NationalLibraryOfScotland/medical-history-of-british-india huggingface dataset:
112
Oesophagostomum radiatum
particles. No larvæ were present in some due, presumably, to a close texture
of the soil, where the number of pore-spaces will vary inversely with the density
It is obvious that in clayey soil this migration will be impossible.
Experiment III.—A mass of fæces containing eggs of O. radiatum was
placed at the base of a grass growing in a mud-pot on 21 February 1941,
and covered with a glass-bell. Water was sprinkled on the fæces every
morning. On 27 February 1941, the blades and stem of the grass were cut
and examined, and two active larvæ and a very few dry ones were obtained
from the middle of the blades. Numerous larvæ were found in the soil.
This scarcity of the larvæ on the grass suggests that the grass may not
be their normal haunt, where the infective larvæ of many other worms lie in
wait for their host, in vast numbers. When extended to conditions in nature,
this will amount to the larvæ thriving better in pools of water in cultivated
fields than in grazing pastures, for, if in the latter they do not ascend the grasses
actively, their chances of being swallowed by cattle will be remote. Perhaps,
even in pastures, a greater availability of moisture and less of warmth may
provoke more larvæ to climb the grasses.
The longevity of the infective larvæ,
The infective larvæ of the hookworm of man have been observed, by
Baermann [Chandler, 1929] to live on soils under different conditions
from three weeks to six months. Veglia [1915] writes that the larvæ of
Hæmonchus contortus died in large numbers during the fourth month of
preservation in water and some lived up to the fifth month. On comparison
with the latter, the infective larvæ of O. radiatum should be said to be some
what short-lived, as larvæ stored in water and exposed to bright light were
alive for nearly two months, and those, which were protected by a black
paper round the bottle against intense light were dead in three months.
By keeping the light off, algal filaments were not encouraged to grow and
entwine round the larvæ.
It can never be judged how long the larvæ may continue to live in the field,
being conscious of the multifarious destructive forces in the environment to
which they are subject. It is common knowledge that in the field conditions
will not be as favourable as in the laboratory, that the continual migration of
the larvæ up and down the grasses or soil to escape the sunlight or drought
would demand an extraordinary energy and that the reserve food in the form
of fat-globules in the intestinal cells could not last long. It will be therefore
understood that in the pastures the life of the infective larvæ cannot exceed
the period observed in the laboratory.
THE PARASITIC DEVELOPMENT
Infection
Infestation by this worm is brought about when the infective larvæ reach
the intestine of the host. All species of Oesophagostomum so far studied have
been known to secure an entry into the host through the mouth by the infec-
tive larvæ being swallowed with grass, water or contaminated food. The
infection experiments during the present work were carried out only with oral
administration of the larvæ.
M.
ANANTARAMAN
113
With regard to the possibility of cutaneous infection with these larvæ,
reference has to be made to a study by Mayhew [1939] on the mode of infection
of Bunostomum phlebotomum and Oesophagostomum radiatum in cattle. The
method he adopted to make the infective larvæ come in contact with skin was
to throw the calf on one side, tie its legs firmly, pour the water containing the
larvæ in small quantities on the unshaven skin of the flank and work the larvæ
into the hair for some time. By pressing the hand on the portion of the body
for about half an hour warmth was preserved. The calf was then placed for
varying periods in a stanchion where it could not turn and lick its body. Of
five experiments performed under these conditions with O. radiatum four
resulted in successful cutaneous infection. It should be agreed with him that
' oral infection by licking the hair contaminated with larvæ in the bedding
places does not seem to have been considered by livestock owners, veterina-
rians, and research workers, even though it is well known that cattle constantly
lick themselves and one another'. From his observation that the larvæ
are able to thrive among the hairs of the calf for at least a week, it could be
imagined how great the opportunities are, for an infestation by licking the
body and how effectively the shaded areas of the cattle-yard would serve as
sources of infection.
Parasitic life
The second half of the third-stage larva, the fourth-stage larva and the
fifth-stage or adult are parasitic. On arrival in the intestine the second
ecdysis is undergone, the exsheathed third-stage larva bores the wall of the
small intestine and forms a nodule. The larva continues to be recognized as
the third-stage larva inside the cyst until after a time when the third ecdysis
is achieved and the fourth-stage is attained. Some days later, the fourth-
stage larva returns to the intestinal lumen, and while moving across the
caecum sheds the cuticle for a fourth time, takes its permanent position in the
large intestine as the adult, matures and oviposits.
