IUBio Biosequences .. Software .. Molbio soft .. Network News .. FTP

No subject

Sun Apr 10 15:49:28 EST 2005

alternation of generation in which the immediate product of the
proglottis (or sexually matured zooid individual) is a six-hooked
brood; by metamorphosis, the latter becomes transformed into the
cysticercus, having a head with four suckers, and a double crown of
hooks; and by germination, the latter gives rise to a whole colony
(strobila) of individuals, the greater part of which are destined to
become sexually mature - zooid individuals or proglottides. It will be
observed, therefore, that the product of a single ovum is, in the
first instance, a single non-sexual embryo; in the second phase, it
becomes a non-sexual cysticercus (these two phases together
constituting the protozooid); in the third change it gives off, by
budding, numerous gemmules, most of them destined to be sexually
mature individuals (or deuterozooids), in this way resembling their
original parents.
The relation and nature of these developmental changes may be further
simplified by placing the various life phases in a tabulated form as
(a) Egg in all stages.
(b) Six-hooked embryo=proscolex.
(c) Resting larvae or Cysticercus (telae) cellulosae (scolex).
(a,b,c) Protozooid.
(d) Immature tapeworm.
(e) Strobila, or sexually mature Taenia solium.
(f) Proglottis (cucurbitinus)= free segment=deuterozooid.

