NationalLibraryOfScotland/medical-history-of-british-india huggingface dataset:
FURTHER OBSERVATIONS ON BOVINE NASAL SCHISTOSOMIASIS
269
The lesions in the nose of this experimental calf were small hard yellowish
nodules, each about the size of a millet seed, scattered over the mucous membrane
of the nose. These nodular abscesses burst and subsequently healed making way
for a fresh crop. These small lesions continued to appear and disappear in
gradually diminishing numbers month after month, but there were no signs
of cessation of the lesions in the course of over a year. The progressive diminution
in the number of ova in the nasal discharge may be due either to a retardation
of ova production or to the increasing difficulty of the ova in making their way
out of the nasal mucous membrane which gets thickened as a result of tissue
repair.
The symptoms shown by this experimental calf were only occasional sneezing,
throwing out some mucous which sometimes contained streaks of blood. But
for the presence of the small nodular abscesses and the occasional manifestation
of discomfort in the nose, a casual observer would not have suspected the animal
as one harbouring nasal schistosomes. This experiment confirms the previous
work of the writer that cercariae Indicae XXX Sewell 1922 are the larv 1 forms
of S. nasalis and that S. spindalis does not produce nasal schistosomiasis.
IMMUNOLOGICAL CONSIDERATIONS.
It has already been said that buffaloes in general and some bovines in parti
cular do not develop gross lesions in the nose, and the infestation is more or less
" symptom-free " though nasal schistosomes are present. The evidence deduced
from experimental calf No. 516 seems to suggest that such differences in the mani
festation of grades of lesions may depend on some degree of immunity against
the later infestation with S. nasalis derived from a pre-existing infestation with
S. spindalis.
On the subject of immunity against schistosomes many workers have demon
strated the presence of a definite bilharzial anti-body in the blood of animals and
men suffering from schistosomiasis. Fairley and Jesudasan [1930] found in goats
a primary rise of the anti-body response following cercarial invasion, and then
a second rise which was related to the defunct schistosomes in portal thrombi.
These workers found that the anti-body response remained at a certain level
even during the second year of the disease. It is clear therefore that an anti
body is produced in the system either stimulated by the schistosomulāe in the
early stages, or by the dead or dying adult worms during the establishment of
a biological equilibrium between the host and the parasite.
Ozawa [1934] immunised some dogs against S. japonicum and found that on
reinfection, the immunised animals harboured fewer parasites than the control,
and that many of the schistosomes in the former showed signs of degeneration.
270
THE INDIAN JOURNAL OF VETERINARY SCIENCE AND ANIMAL HUSBANDRY. [V, III
Fisher [1934] after analysing the previous work of others on the subject,
concludes that two types of mechanisms are involved in the production of anti¬
bilharzial immunity response in animals. One of them manifests itself after
primary infestation with cercariae against a subsequent invasion which he names
a response. The othe one which he calls β response, manifests itself in bringing
about a diminution in the number of adult parasites in the body till a biological
equilibrium is established. He suggests that these two mechanisms are inter
related, because the β response can be speeded up by exposure to cercariae.
He further states that the a response is capable of being overcome in some cases
by a heavy exposure to infestation.
Dixon [1934] observed in Katanga, a falling off in the infestation rate with
S. haematobium in adults after 15 years of age and ascribes this to an immunity
rapidly acquired by them. Perhaps this immunity response is speeded up by
frequent exposures to cercariae, while bathing in the river which is the source of
infestation.
From the researches of Fairley and his collaborators, it would appear that
the β response is stronger as long as it lasts and until a biological equilibrium
is established, than the a response. According to Fisher the α and β responses
work either jointly or severally. These two mechanisms would appear to be
responsible for immunity responses and since they are variable, the degree of
immunity also varies accordingly for different degrees of subsequent infestations
being established in the animals. In other words, the degree of immunity is
directly dependant on the intensity of initial infestation, hence the anti-body
content in the system of the host varies accordingly and on this depends subse
quent successful infestation.
Various workers have found that the anti-body in schistosomiasis is of a
" group " nature, whatever may be the species of schistosome which provokes the
response. If group immunity is what is produced in schistosome infestation,
then a subsequent infestation with S. nasalis is bound to be mild.
