Tropical Diseases/Chapter 44
CHAPTER XLIV
IV. PARASITES OF THE LIVER
Opisthorchis noverca, Braun, 1903
Synonyms.—Distoma conjunctum; Paropisthorchis caninus(Barker, 1912).
History.—Opisthorchis noverca was discovered by MacConnell at Calcutta in 1876. Lewis and Cunningham, who a few years previously had found a similar parasite in the liver of pariah dogs from the same locality, suggested that both their own species and MacConnell's were identical with the D. conjunctum (now called Metorchis conjunctus) found by Cobbold in the liver of an American fox (Canis fulvus) that died in London. In 1903 Braun showed that the Indian trematode belongs to a different species, and gave it the name of Opisthorchis noverca.
Fig. 163.—Opisthorchis noverca.
a, Greatly magnified; b, natural size.
(See text.)
Geographical distribution.—India.
Zoological distribution.—As stated above, it has been found in the gall-ducts of the dog (C. familiaris).
The parasite.—The description of the parasite is chiefly from the data and drawings furnished by MacConnell, and needs revision. O. noverca is of a lanceolate shape, and more attenuated anteriorly than posteriorly. It measures from 9 to 12 mm. in length by 2.5 mm. in breadth. The oral sucker (Fig. 163, m) is terminal and larger than the acetabulum or ventral sucker (Fig. 163, ac), which is situated close to it, just below the bifurcation of the intestine. The cuticle is densely covered with spines. The pharynx (Fig. 163, pb) is large and globular; the intestinal cæca extend to about the posterior eighth of the body. The testes (Fig. 163, t,t) are in the posterior third and somewhat apart. The anterior one is roundish, the posterior one lobate. The ovary (Fig. 163,ov) is placed at about the middle of the body. The uterus (Fig. 163, ut) appears to be poorly developed, its convolutions spreading laterally barely beyond the cæca. The vitellaria (Fig. 163, vt) appear to extend from acetabulum to posterior testicle. The eggs are oval and measure 34 μ by 19 to 21 μ.
Pathogenesis.— Only a very few cases have been reported. In two, described by MacConnell, the parasites were found in large numbers in the bileducts, which were thickened and sacculated.
CLONORCHIS SINENSIS (Cobbold, 1875)
Synonyms.— Distoma sinense; D. spathulatum; D. japonicum; D. innocuum; Opisthorchis sinensis; Clonorchis endemicus.
History.— Clonorchis sinensis was discovered almost simultaneously by MacConnell in India and MacGregor in Mauritius, in 1874.
Geographical distribution— It has been found in many Eastern countries, including India, Mauritius, Japan, Korea, Formosa, China and Tonkin. In the last-named country it appears to be very common. In Central Japan, according to Katsurada, there are certain districts in which it affects from 56 to 67 per cent, of the population.
The parasite.— C, sinensis (Fig. 164) measures from 10 to 20 mm. in length, by 2 to 5 mm. in breadth; it is oblong, narrow, flat and somewhat pointed anteriorly, reddish in colour, and nearly transparent. The oral sucker is larger than the ventral acetabulum, which is situated almost on the border between the first and second fourths of the body. The cuticle has no spines. The pharynx is globular and short (Fig. 164, pb}, the œsophagus is slender and 0.17 mm. long. The bifurcation of the intestine is nearer to the oral than to the ventral sucker. The intestinal cæca are simple, slender, and extend almost to the posterior end of the body. The genital pore opens on the middle line immediately in front of the acetabulum. The testes are branched and situated in the posterior portion of the body, one behind the other. The ovary is trilobate and anterior to the testes. The uterus is moderately developed, and its coils are anterior to the genital glands. The vitellaria are moderately developed and occupy about the middle third of the body. The eggs are 28 to 30 μ in length by 15 to 17 μ in breadth, operculated, almost black in colour, and contain a ciliated embryo. Probably its immature stages are passed in a mollusc (?Melania obliquegranulosa, M. libertina) or other small, soft-skinned, fresh-water animal. According to Yokagawa, cercariæ of this species are found in Japan in fresh-water fish of the family Cyprinidæ. Quite recently Kobayashi has traced the cercariæ into a variety of fresh-water fish in which they become encysted in the muscular tissue and advance in development. In cats, dogs, rabbits, guineapigs, and rats, fed on infected fish, mature C. sinensis, producing eggs, were found after twenty-six days from the time of feeding.
Fig. 164.—Clonorchis sinensis.
(Partly after Looss.) a, Magnified; b, natural size.
(See text.)
