NationalLibraryOfScotland/medical-history-of-british-india huggingface dataset:
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and that as the attack progressed double forms became more frequent, often
to yield, shortly after the crisis, to a relative increase in the single forms.
During the early periods of an attack free forms if present are rare, but at the
crisis free forms lying in groups of two, four, eight or more are a striking feature.
At this time, therefore, one would expect that there would be a greater de-
struction of red cells than at other times, but my observations have as yet been
too few to enable me to determine this.
With the course of infection changes in the blood both as regards the red
and white corpuscles are considerable. The reduction in the red cells has
already been referred to : some interest attaches, however, to the time at which
destruction is greatest. This is undoubtedly during the first few days when
attack after attack occurs and when for days together swarms of parasites occur
in the blood. Very often the number of parasites is out of all proportion larger
in one attack than in the others, and at such times parasites may number more
than the red cells.
Changes in the leucocytes are also considerable. Nocard and Motas de-
scribe an increase in their number reaching in one dog to 54,000 per c. m.
which they say is mainly due to an increase in the polymorphonuclear cells,
J. A. Wright also notes that the number of leucocytes is usually greatly increased
from the time parasites occur in the blood, the number in one of his dogs reach-
ing 60,000. But in one case he notes a reduction.
An increase in the leucocytes has been observed by me in all the cases in
which these cells have been counted; in addition there are changes in the
leucocyte values. This consists of a marked increase in the large mononuclear
elements and often in the transitional cells, extremely large cells being then
present. The percentage of mononuclears is usually raised to 10-15 per cent.
in place of the normal value of two per cent., but has reached in one count
26 per cent. The greatest increase is as a rule seen immediately before and
at the crisis of free forms. At this period also phagocytosis is most intense and
leucocytes are seen packed with more or less altered parasites.
To summarise ; the course of a typical infection the result of subcutaneous
inoculation of infective blood or the bite of pathogenic ticks is as follows :—
At a variable period after infection a few large forms are seen. A day later
parasites are generally numerous, and about this time the temperature is raised;
but the dog is not ill nor does it show any sign of anæmia. During the next
two or three days parasites increase in numbers, being especially numerous dur-
ing periods of variable duration characterised by an increased percentage of
multiple-infected cells, the presence of numerous free forms, a mononuclear
increase, and an intense phagocytosis. Young or very severely infected dogs
usually die at about the third access, which is usually the most severe, very often
32
with hæmoglobinuria. Should the dog not die at this time or shortly after-
wards, it either recovers or exhibits the so-called chronic type of the disease,
which is characterised by a much reduced number of parasites, but in which, if
the case be closely watched, parasites are seen at certain times to increase in
numbers and after showing an outburst of multiple-infected cells and free forms
to disappear quickly. In this form of infection the dog may die at almost any
time, but as a rule eventually recovers, parasites being afterwards present for
weeks.
EXAMPLES OF CASES.
Case 1, Dog No. 98. —Inoculated subcutaneously with infective blood on
22nd October 1906. Parasites were first seen on the morning of 26th October
1906 and were abundant on the morning of 27th October 1906 when the per-
centage of mononuclears had risen to 18. By the afternoon of 27th October
1906 parasites had fallen to less than one in ten fields of the microscope and the
mononuclear percentage to 3. On the morning of 28th October 1906 only a few
parasites were present but the mononuclears had risen to 5 per cent. The
dog recovered after passing through an unusually mild attack. ( Vide Chart I.)
Case 2, Dog No. 99. —Inoculated subcutaneously with infective blood on
22nd October 1906. Parasites were first seen on the morning of the 26th
October 1906 and were numerous on the morning of 27th October 1906 when
there was a mononuclear increase to 6.6 per cent. In the afternoon parasites
numbered only an average of one in ten fields and the mononuclears had returned
to the normal value of 2 per cent. On the morning of 28th October 1906,
parasites were numerous and the mononuclear value was 16 per cent. ( Vide
Chart II.)
Case 3, Dog No. 136. —Infected by the bite of ticks on 10th December 1906.