S. spindalis is met with in buffaloes, bovines, sheep, goats and even equidae,
which means that it is not very selective in its host and is widely spread.
S. nasalis, on the other hand, is found only in buffaloes and bovines, hence it is
more selective in its host and is less widely spread than the other worm. There
fore S. spindalis being more widely found has better chance of pre-infestation and
confers varying degrees of immunity against subsequent infestation with S. nasalis
in the animals concerned.
The buffalo, which has been proved to be the normal host of S. spindalis
[Fairley and Jesudasan 1930], has the habit of wallowing in water for hours
together daily or whenever opportunities occur. In this animal, therefore, varying
numbers of schistosome cercariae, frequently get into the system through the
FURTHER OBSERVATIONS ON BOVINE NASAL SCHISTOSOMIASIS
271
skin in addition to what may be ingested, after the primary infestation has estab
lished itself. The immunity responses in these animals are perhaps similar to
what obtains in man [Dixon 1934]. In this class of animals the β mechanism
should have been speeded up rapidly and perhaps it ceases to operate early enough
after the biological equilibrium between the host and the parasites is established.
Hence in such animals the β response if present, is very low in its level as com
pared with the α response. Nevertheless these two mechanisms together stimulate
a degree of immunity response in the body of the buffalo against subsequent
infestation. Obviously therefore in the buffalo, as in Ozawa's dogs, subsequent
infestation with the cercariae of S. nasalis does not produce such an acute form
of nasal schistosomiasis with gross lesions as in most bovines.
The bovines apparently do not get the same bulk of natural infestation with
S. spindalis as the buffalo, since their habits are different. Yet they are not all
free from infestation with those worms. In them the chief mode of infestation
is by ingestion. Fairley [1930] and Rao [1934] found that bovines get a less
intensive infestation of schistosome cercariae by ingestion. Therefore, it would
appear that the intensity of natural infestation in bovines with S. spindalis is
very much less than in the buffalo, hence the degree of anti-bilharzial immunity
is also comparatively low. This seems to be the reason why many bovines suffer
from nasal schistosomiasis with gross lesions, while some bovines fail to show any
marked clinical symptoms. The experimental calf No. 516 already referred to
showed that with a previous infestation with S. spindalis subsequent infestation
with S. nasalis produced only a symptom-free disease. Incidentally it may be
said here that these two schistosomes have different habitats in the same
animal, hence the value of the immunity responses is better assessed by
counting the number of adults in each case.
The above observations on the immunity problem in schistosomiasis makes
it doubtful if repeated infestation with cercariae will enhance the severity of an
attack first contracted. On the other hand, it should act in reducing it.
Rao [1934] has mentioned that he found S. spindalis in the portal system of
calves experimentally infested with nasal schistosomiasis and he has given reasons
for that finding. It must be remembered that in those calves the infestation
was simultaneous, hence no question of immunity seems to arise, as in the case
of calf No. 516 in the present experiment.
NASAL SCHISTOSOME AND HORN CANCER.
A point of interest which the writer wishes to record is the finding of what
appeared to be bilharzial pseudotubercles in a piece of growth suspected for car
cinoma from the base of the horn of a bullock. The structure of the growth was
found to be denser than that of the growths in the nose. In some sections of
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THE INDIAN JOURNAL OF VETERINARY SCIENCE AND ANIMAL HUSBANDRY. [V, III
pseudotubercles what appeared to be shrivelled up ova of the nasal schistosome
were found (Plates XXIII and XXIV). At the present moment we do not know
if the nasal schistosome could be an etiological factor in causing horn cancer in
bovines. Endeavours are now being made to work on this interesting problem
and it is hoped to obtain additional information on this.
SHEEP AND NASAL SCHISTOSOMASIS.
It has been possible to examine nasal washings of some sheep in the endemic
areas of nasal schistosomiasis, but no ova of S. nasalis could be detected. Sec-
tions of the nasal mucous membrane of a sheep, showing symptoms simulating
the condition in cattle, proved negative for that disease. Hence the question of
the susceptibility of sheep to that disease appears to be doubtful. Rao [1932]
recorded ova of S. nasalis in the nasal discharge of a sheep. It is more than
likely that the nasal washings from that sheep was contaminated with the nasal
discharge from bovines which were also being examined at the time in that
village.
