Trichinella

“ Other examples of species that require an intermediate host are Filaria bancrofti and Dracunculus medinensis.
Peculiar conditions prevail in the case of (b) Trichinella spiralis. This species, which in its adult state lives in the intestine of man and of various mammals, is viviparous; the young Trichinæ, however, do not leave the intestine, but reach the intestinal wall (Cerfontaine, Askanazy) in the following way: the female intestinal Trichinæ bore into the intestinal wall, where they are found in the submucosa, or in the lumen of the dilated lacteal vessels. ”

“ A high temperature (30°C.) must be provided in which to keep the experimental animals to ensure the success of the infection.
Fig. 302.—Trichinella spiralis. ♀, mature female: E, embryos; V, vulva; Ov, ovary. ♂, mature male: T, testes. c., newly born larva. d., larva in the muscles. e., encapsuled larva in the muscles. Magnified. (After Claus.)
History.—Encapsuled Trichinellæ had been observed in London by Peacock (1828) and by J. Hilton (1833) in the muscular system of man ”

“ Fig. 4.—Trichinella encysted among muscular fibres. (After Leuckart.) characteristic of Trichocephalus affinis, Oxyuris ambigua and other species. (2) The life-history of Ollulanus tricuspis is an example of the second class. Ollulanus tricuspis is found in the adult state in the alimentary canal of the cat; the young worms are hatched in the alimentary canal, and often wander into the body of their host and become encysted in the lungs, liver and other organs; during the encystment the worm degenerates and loses all trace of structure. ”

“ Human beings and the pig, rat, mouse, guinea-pig and rabbit are most easily infected; less easily the sheep, calf and horse; with difficulty the cat, dog and badger. Trichinella can also be reared in birds (fowl, pigeon and duck) , but the young do not encyst in the muscular system, but are expelled with the fæces. By cold-blooded animals as well as by insects (Calliphora vomitaria) , encysted Trichinellæ are evacuated without undergoing any change, but they will still develop if subsequently ingested, say, by rabbits. ”

“ Trichinella spiralis, which is found in man, and in the pig, bear, rat, mouse, cat, fox, badger, polecat and marten, and is capable of being artificially cultivated in the dog, rabbit, sheep, horse, in other mammals, and even in birds, is one of the most striking exceptions. ”

“ Inquiries elicited the fact that at about Christmas time the girl had been taken ill after eating pork, and at the same time the butcher from whom the meat was bought as well as several of his customers fell sick: the pickled pieces of the same meat were full of Trichinellæ. In the face of this information it was not difficult to ascertain the cause of the disease and the manner of infection in Zenker’s case, and it was not long before Leuckart, Virchow and Zenker were able by renewed experiments to demonstrate the cycle of development of Trichinella spiralis. ”

“ These animals, especially the last-named species, infect themselves very easily, as they are cannibalistic, and they also transmit trichinosis to other species by which they are devoured, such as pigs, dogs, cats, foxes, bears and martens. Rats are infected also by the ingestion of fæcal matter from infected animals which contains trichinæ (Höyberg) . Man becomes infected with Trichinella by eating the flesh, insufficiently cooked, of infected pigs, also, but more rarely, by eating the infected flesh of wild boars, dogs, cats, bears and foxes. ”

“ Here the young are born, in the intestinal wall, and leave this position with the lymph stream. Some of them, no doubt, actively bore through the intestinal wall, reaching the lymph or blood-stream, or even pass into the body cavity. What occurs during their further migrations is difficult to say at present. It has hitherto been maintained that the wandering is entirely active; for instance, the ligaturing of an artery would be no protection against the part of the body supplied by such artery being invaded by Trichinella. ”

“ That the helminthes like the ectoparasites multiply by sexual processes, that the entire course of development of the helminthes is rarely or never gone through in the same host as is the case with several ectoparasites, that the progeny at an earlier or later stage of development, as eggs, embryos, or larvæ, quit the host inhabited by the older generation, and almost always attain the outer world: only in Trichinella does the development take place directly in the definite host. Where the eggs have not yet developed they go through the embryonic evolution in the outer world. ”

“ 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. ”

“ Take, for instance, the trichina spiralis, a minute worm discovered in 1835 encysted in countless numbers in the muscles of the human body; it was studied by Virchow, Leuckart, and others, by feeding-experiments on animals, and was proved to come from infected 245 half-cooked ham and pork, and to make its way from the alimentary canal all over the body. The name of trichiniasis or trichina-fever was given to the acute illness that came of the sudden dissemination of these myriad parasites into the tissues. Trichiniasis had killed hundreds of people by a most painful death ”

“ 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. ”

“ 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. ”

“ 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. ”

“ 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 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. ”

“ 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. ”

“ 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. ”

“ Trichina, tri-kī′na, n. a parasitic worm, which in its mature state infests the intestinal canal, and in its larval state the muscular tissue of man and certain animals, esp. the hog:—pl. Trichī′næ:—ns. Trichinī′asis (more usually Trichinō′sis) , the disease caused by the presence of trichinæ in the body; Trichinisā′tion.—adjs. Trich′inōsed, Trichinot′ic, Trich′inous. [Gr. trichinos, small like a hair—thrix, trichos, hair.]
Trichite, trī′kīt, n. a spicule of some sponges.—adj. Trichit′ic.
Trichiurus, trik-i-ū′rus, n. the genus of hair-tails. ”

“ The Trichina (Fig. 25) lives in its immature condition in a sac. These sac-like bodies are found in the pig, the meat of which, if not sufficiently cooked when eaten, will cause this very fatal disease, as the sac being destroyed by the juices of the intestine, the young Trichina is set free, and deposits eggs, the embryos from which bore through the viscera of the unfortunate one. The Trichina belongs to the family of thread-worms or Nematoda. ”

“ 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 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. ”

“ More attention has been paid to the round worms. A species of strongyle (S. striatus) infests the lungs, the male being readily distinguished by its nearly round hood. A second species of strongyle has been mentioned by Diesing, but it is more than doubtful. The lungs are also infested by a small trichosome (Eucoleus tenuis of Dujardin) ; another species of the genus (Trich. exiguum) infesting the stomach and small intestine. As the Trichina spiralis has been repeatedly reared by myself and others in the hedgehog, the little flesh-worm must also be noticed in this place. ”

“ 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. ”

“ This worm, if eaten by man with pork, develops with great rapidity within the human digestive system, and produces enormous numbers of young, which, boring their way through the tissues to the muscles of the patient, cause serious and often fatal illness. Once in the muscles, no further change ensues to the worms, which simply degenerate into mere specks of lime. It is this trichina which produces the disease known as trichinosis. Fatal epidemics of this disease are not uncommon on the continent, especially where the unsanitary practice of eating uncooked or dried sausages is greatly in vogue. ”