The parasitic third-stage larva
The second ecdysis which should have marked the transition from the
second to the third (infective) stage occurs when the infective larvæ reach the
small intestine. In a white-mouse, to which 400 larvæ were administered and
which was killed seven hours after, 50 per cent of the larvæ were divested of
the sheath as a result of the second ecdysis, in the small intestine. The ex-
sheathed larva resembled the infective larva proper inside the sheath (Fig. 12.)
The larva had grown and measured 0.76 mm. long as compared to 0.68 mm.
inside the sheath. The œsophagus was 0.16 mm. long somewhat claviform and
transversely striated, the intestine consisted of 10 pyramidal, nucleated cells
on each side with a wavy lumen, and the oblique narrow rectum opened as the
anus, 0.08 mm. from the posterior end. The mouth and anus were open. The
nerve commissure and the excretory canal had the same appearance as in the
infective stage ; the genital rudiment was disposed between the 6th and 7th
intestinal cells on the ventral side, 0.42 mm. away from the oral end and
114
Oesophagostomum radiatum
measured 0.018 mm. in length. When neutral red was applied the larva did
not absorb it.
FIG. 12. Larva in the third parasitic stage, recently exsheathed in the intestine of a
mouse, resembling the infective larva in all characters except the posses-
sion of a sheath.
These exsheathed third-stage larvæ move towards the intestinal wall
and penetrate into it through the mucous membrane causing extensive lesions
and destruction of villi. The penetration is usually completed in about 30
hours, but in rare cases (Plate IX, fig. 6), as in calf No. 10, the larva is seen
to enter the mucosa only after three days. This penetration is recognized
PLATE IX
FIG.
„
„
„
„
„
„
„
1.
2.
3.
4.
5.
6.
7.
8.
An egg in the 4-celled stage. The nuclei of the cells are seen.
An embryo taking the shape of a worm, the broad end being the head and tapering end the
tail.
A just-hatched first-stage larva ; buccal capsule clear.
An infective larva showing the whip-like tail, the oesophagus and the chyle intestine.
The tail of an infective larva.
Section of an intestinal wall of calf No. 10 in which the oesophagostomum larva is seen to have
penetrated the mucosa.
The larva in Fig. 6, under higher magnification.
Section of the wall of the ileum of calf No. 5 showing the nodule in formation, the third-stage
larva, and the cyst.
Indian J. Vet. Sci. & Anim. Hush., Vol. XII, Part II ]
PLATE
IX
FIG. 1 ×230
FIG. 2 ×330
FIG. 3 ×195
FIG. 4 × 95
FIG. 5 ×250
FIG. 6 ×32
FIG. 7 ×230
FIG. 8 ×25
[ For expiation of the lettering please see the text
PLATE
X
[ Indian J. Vet. Sci. & Anim. Hush., Vol. XII, Part II
FIG.1 ×24
FIG. 2 ×18
FIG. 3 ×120
FIG. 4 ×33
FIG. 5 ×26
[ For explanation of the lettering please see the text
PLATE X
FIG.
„
„
„
„
1.
2.
3.
4.
5.
Section of a nodule in the ileum of calf No. 5, where the nodule is advanced in growth, and
the third-stage larva seen inside the cyst. Note the destruction of the villi in the central
region.
Section of an intestinal nodule of calf No. 5 with the larva cut in three portion.
The cyst of the same nodule enlarged to show its non-cellular wall.
Different regions of
the larva are also sectioned.
Section of a nodule of calf No. 3, to show the position of the larva near the darkly stained
region, in which caseation has commenced.
An entire fourth-stage larva from a nodule in calf No. 11, the cuticular inflation in its early
stage and the œsophagus being clear.
M.
ANANTARAMAN
115
by Fourie [1936] as ' primary parasitic migration'. The larva does not
proceed beyond the sub-mucosa, where it forms a cyst located against the
muscularis mucosa (Plate IX, fig. 8). The cyst projects into the intestinal
lumen as a nodule. The encysted larvæ, invariably lie in a coiled state
inside the cyst and undergo rapid development (Plate X, fig. 1).
Such a larva obtained from a nodule 43 hours old has the following
features :—The shape of the larva is appreciably altered since encystment,
the anterior and posterior ends being tapering and the middle region of unifom
thickness (Fig. 13). The larva has the appearance of having grown stouter,
the maximum width being 0.055 mm., and the tail has shortened. The
length of the body is found to be 0.78 mm.
