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TRICHINIASIS (Trichinosis)

Category: Animal Parasites

The disease is caused by the trichina
spiratis, a parasite introduced into the body by eating imperfectly cooked
flesh of infected hogs. The "embryos" pass from the bowel and reach the
voluntary muscles, where they finally become "encapsulated
larvae,"--muscle trichinae. It is in the migration of these embryos that
the group of symptoms known as trichiniasis is produced.

When the flesh containing the trichinae is eaten by man or by any animal
in which the development can take place, the capsules are digested and the
trichinae are set free. They pass into the small intestine and about the
third day attain their full growth and become sexually mature. The young
produced by each female trichina have been estimated at several hundred.
The time from the eating of the flesh containing the muscle trichinae to
the development of the brood of embryos in the intestines (bowels) is from
seven to nine days. The female worm penetrates the intestinal wall and the
embryos are probably discharged into the lymph spaces, thence into the
venous system, and by the blood stream to the muscles, which constitutes
their seat of election. After a preliminary migration in the
inter-muscular connective tissue, they penetrate the primitive muscle-
fibres and in about two weeks develop into the full grown muscle form. In
this process interstitial inflammation of the muscle is excited, and
gradually an ovoid capsule develops about the parasite. Two, and
occasionally three or four, worms may be seen within a single capsule.
This process of encapsulation has been estimated to take about six weeks.
Within the muscles the parasites do not undergo further development.
Gradually the capsule becomes thicker and ultimately lime salts are
deposited within it. This change may take place in man within four or five
months. The trichinae may live within the muscles for an indefinite
period. They have been found alive and capable of developing as late as
twenty or twenty-five years after their entrance into the system. These
calcified capsules appear as white specks in the muscles. In many
instances however these worms are completely calcified. In the hog the
trichinae cause few if any symptoms. An animal, the muscles of which are
swarming with living trichinae, may be well nourished and healthy looking.
An important point also is the fact that in the hog the capsule does not
readily become calcified, so that the parasites are not visible as in the
human muscles.

Modes of Infection. The danger of infection depends entirely upon the
mode of preparation of the flesh. Thorough cooking, so that all parts of
the meat reach the boiling point, destroys the parasites; but, in larger
joints, the central portions are not often raised to this temperature. The
frequency of the disease in different countries depends largely upon the
habits of the people in the preparation of pork. In North Germany, where
raw ham and wurst are freely eaten, the greatest number of instances have
occurred. In South Germany, France, and England cases are rare. Salting
and smoking the flesh are not always sufficient, and the Havre experiments
showed that animals are readily infected when fed with portions of the
pickled or the smoked meat as prepared in this country.

Symptoms. The eating of trichinous flesh is not always followed by this

In the course of a few days after eating the infected meat there are signs
of disturbance of the stomach and bowels, and pain in the abdomen, loss of
appetite, vomiting and sometimes diarrhea; and yet, these preliminary
symptoms do not always occur, for in some of the large epidemics cases
have been observed in which they have been absent. Pain in different parts
of the body, general debility and weakness have been noted in some of the
epidemics. In some instances the stomach and bowel disturbances have been
so marked from the outset that the attack resembled our cholera. The
invasion symptoms develop between the seventh and tenth day. Sometimes not
until the end of the second week, and they are marked by fever, a chill in
some cases and pain and swelling and tenderness along the muscles
involved. The migration of the parasites into the muscles excites a more
or less intense inflammation of these muscles, which is characterized by
pain on pressure and movement, and by swelling and tension of the muscles,
over which the skin may be swollen. The limbs are placed in some position
in which these muscles are more at rest. Difficulty in chewing and
swallowing is caused by the involvement of the muscles controlling these
acts. In severe cases the involvement of the diaphragm and intercostal
muscles may lead to difficult breathing (Dyspnoea) which sometimes proves
fatal. Watery swelling, a feature of great importance, may be seen early
in the face, particularly about the, eyes. Later it develops in the
extremities when the swelling and stiffness of the muscles are at their
height. Profuse sweats, tingling and itching of the skin and in some
instances hives (Urticaria) have been described.

There are emaciation and anemia. In the severe cases the appearance may be
like that in the third week of typhoid fever. In mild cases the fever and
muscular symptoms subside in ten to fourteen days, in others only after
two or three months. The mortality, from one to thirty per cent, seems to
depend upon the virulence and number of parasites.

PHYSICIANS' TREATMENT. If discovered within twenty-four to thirty-six
hours, thoroughly empty the bowel with purgatives. Rhubarb and senna, or
an occasional dose of calomel may be given. Relieve the pains afterwards
and support the strength.


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