The adult tapeworms _Taeniae saginata_ and _soleum_, of which the _Cysticerci bovis_ and _cellulosa_ are the larvae forms, occur in man. The larvae are present in meat and pork, and this form of parasitism is termed beef measles in cattle and pork measles in hogs. Man becomes host for these two forms of tapeworms through eating measly pork or beef that is not properly cooked.
The dog is the host for _Taeniae marginala_, _coenurus_ and _echinococcus_.
The larvae forms of these _taeniae_ are the _Cysticercus tennicollis_, _Coenurus cerebralis_ and _Echinococcus polymorphus_. _C. tennicollis_ is a parasite of the serous or lining membranes of the body cavities. It is not of great economic importance. _C. cerebralis_ is a parasite of the brain of sheep, and may cause a heavy death rate in flocks that are infested with it. _E. polymorphus_ is a parasite of the liver, but it may occur in other organs.
THE THORN-HEADED WORM OR ACANTHOCEPHALE.--This parasite requires a secondary host. In this case a particular species of the May-beetle larva or white grub that is commonly found about manure piles and in clover pastures is the host. The hog eats a white grub that is host for the larval form. The digestive juices free the larva, it then becomes attached to the intestinal mucous membrane and develops into the adult thorn-headed worm (Fig. 74). This parasite is characterized by a hooked proboscis or thorn at its anterior extremity, and the absence of a distinct digestive tract. The male is much smaller than the female. The eggs are passed out of the intestine with the faeces.
[Illustration: FIG. 74.--Thorn-headed worms.]
THE ROUND-WORMS OR NEMATOIDS.--Round-worms are very common parasites of domestic animals (Fig. 75). This group of worms is characterized by their cylindrical form, the presence of a true digestive canal and the separation into two sexes, male and female. The life history is more simple than in the flat worms. Intermediate hosts are not required for the development of the common forms. The eggs and embryos are deposited by the female in the intestinal tract, air passages, or excretory ducts of the kidneys of the host. Development may be completed here, or the eggs and embryos are passed off with the body excretions. They may live for a short time outside the animal body, or undergo certain development and again infest a host of the same species from which they came, through the water, grass and fodder that the animal may take into its digestive tract.
[Illustration: FIG. 75.--Large round-worm in intestine of hog.]
The following species of nematoids are common parasites of domestic animals:
SOLIPEDS
Species Organ Ascaris megalocephala Intestines Sclerostoma equinum Large intestine and blood-vessels Sclerostoma tetracanthum Large intestine Oxyrus curvula Large intestine Oxyrus mastigodes Large intestine
CATTLE
Species Organ Strongylus convolutus Abomasum Ascaris vituli Small intestine (calves) Strongylus ventricosus Small intestine Oesophagostomum inflatum Large intestine Trichocephalus affins Large intestine Strongylus micrurus Bronchi Strongylus pulmonaris Bronchi
SHEEP
Species Organ Haemonchus contortus Abomasum Ascaris ovis Small intestine Strongylus filicollis Small intestine Oesophagostomum columbianum Intestines Uncinaria cernua Small intestine Trichocephalus affins Large intestine Strongylus filaria Bronchi Strongylus rufescens Bronchi and air follicles
SWINE
Species Organ Ascaris suis Intestines Oesophagostomum dentatum Large intestine Trichocephalus crenatus Large intestine Trichina spiralis Muscles and intestines Strongylus paradoxus Trachea and bronchi Sclerostoma pingencola Renal fat and kidney
POULTRY
Species Organ Ascaris inflexa Intestine Spiroptera hamulosa Gizzard Heterakis papillosa Caecum Syngamus trachealis Trachea and bronchi
INTESTINAL WORMS OF SOLIPEDS.--The large round-worms or ascarides and the sclerostomes are the most injurious intestinal parasites of solipeds. The _A. megalocephala_ or large round-worm is from 5 to 15 inches (12 to 35 cm.) long. It may be present in the double colon in such large numbers as to form an entangled mass that completely fills a portion of the loop in which it is lodged. It may interfere with digestion by obstructing the passage of alimentary matter, and irritating the intestine.
