Definition.—A disease of the muscles due to the presence of the trichina spiralis, which results from eating raw or partially cooked pork.
History.—Owen was the first to name and fully describe this parasite, in 1835, though it had been observed and described as "minute white masses" in 1821 by Hilton. To Zenker, however, belongs the honor of reporting the first clinical records, in 1860. The disease was at first diagnosed as typhoid fever, but a train of symptoms developed entirely different from that of enteric fever, the most prominent of which was an intense myalgia. After suffering for a month the patient died.
A post-mortem examination revealed the presence of sexually mature parasites in the intestines, embryos in the muscles in various stages, to those completely developed and encapsuled.
Natural History.—The adult female is from three to four mm. long; the male from 1.4 to 1.6 mm., with a short conical appendage on either side of the cloaca, behind which are two pairs of papillae.
The fully developed larva, or muscle trichina, measures from 0.6 to 1 mm. in length and is coiled in a capsule. Translucent at first, it soon becomes opaque, owing to infiltration of lime salts.
Etiology.—Infection takes place by eating- infected pork, and occurs in the following manner: The capsules of trachinse are digested in the intestines and the parasites set free, which become sexually mature in from two to four days. Each female produces several hundred young, requiring from three to five days for their development, or from the ingestion of the infected pork to the full development of the embryos, a period of from seven to nine days.
The female worm, after penetrating the intestinal wall, discharges the embryos into the lymph spores, thence into the bloodstream, which carry them to the muscles. Mere their further development is completed in about two weeks, when they reach the full grown muscle form.
As a result of their presence, an inflammation is set up, which results in the formation of a capsule in which one or more worms are entombed.
The capsule of connective tissue finally undergoes calcification. The parasite may retain its vitality within the capsule for years.
Swine are generally infected by eating, either intestinal discharges containing the infection or infected cadavers.
The trachina in pork can only be destroyed by thorough cooking, hence raw or rare pork should never be eaten.
Pathology.—The mucous membrane of the bowel becomes hyperemic and swollen; the solitary follicles, Peyer's patches, and the mesenteric glands undergo the same changes. The spleen is but little affected, though the liver, kidneys, and heart may undergo cloudy swelling or fatty degeneration.
The muscles are the parts most affected, and show the changes peculiar to myositis. The trichinous cysts are grayish-white, oat-shaped specks, arranged longitudinally in the muscle fibers. The muscles most affected are the diaphragm, the intercostal, the cervical, the laryngeal, and the ocular. In the extremities, the biceps and triceps are especially the seat of election.
Symptoms.—The symptoms vary according to the number of parasites ingested. Where but few are present, there may be an entire absence of any symptoms to suggest the lesion.
In typical cases, gastro-intestinal disturbances follow shortly after eating the infected meat. It may begin with malaise and nausea, soon to be followed by vomiting and diarrhea. At times it may simulate gastroenteritis, the vomiting and purging being accompanied by quite an active fever.
In the course of a week or ten days, symptoms of rheumatism appear, more in the muscles than in the articulations. The muscles become swollen, tender, and painful when moved, especially in flexion. If fever was present during the gastro-intestinal symptoms, it is now increased, or chilly sensations, followed by an active fever, may usher in the muscular symptoms.
Mastication and deglutition become painful, while flexing the extremities is attended by pain. Dyspnea is due to involvement of the diaphragm. Edema of the face, particularly the eyelids, is quite a constant symptom. Pruritus is often a troublesome feature, accompanied by various skin eruptions and profuse sweating.
Bronchitis is not an infrequent complication, while hypostatic pneumonia or pleurisy may occur. The urine is diminished in quantity, is high-colored, and may contain albumin and casts. In severe cases, insomnia is a troublesome condition.
Diagnosis.—The diagnosis is made by the following characteristic signs: Gastro-intestinal symptoms, consisting of dry tongue, nausea, vomiting, and diarrhea, followed, in a few days, by soreness of the muscles of the neck and extremities; difficult mastication and deglutition; edema of the eyelids, and face; soreness and stiffness of the muscles at large; profuse sweating, attended by an urticarial eruption, and fever of a remittent type.
Prognosis.—In mild cases and in children, the prognosis is favorable. If large numbers of trichina are present in the meat, and they are not destroyed in the cooking, the case will most likely prove one of great severity, the mortality running from five to thirty per cent.
Persistent and profuse diarrhea, high fever, intense muscular soreness, difficult deglutition, profuse sweating, cardiac weakness, delirium, and coma, would suggest an unfavorable termination.
Treatment.—If it were possible to destroy all the rats that infest sties, and thus prevent swine from eating anything but grain and vegetables, and to drink only pure water, trichina would disappear, and prophylaxis will look toward the accomplishment of this end.
The most efficient means, however, is to thoroughly cook all pork, smoked, salted, or fresh, for this completely destroys the parasites.
The bowels should be evacuated as soon as possible after infected meat has been eaten, before the embryos have had an opportunity to penetrate the muscles. It is well to combine santonin, male fern, or thymol with whatever purgative that is used. Cathartics should be used for two or three days, that the bowel be thoroughly emptied of all the parasites.
For the soreness of the muscles, the hot bath will afford some relief. Macrotys in large doses might mitigate, to some extent, the myalgia. When the pain is extreme, morphia may be necessary. Should typhoid symptoms arise, baptisia, echinacea, the mineral acids, the sulphites, and chlorates would be used.