NationalLibraryOfScotland/medical-history-of-british-india huggingface dataset:
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and Lounsbury (210) have found the jackal refractory to inoculation with the
blood of dogs suffering from P. canis and to the bites of hundreds of highly
infected ticks. With this species also Robertson notes failure to infect in the
cases of the horse, ox, sheep, cat, rabbit, guinea pig, rat, mouse, and fowl ;
Nocard and Motas in the horse, ox, sheep, goat, cat, rabbit, guinea pig, white
rat, white mouse, fowl, and pigeon, Nuttall and Graham Smith in the cat, ferret,
hedgehog, guinea pig, and white rat. Monkeys ( Macacus) and brown rats
(M. rattus) inoculated by me with blood swarming with parasites have failed to
show infection.
Normally, transmission of the piroplasmata takes place by ticks. That the
infection of Texas fever was carried by ticks was conclusively shown by Smith
and Kilborne. Even in the eighteenth century it had been recognised in
America that apparently healthy cattle coming from a large but well-defined
territory, including most of the Southern States, caused outbreaks of severe and
fatal disease among healthy Northern cattle, and that Northern cattle proceeding
into Southern territory were attacked with the same fatal malady. In the course
of time many curious facts regarding this disease known as Texas or Redwater
fever, came to light. Especially was it noticeable that it was not communicated
directly from Southern to Northern cattle, but that the ground over which the
former passed was infected by them and that the infection was transmitted thence
to susceptible cattle. The early experiments of Smith and Kilborne pointed
to the cattle ticks as in some way the cause of the disease and they were able to
show that, when these ticks were artificially removed, Southern cattle could be
placed with Northern cattle without ill effects. It was thought at first that
the tick obtained the parasite from the blood of its host and that, on the
dissolution of the tick on the pasture, a resistant spore form was set free which
produced the disease when taken in with the food. But it became evident from
several considerations that this could not be the case, and the fact that infection
nearly always occurred at the time when the young ticks were first noticed on the
animals, led Smith and Kilborne to feed larval ticks hatched in the laboratory
upon oxen kept in stalls. In the first experiment three animals infected in this
way died of Texas fever, and further experiments proved beyond all doubt that
it was the bite of the young brood of infected Southern ticks which caused the
disease. The source from which the mother ticks derived the infection was
made evident when the blood of the apparently healthy Southern cattle injected
into susceptible Northern cattle was found to give rise to the symptoms of Texas
fever and to the presence of the parasite in the blood: The experiments of
Smith and Kilborne were so convincing and the relation of ticks to infection so
obvious when once demonstrated that it was not long before these results were
confirmed by observations in other parts of the world.
But whilst Motas (213) showed that ovine piroplasmosis had been conveyed
by ticks brought from an infected flock more than 200 kilometres distant, and
Koch's researches upon Redwater still further demonstrated the connection of
ticks with piroplasmosis, no very great advance in our knowledge of the subject
occurred until Lounsbury and later Theiler undertook systematic researches upon
the transmission of these diseases.
At the time when Smith and Kilborne first demonstrated the pathogenic
properties of ticks knowledge regarding these pests was most meagre ; it was
these authors who in conjunction with Curtice first brought accurate observation
to bear upon their life history. They noted the hatching of minute six-legged
larvæ and the development of these, after they had attached themselves to
heir host, through the nymphal to the adult stage. But they took notice
of only a single species named by Curtice Boophilus bovis which they found on
the infected Southern cattle.
The life history of other species has become known chiefly from the
researches of Lounsbury, who made the discovery that all ticks had not the same
life history ; the habit of passing through the metamorphosis attached to the
skin of the same host not being universal or even usual among ticks, which in
most cases drop from their host in order to undergo this change. Lounsbury
also proved by a series of experiments lasting over three years that in South
Africa piroplasmosis of the dog is conveyed by the tick Hæmaphysalis leachi,
not by the larvæ from infected mother ticks, but only by ticks which, reared
from eggs laid by infected mother ticks, had passed through two metamorphoses
and had reached the adult stage.
The problem of transmission by ticks was still further complicated by the
facts later demonstrated by this author and also by Theiler in regard to East
Coast fever. In this case transmission by the bite of the progeny of ticks fed
on sick animals always failed to infect ; but infection taken in by the larva was
transmitted by the nymph and that taken in by the nymph was transmitted by the
adult. The same method of transmission occurred in heartwater which was
induced by the bite of nymphs or adults of the tick Amblyomma hebrœum
fed in a previous stage upon sick animals.
It is thus clear that the piroplasmata behave differently as regards the
exac mechanism of their transmission, either in the case of different species of
parasite, or when transmitted by different species of tick, two types of transmis-
sion being noticeable, the hereditary, and that taking place from one stage to
another. Of the hereditary we have two forms, that seen in Texas fever where
transmission is conveyed by the larva of the second generation, and that where
the larva and nymph are both innocuous and infective properties develop in the
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adult only. A third has to be added for I shall show that in the case of R.
sanguineus nymphs of the second generation may be infective.