The _S. equinum_ and _S. tetracanthum_ are small worms. The former sclerostoma is from 0.6 to 1.5 inches (18 to 35 mm.) long, and the latter is from 0.5 to 0.6 inch (8 to 17 mm.) long. Both sclerostomes attach themselves to the lining membrane of the intestine by their mouth parts, and suck blood. The young _S. equinum_ may live in tumor-like cysts that they cause to form in the lining membrane of the intestine. The young worm may penetrate the wall of a small blood-vessel as well, and drift into a large vessel, where it may become lodged and undergo partial development.
The irritation to the blood-vessel results in an inflammation and dilation of the vessel wall. This is termed verminous aneurism. A portion of the fibrin-like lining of the aneurism may flake off and drift along in the blood stream, until finally a vessel that is too small for the floating particle or embolus to pass through is reached. The vessel is then plugged or a thrombus is formed. If the vessel involved by the thrombus happens to be a mesenteric vessel, then a loop of intestine has its blood supply cut off, and colicky pains result. Such colics are dangerous, and may terminate fatally. Intestinal obstruction, thrombo-embolic colics, unthriftiness and a weakened, anaemic condition may be caused by intestinal worms.
_The treatment_ is both preventive and medicinal. The preventive treatment consists in giving young, growing animals the best care possible.
Cleanliness about the stable, giving the colt plenty of range when running in a pasture, and feeding a ration that is sufficient to keep the colt in good physical condition are the important preventive measures. Tartar emetic in one-half to one dram doses may be given with the feed daily until five or six doses are given. Turpentine may be given in one to three ounce doses in a pint of linseed oil. This may be repeated daily for two or three days. Worms located in the posterior bowel may be removed by rectal injections of a weak water infusion of quassia chips. The rectum should be first emptied with the hand, and the nozzle of the syringe carried as far forward with the hand as possible. The injections should be repeated daily for several days.
INTESTINAL WORMS OF CATTLE.--Intestinal worms seldom cause serious losses from unthriftiness or death in cattle. It is in calves only that we are called on to treat this class of disease. The symptoms resulting from the invasion of the intestinal tract by the different worms vary in severity according to the number, habits of the parasite and care that the animal receives. The usual symptoms are unthriftiness, indigestion, diarrhoea and a stunted, anaemic condition. Stiles reported extreme anaemia, unthriftiness and many deaths among cattle in a certain section of Texas, due to extensive infection with the _Uncinaria radialus_.
_The treatment_ is largely preventive. Calves and yearlings should be provided with plenty of feed at all seasons of the year. Good care and careful feeding will keep them in a thrifty, healthy condition and enable them to throw off invasions of intestinal worms. Turpentine is the vermifuge usually administered to calves. The dose is from two to four drams given in a milk or raw linseed oil emulsion.
STOMACH WORM OF SHEEP.--The twisted stomach worm, _Haemonchus contortus_, is the most injurious internal parasite of sheep. It is a very small, hair-like worm from 0.4 to 1 inch (9 to 25 mm.) in length. In the adult form it attaches itself to the mucous membrane of the fourth stomach or abomasum, and lives by sucking blood. The blood present in the digestive tract of the worm gives it a brown color, and the white oviducts which are wound around the digestive canal cause the body to appear twisted. When the twisted stomach worm is present in large numbers, the worms become mixed with the contents of the stomach and can be readily found on making a post-mortem examination.
_Symptoms of stomach worms_ are first manifest in the lambs (Fig. 76). It is not until early summer that the disease appears in the flock. The symptoms are not characteristic unless we consider an unthrifty, anaemic, weak, emaciated condition accompanied by diarrhoea, during the summer months characteristic of stomach-worm disease. The sick animals are unable to keep up with the flock, and they like to stand about in the shade. They move slowly, the back is arched, the appetite poor, the mucous membranes and skin are pale and the hind parts soiled by the diarrhoeal discharge.
More acute symptoms than the above sometimes occur. The disease may last from a few days to several weeks. A large percentage of the affected animals die.
[Illustration: FIG. 76.--Lamb affected with stomach worm disease.]
The _treatment_ is largely preventive. Frequent changing of pastures and dry lot feeding are common preventive measures. Permanent sheep pastures lead to heavy losses from stomach worm disease. A very effective preventive measure, as we may term it, is the practice of administering a vermifuge to the ewes in the late summer and again in early winter. This may be given in a drench, or with the feed. This prevents the reinfection of the pastures every spring, and the young lambs are not exposed to this form of infection. The most effective treatment that the writer has ever used is the following formula recommended by Dr. Law: Arsenous acid one dram, sulfate of iron five drams, powdered areca nut two ounces, common salt four ounces. This is sufficient for one dose for thirty sheep. It may be given with the salt, or in ground feed. If the flock is apparently healthy, four doses given at intervals of three days is sufficient. If symptoms of stomach worms are manifested the animals should be dosed daily until they have received from five to ten doses, depending on the condition of the animal.
