Trichinellosis

“ Such infested muscle or flesh is said to be "trichinosed," and the flesh of a trichinosed human subject has been estimated to contain 100,000,000 encysted worms. To complete the development of the encysted and sexless Trichinæ the infested flesh of the host must be eaten by another animal in which the worm can live, e.g. the flesh of man by a pig or rat, and that of a pig by man. In such a case the cysts are dissolved by the digestive juices, the worms escape, develop reproductive organs and produce young, which then migrate into the muscles and induce trichinosis as before. ”

“ I had myself examined the trichinised flesh taken from a dozen of these corpses, but in no instance had the faintest suspicion of trichinosis been entertained during life. The circumstances attending the only outbreak of trichiniasis that has been witnessed in England are very interesting. In the month of April, 1871, I received from Dr W. L. Dickinson, of Workington, Cumberland, specimens of pork which he requested me to examine; and in complying with his request I confirmed his opinion that the diseased meat was infested with Trichinæ. ”

“ But it has not been found that this microscopic examination serves as an effective check; indeed it is apt to create a false feeling of security. Over 32% of the German cases of trichinosis between 1881 and 1898 were traced to meat so inspected and passed as free from trichinae. In America accordingly microscopic examination is not considered to give any guarantee of soundness from trichinae, in spite of a government mark “inspected and passed” (see B. H. Ransom, Circular 108 of U.S. Dep. of Agriculture, 1907) . ”

“ Perhaps the worst form of dis-ease contamination from fresh flesh food is that of trichinosis. Trichinae are worm-like creatures which have the first stage of their growth in the flesh of swine, and then become encased in a cyst or egg-like structure, which, when taken into the human digestive organs are revived, and the trichinae then bore their way through [260] the walls of the digestive organs, completing their growth in the human muscle-tissue. Trichinosis is one of the most fatal of diseases, but fortunately is not common. ”

“ In the same way calcareous infiltration sometimes occurs, but only when the parasites have lost their vitality. This calcareous degeneration consists in the deposit of carbonate and phosphate of lime in the walls of the cyst; it never begins before the seventh or eighth month after infestation, and is sometimes much longer delayed.
No man or animal ever becomes infested except by the ingestion of meat or drink containing larval trichinæ. The pig and small rodents are most frequently attacked. Man contracts trichinosis by eating insufficiently cooked infected pork. ”

“ Trichiniasis or trichinosis is a disease characterized by fever, muscular pains, an enormous increase in the eosinophil blood corpuscles, and other more or less well-defined symptoms; at the onset it is sometimes mistaken by physicians for typhoid fever. The responsible parasite is a roundworm (Trichinella spiralis, formerly known as Trichina) which is swallowed while in its encysted larval stage in raw or imperfectly cooked pork. ”

“ The larva of the tænia saginata is found in the muscular fibers and connective tissue of cattle and when ingested in man develops into the tænia saginata.
Trichinosis
There is a parasite known as trichina spiralis which is found as a minute spiral worm in the muscular fibers of pork. It is visible to the naked eye as white specks. The ingestion of this parasite into a person with subluxations, causing interference with transmission of mental impulses, produces a condition which is called trichinosis. It is an acute condition and the symptoms resemble typhoid fever. It often results fatally. ”

“ When trichinous pork is swallowed, the eggs develop in the alimentary canal in about a week into complete worms, and in three or four days more each female produces over a hundred young ones. These burrow into every part of the body, producing great irritation and inflammation. In one case after death upwards of 50,000 worms were estimated to exist in a square inch of muscle. Most of the cases of trichinosis have occurred in Germany, from eating imperfectly cooked sausages. The pig becomes trichinous by eating offal, and man is infected by eating pork. This disease is rare in England. ”

“ The parasite Trichina spiralis, was by no means unknown in this country; whilst in Germany and other countries, where the eating of raw pork in the form of ham and sausages is common, cases of this disease are still reported. The presence of this parasite in the human body is most painful, and generally results in the death of the sufferer. Mere salting, smoking, or subjecting to a moderate heat will not kill the parasite in infected meat; thorough and complete cooking alone is sufficient to render the meat innocuous. ”

“ Trichiniasis is generally accompanied by a marked eosinophilia. The diagnosis is made by teasing out upon a slide a bit of muscle, obtained preferably from the outer head of the gastrocnemius, the insertion of the deltoid, or the lower portion of the biceps. The coiled embryos can easily be seen with a two-thirds objective (Fig. 108) .
(5) Uncinaria.—The two varieties of this worm, Uncinaria duodenalis and Uncinaria Americana, are among the more harmful of the animal parasites. They inhabit the small intestine, usually in great numbers, and commonly produce a severe and often fatal anemia. ”

“ The young brood is distributed from the heart throughout the entire body, but the conditions necessary to its further development are found only in striated muscle; the young Nematodes penetrate the capillaries, attain the intramuscular connective tissue and then invade the fibres (Virchow, Leuckart, Graham304) . On the ninth or tenth day after infection the first Trichinellæ have reached their destination; but further invasions are constantly taking place because the intestinal Trichinellæ live from five to seven weeks, and continue to produce their young. ”

“ The males after a time leave the body with the excreta and perish, whilst the larvae of the new brood make their way into the tissues of the host.
Man usually acquires trichinosis by eating uncooked or improperly-cooked pork, and the disease is so widely spread and of such a serious nature that most civilised countries have adopted rigorous methods for the detection of trichinised meat. ”

