NationalLibraryOfScotland/medical-history-of-british-india huggingface dataset:
6
from the liberation of free vermicules to the formation of sporozoits on the
breaking up of the oocyst, can be followed. Development in the tick there
-fore represents the sporogony of this parasite.
Fortunately no parasite that can be confounded with the developmental
forms of Leucocytozoon canis exists normally in this species of tick in Madras,
and a large number of observations extending over many months have estab-
lished the direct relationship of vermicules in the gut of the tick with the presence
of the parasite in the dog. In no instance have vermicules been found on ticks
fed on uninfected dogs, but in every case where females of R. sanguineus are
fed on infected dogs vermicules are present in the gut, and their number bears
a close relation to the number of parasites in the blood of the dog upon which
the tick has fed. Still more, certain proof is afforded by the fact that it is
quite common to see vermicules in the act of leaving their capsule.
Since blood is taken in by the female tick throughout a period of from two
to four days, it is to be expected that all the parasites will not be in the same
stage of development, but this is true only as regards a minority of the parasites
for, as already indicated, the final stages of engorgement are very rapid, and at
least two-thirds of the blood in the fully fed female tick is, as a rule, taken in
during the last twenty-four hours. Development, therefore, in the majority of
forms has started, roughly speaking, from the time when the tick left its host,
and the majority of parasites are at about the same stage of development.
In the .gut of ticks examined immediately after removal from the dog,
encapsuled parasites, or vermicules in their first stages of development, are seen.
At the end of twenty-four hours most of the forms have penetrated the cells of
the gut wall and are seen to be undergoing the different stages of fission which
precede the formation of the sexual forms. By the third day conjugation bodies
and the first stages in the development of the fertilised oocyst are conspicuous.
On the fourth day mature oocysts are present, together with a certain number
of sporozoits. The latter increase in numbers up to about the sixth day, by
which time most of the oocysts have disappeared.
The liberation of vermicules.—James15 has described the liberation of a
vermicule from a leucocyte in vitro, but this phenomenon must be rare, for I
have failed on several occasions to find vermicules even in citrated blood kept
for forty-eight hours. On the other hand I have already noted 10 that vermicules
are freely liberated in the gut of the tick, R. sanguineus, and that very few forms
fail to become free.
Wenyon16 has drawn attention to the frequency with which a U-shaped
nucleus is present in Leucocytozoon canis, and suggests that this arises from a
looped shape of the parasite within the cyst ; but in my specimens it is nearly
always possible to detect one or two fine cross strands of chromatin joining the
limbs of the U, so that the U shape of the nucleus is more apparent than real
7
(Fig. I). Leuocytozoon canis may sometimes be bent upon itself, but it is very
noticeable that in the majority of cases, when the parasite is first liberated,
it is a stumpy form differing from the encapsuled form only in not possessing a
capsule. In is only later that the parasite gradually elongates and becomes an
active attenuated vermicule.
When the gut contents of ticks are examined immediately after they have
left their host, many encapsuled forms are seen, but most of these are no longer
contained in leucocytes, the persistence of the appearance of a capsule under
these conditions being convincing as to the presence of a capsule proper to the
parasite itself. In some cases only an indistinct capsule can be made out, in
others there is no capsule, though the parasite, except that it stains more freely,
is otherwise unchanged the appearances at this time suggesting that the
encysted vermicule does not leave its capsule until this has been partly or wholly
dissolved by the digestive juices of the tick. When the parasite is free from its
capsule changes begin to occur in the arrangement of the chromatin, and a
greater amount of protoplasm passes behind the nucleus (Fig. 3), a vermicule
being eventually formed possessing transparent protoplasm and an elongated oval
nucleus (Figs. 4 to 7), the chromatin of which is arranged in a coarse reticulum.
Later the chromatin is often arranged in the form of almost separate rings (Fig.
8), an arrangement which I have already referred to as figured by Patton in the
case of a vermicule found in the body cavity of Hæmatopinus (Patton,9 P l . 1 ,
Fig. 16).
The formation of the male and female elements.— In the gut of ticks
examined twenty-four hours after they have left their host, many of the vermi-
cules have embedded themselves in the protoplasm of the gut cells, especially in
the younger cells which possess reticular protoplasm more or less free from the
products of digestion, and for the most part they have become stouter (Figs. 9
a n d 1 0 ) , t h e b u l k i e s t f o r m s m e a s u r i n g 1 1 . 5 µ b y 6 µ . T h e y a r e a s a r u l e s i t u a t e d
not very far from the nucleus of the epithelial cell of the gut, and the protoplasm
of the cell is often somewhat condensed around them. Though sometimes
nearly circular they are usually of an oval shape with one side rather flat and
the other much more convex (Fig. 9). The protoplasm is no longer homo-
geneous, but contains vacuoles, the chromatin meshwork which is conspicuously
opened out, is in many instances massed upon either side of the parasite, the
intervening space being bridged as a rule by a few strands. So far as I have
been able to ascertain, this arrangement of the chromatin does not end in its
reduction as in Lankesterella, but is the prelude to actual fission of the organism
(Fig. 11).