Pathogenesis.—C. sinensis inhabits the bile-ducts and gall-bladder. It thickens the biliary canals and expands them in places into cavities and diverticula as large as filberts. In these cavities vast numbers of parasites may be found. The diverticula communicate with the bile-ducts, along which the ova of the parasites, and sometimes the parasites themselves, escape into the intestine. The affected liver is enlarged as a whole, although the tissue in the immediate neighbourhood of the diseased bile-ducts is atrophied. The spleen, also, may be hypertrophied, and the intestine in a condition of chronic catarrh. Some instances are recorded of the presence of this trematode in the pancreatic ducts, in the duodenum, and in the stomach.
This parasite, which for long was supposed to be practically innocuous, is now held to be the cause of a serious disease of the liver, which may terminate fatally; indeed there can be no doubt of this when one considers that in some of the cases recorded several thousand parasites were present. However, we should not forget possible confusion with another grave distomiasis of Japan and other Eastern countries, due to Schistosomum japonicum.
When the infection is severe the liver becomes
Fig. 165.—Ova of Clonorchis sinensis, x 250.
(Photograph by Dr. John Bell.)
enlarged, and chronic diarrhœa, with recurring attacks of jaundice, sets in. Later, anasarca appears, and gradually a cachexia, resembling that of sheep-rot, is established, which, in the course of several years, may prove fatal.
It would be well to bear this parasite in mind in approaching the diagnosis of obscure hepatic disease associated with diarrhœa and jaundice in patients from the East. The discovery of the ova (Fig. 165) in the stools should guide to a correct diagnosis.
Treatment. So far no specific treatment has been found for this disease. The patient should be removed to a non-infected area and given nourishing food. Recently salol has been reported as beneficial in the analogous liver-fluke disease of sheep.
CLONORCHIS ENDEMICUS (Baelz, 1883)*[1]
Synonym.— Distoma japonicum (R. Blanchard, 1886).
This trematode is found in Japan, where it is common in man, and in cats, dogs, and pigs. It is smaller than C. sinensis, 6-13 mm. in length by 1.8-2.6 mm. in breadth. There are no pigment granules in the parenchyma.
Kobayashi has found cats commonly infected with this parasite; he has also found an encysted distome in the muscles of certain fresh- water fish—Pseudorasbora parva, Leucopodia guntheri, and others— especially near the villages of Kogo and Sanban, near Okayama. Eggs of this distome are found in the fæces of kittens one month after they have been fed on the flesh of such fish. On dissection of these kittens numerous adult distomes were found in the bile-ducts, gall-bladder, hepatic ducts, pancreas, and even in the duodenum. Kobayashi was also able to infect rabbits and guineapigs in the same way. Twenty -two days after the first infection the distomes were found to be mature and to contain eggs. In the younger stages the worms possess spines which are deciduous.
The fish act only as the second intermediary host; the first intermediary host still remains to be found.
Pathogenesis.— Lesions similar to those caused by C. sinensis are attributable to C. endemicus, together with a grave cachexia characterized by enlargement of the liver, diarrhœa, and ultimately anasarca.
Prophylaxis.— Manifestly the Japanese habit of eating raw fish is to be deprecated. Animals and men harbouring the parasite should be prevented from fouling water— whether used for drinking, bathing, or for agricultural purposes. Porocephalus armillatus (Wyman, 1848)
Synonyms.—Linguatula armillata; L. constricta; Pentastomum constrictum; P. polyzonum; P. diesingi; P. euryzonum; Nematoideum hominis.
History.—The larval form of this vermiform arthropod, belonging to the family Linguatulidæ, genus Porocephalus, was discovered in 1847 by Pruner, who found it, in Cairo, in the livers of two negroes. It must have been found in man before that date, since Pruner himself informs us that he saw two specimens in the Pathological Museum of Bologna, labelled "Insects from the liver of man." Subsequently it was found in man by Bilharz, Fenger, Kearney, Crawford, Marchoux, Chalmers and others. In 1852 von Siebold proposed to call it Pentastomum constricium; but Shipley, in his revision of the family Linguatulidæ (1898), points out that the adult form was discovered and named Linguatula armillata in 1848 by Wyman, who found it in the lungs of an African python. Shipley further considers that Hoyle's Pentastomum protelis from the aardwolf (Proteles cristata), Wedl's P. leonis from the lion, Van Beneden's P. diesingi from the mandrill (Cynocephalus mormon), and Hartley's P. polyzonum from an African python, belong to the same species. He also states that, in accordance with the rules of zoological nomenclature, the generic name for the cylindrical Linguatulidæ should be Porocephalus, a term introduced by Humboldt eight years before Rudolphi proposed the name Pentastomum. Neumann (1899) refers the larval forms found in man to Porocephalus moniliformis, a species discovered by Diesing in 1836 in the Indian python (Python molurus). Looss (1905) is of opinion that Wyman's and Diesing's species are identical. Sambon agrees with Shipley's determination, based principally on the number of rings, which are never more than 22 in P. armillatus, but 28 to 30 in P. moniliformis.