Parasites first seen on the morning of 18th December 1906 when they were very
numerous, double and single forms greatly preponderating. Later in the day
multiple-infected cells and free forms were abundant. Next morning parasites
were reduced in numbers, but an outburst occurred on 21 st December 1906. A
high mononuclear value was present throughout the 18th and 19th. The dog
died on 23rd December 1906 after an access, but at death parasites were only to
be found with difficulty.
Case 4, Dog No. 139. —Infected by the bite of ticks on 10th December 1906.
Parasites first seen on the morning of 18th December 1906 when they were very
abundant; the mononuclears numbered 13.3 per cent. In the afternoon parasites
were very scanty and the mononuclears formed only 3 per cent. of the total
leucocytes. On the morning of 19th December 1906 parasites were abundant
and the mononuclears had reached 26 per cent. In the afternoon of 19th
December 1906 and morning of 20th December 1906 parasites were still more
CPIROPLASMA CANIS AND ITS LIFE CYCLE IN THE TICK.
HART IV
CHART II
CHART I
PIROPLASMA CANIS AND ITS LIFE CYCLE IN THE TICK
CHART VII
D o g N o . 1 5 2 . I n o c u l a t e d s u b c u t a n e o u s l y o n 1 0 - 1 - 0 7 .
CHARE VI
D o g N o . 1 5 0 . I n o c u l a t e d s u b c u t a n e o u s l y o n 1 0 - 1 - 0 7 . T e n p a r a s i t e s c o u n t e d i n 1 0 0 f i e l d s o n 1 5 - 1 - 0 7 .
N o . 2 6 1 . E . , S a n C o m m r . I n d i a — — A u g . 0 7 . — 1 . 1 3 0
Helio., S. I. O., Calcutta.
33
numerous. On the afternoon of 20th December 1905 their number was greatly
diminished and remained low until the morning of 22nd December 1906, when
another access occurred, ending in an extremely sudden reduction in the number
of parasites.
In this and other examples given examinations were made only two or three
times a day and it is possible that in some cases accessions of parasites and
periods of disappearance passed unnoticed. In the next three cases given in
Charts V, VI and VII, examinations were made every two or three hours and in
several instances throughout the night. In dog 146 a quotidian cycle is present.
In dog 150, in which the disease was of a very severe type, the periods of
access are extended over long periods and there appeared to be two accesses in
the twenty-four hours. In dog 152 a quotidian access is apparent each morning,
but a second less pronounced access was present in the afternoon especially
noticeable on 18th December 1906. As the charts give the observations made it
is not necessary to refer to them in detail. The number of parasites is the number
present in one hundred fields counted as far as possible in corresponding pro-
portions of films of similar character. Whether free forms or multiple-infected
cells are seen depends very much upon the exact stage at which the film happens
to be taken, an hour or even half an hour sufficing to give changed conditions in
their relative proportion. ( Vide Charts I to VII.)
F
35
THE TRANSMISSION OF PIROPLASMA CANIS BY TICKS.
DOG TICKS.
The evidence in favour of transmission of the piroplasmata by ticks has
already been briefly summarised. In the case of Piroplasma canis the evidence
is particularly convincing, though there is still much to be learned of the details
connected with its spread in different parts of the world.
FIG. 2.
Probable geographical distribution of Rhipicephalus sanguineus (Latreille).
On account of the analogy with Texas fever and because they found dogs
infested with Ixodes reduvius, Piana and Galli Valerio thought that this species
might be the transmitter. Similarly Almy, and Nocard and Motas believed that
Dermacentor reticulatus can transmit the disease but actual experimental
demonstration of transmission of the disease in Europe is still wanting,. due very
much, it would seem, to a want of knowledge by the earlier observers of the life
history of the ticks with which they were dealing.