Vermicules lying in pairs (Fig. 12), derived from fission of the bulky
forms just described, are in fact numerous, and parasites in the act of separation
8
are not infrequently seen. These show a pink staining material which lies mainly
between the vermicules, but sometimes also surrounds them. The vermicules.
that have resulted from fission differ from those already described in that their
protoplasm is more granular and contains refractile vacuoles. They frequently
show a trace of the pinkish material already mentioned at one or, more rarely,
both poles. Such an appearance is almost certain evidence that a vermicule
exhibiting it has resulted from fission.
In many cases fission appears to be repeated several times, since groups
of four and even eight vermicules are often seen lying in a pocket in the
protoplasm of a cell (Fig. 13). To ascertain exactly what takes place at this
time is difficult, but there is no doubt that the mature sexual forms are the
result of at least one act of division of the original vermicules.
The sexually mature parasites are large vermicules measuring 13.5µ in
length. The commonest type are stout forms with an oval nucleus, but thin
forms with chromatin arranged along the length of the body are not infrequent.
It is doubtful, however, whether these appearances are constant characters
of the female and male elements, for, as will be seen later, in the conjugation
forms, differences in the component vermicules are not distinguishable. In
addition to the refractile droplets, which are very characteristic of the mature
sexual forms, the protoplasm contains also a few small chromatin granules,
and a darkly stained portion which is noticeable in the conjugation forms.
The chromatin in the stout forms is arranged in an irregular meshwork, but
in the narrow forms is more or less broken up and massed irregularly (Figs. 14
and 15).
Conjugation and the formation of the oocyst. —The vermicules first attach
themselves to each other by one end, the chromatin, of each coming towards the
point of contact. They then arrange themselves alongside of each other and
blend, forming characteristic conjugation bodies (Figs. 16 to 19). The conju-
gation bodies which are oval or round forms measuring from 7.6µ , to 10µ in short
and long diameter are at times very numerous, and it is easy to follow every step
from the coming together of the two vermicules to the formation of the oocyst
and the casting off of the protoplasm of the male form. In the early stages the
line of demarcation between the two forms can still be followed, but later this
becomes imperceptable. In some cases one vermicule is more packed with
refractile vacuoles than the other (Fig. 17), but usually the appearance of the
two halves is exactly similar. In each half the chromatin granules and dark
staining portion of protoplasm can be distinguished, and where the protoplasm of
the two vermicules has come together, one or sometimes two large vacuoles are
usually left (Figs. 16 and 17).
So soon as the vermicules have come together, the two chromatin masses,
9
which are at first separate and situated on the periphery of the conjugation body,
assume a very homogeneous appearance. In this condition they join together
to form a single mass (Fig. 18). The chromatin now opens out in an irregular
manner (Fig. 19) and passes towards the surface of the cell, the major portion
of it being extruded in the form of two large and very darkly staining
masses (Figs. 20 to 23). A portion remains behind and forms the origin of the
chromatin of the oocyst. At the same time that the chromatin masses are
extruded, the body of one of the vermicules, presumably the microgamete, is
thrown off ; and in it can still be recognised the refractile vacuoles, the broken
up and now diffused granules of chromatin, and the dark area of protoplasm
already noted. The mass is always devoid of even a trace of a nucleus (Fig. 21),
differing in this respect from certain degenerated vermicules, referred to
later, where the nucleus is still seen as a collection of deeply stained droplets.
The newly formed body, the oocyst, which enlarges rapidly and quickly,
assumes a very characteristic appearance, is a body with a clear central area
and an outer rim of very conspicuous dark blue protoplasm, the chromatin, in
the form of irregular fragments, being distributed near the periphery (Figs. 20
to 23). As the oocyst increases in size the chromatin becomes more and more
broken up, forming as a rule an imperfect and irregular reticulum. In some
forms the fragmentation is extreme and very fine particles of chromatin are
dusted over the surface, in others the reticulum is much coarser. After the
oocyst has reached a diameter of 14µ the central clear area becomes less
conspicuous, and the surrounding protoplasm much more voluminous ; the
chromatin has also collected into a number of defined masses, which are arranged
more or less regularly. At this stage the oocyst, either from being endowed
with amœboid movements, or from their being easily distorted, is often very
irregular in shape (Fig. 25).
