteristic embolism,
while the great majority of the worms float about in the circulating blood. This