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from the stomach into the intestine, grow to maturity in about two days, and, according to their sex, become adult males or females. The male is the smaller of the two, measuring only about 1.5 mm. in length (about 16 of an inch), the female measuring 3 to 4 mm. in length (about 1/8 to % of an inch). The embryos begin to escape from the bodies of the females into the intestine of the host about six days after infestation, and the production of embryos may continue for a month or more, but abates considerably after the first few days. The adult worms usually disappear from the intestine in five or six weeks, or even sooner if the patient is affected with diarrhoea. The total number of embryos which each female is able to produce has been estimated at 10,000 to 15,000.

As soon as born the embryos begin to migrate, penetrating the intestinal wall and entering the connective tissue, lymphatics and blood vessels. They are apparently aided in their migrations by the blood current, and are carried to various portions of the body, finally entering the muscles. This period of migration lasts from six to ten days. Having reached its final resting place in a muscle, the embryo grows considerably, reaching a length of 0.8 to 1 mm. (about 30 to 25 of an inch) and a thickness of 40μ (about 1600 of an inch). Meanwhile as it grows the embryo coils itself into a spiral and becomes surrounded by a membranous cyst, produced by changes in the interfascicular connective tissue of the muscle, brought about in consequence of the irritating influence of the worm.

In form the trichina cyst is usually ovoid or lemonshaped, with its long axis directed parallel with the muscle fibers. The average size is about 400μ by 250μ (about 60 by 100 of an inch). After a time fat globules are deposited on the outside of the cyst in little masses at each pole. In seven or eight months after infestation the cysts begin to degenerate, commonly becoming calcified, and the vitality of the worms is finally destroyed.

This process of degeneration is completed usually within about two years, although cases are on record in which calcification of the cysts was still very slight as long as eleven years after infestation, and the worms were still alive.

The number of encysted larvæ which may be present in even a small piece of muscle in cases of severe infestation is very large. As many as 1,200 have been counted in a piece of muscle weighing 1 gram, which would make about 500,000 in a pound. If a person were to eat a pound of pork thus heavily infested, and if all of the larva developed to maturity in his intestine, and if each female produced the estimated number of 10,000 embryos, there would be set free in the intestine 2,500,000,000 to 3,000,000,000 embryos. Of course in an actual case not all of the larvæ would develop, and not every female would produce as many embryos as assumed in the estimate, nor would all the embryos succeed in penetrating the intestinal wall and migrating into the muscles. The computation, however, gives an idea of the great intensity which infestation may reach. The number of cysts present in the bodies of persons who have died with the disease has been estimated in various cases at from 5,000,000 to 100,000,000.

SYMPTOMS OF TRICHINOSIS.

The severity of the symptoms of trichinosis depends upon the number of living larval worms taken into the body. Three periods in the course of the disease are commonly distinguished.

The first period begins in from two days to a week, sometimes not for nearly two weeks after infestation. The symptoms appearing in this stage are those of gastro-intestinal irritation, due to the development of the worms in the intestine and the liberation of the embryos, and consist of lack of appetite, nausea, abdominal pains, diarrhoea and fever. These symptoms are not constant, and are often absent.

The symptoms of the second period that corresponding to the migration of the embryos - develop between the seventh and tenth days, sometimes later. There is more or less fever, and the muscles become tense and swollen and are painful on movement or pressure. There may be pain and difficulty in chewing, swallowing and breathing, on account of the involvement of the muscles concerned in these functions.

In the third stage, following the encystment of the worms in the muscles, the patient becomes emaciated and anemic, watery swellings appear, especially in the face, the skin may itch and tingle, and eruptions sometimes appear.

The duration of the symptoms, as well as their intensity, depends upon the degree of infestation.

Trichinosis is often mistaken for typhoid fever, on account of the similarity of the symptoms; and the muscular pains are sometimes taken for rheumatism.