The first to infect dogs experimentally by means of the bite of ticks was
Lounsbury, who in a series of experiments lasting over three years proved
beyond all doubt that Piroplasma canis in South Africa is transmitted by the com-
mon dog tick of that country, Hæmaphysalis leachi :
But Hæmaphysalis leachi is unknown in Europe and has not been found in
F 2
36
Madras. It is therefore certain that other species of tick are also concerned, and
the geographical distribution of ticks found commonly enough on the dog
to be called dog ticks is important. Cur knowledge on such lines is unfortunately
meagre, but recorded * observations would indicate that those species of ticks
found with any frequency on the dog are the following :—
Hæmaphysalis leachi (Andouin).—This is an African species reported from
Egypt, East Africa, Algiers, Sierra Leone, French Congo, Transvaal, Cape, and
Mozambique. Neumann, however, mentions two specimens taken from a tiger in
Sumatra. Careful search for this tick in India has been without result though a
species somewhat resembling it has been found on the mongoose. It certainly
does not occur as a dog tick in Southern India.
From Lounsbury's work it is evident that this is the dog tick of South
Africa. Other ticks are, however, found on dogs at the Cape, notably Ixodes
pilosus and R. capensis. At Nelspruit, in the Transvaal, dogs were found to carry
more R. simus than the ordinary species and specimens of R. appendiculatus,
A. hebræum, and Hyalomma ægyptium were also found on them. Experimentally
also Lounsbury has reared R. decolcratus on dogs and the early stages of A.
hebræum and R. evertsi may feed to repletion. So far nothing is known of the
pathogenicity of these species.
D. reticulatus (Fabr.).—Has a wide distribution, being recorded in Europe
from France, Portugal, Roumania, and England; in Asia from Caucasus, Japan,
Turkestan, Siberia, and Persia; and in America from California, Texas, and New
Mexico.
Ixodes reduvius (Linné).—A species common on dogs. Occurs over the
whole of Europe, the nymph and larvæ being found on lizards, birds, and squirrels,
etc. Also in Algeria, Caucasus, and in the United States, being recorded from
Baltimore, Carolina, Florida, California, Kansas, and Texas.
Ixodes hexagonus (Leach).—Common on dogs in Europe; also upon
various animals, the dog not being noted as a host, in Texas, Kansas, Maine,
New York, Iowa, and Colorado. Nymphs and larvæ occur on small animals and
birds.
R. sanguineus (Latreille).— Has been taken from the dog less often than
from other animals. Neumann mentions it as pre-eminently the dog tick, and
in India with one exception (in which dog ticks sent to me were unfed
H. ægyptium) they have always proved to be R. sanguineus. The distribution
of this tick is extremely wide; in Europe it is recorded from France, Italy and
Sicily, Corsica and Roumania; in Africa from Egypt, Abyssinia, Zanzibar,
Senegal, Algeria, and Tunis; in Asia from Persia, China, Malay, and India;
it is also reported from America, the Philippines, Oceania, and Australia.
*
V i d e
c h i e f l y N e u m a n n ,
2 1 5 — 2 1 7 .
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As this species carries Piroplasma canis in India it would appear in itself
sufficient to account for infection over a great part of the globe.
FIG. 3.
Probable geographical distribution of Ixodes reduvius and Dermacentor reticularis.
R. bursa (Canestrini and Fanzago).—Also frequently found on the dog, but
much more frequently on other domestic animals. In Madras it is much less
adapted for life upon the dog than R. sanguineus
and is seen chiefly as a
parasite of the goat. It is recorded in Africa from Algiers, Senegambia, East
Africa, West Africa, Kilimanjaro, Daresalam, the Congo, the Cape, and Abyssinia.
Experiments with this species in Madras failed.
Dermacentor Americanus
(Linné).—Frequent on the dog. Recorded from
Maryland, Texas, California, Nantucket, Labrador, Minnesota, Alabama,
Colorado, Florida, Kansas, Alaska, and Mexico.
Amblyomma cajennense
(Koch).—Frequent on the dog. Recorded from
Brazil, Cayenne, Mexico, Central America, Cuba, and Vera Cruz.
A. striatum (Koch).—Found on the dog. Brazil, Batua, Marago.
A. calcaratum (Neumann).— Found on the dog. Brazil.
Ixodes ovatus (Neumann).—In Japan and Amoor, on the horse, hare, and
dog.