FIG. 13. Third parasitic larva, inside a nodule 43 hours after oral intake, cylindical
short tail, 3 lips round mouth (shown separatly), œsophagus slightly
club shaped, intestine dark and prominent ending in an obliqeu rectum,
a large cervical gland leading from the excretory canal and lying over
the intestine, nerve-ring conspicuous, and genital cells grown and in front
of rectum.
The cuticle is fairly thick and distinctly striated, with fine lateral lines.
Protruding inside the body cavity are the muscles which could be clearly seen
in an optical section, on the sides, as a row of nucleated cells of varying
dimensions.
M.
ANANTARAMAN
117
and transversely striated, and the lumen is narrow and triradiate. The
general appearance of the œsophagus is that of a club-shaped organ.
FIG. 14. Fourth-stage larva from a nodule, showing cupoliform monodonted buccal
capsule, claviform œsophagus, genital rudiment, and cervical vesicle in
formation. The tapering tail is indicative of the female sex.
The intestine is conspicuous by its dark colour and by its length of 1.84
mm. and breadth of 0.08 mm. The wall is somewhat thick and the cavity
wavy and irregular. Posteriorly, it gradually narrows and joins the rectum,
running as usual at a tangent towards the ventral body-wall. Where the
rectum is joined to the intestine is the pair of rectal ligaments. The anus
is a perforation in the middle of a slightly elevated region of the cuticle.
The cuticle is thick and ringed. For the first occasion in the evolution
of the larva, the cuticle in the œsophageal region is inflated to a small degree,
0.18 mm. from the oral end, to form a small bulbous structure on the ventral
side and a much smaller sac dorsally in the same transverse plane. There is
a sharp furrow behind this inflation known as the cervico-ventral groove which
is distinctly recognizable on the ventral side. On each side, behind the cervico¬
ventral groove and near the nerve-ring is a protuberance of the cuticle the
118
Oesophagostomum radiatum
cervical papilla. There is a flat expansion of the cuticle on each side forming
the lateral line and extending from behind the cervico-ventral groove to about
the anal region.
The nerve-commissure distinguishable as a fibrous structure round the
middle of the œsophagus and as two oval regions in optical section on the sides
of the œsophagus is 0.02 mm. broad and situated 0.015 mm. behind the cervico¬
ventral fissure.
The excretory pore is present on the mid-ventral line, inside the cervical
groove, and is in continuation with a fine arched excretory canal running
posteriorly and traceable into the neck of the two cervical glands, one of which
is very large and occupies nearly two-thirds of the length of the larva. The
glands are disposed on the intestine, and have prominent nuclei.
The development of the reproductive organs has advanced to a great
extent and it is possible to judge at this stage whether a larva will develop into
a male or a female. The structure that presents the distinctive features of a
sex is the tail, and a consideration of the shape and length of the tail will lead
to the correct determination of the sex.
In the larva that would grow into a female adult, the tail is long and
gradually tapering from behind the anus and the tip is slightly knobbed (Fig.
15). The genital rudiment which was just behind the cervical gland in the
FIG. 15. The tail of the same fourth-stage larva to show rectal ligaments, and the genital
rudiment growing longer.
120
Oesophagostomum radiatum
ovary. In all other respects, the larvæ in this stage resemble the fourth¬
stage larvæ inside the nodule, still retaining the provisional ankylostomiform
or cupoliform, monodonted buccal capsule and a feeble cervical cuticular
inflation (Fig. 16).
FIG. 16.
FIG.
17.
FIG. 16. The head of a fourth-stage larva that has just emerged from the nodule. The
ankylostomiform buccal capsule with & tooth and cervical inflation are
figured.
FIG. 17. The caudal region of the same larva, a potential male, with the spicular appara¬
tus dorsal to the intestine and the two rows of cells forming the testis.
One more ecdysis and the adult stage is attained. The ecdysis involves
a separation, as usual, of the outermost skin from the larva beginning from the
anterior end and culminating in the posterior region, around the bursa in the
male and the long tail of the female.
Calf No. 3 which was infected with 2000 larvæ on 29 February 1940
was destroyed on 29 March 1940, i.e. after an interval of 28 days and 19
hours. A number of fourth-stage larvæ were present in the lumen of the
colon and among them were some which had completed the fourth ecdysis and
were undergoing maturation. Some others were only then metamorphosing
into the fifth stage and the majority had not exsheathed for the fourth time.