It is obvious that the explanation of these facts was difficult for, up to quite
recently, when a few of the stages in development were described by Koch and
Kleine, not a single trustworthy observation existed regarding the development
of piroplasma in the tick. Even the work of Koch and Kleine left the nature of
the changes undergone nearly as obscure as before, since the significance of the
stages described by these authors was not at all clear and at most their obser-
vations formed only a few disconnected links in the chain of events.
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II.
THE PARASITE IN ITS MAMMALIAN HOST.
GEOGRAPHICAL DISTRIBUTION.
Piroplasma canis was discovered by Piana and Galli Valerio in the blood of
hunting dogs in Lombardy and described by them. Five years later Celli (32)
noted its presence in hunting dogs brought from Lombardy to the Roman Cam
-pagna. In France the parasite is recorded by Leblanc (150) at Lyons and by
Nocard and Almy (155) at D'Alfort, indigenous cases of infection in both
instances being met with.
It has been described by Marchoux (151) as occurring in the blood of dogs
in Senegal and by Koch (71) in a dog at Dareslam in East Africa.
In South Africa Hutcheon (147) had recognised a disease in dogs related to
redwater in cattle and to biliary fever in horses even before the parasite had been
demonstrated by Carrington Purvis, and had described a fatal epidemic of this
disease which occurred at Herschell, Cape Colony, in the autumn of 1893.
Lounsbury says that the disease appears to occur throughout the colony, but to
be less prevalent in high inland districts than near the coast, a distribution which
coincides with that of the numerical abundance of ticks. In support of the view
that the disease is indigenous he cites the experience of old residents, who had
recognised the disease at Grahamstown, Mowbray, Humansdorp, Cradock, and
other places at dates varying between 1844-54, and quotes an extract from the
published letters of Lady Ann Barnard in which the writer refers in 1797 to a
disease which attacks all newly arrived dogs. On the other hand he quotes
farmers who recollect a time when the disease was apparently first introduced
among their dogs. Since the infecting tick H. leachi appears to be an African
species, it certainly appears probable that the disease was originally endemic in
Cape Colony, if not over the whole of Africa.
In India P. canis has been recorded by myself (144) in Madras, and by
James (149) in Assam. In Madras infection with piroplasma is endemic among
native pariah dogs, which may show but few symptoms even when harbouring
considerable numbers of the parasite. In adult dogs of this class infection is
not common, but a very considerable, though varying, proportion of puppies
show parasites. Out of a batch of 18 young dogs brought from different villages
in the neighbourhood of the King Institute in October 1905 five were infected,
8
one showing a heavy infection and two a moderate number of parasites. In
August 1906 out of eight dogs one was infected and other batches of whi c
no record was kept showed similar results. The greatest number ever examined
without finding parasites was 23 ; parasites were found in the 24th dog.
That the disease occurs in its severest form among European dogs in India
is also certain, for, although I have not had an opportunity of seeing it except as
a result of experimental infection, several persons ignorant of the nature or signi-
ficance of the disease have described very exactly to me the symptoms, and a
convincing account of an epidemic among the dogs of the Madras hunt a few
years ago was given to me by Major Gifford, I.M.S., who, without knowing the
cause, noted at the time the extreme bloodlessness of the tissues and the infective
nature of the disease.*
It has been suggested by Nuttall that the diseases from the different parts of
the world may, especially as they are carried by different species of tick, be due
to distinct species of parasites. The answer to such a suggestion will probably
require to be based on experiments with regard to immunity, but even consider-
able variations in symptomatology may arise from differences in age, nature, and
condition of the dogs studied by different observers. Thus where the disease
is well known as at the Cape and the lives of valuable dogs are at stake its
severity is likely to receive special recognition. The effect of the parasite in
India is seen under different conditions for should European dogs contract the
disease its nature would probably be overlooked, whereas among the pariah dogs
one usually sees cases of the disease only in those which have not succumbed
in early life.
An interesting feature of the disease in India is that, since the infecting
tick of the country is a species found especially in the villages where the indigen-
ous dogs are for the most part congregated, and as in these villages infection
is well nigh ubiquitous, it is probable that hunting dogs, if they contracted the
disease, would do so from ticks picked up in passing through villages or other
haunts of the native dog rather than from those ticks which attach themselves
to the dogs in the open country.
In North and South America, Australia, Polynesia, and many other parts of
the world the presence of P. canis does not appear to have been recorded.
How far this is due to want of observation or to the absence of the parasite
it is impossible to say, but one is almost forced to conclude from the
facts at one's disposal that, as in Texas fever, the disease is prominently
brought to view only where susceptible dogs are brought into areas of endemic
infection, and that the distribution of P. canis is much wider than the record
* Vide also Webb (162b).
