Tropical Diseases/Chapter 41
CHAPTER XLI
I. PARASITES OF THE CIRCULATORY AND LYMPHATIC SYSTEMS (concluded)
SCHISTOSOMUM HÆMATOBIUM (Bilh. - v. Sieb., 1852)
Definition of endemic hæmaturia.— A chronic endemic disease caused by Schistosomum hœmatobium ( = Bilharzia hœmatobia, Distomum hœmatobium), giving rise to cystitis and hæmaturia, or to proctitis, or to other symptoms, and characterized by the presence of the ova of that parasite in the urine, or in the fæces, or in both.
History and geographical distribution.— The frequency of hæmaturia in the natives of Egypt, and in visitors to that country, has long been remarked. The explanation was supplied by Bilharz, who, in 1851, discovered the cause in a peculiar digenetic trematode which Cobbold proposed to name Bilharzia in honour of its discoverer.
In 1864 Dr. John Harley recognized the characteristic ova in cases of hæmaturia from Natal. The disease has since been found in many other parts of Africa, more particularly along the eastern side of the continent as far south as Port Elizabeth. Balfour found it in the Soudan. According to Low it is very frequent in the natives of Uganda. It is met with in West Africa and is very common in Rhodesia. In Egypt, judging from Bilharz's, Griesinger's, and Sonsino's post-mortem records, it is present in quite one-half of the population; in one village, Marg, Leiper found that no fewer than 90 per cent, of the children were infected. It occurs also in Arabia, Syria, Persia, Mesopotamia, Cyprus, and Mauritius. Nelson records two cases in Western Australia in individuals who had never been out of that country; apparently the parasite was introduced by a man who had served as a soldier in the Boer War. As this shows that the conditions (intermediary host, etc.) are present, the spread of bilharzia disease in Australia may be anticipated.
Fig. 129.—Schistosomum hæmatobium, male and female. (Partly after Looss.)
Etiology.—Schistosomum hæmatobium (Figs. 129, 130, 131) is a bisexual trematode belonging to the family Schistosomidæ. The male is white, cylindroid, 11 to 15 mm. in length by 1 mm. in breadth. It possesses an oral and a ventral sucker of about equal size and placed close together. The cylindrical appearance of the worm is produced by the ventral infolding of the two sides of what would otherwise be a flat body. By this infolding a gynæcophoric canal is formed, in which the female can be partially enclosed. The outer surface of the body is closely beset with small cuticular prominences. The female is rather darker in colour than the male, considerably longer (20 mm.), more filiform, her middle being usually enclosed in the gynæcophoric canal referred to, whilst her anterior and posterior portions remain free. The genital openings of the sexes face each other, and are placed immediately posterior to the ventral sucker. The sexes live apart while young, but on reaching maturity the female enters the gynæcophoric canal of the male.
These parasites are found in the blood of the portal vein, in its mesenteric and splenic branches, and in the vesical, uterine, and hæmorrhoidal veins; they have also been found in the vena cava. Sonsino considers that, if searched for, they would probably be found elsewhere in the circulation. Their numbers vary considerably. Sonsino reports finding in one case forty; in another case Kartulis found 300 in the portal vein and its branches. Looss has seen the submucous tissue of the bladder so rich in worms that a pair could be found in every area of half a centimetre square.
The ovum.—On microscopical examination the uterus of the female bilharzia is found to be stuffed with ova of a peculiar and characteristic shape. They are oval, each egg on an average measuring about 0·16 mm. in length by 0·06 mm. in breadth, and one end of the ovum is provided with a short, stout, and very definite spine. (Plate XIII., Fig. 1.)
The exact nature of the process by which the ova leave the body of the human host has not been satisfactorily explained. Apparently the female worm migrates from time to time from the larger veins to their smaller radicles, and in these deposits her ova. The walls of the bladder are the favourite situations for this purpose. Afterwards the eggs are somehow carried, possibly aided by the spine with which they are provided, towards the surface of the mucous membrane, and then, falling into the bladder, are voided with the urine, a certain amount of blood escaping at the same time.
The free larva (Fig. 132).—In newly voided urine the ovum
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| Fig. 130.—Schistosomum hæmatobium; anterior end of male. (After Looss.) |
Fig. 131.—Schistosomum hæmatobium. Diagram of transverse section of male and female. |
presents a somewhat brownish appearance, and generally contains a ciliated larva (miracidium). After a time the larva may escape through a longitudinal rupture in the shell. It then swims about, but, unless supplied with fresh water, soon perishes. If the urine be freely diluted with water, the larva not only escapes more quickly from the shell but also continues to live, swimming and gyrating very actively, for a considerable time. While swimming, the body of the little animal undergoes many changes of shape. For the most part, when advancing, it is oblong, tapering somewhat posteriorly; when more stationary it tends to assume a spherical form. It moves by means of the cilia which, with the exception of the minute papillary beak, thickly cover the entire body. On carefully examining the larva, a canal may be traced from the beak into what looks like a rudimentary stomach; on both sides of this, two much smaller gland-like organs can be seen, from each of which a delicate tube passes forwards and opens, apparently, somewhere in the neighbourhood of the beak.
