CHAPTER XXIV. Minor Helminthic Infections

MINOR HELMINTHIC INFECTIONS

PARAGONIMIASIS

General Considerations

This is an infection with a trematode, Paragonimus westermanni (P. ringeri) (Distoma pulmonale). It is rather common in some parts of Japan and Formosa.

Arce has recently reported cases of paragonomiasis in three Peruvians who had been in contact with Japanese immigrants.

In 1880, Baelz found the ova in the sputum of a case of haemoptysis in a Japanese, as did also Manson in a Chinaman. Manson’s case subsequently died and when autopsied showed in his lungs a fluke which was responsible for the eggs seen by Manson. The fluke itself is a little more than ⅓ of an inch (8 mm.) long and is almost round on transverse section, there being, however, some flattening of the ventral surface. The acetabulum is conspicuous and opens just anterior to the middle of the ventral surface.

The branched testicles are posterior to the laterally placed uterus and the genital pore opens below the acetabulum. The branched ovary is opposite the uterus on the other side.

It is rather flesh-like in appearance and is covered with scale-like spines. The flukes are usually found in tunnels in the lungs, the walls of which are thickened connective tissue. These tunnels result from hypertrophy of the bronchioles. There may be also cysts formed from the breaking down of adjacent tunnel walls. In addition to lung infection with this fluke, brain, liver and intestinal infections may be found.

The life history and mode of infection of man, further than the miracidium stage, has been unknown until recently. If the eggs in the sputum are shaken up with water and the water renewed from time to time a ciliated embryo or miracidium develops after a few weeks and, at this time if one presses on a cover-glass covering some of these more mature ova, the miracidium will break through the operculated extremity of the egg and swim about actively in the surrounding water.

Nakagawa has found that the miracidia infest certain fresh water molluscs and become cercariae in this first intermediate host. From this host the cercariae go to certain fresh water crabs and encyst in this second intermediate host, either in the liver or in the gills. In Japan one of these crab hosts, Potamon dehaanii, is eaten both raw and cooked.

Experimental feeding of puppies on infected crabs brought about infection with the lung fluke. It is thought that the fluke, after leaving the cyst, goes through the intestine to the abdominal cavity. Thence it perforates the diaphragm and enters the pleural cavity, finally penetrating the lung to become encysted there. The lung is the favorite site but wandering flukes may invade other tissues and organs even invading the central nervous system.

Besides man, dogs, cats and especially hogs may be infected.

Symptomatology, Diagnosis and Treatment

The case is usually considered as one of chronic bronchitis on account of the occurrence of cough and morning expectoration of a gelatinous sputum which is usually brownish. It is popularly known as endemic haemoptysis for the reason that after violent exertion, or at times without manifest reason, attacks of haemoptysis of varying degrees of severity come on. The signs on percussion are usually insignificant while those on auscultation at the time of haemoptysis are often marked. The symptoms often disappear for months to again reappear.

The course of the disease is very chronic, often lasting many years. As a rule the patient is fairly well nourished although recurring attacks of haemoptysis may bring on a rather marked anaemia. Jacksonian epilepsy has been reported as occurring in paragonomiasis, the ova being found in cysts of the brain. There is some question as to whether some of the reports as to paragonomiasis may not have been connected with infections with Japanese schistosomiasis.

The diagnosis of endemic haemoptysis is readily made by finding the operculated eggs in the more or less sanguinolent sputum. These eggs are of a light yellow color and average 90 × 65 microns. One often sees Charcot-Leyden crystals in the sputum.

As prophylactic measures we should forbid uncooked crabs or crayfish. The sputum should be sterilized.

The treatment is entirely symptomatic.

CLONORCHIOSIS

This is an infection due to a trematode, Clonorchis endemicus (Opisthorchis sinensis). It is also referred to as human liver fluke disease. It is true that the common liver fluke of sheep, Fasciola hepatica, may occur in man but such infections are rare, only 23 cases having been reported. Another liver fluke of ruminants is the lancet fluke, Dicrocoelium lanceatum, but it is also unimportant for man, only 7 cases having been reported.

Clonorchis infections are common in China and Japan, the fluke being about ½ inch long by ⅛ inch wide. There is considerable dispute as to whether we have a pathogenic and nonpathogenic Clonorchis; the name C. endemicus applying to the former and C. sinensis to the latter.

Looss considered the nonpathogenic C. sinensis to be larger (13-19 mm.), to show pigment in its parenchyma and to have breaks in the vitelline glands. C. endemicus was reported as smaller (10 to 13 mm.), and without pigment or breaks in the continuity of the vitellaria.

The eggs of this fluke show slightly concave bending of the sides at the operculated end and are about 30 × 16 microns. These flukes are found within the thickened bile ducts and may be present in great numbers. They may invade the pancreas as well as the liver.

These flukes are found in dogs and cats as well as man.

This fluke is supposed to produce most serious symptoms as indigestion, swelling and tenderness of liver, bloody diarrhoea, ascites, oedema and a fatal cachexia.

The course of the disease is insidious and chronic with periodic improvement.

As a matter of fact, many physicians in China attribute very little pathogenic importance to it. The disease is diagnosed by the presence of the ova in the stools. The source of infection is probably through the eating of uncooked fish.

Kobayashi has examined various molluscs and fish for trematode larvae. He succeeded in infecting nine kittens and two cats by feeding them with certain fresh water fishes whose flesh contained trematode larvae. These fishes were found in districts where human distomiasis was common.