It is not unusual to find groups of three or four oocysts in close contact.
In such cases the individuals of the group may be all in the same stage of deve-
lopment, or, as often happens, they may exhibit a regular series of stages,
suggesting the fertilisation of a number of females by successive wandering
males.
The formation of sporozoits.— Shortly after the oocyst has assumed the
appearance of a large amœboid body with voluminous protoplasm and scattered
masses of chromatin, it breaks up to form the sporozoits. A single form has
been seen, in which immature sporozoits w ere present, lying in what appeared to
be an extremely delicate cyst wall (Fig. 24), but I am very doubtful if this
represents the usual method of the formation of the sporozoits, the oocyst
breaking up into naked sporozoits not contained within any cyst wall.
The number of sporozoits found in groups is usually from twelve to fourteen
(Fig. 26), but groups have been seen containing many more. It is possible that
10
these larger groups have originated from three or four oocysts in close proximity
to each other.
The sporozoits resemble somewhat the original vermicules, but they differ
in being for the most part narrower forms with a very compact almost globular
or short oval nucleus. Occasionally very stumpy forms are seen (Fig. 28). The
presence of one or two large non-refractite vacuoles in the protoplasm is a
characteristic feature. In the fresh state they exhibit a very curious spring-like
action, bending slowly into a curve and straightening themselves with a jerk.
Sporozoits are most frequent in the lumen of the gut ; this is probably
due to the fact that, though the vermicules originally embed themselves in the
young cells near the basement membrane, they are carried during their develop-
ment by the growth of the cell towards the lumen. The large oocysts them-
selves, if not actually free in the lumen, are not far removed from this situation,
and the sporozoits when liberated for the most part therefore find themselves
already in the lumen.
The ultimate fate of the sporozoits and the method of re-entry of the parasite
into the dog. —As the female tick after repletion does not again suck blood, the
passage of the sporozoits into the ova seems a necessity, if the parasite is to
regain an entrance into the mammalian host. It is to be noted also that the
sporozoits are formed throughout the whole period of oviposition. Yet in the
ova I have never been able to find sporozoits, nor indeed have I ever encountered
these except in the gut.
Failing to find sporozoits in the egg I thought it probable that infection
took place by sporozoits, formed in the gut of the nymph, gaining entrance
into the dog when the tick in its adult stage fed again. Unfortunately for this
hypothesis experiments have shown that, though in the nymph parasites exhibit
the early stages of development, they have, in the two batches of nymphs
examined, completely disappeared by the fourth day.
In the larva and in the male tick I have been unable to trace any develop-
ment ; so that at present the method by which the parasite re-enters its mam-
malian host is very uncertain.
That the shrivelled ticks should be consumed with food is a possible, though
improbable, method of infection. If Durham's 4 observation that the young
ticks consume the contents of the mother be correct, it allows of another explana-
tion, but I am unable to confirm Durham in this respect, and the exact method of
infection has still to be ascertained.
SUMMARY AND CONCLUSIONS.
In the cycle which has been described there are some points in common
with that of Lankesterella, but in the formation of the sexuals form and in the
details of conjugation, there are very considerable differences. If one considers
the original vermicules to represent the microgametoblasts and macrogametes
of Lankesterella, one must in the case of the male element suppose that it is
formed by repeated fission of the mother-cells. In the case of the macrogametes
division more than once is unlikely, and even the formation of two forms each
capable of development is improbable. It is possible that one of the forms
-degenerates. This view is favoured by the fact that a considerable number of
degenerated vermicules, in which the chromatin is in the form of droplets, are
seen about the time that conjugation is in progress. The group depicted in
Fig. 29 , in which a degenerated vermicule is seen separated from a fertilised
oocyst by the pink substance characteristic of fission, also supports this view.
On the other hand, in the groups of fertilised oocysts, only the cast-off bodies of
the males are seen, so that if one of the products of division degenerates the
other must move away from its original position.
Another view regarding the nature of the changes seen may of course be
taken, namely, that the fission in the gut of the tick is a special schizogony
resulting eventually in male and female forms. But the first hypothesis seems
to be more likely.
The characters of the oocysts, and the fact that each of the limited number
of sporozoits apparently represents a sporoblast; recall Lankesterella.
As the sporozoits represent sporoblasts it is possible that they further
sub-divide, but there is no evidence to support such a view, and their formation
would appear to complete the sexual life cycle of Leucocytozoon can is, the
merogamous cycle of which I have already described elsewhere.
PAPERS REFERRED TO IN THE TEXT.