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of its presence would indicate. At any rate its existence may be expected
throughout Southern Europe, the whole of Africa, and almost certainly much of
Asia.
SYMPTOMATOLOGY.
Canine piroplasmosis has been studied in Europe and in South Africa.
The most complete account of the European disease is given by Nocard and
Motas (157), who differentiate an acute form ending in death and a chronic form
ending most frequently in recovery.
In the acute disease the dog is profoundly affected. Loss of appetite is
complete and except in very young dogs, where a high temperature is absent, there
is marked fever. In all cases there is intense pallor of the mucous membranes
due to blood destruction, and jaundice occurs in about half the cases. Weakness
may advance to actual paresis of the hind legs, dogs rising with difficulty and
falling if forced to walk. Towards the end the animal becomes comatose.
With the appearance of the first symptoms, even before parasites are
present, the urine is albuminous and remains so until death. Hæmoglobinuria was
observed in 43 out of 63 cases ; it is not constant and when present is often
evanescent and may be overlooked. The blood is pale and watery, the cor-
puscles which normally number 6,000,000 or 7,000,000 per c.m. diminishing
with the appearance of the first symptoms and falling at the hæmoglobinuric crisis
as low as 2,000,000 per c.m. The hæmoglobin percentage also falls, reaching
in some cases 3½ per cent. instead of the normal value of 12—13 per cent. The
leucocytes on the contrary, which number in the normal dog from 7,000—8,000
per c.m., increase greatly in number and may reach 40,000 per c.m.
The chronic form is associated with intense anæmia, but rarely with
icterus or hæmoglobinuria.
Fever, if it is present, exists only at the outset and lasts only a few days.
There is in addition emaciation, anorexia, weakness, and a scurfy skin. Little
by little appetite returns and the mucous membranes regain their colour, con-
valescence taking from six weeks to three months.
The disease as seen in Madras shows nothing in the clinical symptoms to
suggest that it is essentially different to the European disease or to the South
African disease, the symptoms of which as described by Robertson, Lounsbury,
and Nuttall correspond closely with the above.
Young pups may die within 24 hours of the time when parasites first appear
in the blood. More usually they live for two or three days. The temperature is
generally not raised and there is nothing except the pallor of the tongue and
possibly hæmoglobinuria to distinguish the condition from any other rapidly-
fatal condition in very young pups. In older dogs more characteristic symptoms
C
are present, but the severity of the disease varies very greatly in different dogs,
and even when parasites have been present in large numbers thet symptoms
may be so slight as to pass unnoticed. If it is looked for, pallor of the tongue
can generally be detected at some stage, but it may not be apparent until after
the first few days and may disappear again very quickly after the crisis though
parasites may still be present in reduced numbers.
Whilst the two types of the disease described by No card and Motas can be
distinguished clinically, it is doubtful if they represent essential differences in the
type of infection ; and a study of reported cases taken in conjunction with my own
observations makes it more than probable that infection in all cases goes
through certain phases, if the dog lives long enough. Thus in all my cases
there has been at the commencement of infection a period lasting for
several days during which parasites swarm in the blood, a period which cor-
responds as a rule with the onset of severe symptoms. If the dog, as often
happens, succumbs at the end of, or shortly after this period the type of the
disease is that called acute; but should it survive there follows a new phase
characterised by the presence of few parasites in the blood, and from this con-
dition the dog may pass to recovery or to death within a longer or shorter period,
all gradations between attacks ending at once in recovery and attacks ending
fatally after many weeks of sickness being seen.
Thus in the type case 61, given by Nocard and Motas to demonstrate the
chronic form, if the dog had died when the temperature fell on the 18th Octo-
ber, all the characters of the acute disease would have been seen. The same
initial severity of the symptoms and marked variation of the temperature during
the first few days of the illness is seen in case 42, which is given as a type of
the chronic disease. In Lounsbury's case No. 17, quoted by Nuttall, there
appear to have been two initial attacks of the severe disease, and another
attack of the same character later on in the disease, a condition which has
occurred in my own experience.
The relation of the two types is well exemplified in the following series:—
Dogs 135 and 136 were from the same litter and were bitten at the same time
by infective ticks. In each the disease developed on parallel lines until, at the
period of maximum infection (parasites numbering some 200—300 per field) dog
135 died with hæmoglobinuria (acute type). Dog 136 which also had a
maximum infection managed to survive this critical period and died five days
later, no hæmoglobinuria being present (sub-acute type(. Dogs 105 and 107,
which whilst they were in the same cage were infected by pathogenic ticks also,
both showed a severe infection at the start, but dog 105 got over this and,
showed the chronic form ending in recovery, whilst dog 107 which died at the
time of severe infection showed typically the acute form.