I x o d e s h o l o c y c l u s
( N e u m a n n ) . — A u s t r a l i a a n d I n d i a , o n t h e d o g a n d s h e e p .
Other species are recorded from the dog, but do not appear to frequent
this host as a rule, such as H. ægyptium, a species most frequent on the ox,
dromedary, and camel, and in Algeria on the horse, mule, and ass, occasionally
also on the sheep, stag, dog, cat, and man. It is improbable that these are to
any extent concerned in the spread of canine piroplasmosis, although it is possible
some of them might transmit the disease experimentally.
Of those specified R. sanguineus is probably the species having the widest
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distribution and would in itself serve as a transmitter in Southern Europe, North
Africa, and much of the East. For South Africa there is a special dog tick, H .
leachi. In Europe and more temperate regions the various species of Ixodes
seem to act as carriers. In Japan the only dog tick noted is an Ixodes and an
Ixodes is found on dogs in Australia. In Central America several species of
Amblyomma seem to be associated with the dog.
TICKS OF MADRAS.
In Madras the common ticks are Hæmaphysalis flava (Neumann), H.
spinigera (Neumann), Rnipicephalus sanguineus (Latreille), R. bursa (Can. et
Fanz.), R. simus (Koch), R. annulatus (Say), Aponomma gervazsi (Lucas), and
other species on reptiles, various species of amblyomma on pigs, cattle, etc., and
Hyalomma ægyptium (Linné).
R. Simus I have found only in the hill districts (Nilgiris) on cattle, especially
the buffalo. H. spinigera occurs on the tiger and panther on the lower slopes of
the hills. The others are all more common on the plains. Cattle rarely shew
other species than R. annulatus and H. ægyptium. The commonest horse
tick is H. ægyptium, which is also found on goats and sheep. In Northern
India this tick infests the camel, and I have received specimens sent as dog ticks.
H. flava is the common tick of the goat, sheep, and buffalo. It is found on dogs
when these are used for herding goats and sheep, and the same or a closely
related tick is found on the cat. R. bursa is also most common on the goat and
sheep, and though it will go through all its metamorphoses on the dog it is not
often seen naturally in this situation. R. sanguineus is, in contradistinction to all
these, the dog tick; it is found in considerable numbers on almost every dog, but
is very rarely found on other hosts.
The different species of tick mentioned differ very markedly in their
appearance, their habits, and even in the general aspect of the immature stages.
R. bursa is a larger tick than R. sanguineus and becomes so completely
distended as to resemble an oval bladder, whilst R. sanguineus after it has
dropped from its host after engorgement is somewhat flattened and the dorso-ventral
muscles cause deeper indentations and puckerings than in R. bursa. H. flava,
which in the unfed condition is a much smaller tick than either of the above,
becomes when distended nearly equal in size to R. sanguineus, the cuticle of
the belly becoming so stretched that the dark colour of the blood shews through,
giving the fed tick the appearance of a black currant.
R. sanguineus and to a less degree R. bursa when gorged climb upwards,
but H. flava drops to the ground. The result is that the adult females of H.
flava are apt where dogs are kept in cages to be removed in the tray with the
urine and fæces, or to be swept away in the course of cleaning up. It is possibly
39
partly on this account that, although large numbers of H. flavah a v e f r o m t i m e t o
time been imported into the laboratory, the progeny have scarcely ever been
seen; but even when the adults are placed in cages from which they cannot
escape the result is identical. H. flavai s n o t a d o g t i c k , n o r i s i t a d a p t e d f o r
living upon dogs; and the same remark applies in a lesser degree to R. bursa,
which also for some reason tends to disappear when introduced among dogs.
Experiments in Madras have therefore been conducted mainly with R.
sanguineus, which has been found to transmit the disease.
GENERAL LIFE HISTORY OF TICKS.