1 . H i n t z e ,
1 9 0 2 . — L e b e n s w e i s e u n d E n t w i c k l u n g v o nL
a n k e s t e r e l l a
m i n i m a ( C h a u s s a t ) .
Zool. Jahrb. abth. fur anat. XV, pages 693-730, one plate.
2, Labbé.—Recherches zoologiques et biologiques sur les parasites endoglobulaires du-
sang des vertébrés. Arch. de Zool. Exper. 3 sér., T. II, pages 55 to 258,
Pl. 1-10.
3. Siegel.—Die geschlechtliche entwicklung von Hæmogregarina stepanovi im Rus-
selegel (Placobdella catenigera). Arch. Protist. II, pages 339-342.
4. Durham.—1902. Report of Yellow Fever Expedition to Para. Liverpool School
of Trop. Med. Memoir 7.
5 . B i l l e t . —
C u l t u r e d ' u n t r y p a n o s o m e d e l e g r e n o u i l l e c h e z u n e h i r u d i n e e ; r e l a t i o n
ontogenique possible de ce trypanosome avec une hæmogregarine. C. R. Acad.
Sc. CXXXIX.
6. Laveran and Negré.—Sur un protozoaire parasite de Hyalomma Aegyptium. C
R. Soc. de Biol., T. 58, Nr. 21, pages 964-966.
7. Nicolle and Comte.— Sur le rôle possible de Hyalomma Aegyptium dans l'infection
hæmogregarinienne de Testudo mauritanica. lbid, T. 58, Nr. 23, pages 1045-
1046.
8. Christophers.—Hæmogregarina gerbilli. Sc. Memoirs by Offs. of the Med. and
San. Departs. of the Govt. of India (new series), No. 18.
9. .Patton.— On a parasite found in the white corpuscles of the blood of palm squirrels.
Sc. Memoirs by Offs. of the Med. and San. Departs. of the Govt. of India (new
series), No. 24.
1 0 .
C h r i s t o p h e r s . — L e u c o c y t o z o o n c a n i s . S c . M e m o i r s b y O f f s . o f t h e M e d . a n d S a n .
Departs. of the Govt. of India, No. 26.
11. Neumann.—Memoirs de la Soc. Zoologique de France, T. X, 1897, page 385.
12. Loundsbury.—Transmission of Malignant Jaundice of the Dog by a species of Tick..
Cape of Good Hope Depart. of Agriculture. Repr. from Agricult. Journal, 21st
Nov. 1901.
13. Nuttal.— Canine Piroplasmosis. Jour. of Hygiene, Vol. IV, No. 2, April 1904.
14. Christophers.— On the Anatomy and Histology of Ticks. Sc. Memoirs by Offs.
of the San. and Med. Departs. of the Govt. of India (new series), No. 23.
15.
J a m e s . —
O n
a p a r a s i t e f o u n d i n t h e w h i t e c o r p u s c l e s o f t h e b l o o d o f d o g s . S c .
Memoirs by Offs. of the San. and Med. Departs. of the Govt. of India (new
series), No. 14.
16. Wenyon.—Report on Dr. Gerrard's preparations accompanying the foregoing
communication. On a protozoon parasite found in the polymorphonuclear
leucocytes of a dog. Gerard. Jour. of Hygiene, Vol. 6, No. 3. (Jour. Hygiene,
Vol. 6, No. 3.) July 1906.
17. Minchen.— The Sporozoa. In Ray Lankester's Treatise on Zoology. Part 1,
2nd fascicle, 1903. A. and C. Black. London.
EXPLANATION OF PLATE.
Fig. 1. Two encapsuled parasites in the gut of the tick. x 2,000.
Fig. 2. Parasite in which the capsule is no longer to be made out. x 2,000.
Figs. 3 and 4. Formation of the vermicule. x 2,000.
Figs. 5, 6, and 7. Vermicules of the first stage with clear protoplasm. x 2,000.
Fig. 8. Vermicule with chromatin arranged in four separate rings. x 2,000.
Fig. 9. Vermicule which has embedded itself in a cell of the gut and is preparing for
fission. The cell is a young epithelium cell free from digestion products.
x 1,000.
Fig. 10. Swollen vermicule embedded in a cell of the gut. x 2,000.
Fig. 11. Vermicule in the act of fission within a cell of the gut wall x 2,000.
Fig. 12. Two vermicules of the second stage, the result of fission. x 2,000.
Fig. 13. A single stout form and a group of four vermicules (microgametes ?) embedded
in a cell of the gut. The cell contains a number of black granules, the
result of digestion. A stout vermicule in the act of fission is seen lying in
among the granules immediately beneath the group of four vermicules,
x 1,000.
