Historic Article - Universal Formulary on Tapeworms

from the 1887 Universal Formulary Encyclopedia


Tape-worm is a word popularly used in vague sense to designate any worm of the group Cestoidea (see CESTOID WORMS). according to Dr. Cobbold, upwards of 250 distinct forms of cestoid worms have been described, of which probably somewhat less than 200 mat be regarded as really good species. These he divides into the three families of (1) Taeniadae, or true tape-worms; (2) Bothriocephalidae, and (3) Tetrarhynchidae.

For the natural history of the tape-worm generally, we must refer to the article CESTOID WORMS. We will hear only remind the reader of the following points necessary for the due understanding of this article, and that every T. passes through several distinct phases during its life-history. In the ordinary colonial or tape-worm condition, says Dr. Cobbold, 'it has been termed the strobila (Van Beneden). The separate joints of which the strobila is composed are denominated proglottides, or zooids. The anterior segment forms the head, and remains barren, those of the neck and front part of the body being sexually immature during the process of strobile-formation. The mature proglottides at the caudal end are capable of realizing an independent existence, and the eggs which they contain develop the six-hooked embryos, or proscolices (Van Beneden), in their interior. These latter become metamorphosed into scolices or nurses, representing the well-known cysticercal state, which, in its sterile or aborted condition, forms the common hydatid.'

During the greater part of their existence, the tapeworms are parasitic animals, the mature proglottides and eggs being free only during a comparatively short interval. They are mostly restricted in their distribution to the vertebrate animals, comparatively few of the invertebrates (excepting the cuttle-fish) appearing to harbor them in their adult condition, although the T. larvae, nurses, or scolices probably abound in various invertebrate groups. In the human body, no less than ten species of T. occur, viz., eight true tape-worms, and two species of Bothriocephalus ; and as four distinct species have been found in the Barbary ape, it is obvious that errors of diet, due to civilization, are not the cause of these parasites.

Amongst the animals with which we are most familiar, the species are plentiful in the common dog (and in true carnivora generally), in rats, and mice. The typical ruminants are almost constantly infested both by mature and immature forms; while the larger pachyderms, and solidungulates (the horse, ass, &c.) harbor only a few adult forms; but only larvae appear to be known in swine. These worms appear to be as abundant in granivorous birds as in Carnivorous hawks, owls, &c. In the water-birds generally, the adult worms are very abundant, their larvae existing in the food of such birds, in fishes, molluscs, &c. In reptiles, these worms are extremely rare, although other parasitic worms abound; while in fishes they are very abundant both in the adult and larval forms.

The Taeniadae, or true tape-worm, may be distinguished from the other families of the order Cestoidea (cestoids or tapeworms in the popular sense) ' by the possession of a small distinct head, furnished with four simple oval or round suctorial discs (suckers), and commonly also with a more or less strongly pronounced rostellum (proboscis) placed at the summit in the median line. This prominence, when largely developed, becomes retractile, and when not in use, is lodged within a flask-shaped cavity, lined by a sheath, and supplied with special muscles; it is also very frequently armed with a single or double crown of horney chitinous hooks, there being occasionally as many as five or six separate circular rows of these organs. attention to the number, relative size and disposition of the hooks is often sufficient to determine the particular species. In nearly all cases, the reproductive orifices are situated at or near the margins of the joints which are bisexual.'

The eight true tape-worms accuring in man are (1) Taenia solium, Linnaeus; (2) T. mediocanellata, Kuchenmeister; (3) T. acanthotrias, Weinland; (4) T. flavopuncta, Weinland; (5) T. nana, Von Siebold; (6) T. elliptica, Batsch; (7) T. marginata, Batsch; (8) inococcus, Von Siebold.

The common tape-worm, taenia Solium, derives its Linnaean title from the idea that it is always a solitary worm. Although this is commonly, it is not by any means always the case: Kuchenmeister has several times found two or three together, and cases are recorded in which 30 and even 40 worms have been expelled from one patient.

The full-grown T. (strobila) has been known from the earliest times, and is described by Hippocrates, Aristotle, and Pliny; but its organization and mode of development have only been properly understood during the last few years. The segments of which it is composed vary in size, and number from 800 to 1000, the earlier immature ones being extremely narrow, and the sexually mature joints commencing at about the 450th segment. From 10 to 35 feet may be regarded as representing its ordinary length; its breadth at about the widest part being one-third of an inch.