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| Fig. 1.—Terminal-spined egg of Schistosomum hæmatobium. (Microphotograph: Dr. Bell.) |
Fig. 2.—Lateral-spined egg of Schistosomum mansoni. (Microphotograph: Dr. Kerr.) |
| Plate XIII. | |
Fig. 132.—Schistosomum hæmatobium miracidium. (After Looss.)
Life-history.—Beyond its first stage of free-swimming ciliated larva, the extracorporeal life of Schistosomum hæmatobium was until quite recently unknown. Leiper's remarkable work in Egypt, however, has completely filled in this hiatus in our knowledge of the life-history of this important parasite. It is therefore no longer necessary to describe, as in previous editions of this manual, the many attempts that had been made previously to trace the progress of the miracidium. Leiper has shown (1916) that the miracidia of S. hæmatobium and of S. mansoni, after escape from the egg, enter a fresh-water snail: in the case of S. hæmatobium, a Bulinus (B. dybowski, B. innesi, B. contortus) (Figs. 133, 134, 135); in the case of S. mansoni, Planorbis boissyi (Fig. 136)—small molluscs abounding in the irrigation canals of Egypt. The miracidia, after penetrating the integument of the mollusc, pass to the liver, wherein they develop into sporocysts and daughter sporocysts (Fig. 137), multiplying to such an extent that the entire liver becomes permeated with the long, delicate, transparent tube-like bodies. Presently numberless bifid-tailed cercariæ develop within the sporocysts (Figs. 138, 139), and on maturing escape spontaneously into the surrounding water. Opportunity occurring, the now free cercariæ penetrate the skin of some suitable vertebrate—man, mouse, rat, monkey—dropping their tails in the passage. Entering lymphatics or blood-vessels, they proceed to the liver of the definitive host, wherein, in the course of about six weeks, they attain sexual maturity and produce terminal- or lateral-spined eggs according to species. To obtain these results in the laboratory, all that is necessary is to place the living experimental animal, or a part—tail, limb, etc.—of such animal, in the water into which cercariæ have escaped from the snail, care being taken that the dose of cercariæ is not too large, as in such case the excessive invasion of the liver may prove rapidly fatal. The experimenter should be very careful to avoid bringing cercariæ-containing water into contact with his own skin. As molluscs are liable to invasion by the miracidia, sporocysts, and cercariæ of many species of trematodes, it is necessary for those who would confirm Leiper's discoveries that they should be able to recognize the specific features of the cercariæ of S. hæmatobium and S. mansoni. Leiper lays stress on four points, viz.: (1) that these cercariæ
Fig. 133. Bulinus dybowski. (After Leiper.)
Fig. 134. Bulinus innesi. (After Leiper.)
Fig. 135. Bulinus contortus. (After Leiper.)
Fig. 136. Planorbis boissyi. (After Leiper.)
have no pharynx (an adult character); (2) they have forked tails; (3) they have no "eyespots," that is, two minute collections of dark pigment located in the anterior third of the body on either side of the middle line between the suckers—a feature of certain other fork-tailed cercariæ, but absent in bilharzia; (4) the presence of two sets of glands communicating with the mouth, and lying on both sides of the posterior end of the body. Leiper has shown further, to use his own words, "that those animals infected with cercariæ from Bulinus dybowski, etc., always produce adult worms which give rise to terminal-spined eggs only, while those infected with cercariæ from Planorbis boissyi give rise equally constantly to lateral-spined eggs. In no case do both varieties arise from the same intermediate host. Moreover, the adult worms reared from these two sources show constant ..... morphological differences." In S. hæmatobium, reared from Bulinus, there are four or five large testes and the gut
Fig. 137.—Bilharzia daughter-sporocysts teased from liver. (Leiper.)
branches do not unite until late, resulting in a short cæcum. In S. mansoni, reared from Planorbis boissyi, there are eight or nine testes, and the gut branches unite early, forming a long cæcum. In S. hæmatobium the uterus contains many eggs, whereas in S. mansoni it is short and contains only one or two eggs. S. mansoni, unlike S. hæmatobium, always causes a heavy deposition of black granules in the liver of the human host. "Lastly, as regards habitat. The males of S. hæmatobium appear to leave the liver early and to pass down into the finer branches of the mesenteric veins before they attain maturity. The females found in the gynæcophoric canal are diminutive. The males of S. mansoni remain in the liver until the females in copula begin to lay eggs, and large numbers of lateral-spined eggs are frequently laid in series by coupled worms in the veins even of the edge of the liver."
Lutz, in Brazil, has confirmed Leiper's discovery of the role of the genus Planorbis in regard to S. mansoni, the species in that country being P. olivaceus; and Becker in South Africa has similarly confirmed Leiper's work as regards S. hæmatobium, the efficient species being Physopsis africana, a mollusc closely allied to Bulinus.