SUMMARY.
1. The length frequency curves of the ova of S. nasalis and S. spindalis
provide additional proof that these two worms are different.
2. No abnormal shapes of ova of S. nasalis could be detected in mature
ova examined.
3. The previous experiments of artificial infestation with cercariae indicae
XXX Sewell 1922 to produce nasal schistosomiasis are confirmed.
4. The buffalo and some bovines appear to have a partial immunity
conferred by S. spindalis against a later infestation with S. nasalis.
5. The presence of what looked like ova of S. nasalis in a growth from the
base of horn of a bullock is recorded.
6. Susceptibility of sheep to nasal schistosomiasis appears to be doubtful.
Acknowledgments.—I am grateful to Mr. T. J. Hurley, M.R.C.V.S., D.V.S.M.,
Principal, Madras Veterinary College, for obtaining for study from Tiruvannamalai
a sheep with symptoms simulating nasal schistosomiasis. My thanks are due
to Mr. S. Vaidyanatha Mudaliar for the assistance rendered.
REFERENCES.
Bhalerao, G. D. (1932). On the identity of the Schistosome found in cases of
Bovine Nasal Granuloma, etc. Ind. Jour. Vet. Sci. & Anim. Husb. 2, 341.
Datta, S. C. A. (1932). Etiology of Bovine Nasal Granuloma. Ibid, 133.
Dixon, P. K. (1934). Age incidence of Schistosome infection ; and species of
malarial parasite in Katanga. Trans. Roy. Soci Trop. Med. & Hyg. 26, 505.
Ind. Jour. Vety. Sci. & Anim. Husb. Vol. V, Pt. 3.
PLTAE XXIII.
FIG. 1.
FIG. 2
Photo-micrographs of sections of a growth from the base of horn. (Note the pseudo-tubercles in
Fig. 1 (×20), and shape of the crumpled shell of the ovum in Fig. 2 (×80).
Ind. Jour, Vety. Sci. & Anim. Husb. Vol. V, Pt. 3.
PLATE XXIV.
FIG. 1.
FIG. 2
FIG. 3
Photo-micrographs of a growth from the base of horn. Note the crumpled ova and actino body in Figs. 1—3 (× 60).
FURTHER OBSERVATIONS ON BOVINE NASAL SCHISTOSOMIASIS
273
Fairley, H. N., & Jesudasan, F. (1930). Studies on Schistosoma spindale.
Ind.
Med. Res. Memoirs, No. 17, Part IV.
Fisher, A. C. (1934). A study of Schistosomiasis of the Stanley Ville District of
the Belgian Congo. Trans. Roy. Soc. Trop. Med. & Hyg. 28, 277-306.
Ozawa, M. (1934). Experimental Study of acquired immunity to Schistosomiasis
japonica. Japanese Jour.Exper. Med. 8, 79. Quoted by Fisher, A. C. (1934).
Rao, M. A. N. (1934). A preliminary Report on the successful infection with Nasal
Schistosomiasis in experimental calves. Ind. Jour. Vet. Sc. & Anim.
Hus. 3, 160-162.
Rao, M. A. N. (1934) A comparative study of Schistosoma spindalis Montgomery,
1906, and Schistosoma nasalis, n. sp. Ibid. 4. 17.
I
SELECTED ARTICLES
THE BEARING OF THE PHYSIOLOGY OF PARASITIC
NEMATODES ON THEIR TREATMENT AND CONTROL.
BY
GEOFFREY LAPAGE, M.D., M.Sc.,
Institute of Animal Pathology, University of Cambridge.
The following abstract from the article is published with the kind permission of the
Imperial Bureau of Agricultural Parasitology, St. Albans.)
There is no need nowadays to emphasise the economic importance of the
study of parasitic nematodes. They are the cause of some of the most serious
and least controllable of human diseases, especially in the tropics ; the unanimous
opinion of agricultural authorities is that they are one of the most serious menaces
to the continued success of our domestication of animals useful to man ; in some
of our colonies they threaten the very existence of the sheep-rearing industry;
and they are also the cause of incalculable suffering and disease in animals which
man is not concerned to conserve. The control of them is, therefore, one of the
most important problems which the medical man and the economic biologist
have to face. It is also one of the most interesting problems which the academic
biologist can study.
