Chapter XXIV: 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.