Symptoms.—The symptoms produced by schistosomum vary in degree within very wide limits. In the vast majority of instances the patient experiences
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| Fig. 138.—Bilharzia hæmatobia cercaria Bulinus species. (Leiper.) |
Fig. 139.—Bilharzia mansoni cercaria in Planorbis boissyi. (Leiper.) |
no trouble whatever; in other instances the suffering is very great. Indirectly, from the serious nature of the lesions of the urinary organs to which it may give rise, schistosomum is an occasional cause of death.
The most characteristic symptom of its presence in the wall of the bladder is the passage of blood at the end of micturition, with or without a sense of urinary irritation. The quantity of blood passed and the degree of irritation are increased by exercise, by dietetic indiscretions, and by all such causes as are calculated to induce or aggravate cystitis. As a rule, it is only the last few drops of urine that contain blood; sometimes, however, the hæmorrhage is more extensive, and then the entire bulk of the urine may be blood-tinged. Occasionally, clots are passed.
If in a case of moderate infection the urine be passed into a glass and held up to the light, minute flocculi or coiled-up mucoid-looking threads will be seen floating about in the fluid. If it be allowed to stand, the flocculi, and perhaps minute blood-clots, will subside to the bottom of the vessel; these, on being taken up with a pipette and placed under the microscope, will be found to contain, besides blood corpuscles and catarrhal products, large numbers of the characteristic spined ova.
In doubtful cases, where ova are few, the best way to find them is to get the patient to empty the bladder and to catch in a watch-glass the last few drops of urine which can be forced out by straining; these invariably contain ova. A low power of the microscope suffices, and is best for diagnosis.
Endemic hæmaturia lasts for months or years. Recovery is rarely complete. In ordinary cases, provided no reinfection take place, the hæmaturia tends to decrease, although ova may continue for years to be found in the last few drops of urine passed. In severe cases, sooner or later, signs of cystitis supervene and give rise to a great deal of suffering. Not infrequently the ova become the nuclei for stone, and symptoms of urinary calculus are superadded. (Fig. 140.) Sometimes the pathological changes induced by the presence of the parasite in the bladder lead to the development of new growth, in which event the symptoms become more urgent and the hæmaturia perhaps excessive. Hypertrophy, contraction, and even dilatation of the bladder, are not unusual. Besides the bladder symptoms there may be signs of prostatic disease, or of disease of the vesiculæ nales causing spermatorrhœa. In the latter case, ova may be detected in the semen. In other instances the ureters and kidneys become involved and grave disease of these organs ultimately ensues. In consequence of the suffering which these aggravated forms of infection produce, the patients become anæmic, wasted, debilitated, and a ready prey to intercurrent disease.
Milton has pointed out the extreme frequency of urinary fistula in Egypt, the result of schistosomum disease of the urethra. These fistulæ may occur anywhere in the neighbourhood of the genitals, but are especially common in the perineum and posterior surface of the scrotum, and originate from schistosomum disease of the pubic surface or roof of the urethra just in front of the bulb, the eggs of the parasite being deposited in the mucous or submucous tissue. Stricture of the urethra is by no means uncommon from a similar cause, especially in the case of fistulæ connected with the floor of the urethra.
Vaginitis and cervicitis have been known to be produced by this parasite. On the vulva papillomatous masses containing schistosomum ova are, according to Madden, very common.
Besides the lesions of the genito-urinary organs, rectal symptoms have been described and the characteristic ova of S. hœmatobium have been found in the rectum. Frequently, however, another species (S. mansoni), which invariably extrudes its eggs through the intestine, has been confounded with the old classic species. The intestinal lesions give rise to dysenteric-like symptoms. Very often mucus and blood are passed without any fæcal matter, and the continuous straining may be distressing, especially when large polypoid masses protrude from the anus. I have seen a case (which had been diagnosed and treated as syphilis) of which extensive condyloma-like growths around the anus, in the perineum and groin, and full of ova, were a remarkable feature.
Pathological anatomy.— The character of the changes brought about by S. hœmatobiumvaries very much according to the degree and the duration of the infection. In almost every case of the Egyptian type of the disease the walls of the urinary bladder are early affected. All that may be apparent to the naked eye at this stage is a certain amount of injection of the small vessels of the mucosa vesicæ, and, according to Sonsino, certain exceedingly minute vesicular or papular elevations of the surface of this membrane. When these minute elevations are examined microscopically they are found to contain ova. Ova are also to be found in the dilated minute blood-vessels. Later, especially in the trigone of the bladder, there are found rounded patches of inflammatory thickening which project somewhat, are granular on the surface, and dense in consistence; on section they creak under the knife as if they contained gritty particles. It is evident that these elevated^ thickened patches are the result of an inflammatory, process provoked by the clusters of ova which the microscope reveals scattered throughout their entire extent. The ova are principally deposited in the submucosa, less extensively in the mucous membrane itself, still less abundantly in the muscular walls of the organ or in its subserous connective tissue. They tend to occur in groups, each of which is invested with a sort of connective-tissue capsule; or they may be lying in small blood-vessels which they occlude. Some ova are seen to have undergone calcification; others are still fresh, either segmenting, or already containing a miracidium. On the surface of the rounded patches already mentioned phosphatic deposits, also containing ova, are not uncommon; and sometimes the patches present minute sloughs. Besides these indurated patches, various forms of polypoid excrescence sometimes ulcerated may protrude from the mucous surface into the cavity of the bladder. These various hyperplasiæ frequently contain the adult parasite as well as ova.