In light cases recovery occurs in about two weeks; in severe attacks it does not begin for six weeks, and several months may elapse before the patient entirely recovers. In fatal cases death rarely occurs earlier than the second week or later than the seventh, usually between the fourth and sixth weeks, when the muscular symptoms are at their height.

The symptoms of trichinosis in hogs are similar to those in the human patient, ordinarily much less pronounced, and recovery usually follows. During the migrations of the worms into the muscles the animal moves with difficulty, the limbs are stiff, and the hind quarters sometimes seem to be paralyzed. There is soreness of the muscles, more or less diarrhoea, and sometimes skin eruptions, so that hog cholera may be suspected by the layman. As a rule, however, the symptoms are so slight that the disease in hogs passes entirely unnoticed.

TREATMENT OF TRICHINOSIS.

If the disease is recognized early, the patient may be treated with purgatives and vermifuges, to expel the worms from the intestines. There is no treatment which will affect the embryos after their migrations are begun.

FREQUENCY OF TRICHINOSIS.

The frequency of the disease in man depends upon the frequency of infection in hogs used for food, and upon the extent to which insufficiently cooked, or raw, imperfectly cured pork is eaten. Nearly a thousand cases have been placed on record or are definitely known to have occurred in this country, and a large percentage of those patients whose nationality has been ascertained were Germans. In certain States of the German Empire the custom of eating raw pork is a common one; and, out of 6,329 cases which occurred in that country during the years 1881 to 1898 (as collected by Stiles 1), 5,456 cases occurred in States where raw pork is an established article of diet.

The frequency of trichinosis in hogs in this country, as indicated by the microscopic examination of pork for export, formerly carried on by this Bureau (not because it was considered of value as a sanitary measure, but for the purpose of meeting the requirements of foreign trade), averages from 1 to 2 per cent. In some localities the percentage is much higher than this, in others it is less, and there is more or less variation from year to year.

PREVENTION OF TRICHINOSIS.

In spite of the prevalence of trichinosis among hogs in this country, there need be no fear of infection in man if the proper precautions are taken. The danger of infection may be entirely avoided, and only avoided, if pork is not eaten until after it has been thoroughly cooked or thoroughly cured. By either of these means any trichina which may be present are killed and rendered harmless. Trichinous meat thus treated is perfectly fit for food and just as wholesome as non-infested meat, except in rare instances, when the infestation is so severe as to cause extensive pathologic changes.

Consumers should understand that the government mark, "U. S. Inspected and Passed," does not guarantee that the meat has been inspected for trichinæ. In all cases, therefore, whether pork has been inspected or not, it should be thoroughly cooked or thoroughly cured before it is used for food.

RESIGNATION AND APPOINTMENT.

Dr. Richard S. Benner of Springfield, State Inspector of Health of District No. 14, submitted his resignation to the Governor early in October. Dr. Herbert C. Emerson of Springfield was appointed to fill the vacancy, and the appointment was confirmed by the Governor's Council on October 23.

Bureau of Animal Industry, Bulletin No. 30.

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An official publication of the State Board of Health of Massachusetts, issued monthly from the office of the Board, 141 State House, Boston, Mass.

New Series.

NOVEMBER, 1907.

Vol. 2. No. 11.

ENTERED AT THE POST-OFFICE AT BOSTON, FEB. 15, 1906, AS SECOND-CLASS MATTER.
OF JULY 16, 1894.

STATE BOARD OF HEALTH.

HENRY P. WALCOTT, M.D., CAMBRIDGE, Chairman.

ACT

JULIAN A. MEAD, M.D., WATERTOWN.

HIRAM F. MILLS, C.E., LAWRENCE.
GERARD C. TOBEY, ESQ., WAREHAM.

JAMES W. HULL, PITTSFIELD.
CHARLES H. PORTER, QUINCY.
ROBERT W. LOVETT, M.D., BOSTON.

CHARLES HARRINGTON, M.D., BOSTON, Secretary.

BOSTON:

WRIGHT & POTTER PRINTING CO., STATE PRINTERS,

18 POST OFFICE SQUARE.

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