Fig. 14. Thin form of sexual vermicule. x 2,000.
Fig. 15. Stout forms of sexual vermicules. x 2,000.
Fig. 16. A conjugation body. Early stage. x 2,000.
Fig. 17. A conjugation body. Early stage. Shows one vermicule much more loaded
with refractile vacuoles than the other. X 2,000.
Fig. 18. A conjugation body. Later stage. Shows the blending of the two chromatin
masses. x 2,000.
Fig. 19. A conjugation body. Late stage. Shows the chromatin opening outwards
X 2,000.
Fig. 20. A fertilised oocyst with two extruded masses of chromatin and the protoplasm
of the cast-off male vermicule. X 2,000.
Fig. 21. The same showing the absence of any trace of a nucleus in the cast-off male.
X ,2000.
Figs. 22 and 23. Nearly mature oocysts. X 2,000.
Fig. 24. Formation of sporozoits. x 2,000.
Fig, 25. Fully mature oocyst showing irregular form. x 1,000.
Fig. 26. A group of sporozoits resulting from the breaking up of an oocyst.
X 2,000.
Fig. 27. Usual form of sporozoit. x 2,000.
Fig, 28. Stumpy form of sporozoit sometimes seen.
Fig. 29. Oocyst showing degenerating vermicule still separated by the pink substance
characteristic of fission. x 2,000.
Fig. 1.
Fig. 2.
Fig. 3.
Fig 4.
Fig.. 5.
Fig. 6.
Fig. 7.
Fig. 8.
Fig. 9.
Fig. 10.
Fig. 11.
Fig.12.
Fig. 13.
Fig. 18.
Fig. 14.
Fig.16..
Fig. 17.
Fig. 20.
Fig. 22.
Fig. 26.
Fig. 24.
Fig. 21.
Fig. 25.
Fig. 29.
THE SEXUAL CYCLE OF LEUCOCYTOZOON CANIS IN THE TICK.
Fig 23.
Fig. 28.
Fig. 27.
Photogravure.
Survey of India Offices , Calcutta, December 1906.
NO. 28.
(NEW SERIES.)
SCIENTIFIC MEMOIRS
BY
OFFICERS OF THE MEDICAL AND SANITARY DEPARTMENTS
OF THE
GOVERNMENT OF INDIA.
THE SEXUAL CYCLE OF LEUCOCYTOZOON CANIS
IN THE TICK.
BY
CAPTAIN S. R. CHRISTOPHERS, M B., I.M.S.
(Superintendent of the King Institute of Preventive Medicine, Madras.)
ISSUED UNDER THE AUTHORITY OF THE GOVERNMENT OF INDIA
BY THE SANITARY COMMISSIONER WITH THE GOVERNMEN
T OF INDIA, SIMLA.
CALCUTTA:
OFFICE OF THE SUPERINTENDENT OF GOVERNMENT PRINTING, INDIA
1907.
Price annas twelve or 1s. 2d.
Ip/Q BoodO
No. 7.
(NEW SERIES.)
SCIENTIFIC MEMOIRS
BY
OFFICERS OF THE MEDICAL AND SANITARY DEPARTMENTS
OF THE
GOVERNMENT OF INDIA.
SOME OBSERVATIONS ON THE POISON OF THE
BANDED KRAIT BUNGARUS FASCIATUS).
BY
CAPTAIN GEORGE LAMB, M.D. (GLAG.), I.M.S.
ISSUED UNDER THE AUTHORITY OF THE GOVERNMENT OF INDIA
BY THE SANITARY COMMISSIONER WITH THE GOVERNMENT
OF INDIA, SIMLA.
CALCUTTA:
OFFICE OF THE SUPERINTENDENT OF GOVERNMENT PRINTING, INDIA.
1904.
Price 8 Annas or 9d.
No. 7.
(NEW SERIES.)
SCIENTIFIC MEMOIRS
BY
OFFICERS OF THE MEDICAL AND SANITARY DEPARTMENTS
OF THE
GOVERNMENT OF INDIA.
SOME OBSERVATIONS ON THE POISON OF THE
BANDED KRAIT (BUNGARUS FASCIATUS).
BY
CAPTAIN GEORGE LAMB, M.D. (GLAG.), I.M.S.
ISSUED UNDER THE AUTHORITY OF THE GOVERNMENT OF INDIA
BY THE SANITARY COMMISSIONER WITH THE GOVERNMENT
OF INDIA, SIMLA.
CALCUTTA:
OFFICE OF THE SUPERINTENDENT OF GOVERNMENT PRINTING, INDIA.
1904.