In addition to what may be designated the specific changes in the mucosa, the muscular coats of the bladder are generally hypertrophied. In consequence of this, as well as of the ingrowth of villosities and different forms of new growth, the capacity of the organ may be much diminished. Its mucous surface is generally coated with a sanguineous mucus containing myriads of ova. Gravel, or small stones —generally phosphatic— are sometimes found either embedded in lacunae in the hypertrophied and roughened bladder wall, or free in the cavity. Not infrequently a similar hyperplasia occurs in the ureters, and particularly towards their lower ends. In rare instances the pelvis of the kidney itself is affected. Obliteration of the ureter, both from small stones and from thickening of the mucous membrane, has sometimes been met with; this leads to dilatation of the pelvis and atrophy of the parenchyma of the kidney. It is easy to understand how, in time, these changes in the bladder and ureters may give rise to hydronephrosis, pyelitis, abscess of the kidney, and similar secondary affections.
Hyperplasia from schistosomum infection may also occur in the vesiculae seminales, in the walls of the vagina, and in the cervix of the uterus, leading to corresponding bloody, ova-containing discharges.
When the intestinal tract is involved, numerous polypoid adenomatous growths are found, especially in the rectum; these usually slough off, leaving ulcerations with ragged edges. The coats of the gut become thickened and indurated owing to extensive fibrous tissue formation between the layers of the peritoneal attachments.
It may be mentioned that schistosome ova in small numbers have been found in the liver, in gall-stones, in the lungs, in the heart, and in the kidneys. We have no knowledge of any definite pathological change entailed by their presence there.
Tumours of schistosomum origin have sometimes been found in connection with the peritoneum and ligaments of the uterus.
Diagnosis.— The diagnosis of this disease is not difficult; the presence of ova in the urine is decisive. In countries like Egypt, where the disease must often concur with chyluria, with stone, with vesical tumour, with gonorrhœal cystitis, and with pyelitis, as well as with prostatic disease, care must be exercised in each particular case to separate the special factors to which the various symptoms are attributable. Thus in chyluria concurring with schistosomum disease there will be chyle in the urine in addition to blood. In such a combination the clot which forms will be large, will contain oil granules and globules and, very probably, microfilariæ, in addition to schistosomum ova; moreover, the microfilariæ will generally be detectable in the finger blood if looked for at night. Stone in the bladder, when suspected, has to be searched for with the sound. In gonorrhceal cystitis the history of gonorrhœa will be forthcoming. In prostatic disease enlargement of this organ may be made out. Difficulty may sometimes arise when ova are few in number, or when they have ceased altogether to come away in consequence of the death of the parent worms. The mischief wrought by the parasite remains, although the ova the most certain evidence of the parasite's previous presence may be discharged no longer. But, even if ova are very few, they may still be found in the last drop or two of urine passed. If they are no longer to be found in the urine, sometimes, by scratching the surface of the bladder with a sound and examining the shreds of mucus so obtained, a few— calcified, it may be, but presenting the characteristic spine may be seen with the microscope.
In rectal disease, if schistosomum be suspected, the mucus and fæces, or failing these one of the adenomatous growths, after removal by finger or forceps, should be examined for ova.
Prognosis.— An important element to be considered in venturing on a prognosis is the long life of the parasite. Sonsino mentions a case in which living ova were still being passed nine years after their first appearance, and after all chance of reinfection had ceased. Another important element in prognosis is the degree of infection; the greater the number of worms the more severe and the more extensive the disease they produce. As with filarial infection, the greater the number of cases in a district the greater the proportionate probability of severe infections being met with. The prognosis is practically that of a chronic cystitis depending on an irremediable, but not in itself fatal, cause. Much suffering may often be produced, and, as a consequence, anæmia and debility. Possibly calculus may be formed; possibly grave renal disease may ensue; possibly villous or epitheliomatous growths in the bladder. In the milder degrees of infection, which fortunately are the commonest, the patient seems to be in no way inconvenienced by the parasite, and generally escapes all serious consequences. In any case, mild or severe, there may be attacks of hæmaturia from time to time; as a rule, the quantity of blood lost is insignificant.