Fig. 166.—Porocephalus armillatus, natural size. (After Sambon.)
Porocephalus moniliformis, together with similar parasites found in the Indian civet and in the tiger.
Zoological distribution.—The adult form inhabits pythons and other snakes. It has been found in Python sebæ by Wyman, Sambon, and others; in the royal python (Python regius) and in the nose-horned viper (Bitis nasicornis) by Sambon. The larval—or, more correctly, the nymphal—form has been found in the lion, in the leopard, in the mandrill, in the aard-wolf. Pruner found it in the giraffe, Looss in Syke's monkey (Cercopithecus albigularis), and Sambon in the Pousargues guenon (Cercopithecus pousarguei) and in the African hedgehog (Erinaceus æthiopicus).
Fig. 167.—Nymph of Porocephalus armillatus. (After Sambon.)
The parasite (Fig. 166).—Body vermiform, yellowish translucent, larger in females (9-12 cm. long by 5-9 mm. broad) than in males (3-4·5 cm. long by 3-4 mm. broad); cylindrical in the anterior half, slightly tapering posteriorly, and terminating in a blunt-pointed cone. It is characterized by the presence of prominent opaque rings 1-2 mm. wide, numbering 16 or 17 in the males, 18 to 22 in the females, placed somewhat obliquely and separated by interannular spaces 2-5 mm. wide except between the first rings, which are faintly indicated by shallow linear furrows. There is no clear distinction between cephalothorax and abdomen, and the rings nearest the cephalothorax are sometimes so indistinct that it is almost impossible to make out their actual number. The cephalothorax is depressed, slightly convex on the dorsal surface, more or less concave on the ventral surface. It is rounded anteriorly; posteriorly it is limited by the first body rings. It varies considerably in length; its breadth is from 4 to 7 mm. The mouth, opening on its ventral surface about 1 mm. from the anterior border, is lipped by a chitinous ring. Above it are two prominent papillæ. On either side of the mouth are two protractile chitinous hooks similar in shape to feline claws. The anus is terminal at the posterior end. The genital orifice of the male is at the anterior end of the abdomen in the middle of the ventral surface of the first body ring; that of the female opens in the middle of the ventral surface of the caudal cone at about 1 mm. from the anus. The female is oviparous; the eggs are broadly elliptical.
The nymphal form (Fig. 167) is usually found spirally coiled within a cyst, the ventral surface corresponding, as a rule, to the convexity of the curve. In shape and structure the nymph closely resembles the adult, and the number of rings is the same. Calcification of the nymphal form in the liver may take place.
Life-history.—Little until lately was known of the life-history of P. armillatus; it is similar to that of the European linguatulid (Linguatula tœnoides), which is also an occasional parasite of man. The ova, disseminated by snakes harbouring the adult form, reach the intermediary host probably with its food or drinking-water.*[2] The larvæ then penetrate the mucosa, where some remain (Fülleborn); others pass on and become encysted in almost any organ or tissue, more especially liver, mesentery, or lungs. At a certain stage of development they escape from their cysts and migrate to the serous cavities, where they cause considerable inflammation. As a rule at this stage they are swallowed by their definitive host.
Pathogenesis.—There is much uncertainty as to the pathogeny of this parasite. Some consider it quite harmless. There can be no doubt as to the gravity of a heavy infection at the time when the parasites are migrating in their intermediary host. In Kearney's case, reported by Aitken, twenty or thirty parasites were found encysted in the liver and one or two in the lungs. The lungs were greatly congested. In Marchoux and Clouard's case the parasites were found in the liver and in the mesentery all along the intestine, but especially about the cæcum. In Chalmers' case numerous parasites were found moving freely in the abdominal cavity over the surface of the various organs. A large number were found within the lumen of the small intestine. Many were still encysted in the lungs.
The diagnosis of porocephalus infection is impossible.
GIGANTORHYNCHUS MONILIFORMIS (Bremser, 1911)
This is a common parasite of the rat in many parts of the world. Christopherson found one specimen in the intestine of a Soudanese. It is a white parasite with attenuated extremities, with many rings, resembling a porocephalus. The male is 4-5 cm., the female 7-10 cm. in length.
- ↑ * According to Leiper, C. endemicus is not a distinct species-but only a small form of C. sinensis.
- ↑ * Experimental work has been done in this direction by Broden and Rodhain, who gave porocephalus eggs in drinking-water to sleeping-sickness patients in whom post mortem the larvæ were found encysted in the liver. Fülleborn fed two monkeys on eggs obtained from trachea! mucus of an infected python: one monkey died after 60, the other after 300 days, enormous numbers of encysted larvæ being found in every organ of the body. Twelve snakes were fed on the monkeys' bodies: one developed adult porocephali in the lungs, the larvæ having bored their way through the stomach wall.