How long a T. can naturally exist in an intestinal canal is not known;
but there is doubtless a period at which the parasitespontaneously
separates from the intestional mucous membrane of its host - a period
probably coinciding with the shedding and non-renewal of the circlet
of hooks. When this separation occurs, the whole length of the worm is
expelled in the same manner as if the parasite had been first killed
by the administration of a vermifuge medicine. From this history of
the structure and life history of this organism, which applies with
slight difference in minor points to all other tape-worms, we proceed
to describe the injurious effects which the worm in its adult and
larval stages produces on man, and the precautions which should be
taken to prevent its entrance into the system; while the discussion of
the means of expelling it when it has once found a lodgement in the
intestional canal, will be postponed to the article on Vermifuges.
The common T. may cause disease, and even death, by its aggressions
either in the adult or in the larval stage of its existance. A mature
T. in the intestinal canal may give rise to a series of anomalous
symptoms, including ' vertigo, noises in the ears, impairment of
sight, itching of the nose and anus, salivation,dyspepsia, and loss of
appetite, coloc, pains over the epigastrium and in different parts of
the abdomen, palpitation,syncope, the sensation of weight in the
abdomen, pains and lassitude in the limbs, and emaciation.'  Many
cases are on record in which histerical fits, chorea, epilepsy,
convulsions of various kinds, and even mania, have been induced by the
irritation excited by this parasite, and have ceased at once on its
removal. But distressing as these symptomatic phenomena may be, their
injurious effects are trifling as compared with the troubles which
follow the deposition and growth of the larval form within the body,
especially when the cysticerci find a home in the more important vital
organs. There are at least a hundred cases on record in which the
cysticercus has caused death by its development within the human
In the present state of our knowledge, it is impossible to diagnose
these cases; and even if a correct diagnosis were possible, nothing
could be done in the way of treatment. Epilepsy, with or without mania
or imbecility, is commonly, but not invariably present in these cases.
' Cysticerci,' says Dr. Cobbold, ' may develop themselves in almost
any situation in the human body, but they occur most frequently in the
subcutaneous, areolar, and inter-muscularconnective tissue; next, most
commonly in the brain and eye, and lastly, in the substance of the
heart and other viscera of the trunk. The adult form of the worm
enters the system as the cysticercus of measly pork, and to eat raw or
underdone measly pork is an almost certain means of introducing this
parasite into the body. It is satisfactory to know that the
temperature of boiling water is quite sufficient to destroy the
vitality of the measles; and that in ordinary salted pork, and in
hams, they are destroyed by the action of the salt in the one case,
and of the combined salt and smoke in the other. Sausages, into which
it is to be feared measly pork too often finds its way, are rendered
safe if they are cooked till no pink, raw like, fleshy look can be
seen in their center. Butchers are especially liable to T., in
consequence of their touching and cutting measly pork, and then
accidentally transferring the cysticercus by the hand, or even by the
knife for various meats, both butchers and cooks may readily
disseminate the infection over various articles of food.
The larval worm may gain access into the human body by our swallowing
the mature eggs of the tape worm. Those who, as students of this
department of natural history, handle fresh tape-worms, are perhaps
especially liable to this misfortune; but, says Dr. Cobbold, ' our
neighbors, who devour choice salads, also run a certain amount of
risk, not only as regards this entozoon, but as respects several
others. The vegetables may be manured with night-soil containing
myrads of tapeworm eggs, or they may be watred with fluid into which
eggs have been cast. In such cases, one or more tape-worm ova may be
transferred to our digestive organs, unless the vegetables are
carefully cleansed before they appear on the table. In the same way,
one perceives how fallen fruits, all sorts of edible plants, as well
as pond, canal, or even river water, procured from the neighborhood of
human habitations, are liable to harbor the embryos capable of gaining
an entrance to our bodies. It thus becomes evident also how one
individual suffering from tapeworm may infect a whole neighborhood,
rendering the swine measly, these animals in their turn spreading the
disease far and wide.' Such a person may also prove dangerous - even
fatal to his neighbors directly (without the intervention of a pig),
by ejecting mature proglottides, from which thousands of eggs may
escape, some of which may readily come in contact with human food or
drink, make their way into the stomach, and from thence get into the
circulation, and finally to the brain.
The most remarkable case on record of what may be termed a measly man,
is the one described, in 1864, by Delore, in the Gazette Med. de
Paris, and quoted by Dr. Cobbold. He died at the age of 77, from
pulmonary catarrh, old age, and fractured neck and thigh bone; and on
examinating his body after death, no less than 2000 cysticerci were
found, of which 111 occurred in the nervous centers.
The T. that ranks next in importance to the Taenia solium is the
Taenia mediocanellata, which was first established as a distinct
species by Kuchenmeister only a few years ago. It exceeds the T.
solium both as regards length, breadth, and the thickness of the
individual segments; the head is also somewhat larger, abruptly
truncated at the crown, destitute of a proboscis and a hook -
apparatus - hence this species has been described as the hookless
tape-worm - but furnished with very large sucking disks, surrounded by
much dark pigment, which gives the head a blackish appearance. The
specific name of mediocanellata has reference to an interesting and
almost specific charactor in connection with the water-vascular
system, into which we have not space to enter.
Leuckart has proved by experiment that the measles or cysticerci which
produced this worm are to be found in the muscles and internal organs
of cattle. He administered proglottides of T. mediocanellata to three
calves, a sheep, and a pig. In the two last-named animals, they
produced no effect, as was shown by their post-mortem examination;
while in the calves they produced a kind of leprosy, which has since
been characterized as ' acute cestoid tuberculosis, ' and which proved
fatal if too large a dose of eggs was administered. On examinating one
of these animals after its restoration to health - 48 days after the
eggs were swallowed - he found numerous cysticercus-vesicles, larger
and more opalescent than those of the pig, lodged within the muscles;
and as the heads of the contained cysticerci exhibited the distinctive
peculirities presented by the head of the adult worm, ' we are
supplied with the most unequivocal evidence that man becomes infested
with this second form of tape-worm by eating imperfectly cooked veal
and beef.' Hitherto, the two above-described species have commonly
been included under T. solium, from want of due examination,
especially of the head. Dr. Cobbold believes that their respective
frequency will ultimately be found pretty well on a par, though
probably the T. solium will maintain a slight ascendency, in
consequence of the relative cheapness of pork. ' Admitting occasional
exceptions,' he observes, ' the hooked worm infests the poor, and the
hookless worm the rich. This circumstance accords with the fact, that
the lower classes subsist chiefly upon pork, whilst the wealthier
prefer mutton, veal, and roast beef. It gives rise to the same
symptoms as the T. solium.
The next five tapeworms infesting man, Taenia acanthotrias is only a
rare case, in the larvae stage, it was found in the muscles of a
woman. The last species we shall describe, the T. echinococcus, is, in
its larval condition, probably more fatally injurious to the human
race than all the other species of entozoa put together. In its mature
(strobila) condition, in which it is found only in the dog and wolf,
it seldom exceeds the fourth of an inch in length, and develops only
four segments, including that of the head. The final segment, when
sexually mature, equals in length the three anterior ones, and
contains as many as 5000 eggs. The proscolex or embryo forms large
proliferous vesicles, in which the scolices or larvae (known also as
acephalocysts, echinococci, echinococcus heads or vesicles, pill-box
hydatis, &c.) are developed by germination internally. The eggs
develop in their interior a six-hooked embryo, and these embryos are
introduced into our bodies with food or water into which the eggs have
been carried.
' With a special liking for the liver,' says Dr.Cobbold, ' they bore
their way into this organ or are carried along the circulating current
to other organs. In these situations, they sooner or later become
transformed into simple vesicular, bladder-like bodies, commonly
called acephalocysts or hydatids.' Instead, however, of displaying the
head, neck, and body of a cysticercus, the vesicle retains a globular
figure. Its growth is slow, and many months elapse before echinococci
are developed within our bodies, after we have swallowed the proper T.
eggs and their contained embryos. There have been great differences of
opinion amongst physiologists as to the mode of development of these
echinococci; but the following is probably the current view. The inner
surface of the vesicle presents after a time slight papillae or
prominences, which, as they enlarge and become oval, are eventually
scoleciform, and contain a cavity filled with a limpid fluid. This
scolex-like development produces in its interior a brood of scolices
or echinococcus heads, or, in other words, becomes gradually
transformed into the so-called 'brood-capsules' of helminthologists.
It is almost impossible to explain the nature of these brood-capsules
with young echinococci in their interior, without the aid of such
diagrams and illustrations as are given by Cobbold in his chapter on
T. echinococcus.
In the fully developed state, the echinococci vary from 1/60th to
1/100th of an inch in diameter. The rostellum supports a double curve
of hooks, those in the smaller row varying in size from 1/1040th to
1/1780th of an inch, whilst those of the larger series are from
1/830th to 1/1780th of an inch. Below the hooks are four suckers, and
the general appearance of the body is finely granulated, from its
containing calcareous particles. These hooklets are so characteristic
and important in diagnosis, that we give a highly magnified
representation of them. It often happens that the discovery under the
microscope of a few of these little hooks at once decides the nature
of an otherwise mysterious tumor. Of 373 cases of the parasite
occurring in man, collected by Davaine (who devotes more than
one-third of his Traite des Entozoaires to this subject), 165 affected
the liver, 40 the lungs, 30 the kidneys, 20 the brain, and 17 the
bones, while the remainder were spread over other parts; and of 136
cases collected by Cobbold, 51 affected the liver. No less than 35 of
these 51 cases recovered. ' Four of them were complete natural cases;
two others being also temporarily cured in the same way. All the rest
were cured by surgical operations.'

Historical Information Only


More information about the Parasite mailing list

Send comments to us at biosci-help [At] net.bio.net