The result of all the work that has been done, however, has been only a
limited degree of control; and even this is confined to one or two species of
nematodes only, of which Haemonchus contortus, infecting the abomasum of
sheep is an example. The other species found in the intestines of sheep, which
probably do a great deal more harm, are little affected by any known treatment,
so that the best measures we can take are quite inadequate. Those nematodes
which inhabit less accessible situations, such as the lung worms which cause the
disease called husk or hoose in sheep, cattle and swine, or the Filariae which
live in the blood, or Trichinella which migrates into the muscles, are even less
amenable to treatment, although such preventive methods as meat inspection
have practically eradicated the latter from human beings in this country. There
is thus no doubt that diseases caused by nematodes belong to that diminishing
group which still baffles scientific workers.
When we try to explain this striking failure, we may find one of the most
important reasons for it in the fact that a great deal of the work done in the past
on nematodes has been morphological, so that we have very little sound and
( 274 )
BEARING OF PHYSIOLOGY OF PARASITIC NEMATODES ON THEIR CONTROL.
277
very like those to which non-parasitic species of nematodes are exposed. Their
environment is very like that of the nematodes living in the soil, for example.
Any knowledge of non-parasitic nematodes that we may have, and any that we
may gain, may therefore be applicable to the control of the free-living non-
parasitic larvae of parasitic nematodes, provided that we bear in mind the greater
resistant powers of the latter. The study of non-parasitic nematodes may also
have its own agricultural value, because these organisms may affect the agri-
cultural properties of the soil, or because they affect other necessities of civilisa-
tion, such as sewage disposal.
I. THE EGGS AND FREE-LIVING LARVAE.
A. The Eggs. A good deal of work has been done on the effect of the
environment upon the eggs. It will not be here discussed, because it is
doubtful whether any attempts to kill the eggs of nematodes will be practicable
or economically worth while. They are almost as resistant as coccidian oocysts
and all the objections stated below to attempts to kill the infective larvae, apply
also to measures directed against the eggs. The use of hypochlorite solutions
against them has been suggested, and especially the use of acidified hypochlorite
solutions. The writer (1933) came to the conclusion that Milton hypochlorite was
more lethal to the eggs than other antiseptics which were tried for the sterilisa-
tion of eggs for the cultivation of larvae from them. Dressings of bleaching
powder upon pastures or other situations might kill many nematode eggs. Such
methods are further discussed below, where it is suggested that they could only
be subsidiary to other methods of control.
B. The Infective Larvae. The study of the physiology of the non-parasitic
larvae, and especially of their reactions to physical and chemical factors in their
environment, may suggest to us subsidiary methods of control designed to attack
these larvae. We already have a good deal of knowledge of this kind which will
guide future work. We can supplement it with what we know of analogous phases
of other parasites, such as the protozoa and other helminths.
The first and the infective larvae which live on the pastures must both
perform an ecdysis which may be the most vulnerable point at which to attack
them. If we could control these two ecdyses, we could prevent, at its beginning
outside the host, the development of those parasitic nematodes which have a free-
living phase. The successful accomplishment of the second ecdysis is particularly
important to the parasite. It divests the third larva of the remarkably efficient
sheath without which it cannot survive for long outside the host, and renders
it dependent upon parasitic life. If, therefore, we could control this ecdysis, we
could control the infection of the host.
278 THE INDIAN JOURNAL OF VETERINARY SCIENCE AND ANIMAL HUSBANDRY. [V, III
Any method, for example, which would prevent this ecdysis occurring would
prevent the onset of the third parasitic phase inside the infective larva and so
would limit infection of the host. Such larvae entering the host would not
exsheath and would be passed out again with the faeces ; presumably they would
eventually die. If, however, we succeed only in delaying this second ecydsis
we might do more harm than good, by enabling infective larvae to pass through
various hosts unchanged, until they eventually exsheathed in one or other of them.
The hosts would thus be passing out not only eggs, the larvae developing from
which could not infect new hosts for at least three days, but infective larvae as
well, and so would be distributing these latter over a wide area. We should be
making each individual host a more efficient carrier of the disease we were trying
to control.