From this it may be approximately calculated that the transformation into
the adult after the fourth ecdysis takes place about the 28th day.
In Fig. 19, the structural organization of the head of a larva some time
before ecdysis is indicated. The noteworthy feature is that the definitive
œsophagostomiform buccal capsule is making its appearance between the
M. ANANTARAMAN
121
posterior limit of the ankylostomiform capsule and the anterior end of the
œsophagus. There is a prominent annular chitinisation of the wall of the
œsophageal funnel.
FIG. 18. The caudal region of a female in the same stage as in Fig. 17, where the female
organs, viz. the ovary, uterus, and pars ejectrix are being differentiated.
D 2
122
Oesophagostomum radiatum
The larvæ undergoing these changes gradually migrate down the ileum and
caecum and reach the colon which is the habitat of the adult worm.
FIG. 19. The anterior end of a larva before fourth ecdysis. Between the provisional
ankylostomiform buccal capsule and the œsophagus is observed the defini-
tive oesophagostomiform capsule in development.
The fifth or the adult stage
Figs. 21 and 22 and photographs (Plate XI, figs.3 and 4) represent the
tails of a male and a female and fig. 20 the head of one of them, soon after the
fourth ecdysis. In the head, the primary changes are that the œsophagostomi¬
form buccal capsule and the cuticular vesicle are established. The mouth is
surrounded by six papillae and the buccal capsule is ring-shaped 0.045 mm.
in diameter and provided with only internal leaf-crowns. The œsophageal
funnel leads into the lumen of the œsophagus. The cervical cuticular vesicle
is highly inflated with an insignificant transverse constriction about two-thirds
its length, and a definite cervical groove more conspicuous in the ventral
region than in the dorsal. Behind this is the cervical papilla at the origin of
the lateral membrane on each side.
The tail of the male has acquired more definition of the sexual characters,
the bursa being formed in its extremity. The cloaca is unmistakable and into
it the rectum, the vas deferens and the spicular canals open together. The
spicules are forming, and the vas deferens connects the testes with the cloaca.
The testis lies ventrally to the intestine and commencing from about the middle
of the worm travels down as a solid cord with two rows of cells till near the
rectum, then widens into the seminal vesicle and the ejaculatory duct. The
bursa is in two lateral halves meeting one another on the mid-ventral line, and
on each of which the rays are being differentiated. As in the adult, the ventral
and the latero-ventral; the antero-lateral, the medio-lateral and the postero-
lateral ; the externo-dorsal; and the dorsal rays can be identified. The dorsal
portion of the bursa is projected obliquely to some distance and ends in a
knob.
Indian J. Vet. Sci. & Anim. Husb., Vol. XII, Part II
]
PLATE
XI
FIG. 1. The head-end of the same larva indicating the ankylostomiform mouth and the cervical en-
largement of the cuticle.
„ 2. The head of a fourth-stage larva about to undergo the fourth-ecdysis. The provisional buccal
capsul is still present.
„ 3. The caudal region of the same larva with the ovary, the pars ejectrix and the vagina formed,
but no vulva.
„ 4. The caudal region of a, male larva in the same stage, in which the genital bursa has developed ;
a few of the rays, and the testis are recognized.
[ For explanation of the lettering please see the text
FIG. 1 ×120
FIG. 2 ×184
FIG. 3 ×120
FIG. 4 ×110
M. ANANTARAMAN 123
The female characters, at this stage, are that the posterior portion of the
genital rudiment which was situated in front of the rectum has enlarged
into an oval body and acquired a prominent cavity inside. This is the par
FIG. 20. The head of worm which has just completed its fourth ecdysis. The three
oral papillae on each side, the œsophagostomiform capsule with the inter-
nal leaf-crown and the highly inflated cervical vesicle are significant.
ejectrix of the ovijector apparatus and it sends out a blind protuberance of its
wall towards the cuticle which is the vagina. The vulva is not established yet.
Anteriorly as well as posteriorly, the pars ejectrix is in connection with a
short hollow tube, the uterus with fairly thick walls and of a length of 0.05 mm.
The pars haustrix is undefined now. The ovary joined to the uterus in front
appears as a solid structure with its cells well-defined and taking a wavy
course traverses the coelom to about half the length of the worm.