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Very young dogs practically never recover from the initial attack so that
in them the disease is always of the so-called acute form. Older dogs which
do not die from the severity of the infection within the first four or five days
appear generally to develop some degree of immunity, parasites after this period
rarely being very abundant. It is not unusual for dogs after a long period of
low oscillatory temperature and scanty parasites again to have numerous para-
sites in the blood with high fever, and very possibly they die at this stage. This
occurred with dogs 95 and 96. These were dogs from the same litter inoculated
on the 24th of October 1906 with blood of a not very virulent strain and they
developed a mild attack in which parasites averaged about two per field and the
temperature rose to 103°. At various periods after this they were observed
to have a few parasites in their blood. On the 21st November 1906 the dogs
were observed to be very ill and blood examination showed abundant piroplasmata.
On the 22nd November 1906, dog 19 died and dog 20 died the next day, both
having very greatly enlarged spleens. It is quite possible that such cases are
due to reinfection by ticks, but exacerbations of parasites have been seen in dogs
in which fresh tick infection was impossible.
Dogs which get over the initial invasion may die with progressive anæmia
and emaciation, or they may recover. As noted by Robertson many dogs which
appear to have recovered succumb eventually. In some cases this may possibly
be due to reinfection by ticks infected by the dog itself, and is very characteristic
of the disease as seen in dogs at liberty. Very mild infections, in which the dog
exhibits no sign of illness, and recovery is rapid and complete, are also quite
common even among European dogs.
Temperature. —All observers agree that the first sign of infection is a rise
in the temperature. This may occur before the dogs show any sign of ill health,
but it has been associated in all my cases that have been examined at this time
with abundant parasites in the blood. Twenty-four hours later the dogs usually
show obvious signs of illness, though as yet no great pallor is visible. Pallor,
however, becomes apparent a little later and then the tongue may in severe cases
be the colour of pipe clay. A change of expression in the eyes is also
noticeable, possibly a result of the increased whiteness of the sclerotic, though
the eyeball also appears unduly prominent.
Destruction and re-formation of red cells.—The rapidity with which the
red cells are destroyed is the most characteristic feature of the disease, and can
be followed even by the unaided eye in the rapidly increasing thinness of the
blood. In the loss of a million or more corpuscles in a few hours it almost
exactly resembles blackwater fever in man, a disease in which the destruction of
red corpuscles is every bit as rapid and as extensive. The rapidity with which
new corpuscles are made is also very great and is well exemplified in case No. 61
C 2
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of Nocard and Motas where the number rose from 2,430,000 to 4,340,000 in five
days and in another two days reached 5,100,000.
Hæmoglobinuria.—Hæmoglobinuria is described as frequent in both the
European and South African disease. It is also present in the Madras disease,
though I have never seen the urine of the dark porter colour so characteristic of
severe cases of blackwater fever in the human subject. Nocard and Motas de-
scribe the urine as containing hæmoglobin in three out of six naturally infected
cases and in 43 out of 63 dogs suffering from the inoculated disease. They note
that it is sometimes very fugitive and may be overlooked. Nuttall notes hæmo-
globinuria in all his cases except one, but describes the urine only as dark iodine
colour. In the cases seen by me the urine was most frequently of a light reddish
tint or of a darker prune juice colour. Very often when hæmoglobinuria is not
present the urine is pale ; at other times it is of a dark yellow. I have seen
hæmoglobinuria only in dogs which have died during the initial severe attack.
In dog 135, which died at a period of very intense infection, hæmoglobinuria was
present, but in dog 136, which had passed through nearly as severe an attack and
died five days later, the urine in the bladder did not contain hæmoglobin. Even
dogs which die of the acute disease do not necessarily show distinct hmoglo-
binuria.
Nervous symptoms.— In very severe cases there is nearly always marked
paresis amounting to distinct paralysis in the hind legs. This is usually observed
in dogs which die at the first invasion.
Immunity. —The only observers who have followed closely the process of
immunity in canine piroplasmosis are Nocard and Motas. These authors
demonstrate not only a high degree of immunity resulting from previous infection
lasting many months, but also show that the blood of immunised dogs has a
marked bactericidal effect upon the parasites, mixture in vitro with four or five
times its volume of serum from an immunised dog rendering virulent blood
ineffective.
The serum of immunised dogs has, however, but slight effect in preventing
or modifying an attack.
PATHOLOGICAL CHANGES IN CANINE PIROPLASMOSIS.
The pathological changes which occur as a result of infection by the different
piroplasmata are in the main similar ; the changes in East Coast fever, however,
are peculiar to this disease. In all cases the chief characters noticeable at the
autopsy are the extremely watery condition of the blood and the pallor of the
tissues. The degree of icterus varies in the different diseases ; it occurs only