Before approaching the question of the part taken by R. sanguineus in the
transmission of Piroplasma canis a brief summary of the life history of ticks is
necessary. All members of the scutum bearing ticks undergo after hatching
from the egg two metamorphoses, namely, that from the larva to the nymph and
that from the nymph to the adult. The larvæ are hexapod with a shield
covering the anterior portion of the dorsum and have the skin of the posterior
portion thrown into innumerable fine folds to allow of the great expansion which
takes place during engorgement.* The nymphs are octapod and resemble in
general appearance minute adult females. They also have a scutum anteriorly
and a plicated integument over the posterior portion.* At each stage the tick
gorges itself with blood, and the increase they undergo in size at this time
brings them approximately to the size of the next stage.
Each immature tick becomes motionless after feeding and remains for
a considerable period as incapable of movement as the pupæ of insects.
The final metamorphosis results in the formation of sexually differentiated
or adult ticks. The dorsum of the female like that of the larva and nymph is
covered only in its anterior portion by a scutum and the integument over the
posterior portion is plicated like that of the larva and nymph to allow of the
extreme distension which takes place at engorgement. The male, which does
not increase in size after feeding, possesses a scutum covering the whole
dorsum.
Unfed adult ticks measure about 2 to 3 mm. in length, but small species,
especially the males, may measure considerably less, and large species such as A.
hebræum may measure 5 mm. or more. When fully gorged, the female tick
reaches a length of from 6 to 10 mm. or more. The males are generally found
associated with a female, and Lounsbury notes that in H. leachi the males
* Allen 90 in his recent work on the anatomy of the tick describes this condition minutely and notes
that the outer portion only of the cuticle is plicated.
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move their position to find mates. On the other hand in A. hebræum the female
is attracted by the male and will not attach herself except in his immediate
neighbourhood. The males in most species remain on the host after the gorged
females have dropped off.
The different species often spew a marked predilection for certain sites of
attachment. Thus Lounsbury notes that the larvæ of R. evertsi are found
always deep within the ear, whilst the adults choose the regions about the anus,
and that H. ægyptium fixes itself upon the scrotum and groin. In India
R. annulatus attaches itself to cattle almost anywhere on the belly, whilst
H. ægyptium as in South Africa selects the groin. H. flavawhen upon goats
and sheep is almost always upon the ears.
The behaviour of the gorged female prior to laying her eggs, and the position
in which these are laid, differ in different species. Most of the cattle ticks when
gorged crawl to the nearest shelter or bury themselves in the ground. H. leachi
is described by Lounsbury as hiding itself among rubbish. The female R.
sanguineus climbs upwards and lays her eggs by preference in cracks, squeezing
herself into these so tightly that it is often impossible to remove her intact.
The eggs of the Ixodidæare always very numerous. As a rule each female
lays about 4,000 eggs, but in the case of large ticks the number is greater,
reaching in A. hebræum 10,000 to 20,000. (Lounsbury.)
The time taken in hatching and the duration of the different stages vary
greatly in different species and at different temperatures. According to Smith
and Kilborne the eggs of R. annulatus in the States take from 15 to 18 days
to hatch in very hot weather and 40 days in colder seasons. In the case of
H. leachi Lounsbury notes the time of hatching at the Cape to be from 5 to 7
weeks in summer and 12 to 16 weeks in winter. Lounsbury notes the time of
hatching of the eggs of the Bont tick to be eleven weeks in summer and many
months in winter. The changes from larvæ to nymph are more rapid. In H.
leachi the larva and nymph feed and drop from the host in from 48 to 75 hours.
In summer the gorged nymphs hatch into adults in 18 to 20 days. It is interest-
ing to compare these figures with those given later for R. sanguineus in
Madras, where except during one or two months the climate is tropical.
Most important variations from the point of view of disease transmission
occur in the relation of ticks in their various stages to different hosts.
The only group known to pass all the stages on the same host are the
Boophilus group of the Rhipicephalidæ. In these the time for the changes are
very short, being given by Smith and Kilborne as about a week in each case.
Many ticks drop from their host at each stage to undergo their metamor-
phosis. This habit was first described by Lounsbury in the case of H. leachi
but it has since been described by him in the case of R. appendiculatus,