“ The further development of the muscle-Trichinæ into adult animals is altogether independent of the formation of the calcareous shell, and occurs as soon as the former have reached their completion. (14) Males and females are already recognisable in their larval state. (15) The immigration of the Trichina-brood in masses produces very grave or even fatal consequences, such as peritonitis (from the embryos perforating the intestinal walls) , pain, and paralysis (resulting from the destruction of the infected muscular fibres) . (16) The infection of man occurs especially through swine. ”

“ Tiedemann (1822) , Peacock (1828) described “little bodies” in the muscles of human cadavers which Hilton (1832) considered to be parasitic in nature. Paget (1835) showed that these bodies were round worms and Owen (1835) described them more accurately and gave the name Trichina spiralis to them. Leidy (1846) found organisms in the muscles of hogs which he considered to be the same as Owen’s Trichina and paved the way for the work of Zenker (1860) in showing the pathological relation between the Trichina of pork and human Trichinosis. ”

“ Human infection is practically accidental and self-limited; biologically speaking, man as a host does not enter into the calculations of the parasite.
Treatment of established trichiniasis infection is palliative, not truly remedial. The parasites, once inside the body, cannot be materially affected by the administration of any drug. While cure of trichiniasis is thus difficult, if not impossible, prevention is very simple. The thorough cooking of all food is sufficient to preclude infection. ”

“ The trichinæ occupying the muscles are immature, and it is only after they are swallowed and the parasites are freed by digestion of the envelopes and pass into the intestine that they undergo development to sexual maturity. In this state the female is viviparous and gives birth to a multitude of active embryos, which immediately commence to migrate to the muscular system. As it is estimated that each female may give birth to upward of a thousand embryos, it is readily conceived to what an extent the body may become infested from eating a few ounces of trichinous pork. ”

“ Recovery from these phases of trichinal infection may be apparently perfect. A rabbit which M. Davaine kept during five months became large and fat, although it had a large number of Trichinæ in its muscles; a rat which had had these entozoa in considerable numbers during six months was, to all appearance, in good health. Hence he concludes that the Trichinæ produce symptoms only when they are in the intestinal canal, and when they are entering the muscles. Having become lodged in their cysts among the muscular fibres, they may remain harmless for an indefinite time. ”

“ The notion that particular breeds of swine are more liable to be infested than others is absurd, since infection must be due to the facilities offered for swallowing garbage, especially dead rats. According to Drs Belfield and Atwood 8 per cent. of slaughtered American swine contain Trichinæ. In infested hogs they found from 35 to 13,000 parasites in a cubic inch of muscle, and by repeated feedings they succeeded in rearing about 100,000 Trichinæ in the body of a rat.
In regard to the disease in man let us glance at the phenomena that presented themselves in Plauen, a town of Central Saxony. ”

“ I find that a relatively similar degree of infection in an ordinary human “bearer” would yield thirty millions. In the case of one of my own experimental animals, a pig, I reckoned that there were at least sixteen millions of Trichinæ. The larvæ were about ten months old and enclosed within perfectly formed capsules; nevertheless, the animal had never displayed any symptom of irritation. In a trichinised human subject, examined by Dr Thudichum, it was estimated that 40,000,000 parasites were present. ”

“ Cases of trichinosis have been known to occur in nearly all the countries of Europe; further, in Egypt, Algeria, East Africa, Syria, India, Australia, and America. North Germany, more especially the Saxe-Thüringian states, is the classical land for epidemics of trichinosis; the mortality varies, but it may be very high.306
Prophylaxis.—The grave nature of the disease and the comparatively high mortality relating to trichinosis led the authorities to adopt certain preventive measures, which are the more necessary as national customs cannot be altered in a short time. ”

“ On the other hand, many infections are so light as to pass unnoticed. Williams [91] found Trichinella embryos present in 5.4 per cent of the bodies of persons dying from other causes. Such findings are considered to indicate that occasional slight Trichinella infections even in the United States are quite common. This might indeed be expected from the frequent occurrence of infection in swine, about 6 per cent of these animals being found to harbor the parasite. ”

“ Diagnosis in the presence of several cases, or in epidemics, is not difficult, but in isolated cases, on the other hand, it is not easy. If there is a suspicion of trichinosis, from the muscular fatigue and the œdema of the eyelids, the diagnosis can be made by excision of a piece of muscle and by finding the Trichinæ in the tissue, taken with the results of the examination of the previously eaten sausage or meat. ”

“ If, for example, we take the case of Trichina we find that several millions of entozoa may exist in the human, or, at all events, in the animal bearer, without producing any symptom of discomfort. In such cases it is not possible to determine the strict limits of health and disease; nevertheless, were we to double the amount of infection, the imaginary line of demarcation is at once bridged over and the parasites become acknowledged as directly responsible for grave symptoms which may even prove fatal to the bearer. ”

“ We have evidence on this point from the case in which I estimated that there were upwards of 100,000,000 of Trichinæ present, and yet the man survived the attack.
“Incidentally I may remark that in the course of the last twenty years, although millions of parasites and their eggs have passed through my hands, I have almost entirely escaped infection. It is something to know what you are either handling or looking at, because there are many parasites besides Trichina which are dangerous. There are gregariniform entozoa residing in meat which we eat every day without any bad consequences. ”

“ The symptoms in man are occasioned by the presence of the free parasites in the intestine, by the development of young trichinae from the eggs, and most of all by the migration of the parasites from the intestinal canal to the muscles, where they become quiescent. ”

“ SYMPTOMS.—In general, the effect produced by eating trichinous meat [p. 960] is proportioned to the number and condition of the trichinæ ingested and to the susceptibility of the patient. A few of the parasites may pursue their entire career and die within their host without ever exhibiting any obvious evidence of their presence. Sometimes the symptoms of trichinosis are obscure or trifling, sometimes sufficiently well marked, but moderate, and often they are more or less striking and violent. ”