The head, which is seldom seen in the tape-worms exhibited in our museums, although the evacuation of the head with the rest of the worm is not very rare, is very small and globular (about the size of a pin's head), with black pigment ingrained in it. On examining it with a low magnifying power, it displays four circular sucking discs, in front of which is a conical proboscis, armed with a double crown of hooks, from twenty-two to twenty-eight in each circular row. The head is succeeded by a very narrow neck, nearly half an inch in length, which is continued into the anterior or sexually immature part of the body, in which traces of segmentation first appear in the form of fine transverse lines, which are gradually re-placed by visible joints.

These joints or segments contains both male and female organs of generation; and in addition to these structures, the entire series of joints is traversed by a set of vascular canals constituting the so-called aquiferous system, which consists of two main channels, one passing down on either side of the worm, and both being connected by transverse vessels, which occur singly at one end of every joint. It is only in the alimentary canal of man or some other animal that a T. of any kind can attain to sexual maturity; and in all of these the eggs are fecundated before being discharged.

The expulsion of the eggs may take place in any of the following ways: First, the mature segments separate from each other, and passing out of the body, either with the ordinary evacuation of the bowels or independently, become decomposed, and set free the enclosed eggs. The single joints thus discharged undergo violent contraction after being expelled, which led to their being formerly mistaken for a distinct species of worm, to which the title Vermes cucurbitini was applied, from their resemblance to a pumpkin seed.

Examining the recently discharged excrement of a constipated dog, the same phenomenon may be very frequently observed. Secondly, the eggs may be discharged through the genital pore by pressure from any cause. It is only thus that we can account for the occasional co-existence of a Cysticercus cellulosae (the embryo of the worm) and an adult T. in the intestinal canal of the human subject - an association which constitutes one of the most serious dangers which the matured worm can inflict upon the host, and one of the strongest indications for its removal.

Thirdly and lastly, the mature joints sometimes appear to undergo disintegration within the intestine, and to liberate the eggs; but the conditions under which this disintegration occurs are unknown. In reference to the ultimate fate of the embryos in ovo, that are liberatedin the intestinal canal, Dr. Cobbold has informed the author of this article in a private communication, that, in his opinion, they do not migrate in the living host, except when by regurgitation they occasionally get into the stomach, when after their shells have been dissolved by the gastric juice, the young organisms commence their wanderings. The mature segments are usually expelled from the human bowel at the rate of six or eight a day. Their vitality is prolonged by moisture, which favors the distribution of the liberated eggs over grass and other vegetables, or in water, which may be used as food or drink by animals.

For a full description of the eggs, we must refer to Dr. Cobbold's work. It is sufficient here to remark, that, in their mature condition, they 'present a globular figure,and are easily recognized by their remarkably thick shell, which surrounds the six-hooked embryo. They present an average diameter of 1/694th of an inch, the shell itself measuring about 1/4000th of an inch in thickness.

After a while, by accident, as it were, a pig coming in the way of these embryos, or of the proglottides, is liable to swallow them along with matters taken in as food. ' The embryos, immediately on their being transferred to the digestive canal of the pig, escape from the egg-shells, and bore their way through the living tissues of the animal, and having lodged themselves in the fatty parts of the flesh, they rest to await their further transformations or destiny. The animal thus infected becomes measled, its flesh constituting the so-called measly pork.

In this situation, the embryos drop their hooks, and become transformed into the Cysticercus cellulosae. A portion of this measled meat being eaten by ourselves, either in a raw or imperfectly cooked condition, transfers the cysticercus to our own alimentary canal, in which locality the cysticercus attaches itself to the wall of the human intestine, and having secured a good anchorage, begins to grow at the lower or caudal extremity, producing numerous joints or buds to form the strobila or tapeworm colony.'

In its fully mature stage, the measle presents the appearance of an elliptical hydatid, varying in size from that of a pea to that of a small kidney-bean, the average diameter being one-third of an inch. On dissecting or breaking up a measle, it will be seen that the great vesicular portion constitutes the bladder-like caudal extremity of the cysticercus, while the head, neck, and body can be drawn out so as to exhibit a vermiform character.

From what has been already shown, it appears that we have a simple 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 follows:

(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 parasite spontaneously separates from the intestinal 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 lodgment in the intestinal 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 existence. 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, colic, 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 hysterical 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 brain. 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-muscular connective 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 myriads of tapeworm eggs, or they may be watered 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 examining 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 character in connection with the water-vascular system, into which we have not space to enter in this article. 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 examining 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 peculiarities 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 ascendancy, 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 prominence, 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.'