Treatment.— Our knowledge of the situations occupied by the parasite indicates the futility of attempting a radical cure by means of poisonous substances, whether introduced by the bladder, by the rectum, or by the stomach. As yet we know of no direct or other means by which the schistosomes can be destroyed. Only harm can result from attempts at a radical cure of endemic hæmaturia on such lines. Our efforts must, therefore, be confined to palliating the effects of the presence of the parasite. Practically, the treatment resolves itself into that of chronic cystitis. The diet should be bland but nutritious; stimulants and spices are to be avoided. Excess of all kinds, violent muscular efforts, cold and other causes of catarrh, must also be guarded against. During exacerbations of hæmaturia, or of cystitis, rest should be enjoined and diluents freely partaken of. Milton has obtained good results from gramme doses of extract of male fern three times a day in schistosomum hsematuria. A recent writer has advocated the use of methylene blue (3 gr. three times a day) in similar circumstances. Adrenalin has some influence in controlling hæmorrhage. Salvarsan has been tried, but was found to be of no use. Pain may demand anodynes. Excessive catarrh of the bladder suggests washing out with weak boric-acid lotion, and the internal administration of urotropine, uva ursi, buchu, perhaps small doses of cubebs, copaiba, or sandal- wood oil, salol, benzoic acid, and so forth. Stone, and troublesome new growths, are to be removed by operation. Where distress was extreme, Mackie and others have had good results from perineal cystotomy and drainage. Adenomatous growths in the rectum, where accessible, should be removed. In severe rectal disease, milder measures failing, excision of the affected part of the gut may be necessary. Perineal fistula must be dealt with on ordinary surgical principles. Hyperplasia in the vagina and cervix is best treated by scraping. Provided reinfection be avoided by the exercise of prudence in the matter of water, there is no necessity for sending the patient with schistosomurn disease away from the country in which the parasite was acquired.
Prevention.— In the endemic districts, children, in particular, should be carefully and repeatedly warned against drinking or bathing in rivers, ponds, and canals. Seeing that the larva of schistosomum, on obtaining access to fresh water, enters a fresh-water mollusc and, after undergoing developmental changes, obtains access to the human host, it is evident that if the larva be kept from getting into the water, or if drinking-water be boiled or filtered,the spread of the disease from man to man would be effectually prevented; therefore every care should be exercised to prevent the diffusion of the disease, by prohibiting the evacuation of excreta into water where the miracidia might find the opportunity of development and transmission. This prohibition should not be restricted to patients exhibiting definite symptoms of the disease, but extended to all, because, as special inquiries have shown, a large proportion of the infected do not suffer from any troublesome symptom, and are often unaware of the infection. Leiper points out that much might be accomplished by attacking the mollusc intermediary and the free cercaria. As regards the former, he suggests periodic drying of irrigation canals and the use of chemical manures; as regards the latter, the use of cercariacides such as sulphate-of-soda tablets or chlorine (1-500,000) for drinking-water, and boiling, lysol, creolin, or creosol (1-10,000) for bathing- water. The free cercaria lives but a short time— at most forty-eight hours— in water, but a molluse once infected continues infective for months. The free cercariæ readily pass through the ordinary municipal filter-bed; they can traverse 30 inches of fine sand in five hours, but they perish, as has been stated, if they do not get access to an appropriate host within forty -eight hours. These facts should be taken into account by the sanitarian.
SCHISTOSOMUM MANSONI, Sambon, 1907
The occurrence of a schistosomum producing lateral-spined ova (Plate XIII. } Fig. 2) was noticed by Bilharzin 1851, but, believing the ova to represent peculiar capsules formed by the larvae after hatching, he confounded it with S. hœmatobium. After Bilharz several observers encountered female worms with lateral-spined ova in utero, and the idea of a dis- tinct species suggested itself to Sonsino and others, but this idea was at once discarded for other hypotheses. The lateral-spined ova being found only*[1] in the fæces of Egyptian patients suffering from hæmaturia, the majority of physicians held that the peculiar position of the spine was due to distortion of the eggshell in passing through the muscular coat of the rectum, forgetting that oviposition takes place in the submucous layer, and that lateral-spined ova are found in the uterus of the parent worm. Sonsino suggested that the two kinds of eggs might represent respectively male and female embryos. Looss surmised that the lateral-spined ova might be the product of unfertilized females; but if the lateral-spined are merely unfertilized ova as he suggests, it is difficult to explain the presence of the species in America, where the lateral-spined ova are the only ones found.
In 1903, in examining a patient who had long resided in Antigua and other West India Islands and who had never visited Africa, I found in his fæces numerous schistosomum eggs all bearing a lateral spine. Repeated examination of the urine proved negative, and the patient stated that he had never at any time suffered from hæmaturia. This case, together with the absence of endemic hæmaturia in the West Indies, led me to think that probably the lateral-spined ova indicated a distinct species of schistosomum, and I suggested this in a previous edition of this manual and elsewhere. Since then a considerable amount of information has accumulated in favour of my conjecture. A new species of schistosomum (S. japonicum), with what are practically spineless ova, and affecting the intestine only, has been discovered in Japan, and careful examinations for helminths in the Congo Free State (Broden) and in Porto Rico (Gunn and others) have shown the absence of urinary schistosomum disease and the frequency in these regions of a rectal schistosomum infection in which the ova of the parasite bear invariably a lateral spine. Finally, Sambon (Proceedings of the Zoological Society, March 9th, 1907), having had the opportunity of comparing specimens of the type characterized by lateral-spined ova with S.hœmatobium and other schistosomidæ, and taking into consideration its peculiar geographical distribution and distinct pathogeny, proposed that it should be ranked as a distinot species, and paid me the compliment of naming it S. mansoni in recognition of my suggestion. Since that time many cases of lateral-spined rectal bilharziosis have been reported from America by Flu (Surinam) and others. So far as I am aware, not a single case of terminal-spined bilharziosis of indigenous origin has been observed on that continent.
