Trematode

“ Any one of numerous species of trematode worms belonging to Tristoma and allied genera having a large posterior sucker and two small anterior ones. They usually have broad, thin, and disklike bodies, and are parasite on the gills and skin of fishes. ”

“ The flat, lancet-shaped worm, sometimes found up the nose, is spoken of as a trematode; the round-worms in the stomach and bowels as nematodes; whilst the other long, flat, or tape-like worms, are called Tænia.
Very few dogs are entirely free from worms of one sort or another, though it is only when these become numerous that the dog shows signs of having these pests.
Gradual loss of condition, irregular appetite, irregular evacuations, harsh coat, sometimes vomiting, and increased redness of the membranes lining the eyelids, are the usual signs, significant of internal parasites. ”

“ Schistosomiasis - caused by parasitic trematode flatworm Schistosoma; fresh water snails act as intermediate host and release larval form of parasite that penetrates the skin of people exposed to contaminated water; worms mature and reproduce in the blood vessels, liver, kidneys, and intestines releasing eggs, which become trapped in tissues triggering an immune response ”

“ Some Trematodes lodge in the mouth; others wander down the oesophagus into the stomach or intestine, where they fix themselves to the mucous membrane. Again, others work their way into the digestive glands by the ducts, and thus become further and further removed from the external world, and more adapted to live in the particular organs of that host in which they best flourish. The most important result of the adoption of this internal habitat by endoparasitic Trematodes is, however, seen in their life-history. ”

“ I have received evidence of fatal epizoöty amongst chameleons from this source; and I have been requested to suggest a remedy. To prevent outbreaks of entozoal disease is one thing; to offer a radical cure when the parasites are firmly anchored within the pulmonary organs is quite another matter.
As remarked in my ‘Entozoa,’ the trematodes display a great partiality for batrachians, more than half a dozen different species of fluke being known to infest the common frog. Flukes are likewise tolerably abundant in the saurian and chelonian reptiles. ”

“ Trematodes live free and active within the organs attacked, though they may attach themselves by suction for a longer or shorter period; in other cases, however, they bore more or less deeply into the intestinal wall with their anterior end, or lie in cysts of the intestinal wall which only communicate with the lumen through a small opening; in those species living in the lungs of mammals the host likewise produces a cyst, which usually encloses two specimens ”

“ Parasitic Habits.—The Trematodes with few exceptions select a vertebrate for their host. Speaking generally each species of parasite has a particular host, upon the blood of which it nourishes itself and matures its reproductive organs. ”

“ The parasite (Fig. 193) is the largest trematode inhabiting man. It measures 24 to 40 mm. or more (75 mm. according to Busk) in length by 12 to 14 mm. in breadth. In shape it is an elongated oval, rather narrower anteriorly than posteriorly, with flat ventral surface, slightly convex dorsal surface, and very thin margins. It has a smooth skin without spines. The oral sucker (0·5 mm. in diameter) is subterminal and placed on the ventral surface. The ventral sucker is larger (1·6 to 2 mm. in diameter) and placed close to the oral. It is ”

“ Many inhabit the lungs, or the air sacs in fowls, a few the trachea. Trematodes have also been known to occur in the urinary bladder, the urethra and the kidneys of all classes of vertebrates; they are also present in the vascular system of a few tortoises, birds and mammals; in birds they even penetrate from the cloaca into the oviducts, and are occasionally found enclosed in the laid eggs; one species is known to occur in the cavum tympani and in the Eustachian tube of a mammal (Dugong) , another in the frontal sinus of the polecat ”

“ Perhaps the destruction of single mature individuals does not play so important a part as the destruction of their generative organs. The ravages of parasitic animals (Trematodes) in the internal organs of snails and bivalves are well known to zoologists. The ovaries of the latter are often entirely filled with parasites, and such animals are then incapable of reproduction. ”

“ Many species are found, also, on the gills and skin of fishes. A few species are parasitic on man, and some, of which the fluke is the most important, are injurious parasites of domestic animals. The trematodes usually have a flattened body covered with a chitinous skin, and are furnished with two or more suckers for adhesion. Most of the species are hermaphrodite. ”

“ FLUKE (probably connected with the Ger. flach, flat) , a name given to several kinds of fish, flat in shape, especially to the common flounder; also the name of a trematoid worm, resembling a flounder in shape, which as a parasite infects the liver and neighbouring organs of certain animals, especially sheep, and causes liver-rot. The most common is the Fasciola hepatica (see Trematodes) . ”

“ Wednesday, May 24.—A quiet day with northerly wind; the temperature rose gradually to zero. Having the night duty, did not go out. The moon has gone and there is little to attract one out of doors.
Atkinson gave us an interesting little discourse on parasitology, with a brief account of the life history of some ecto- and some endo-parasites—Nematodes, Trematodes. ”

“ As regards the AGE attained by endoparasitic Trematodes, there are but few reliable records, and these differ considerably; the overwhelming majority of species certainly live about a year, or perhaps a little longer, but there are some whose term of life extends to several or many years. ”

“ The vulgar mind sees nothing attractive in the morphology and organisation of a parasitic worm, and common-place conceptions of the beautiful cannot be expected to embrace within their narrow grasp the marvelous harmony and order that pervade the structure and economy of the individual members of this remarkable class of beings.
SECTION I.—Trematoda (Flukes) .
Fasciola hepatica, Linneus.—The first form I have to consider is the common liver fluke. The part this entozoon plays in the production of disease will be fully stated when treating of the parasites of the sheep and other ruminants. ”