Methods, however, which would cause the second ecdysis to occur on the
pastures outside the host, or to occur more readily here, would kill many larvae,
because they would expose the parasitic third larvae to climatic conditions which
they could not survive without their protective sheaths. The possibility that we
may be able to do this certainly merits further study. The writer's work on the
second ecdysis (shortly to be published) shows that a relation between the second
ecdysis and the acid-base equilibrium in the alimentary canal may be demonstrable;
and that methods directed to the alteration of the permeability of the sheaths of
infective larvae would be effective as a means either of killing them or of causing
them to exsheath outside the host, so that they would die from exposure. That
the larvae might possibly be attacked also through their second ecdysis inside
the host, as well as outside it, is suggested by the effect observed by the writer
of sulphides on the infective larvae and of solutions containing organic sulphides
in the presence of common intestinal bacteria such as B. coli, which produces
H 2 S from these compounds. It is also worth remembering that the protective
sheaths of the infective larvae are the skins of the second larvae, so that any
knowledge we acquire about the chemical composition or permeability of these
sheaths, or of means of rendering them more vulnerable to our attack may give
us valuable indications for similar methods to be applied to the later parasitic
larvae or the mature worms. The parasitic larvae are also dependent upon
successful accomplishment of a series of ecdyses, and if we could control these,
we could control the parasitic life of nematodes.
*
*
*
*
As a result of the writer's observations on the second ecdysis, some pre-
liminary experiments have, in fact, been done by Wood, in the Institute of Animal
Pathology, to determine whether the lethal effect of bleaching powder upon
the infective larvae could be economically applied to them upon the pastures.
It will be remembered that bleaching powder is also used, as Goodey (1933) points
out, for combating the adults of the plant parasitic nematode Heterodera. It
BEARING OF PHYSIOLOGY OF PARASITIC NEMATODES ON THEIR CONTROL.
279
is too early yet to state any conclusion about these experiments. Before the effect
of any dressing could be estimated, it was first necessary to devise a method of
estimating the number of larvae killed by it, so that a method of estimating the
number of larvae upon a given area of pasture was required. This latter has,
indeed, long been desirable as a means of enabling farmers to estimate the degree
to which any pasture is infected, so that they may judge its possible effect upon
sheep put upon it. Another problem was the elimination of the numerous non-
parasitic nematodes found upon the pastures. Wood found that the number
of infective larvae could be at any rate roughly estimated by extracting the larvae
with a modification of a Baermann apparatus, and that the non-parasitic nematodes
were mostly killed, or at any rate immobilised, if this apparatus was filled with
a 1 % solution of cone. HCl. instead of with water. The infective larvae of parasitic
species are not affected by a few hours immersion in this, at room temperature.
This rather rough preliminary technique is being further developed; at the
same time the effect of bleaching powder on the pastures is being investigated.
Enough has been learnt to show that dressings which bleach but do not necessarily
kill the pastures will kill a great many infective nematode larvae. It may therefore
be found that such dressings may be of value, if the labour and expense of applying
them justifies their use.
*
*
*
*
II. THE PARASITIC LARVAE AND MATURE WORMS.
Veglia (1915) studied the parasitic larvao of Haemonchus contortus, and a
considerable literature exists about the parasitic larvae of nematodes inhabiting
other parts of the body than the alimentary canal. There is therefore no lack
of a basis for further work of this kind, which is important, apart from its bearing
on our knowledge of the relationship between host and parasite, because these
larvae may do at least as much damage to the host as that done by the mature
worms, especially when they migrate through the tissues, like, for example, the
parasitic larvae of Ascaris. The environment of both the parasitic larvae and
the mature worms contains similar factors, namely, those which govern the
physiology of the host, so that the work on the physiology of the mature worms
about to be described may be used as a guide for work on the parasitic larvae. It
should be remembered, however, that whenever this work on the mature worms
has been done upon nematodes removed from their hosts and studied in artificial
media, it is doubtful whether it represents normal nematode physiology, because
no nematode has ever been kept alive for longer than a few days in any artificial
medium. We shall not be able to study the normal physiology of nematodes
by direct observation until we can either cultivate them from the egg, or at least
keep them alive and healthy under experimental conditions which we can
control.