The available material being very badly preserved, Sambon was unable to furnish the exact dimensions and the anatomical details of the new species, which closely resembles S. hœmatobium in general appearance and structure.* [2] In careful comparative examination Flu has shown that there are several structural differences between the adult S. hœmatobium and S. mansoni. He finds that whereas in the male S. hœmatobium the anterior border of the lateral folds forms almost a right angle with the long axis of the body, in S. mansoni the folds are gradually sloped off. In the female S. mansoni the ovaries run a tortuous course unlike those in other schistosomes, the ootype is asymmetrical, and the oviduct opens laterally on the ventral side where the shell gland is situated. In sixty females he found only lateral-spined ova.*[3] Leiper has made out several additional points of difference in anatomical detail, particularly as regards the testes and alimentary canal (see p. 747); these, together with his discovery that S. hœmatobium makes use of a Bulinus and S. mansoni of a Planorbis as intermediary host, are conclusive evidence that these trematodes belong to different species.
Apparently S. mansoni, like Necator americanus, is a West African species which had been introduced into the western hemisphere by the African negro; and just as N. americanus and Ankylostomum duodenalefrequently concur in the same country and even the same individual, so it is with S. hœmatobium and S. mansoni.
S. mansoni inhabits chiefly the mesenteric veins, and its ova deposited within the submucous layer of the rectum give rise to dysenteric-like symptoms, mucus with blood being passed from time to time, the ova-laden stools becoming frequent and their passage perhaps being attended with tenesmus. As in the case of the schistosomum next to be referred to, the initial stages of the infection are apt to be attended with urticarial eruption, eosinophilia, and fever apt to be regarded as enteric. In certain well-established cases small, sometimes large, branching, soft growths are to be felt inside the sphincter ani. They
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| Fig. 1.—Schistosomum japonicim in vessels of mesentery. (Microphotograph: Dr. Henderson.) |
Fig. 2.—Eggs of Schistosomum japonicim embedded in walls of appendix vermiformia. (Microphotograph: Dr. Kerr.) |
| Plate XIV. | |
resemble polypoid growths, and are apt to be mistaken for piles. They may extend as high up the bowel as the sigmoid flexure. On tearing up one of these growths the ova can be seen in the débris.
The eggs of S. mansoni may be found in great numbers in the liver, giving rise to a peculiar form of cirrhosis. They occur, too, in the lungs and other organs.
SCHISTOSOMUM JAPONICUM (Katsurada, 1904)
(Plate XIV.)
Synonym.—Schistosomum cattoi, Blanchard.
History.— For some years Japanese physicians had observed in the provinces of Yamanashi and Hiroshima in Central Japan, and at Saga in the North Island, an endemic disease characterized by enlargement of the liver and spleen, cachexia, and ascites. The patients suffered from diarrhœa, their motions containing mucus tinged with blood. Occasionally they had fever. They became anæmic, and many of them died from exhaustion. At the autopsy the liver and other organs were found to contain the ova of some unknown helminth.*[4] In April, 1904, Katsurada discovered that the eggs found in the stools of these patients contained a ciliated embryo not unlike the miracidium of Schistosomum hæmatobium. Disappointed of an autopsy, he examined dogs and cats in the endemic area, and had the good fortune to find at once in the portal system of two cats from the province of Yamanashi numerous schistosomidæ containing eggs exactly similar to those previously found in man. He published this information on August 13th, 1904, and named the new trematode S. japonicum. Almost simultaneously, and independently, Fujinami observed cases of the disease in the village of Katayama, in the province of Bingo, and found in his first fatal case the characteristic ova in various organs. In a second necropsy, besides the ova in the liver, intestinal wall, and mesenteric glands, he found in a branch of the portal vein a parasite which he regarded as S. hæmatobium. In November, 1904, Catto discovered the same parasite in sections of the mesocolon from a Chinaman of the province of Fukien who died of cholera at St. John's Island Quarantine Station, Singapore. Later, Katsurada succeeded in communicating the parasite to cats by immersing their legs in the water of certain ponds and streams reported to convey the disease; and finally, in 1913, Miyairi and Suzuki traced the parasite, through a snail common in the infected districts, back to the vertebrate host.
Fig. 141.—Schistosomum japonicum (male).