“ Some of the worst of all among them, the germs of typhoid fever, are carried on the feet of the common house fly, and planted all over the things that we are going to eat. Rats and mice also carry diseases—in their fur, on their feet, or even in their blood. So, too, do certain stinging, biting, and sucking insects; and when they bite or sting or suck the blood of some larger creature, they plant the seed of some disease in his body, where it grows and flourishes until the animal sickens and perhaps dies. ”

“ More repulsive than the parasite female herself, because a yet further product of decay, it is yet only the scent of his mother’s boudoir that we smell in his hair. He is like to the bald patches and rotten wool on the back of a scabby sheep; which indeed indicate that, deep beneath the surface, a parasite insect is eating its way into the flesh, but which are not so much the cause of disease, as its final manifestation. ”

“ Since Glossina palpalis acts as an essential host of the parasite and the chief, if not the only, transmitter, the fight against sleeping sickness, like that against malaria and yellow fever, becomes primarily a problem in economic entomology. The minutest detail of the life-history, biology, and habits of the fly, and of its parasites and other natural enemies becomes of importance in attempts to eradicate the disease. ”

“ These and many other facts in the epidemiology of plague are probably to be explained by the connection of the disease with the rat - flea. When we have fuller information about the migrations of the rat, the breeding seasons of the rat-flea, the influence of food and temperature and other circumstances on these animals, it is reasonable to expect that our knowledge of the principles that underlie the transmission, the spread, and decline of plague will be more satisfactory than it is at present. ”

“ The adult life of the malarial parasite begins after its escape into the blood plasma, and it is there that the organism is most susceptible to high temperature. We must infer, therefore, that the fever is an adaptation on the part of the host for despatching the enemy. ”

“ Causes.—Bubonic plague, which is due to a small vegetable organism, the Bacillus pestis, exists primarily as a disease in rats and other rodents, such as the Manchurian marmot and the Californian brown squirrel, and is transmitted from these animals to man by means of the flea. It is the rat flea that is chiefly concerned in the spread of plague. Both the brown and the black rat are affected and, speaking generally, the black rat is the more dangerous, as it lives in closer association with man. ”

“ Definition.—Plague is primarily a disease of rats or other rodents and is caused by a bacterium of the haemorrhagic septicaemia group, Bacillus pestis. The disease exists in the rodent in both an acute and chronic form. Acute plague of the rat is apt to be septicaemic, so that when certain species of fleas which infest the rat feed on the blood of their host they ingest plague bacilli. These seem to multiply in the region of the proventriculus and cause thereby an obstruction to the stomach. As a result the flea makes vigorous and repeated but ineffectual efforts to feed. ”

“ Trematoda, trem-a-tō′da, n.pl. a class of flat-worms whose members are parasitic in or on a great variety of animals, the body unsegmented, leaf-like or more or less cylindrical, and provided with adhesive suckers.—n. Trem′atode, one of the foregoing—also Trem′atoid.—adj. ”

“ The rat lives in the dirt. The fleas live on the rat, and when they bite the rat, get a stomachful of blood, and with it some five thousand or so of the little plants that cause the plague. Then the flea jumps off the rat, on to a man, and bites him. Then a few of these five thousand germs get into the man’s blood. By the next day, these few have become millions. Within a week, often within two days, the man is dead—simply poisoned. But if the man had kept his house clear of rats and his skin clear of fleas, by keeping them both clean, he would not have been poisoned at all. ”

“ Scavengers of a hundred kinds remove decaying animal matter—from the carcass of the fallen elephant to the broken wing of a gnat—eating it, or carrying it out of sight, and burying it in the deodorizing earth. And these countless millions of termites perform a similar function for the vegetable world, making away with all plants and trees, all stems, twigs, and tissues, the moment the finger of decay strikes the signal. ”

“ As the film advances, showing the progress of the disease, the parasites are to be seen increasing rapidly in number. At last they appear to overwhelm the blood corpuscles, this multiplication continuing until death supervenes some four or five days after injection. The film was shown lately before a gathering of medical men, and created widespread interest, as it introduced them to a phase in the life of the parasite which hitherto had been beyond their comprehension. ”

“ Under ordinary conditions rat fleas do not attack the human subject, but, as the rats are attacked by plague and die, the infected fleas, starve out as it were, leave them and transfer their attentions to other animals and the human subject, infecting many of those they bite. Colonel Bannerman maintains that this infection takes place in the majority of cases, by this chain of transmission, and that there is no evidence that the excreta of these rats infect food or contaminate the soil. ”

“ The victim is in possession of its full power of sensation; and it expresses the pain experienced as best it may, by contractions. Embarrassed by these tremors, these twitches of suffering flesh, incommoded at every mouthful, the grub chews away at random and kills the larva almost as soon as it has started on it. In a victim paralysed by the regulation sting, the conditions would be very different. There are no external movements, nor any internal movements either, when the mandibles bite, because the victim is insensible. ”

“ This flea is without combs like Pulex irritans, the human flea, but is of a lighter color and has an ocular bristle near the upper margin of eye and two bristles posterior to the antennae. In Europe and the United States Ceratophyllus fasciatus is the common rat flea. Many other species of fleas transmit plague and it is also possible that the bedbug may play a part in spreading infections from man to man. Vergbitski has transmitted plague from man to the rat by infected bedbugs. In Siberia, a marmot, the tarabagan, is supposed to play the part of the rat in plague transmission. ”

“ One had even crawled down to my foot, and made an incision which allowed the blood to pour out through my canvas shoe. All this day we have suffered from these disgusting pests. Our horses became quite striped with their own blood, and a dog that followed us looked as if he had run through a pool of clotted gore before we reached the highway again. Of all the pests I have experienced in the tropics, or in any land, whether mosquitoes, black flies, ants, snakes, or viler vermin, these are the most annoying and disgusting. ”