Further experiments by Kobayashi have shown that the larval flukes leave the cyst and start for the biliary passages. When the flukes are very numerous the size is smaller. Maturity is reached in four weeks. This investigator believes that the primary intermediate host is a mollusc as cercariae found in these hosts are very similar to the larval forms found in fish.

He does not consider that there are two species concerned in Clonorchis infections, as he has found variations in continuity of vitellaria in small as well as large flukes. Number of parasites present influences size. Age influences pigment production.

Another human fluke, Opisthorchis felineus, inhabits the gall bladder and bile ducts of man and it is stated that the infection is quite common in Siberia.

It is also a parasite of cats and dogs.

Both Clonorchis and Opisthorchis have the testicles in the posterior end with the uterus anterior. The testicles of Clonorchis are branched (dendritic) while those of Opisthorchis show as two lobes. In Dicrocoelium the lobed testicles are anterior to the uterus, which fills up the posterior end of the fluke.

The mode of infection as well as the life history is not known but is probably connected with the eating of raw fish.

The symptoms are similar to those caused by C. endemicus.

The fluke has two-lobed testicles as against the dendritic one of C. endemicus.

INTESTINAL DISTOMIASIS

The most important intestinal fluke is undoubtedly Fasciolopsis buski. It is now thought that this infection is more common than was previously stated. Goddard states that more than 5% of stools examined in Shaohing, China, show eggs of this parasite. It is a very large fluke with an acetabulum 4 times the diameter of the oral sucker. It is characterized by a very long and prominent cirrus.

F. buski and Fasciola hepatica are much alike in size and outline. The acetabulum of the latter is only 1.6 times the diameter of the oral sucker and the alimentary tract shows branching which is best seen in the cone-shaped projection of its anterior extremity. F. hepatica is a liver fluke rarely found in man.

F. buski is found in China, Assam and India. It is a parasite of hogs as well as man. The eggs measure from 80 to 120 microns, are nearly colorless and have a thin shell with a very small operculum.

The symptoms are chiefly those of a chronic diarrhoea followed by anaemia and wasting. The stool is light yellow in color, exceedingly offensive and does not contain blood. Goddard thinks that they live in the upper part of the small intestines.

The life history is unknown but Goddard states that fresh water snails are much eaten by the people of Shaohing. Nakagawa notes that the eggs of Fasciolopsis hatch in two to three weeks. The miracidia penetrate various species of snails in which the cercariae may encyst and infect pigs eating such snails. The cercariae may also leave the snail and encyst on blades of grass, to later infect an animal feeding on the grass, this latter method of infection resembling that of Fasciola hepatica.

Noc has reported success with treatment with thymol and Goddard with beta-naphthol.

Other intestinal flukes such as Cladorchis watsoni, Gastrodiscus hominis, Heterophyes heterophyes, and Fascioletta ilocana are of less importance. Heterophyes is probably a rather common parasite but owing to its very small size (2 mm.) has been generally overlooked at autopsy.

STRONGYLOIDES STERCORALIS

It was formerly supposed that a chronic form of diarrhoea in Cochin China was due to an infection with the parthenogenetic female of Strongyloides stercoralis. It is now known that the parasite is widely distributed over the tropical and subtropical world and that it rarely gives rise to manifest symptoms although some observers regard it as capable of producing diarrhoea and more or less anaemia.

It seems to be capable of setting up quite an eosinophilia at the time the adult female is penetrating the crypts of Lieberkühn, so that it is probably of pathogenic importance.

The parasitic or intestinal form (also known as Anguillula intestinalis) is represented only by females. These are about 1/12 of an inch (2 mm.) long and reproduce parthenogenetically. They have a pointed, four-lipped mouth, and a filariform oesophagus which extends along the anterior fourth of the body. The uterus contains a row of 8 to 10 elliptical eggs which stand out prominently in the posterior part of the body by reason of being almost as wide as the parent worm.

They usually live deep in the mucosa and the embryos emerge from the ova laid in the mucosa. The embryos escape from the eggs while still in the intestines, so that in the faeces we only find actively motile embryos. The eggs, which are strung out in a chain, never appear in the faeces except during purgation. As they greatly resemble hookworm eggs this is a point of great practical importance.

In fresh faeces we find hookworm eggs and Strongyloides embryos. The embryos are rather common in stools in the tropics. These embryos have pointed tails and are about 250 × 13 microns. They have a double oesophageal bulb. They are about 250 microns when they first emerge but may grow until they approximate 500 microns in the faeces. The mouth cavity of the embryo of the hookworm is about as deep as the diameter of the embryo at the posterior end of the mouth cavity; that of Strongyloides is only about one-half as deep as the diameter. If the temperature is low, below 15°C., these rhabditiform embryos develop into filariform embryos, which form the infecting stage.

It has been demonstrated by Fülleborn that infection of man takes place through the skin. If the temperature is warm, 25° to 35°C., these embryos develop into the free-living form. In this we have males and females, with double oesophageal bulbs, the male about 1/30 of an inch (¾ mm.) long with an incurved tail and 2 spicules and the female about 1/25 inch (1 mm.) long with an attenuated tail. These copulate and we have produced rhabditiform larvae, which later change to filariform ones. At this time the length is about 550 microns. These start up the parasitical generation.

For treatment thymol is usually recommended. Stiles speaks highly of sulphur.