The parasite (Fig. 141).—Schistosomum japonicum closely resembles in general structure S. hæmatobium. As in the latter, the suckers are placed close together at the anterior extremity of the body, the acetabulum or posterior sucker being distinctly pedunculated and funnel-shaped. The suckers in both sexes and the ventral surface of the body in the male are provided with minute spines. The distinctive characters of the new trematode are its smaller dimensions (male, 9 to 12 mm. in length by 0.5 mm. in breadth; female, 12 mm. in length by 0.4 mm. in breadth), and the larger size of the acetabulum as compared to the oral sucker. In the male the integument is smooth and non-tuberculated, and the posterior part of the body in the male is relatively wider, the sides overlapping one another far more extensively than in S. hæmatobium. Finally, the ova (70 to 75 μ. in length, 45 to 55 μ. in breadth) are smooth and possess no spine; but they possess, as Leiper has pointed out, what may pass as a rudimentary lateral spine in the form of a very minute and easily overlooked papilla—like an excrescence, in a cup-like depression in the shell. (Fig. 142.) A comparative study of the anatomy of the two schistosomidæ will probably show other morphological differences. Catto mentions a larger vas deferens and lobular testicles in the male, and a different arrangement of the yolk cells in the female. Looss notices a greater development of the muscular system in the male S. japonicum, which he thinks may take the place of the absent cuticular eminences.
Catto found the adult worms in the smaller mesenteric blood-vessels, but he was unable to determine whether they occupy the arteries or the veins. He believes they occur in both. The smooth, non-tuberculated skin of S. japonicum seems to suggest a different anatomical habitat from that of S. hæmatobium, the integument of which is beset with numerous spine-bearing protuberances. S. hæmatobium, inhabiting the venous system, has a rough integument, it may be to enable it to adhere to the inner coat of the venules, and to stem the blood-stream during oviposition. S. japonicum, which inhabits the arteries, requires no integumental protuberances, the direction of the arterial current maintaining it in its proper position.
In Catto's case the ova were found chiefly in the mucous and submucous coats of the intestinal tract from cæcum to anus, more especially in the rectum and appendix. They were also found in the liver, in the gall-bladder, in the pancreas, in the mesenteric glands, and in the fibrous coat of the larger mesenteric vessels. In the liver they were very plentiful, lying singly or in clusters embedded in the hypertrophied connective tissue. The female schistosomum probably has a special means of extruding her eggs through the walls of the blood-vessels; the further distribution of the eggs being effected by the lymph-stream. Where the ova accumulate they provoke a small-cell infiltration, which gives place later to fibrous tissue.
The ova are discharged in the fæces of the vertebrate host. In this way they get carried to water, where the ciliated miracidium escapes. In 1913 Miyairi and Suzuki traced the ciliated miracidium into a fresh-water mollusc, Katayama nosophora (Fig. 143), wherein, after shedding its cilia, it becomes a sporocyst (Fig. 144, a), in which ultimately numbers of fork-tailed cercariæ are developed (Fig. 144, b). On maturity the cercariæ escape into the water and, opportunity presenting, penetrate the skin of some appropriate vertebrate (man, cat, dog, mouse, etc.), in whom they attain sexual maturity. These observations have been confirmed by Leiper.
Geographical distribution.—The distribution of S. japonicum is probably a wide one. So far it has been found principally in Chinese and Japanese. It is far from uncommon in the Philippines, or in the Yangtze valley, where a notable proportion of the boatmen and raftsmen and farmers have been found infected. Europeans also have acquired the disease in the latter district, mostly sportsmen addicted to snipe-shooting in the rice fields.
Morbid anatomy.—Catto's patient during life presented enlargement of the liver and spleen. At the autopsy the appearance of the peritoneum suggested repeated attacks of peritonitis. The appendices epiploicæ were thickened, and in some places matted together. The recto-vesical pouch was almost obliterated. The mesenteric and prevertebral glands were enlarged, the largest group forming a cluster near
Fig. 143.—Operculum and shell of Katayama nosophora. (After Robson.)
a, Operculum, x 12, diagrammatic to show scheme of coiling; b, oral aspect of shell, x 4; c, lateral aspect of shell, showing labial swelling, x 4.
the duodenum. The liver was considerably hypertrophied, its surface nodular, its consistence greatly increased. The coats of the gall-bladder were thickened, and a layer of fat almost completely encased this organ, which was distended with clear mucoid material containing several minute black gall-stones. The spleen was enlarged and pigmented. The colon was much thickened throughout. Its mucous membrane was swollen, hyperæmic, and friable; it presented numerous small circular superficial erosions and patches of necrosis. The outer coats were very tough, almost cartilaginous. The walls of the rectum were three-quarters of an inch thick and adhered to the bladder. It nearly filled the true pelvis. The sigmoid flexure also was uniformly thickened. In tracing the bowel upwards the thickening became less marked and more patchy. The liver and bowel cut gritty on section. The bladder was thickened where adhesions had formed with the rectum, but elsewhere it was healthy, and nowhere was the vesical mucosa diseased. Sections of the liver, mesenteric glands, and bowel were found to contain the ova of S. japonicum.