The growing adult having reached its permanent locality in the colon has
yet to prepare itself for complete development. There is marked growth in
size coordinated with sexual development, involving maturation of the testis
or ovary, copulation and fertilization. The period, during which the worm
grows, from the moment of ingestion to adulthood is known as the ' Incuba-
tion period ' [Veglia, 1928] and this has been found, in the case of O. columbia-
num, to vary from 38 days to over a hundred days. This is judged from the
time that lapses from the day of infection to the day of the first appearance
of the worm's egg in the faeces of the host.
124
Oesophagostomum radiatum
FIG. 21. The caudal extremity of a male soon after fourth ecdysis. The genital bursa
with its characteristic rays, the spicules, the testis and vas deferens are
differentiated.
FIG. 22. The caudal end of a female after ecdysis showing the uterus, pars ejectrix and
the formation of the vagina.
In calf No. 4, to which repeated doses of infective larvæ of 0. radiatum
were administered from 16 October 1939, infective larvæ were trapped for
the first time in the water-jacket of a culture of faeces passed on the 41st
day after the first drench. Again calf No. 11 swallowed infective larvæ on
19 August 1940 and the first occasion when infective larvæ were obtained
was from the fæces passed on 14 September 1940, i.e. the 26th day after
ingestion. This is a surprisingly short period as compared to the previous
record of 41 days and to the smallest period, viz. 38 days, in the case of O.
columbianum. It may be presumed that in O. columbianum [Veglia, 1928]
records the ' first appearance of eggs in the faeces '. and not the first occurrence
of infective larvæ in it, and as it has been experienced that eggs in the fæces
may be missed in the early stages on account of their scantiness, it is possible
that Veglia would have recorded the first appearance of the eggs earlier if he
had cultured the faeces, to look for the infective larvæ, and not examined
them for eggs, as is apparent.
The fully-developed worms are easily distinguished into males and female
even with the naked eye, and mostly have a hooked anterior end. The male
M. ANANTARAMAN 125
are generally smaller than the females the average length of a male being
17.1 mm. and that of a female 19.7 mm.
In the mature or gravid worms the head (Fig. 23) shows an oral cuticular
collar appearing as two vesicles on the sides of the mouth, six papillae round
the mouth, a much dilated and conspicuous cephalic vesicle and a deep cervical
groove on both the dorsal and ventral sides taking an anterior bend on the
lateral lines. The lateral alae begin behind this indentation and are pierced
by the cervical papilla near that region.
FIG. 23. The head of an adult. The cervical vesicle is expanded to the maximum and
the cervical groove is distinct.
The mouth is circular, 0.06 mm. in diameter, and leads into the buccal
capsule which is annular and broader anteriorly than behind. There are pre-
sent only diminutive internal leaf-crowns. The œsophageal funnel is 0.02
126
Oesophagostomum radiatum
mm. long and is continued as the lumen of the œsophagus. The œsophagus
has its characteristic claviform shape and striated, highly muscular walls.
There are two hardened structures functioning as valves between the œsopha-
gus and intestine.
FIG. 24. The genital bursa of an adult male.
The nerve-ring and the excretory opening are placed in the same trans-
verse plane about the middle of the œsophagus. The cervical glands are as
usual very large.
In the male, the tail is expanded into the genital bursa (Fig. 24) which
on each side bears the dorsal, externo-dorsal, postero-lateral, medio-lateral,
antero-lateral, latero-ventral and the ventral rays. The dorsal ray has a
short branch about its middle in the ventral direction, the externo-dorsal ray
is the thickest of all, the antero-lateral, medio-lateral and the postero-lateral
are clubbed together except at their distal ends, and the latero-ventral and the
ventral rays are likewise adjacently placed. The cloaca opens on the genital
cone which consists of two lips, each with two papillae. Into the cloaca open
the ejaculatory duct, the rectum and the spicular canal. The spicules are
two closely apposed, somewhat slender, structures. The ejaculatory duct
leads inwards into the seminal vesicle, vas deferens and the testis, the last of
which is highly convoluted round the intestine.
The female is characterized by the conical tapering tail (Fig. 25), in which
the vulva can be identified on a cuticular eminence 0.45 mm. in front of the
anus. It is in communication with the pars ejectrix through a short vagina.
The pars ejectrix is a hollow reniform body laid parallel to the long axis of the
body, is lined with cuticle and contains protuberances at each end into its
cavity. Both anteriorly and posteriorly it is continued as the pars haustrix,
0.13 mm. long and tubular. To the anterior end of each pars haustrix is
attached the uterus extending in front to a comparatively greater distance
where it joins the ovary. The ovary is extremely long and proceeds backwards