In a case from Katayama, described by Tsunoda and Shimamura, the necropsy revealed, besides the ordinary lesions in the liver, intestine, and pancreas, thickening with hæmorrhagic infiltration of both the dura and pia mater. In the brain itself a number of wedge-shaped sclerosed areas of greyish colour, and surrounded by some ecchymosis, were found. In the lenticular nucleus, optic thalamus, and internal capsule of the left side there was an area of softening the size of a walnut. On histological examination these areas were found to contain ova embedded in neuroglia and surrounded by softened and degenerated brain tissue. Similar ova were found in the membranes, and a few in the right hemisphere and in the choroid plexuses of the lateral ventricles. In connection with these lesions the patient during life suffered from disorder of speech and tremor in both upper and lower extremities, with headache and mental disturbance, later from vertigo and Jacksonian fits (two or three daily), and finally from right hemiplegia.
Katsurada has drawn attention to the fact that S. japonicum does not affect the bladder. The two cases described in Chinamen confirm this experience. There are, therefore, important pathological and
Fig. 145.—Eggs of S. japonicum, x 250. (Photograph by Dr. J. Bell.)
clinical features which, in addition to the zoological characters of the parasites, show that S. japonicum is specifically distinct from S. hæmatobium and S. mansoni.
Symptoms.—The disease produced by S. japonicum, sometimes called "Katayama disease," is a grave one, and when pronounced proves fatal sooner or later. The gravity of any given case will depend, amongst other things, on the degree of infection and the circumstances of the patient. Of 1,077 persons near Shushima, Japan, examined by Koiki, 42 were found infected. Of these 42 only 22 were not in good health, and 10 of them had enlarged livers. A history of fever accompanied by an urticarial eruption is generally given— sometimes there are associated with this symptoms of pulmonary congestion. After an interval of several weeks or months, intestinal troubles, in the form of dysenteric discharges, dyspepsia, together with great enlargement of liver and spleen, set in; these persisting, a characteristic cachexia— intense anæmia, ascites, wasting, and progressive debility— supervenes; ultimately, if the patient does not succumb to some superadded disease, terminating— it may not be for many years— in death.
Diagnosis.— All cases of urticarial fever from the endemic districts should be watched for many months, especially if eosinophilia persists after the subsidence of the primary attack, and the stools examined for ova of S. japonicum. All cases of chronic intestinal disturbance, especially if associated with enlargement of liver and spleen, from these districts should be regarded as, possibly, cases of schistosomiasis and have the blood and stools examined. If the ova (Figs. 142, 145) are discovered the diagnosis is established.
Prevention.— Water reported to cause the disease should be boiled, or avoided, for drinking or bathing purposes. Sportsmen, if they must wade in such waters, should wear long boots or waterproof waders.
Treatment.— No specific remedy is known. Filix mas may be tried, otherwise the treatment is entirely symptomatic.
CHAPTER XLII
II. PARASITES OF THE CONNECTIVE TISSUE
DRACUNCULUS MEDINENSIS, Velsch, 1674
Synonyms.—Vena medinensis; Dracunculus persarum; Gordius medinensis; Filaria dracunculus; F. medinensis; Guinea-worm.
Geographical distribution.— This important parasite is found in certain parts of India— the Deccan, Scinde, etc.— in Persia, Turkestan, Arabia, tropical Africa— particularly on the West Coast, and in a very limited part of Brazil (Feira de Santa Anna). Formerly it was supposed to be endemic in Curagoa, Demerara, and Surinam; apparently it has now disappeared from these places. Dracunculus is not equally diffused throughout this extensive area; it tends to special prevalence in limited districts, in some of which it is excessively common. In parts of the Deccan, for example, at certain seasons of the year nearly half the population is affected; and in places on the West Coast of Africa nearly every negro has one or more specimens about him. Although guinea-worm is sometimes seen in Europe, this is only in natives of, or in recent visitors from, the endemic areas. Though frequently introduced in this way, it has not become established either in Europe or in North America. We have no account of the parasite as endemic in any part of Asia east of Hindustan, in the Eastern Archipelago, in Australia, or in the Pacific islands.
Dracunculus medinensis has been reported for horses, oxen, dogs, wild cats, jackals, leopards, and other animals. Possibly some of the parasites in the lower animals described as guinea-worm may belong to quite a different species.
- ↑ * More recently, Bandi states that he found in Tunisia 25 cases of vesical bilharziosis with lateral- and terminal-spined ova in the urine. His experience is certainly very exceptional.
- ↑ * In both species the males present a tuberculated outer surface, but the number and shape of the prominences seem to differ somewhat.
- ↑ * Holcomb mentions five autochthonous cases of intestinal schistosomum infection in the island of Vieques. The ova of the parasite were invariably lateral-spined. He states that 167 similar cases have been reported in Porto Rico; the eggs being found solely in the fæces, never in the urine.
- ↑ * As far back as 1888, Majima, in Tokio, found peculiar ova in the liver of a case of cirrhosis. These he described as the ova of an unknown parasite. In 1890, in a similar case, Yamagiwa found ova which he ascribed to the lung trematode.