INTESTINAL WORMS OF SHEEP.--The most widely distributed and seemingly most injurious intestinal worm of sheep is the _OEsopliagostomum columbianum_.
It is a small worm from 0.5 to 0.75 inch (12 to 18 mm.) long. It penetrates the lining membrane of the intestines and encysts in the intestinal wall. A tumor, varying in size from that of a millet seed to a hazelnut, then forms in the wall of the intestine. These tumors undergo a cheesy degeneration, and when mature, may appear as greenish, cheesy-like masses, covering a large portion of the lining membrane of the intestine. Diarrhoea and emaciation may result. These symptoms are most evident during the winter months.
_The treatment_ recommended for ridding sheep of this intestinal worm is largely preventive. Very little can be done with the medicinal treatment of a sheep whose intestinal tract is badly infested with this parasite. Good care and the feeding of a proper ration are the only curative measures that are effective in such cases. The occasional administration of a vermifuge for the purpose of ridding the digestive tract of worms, together with the frequent changing of pastures during the spring and summer, are the most effective preventive lines of treatment. The same treatment recommended for stomach worms may be used for this disease.
INTESTINAL PARASITES OF HOGS.--The _Ascaris suis_ or _common round_ worm is very commonly found in the small intestine. It is quite frequently found in large numbers, almost filling the lumen of the intestine of an unthrifty pig (Fig. 75). It may also work its way into the bile duct. Sometimes, after a hog has died, this parasite migrates forward into the stomach and gullet. The _A. suis_ is from 4 to 10 inches (10 to 26 cm.) long.
_The Echinorhynchus gigas_ or _thorn-headed_ worm is the most dangerous of all intestinal worms (Fig. 74). It is usually found with its proboscis or thorn imbedded in the wall of the small intestine. The Echinorhynchus is not as common a parasite as the Ascaride, and it is not usually present in large numbers. Usually, not more than a half-dozen of these worms are found in the intestine of a hog, but in some localities and in hogs that are allowed to root around manure piles and in clover pastures the herd may become badly infected with them and serious losses occur. The average length of the male is about 3 inches (8 cm.) and the female 10 inches (26 cm.).
[Illustration: FIG. 77.--Whip-worms attached to wall of intestine.]
[Illustration: FIG. 78.--Pin-worms in intestine.]
The _Trichocephalus crenatus_ or _whip worm_ (Fig. 77) is slender or hair-like in its anterior two-thirds and thick posteriorly. It is from 1.5 to 2 inches (40 to 45 mm.) long. It is found in the caecum attached to the wall by the hair-like portion.
The _OEsophagostomum dentatum_ or _pin worm_ is from 0.3 to 0.6 inch (8 to 15 mm.) long. It is found in the large intestine (Fig. 78).
The _symptoms_ of intestinal worms are not very evident in the average drove of hogs. None of the other farm animals are such common hosts for intestinal worms as hogs. But it is only in extreme cases of infection by intestinal worms, and in stunted and poorly-cared-for hogs, that very noticeable symptoms of disease are manifested. We must not take from the above statement that it is unnecessary to resort to treatment unless in exceptional cases. Intestinal worms interfere with the growth of young hogs, and may irritate and inflame the intestine, causing chronic indigestion, nervous symptoms, and in some cases death. This irritated and inflamed condition of the intestine is best noted in the abattoir by the ease with which the wall of the intestine that contains large numbers of worms tears when handling it.
_The treatment_ of intestinal worms in hogs is both preventive and medicinal. If the conditions in the pens and houses are such as to enable the eggs and embryos to live for a long time, or the surroundings are favorable for infection of the animals through their feed and water supply, the herd may become badly infested with intestinal parasites. The preventive treatment consists in keeping hogs in clean, well-drained yards or pastures, and feeding them from clean troughs and concrete feeding floors that can be washed, when necessary, in order to keep them clean.
Turpentine, given in a milk emulsion, is a common remedy for intestinal worms in hogs. The dose is one teaspoonful for every eighty pounds weight.
This dose should be repeated daily for three days. The following vermifuge can be recommended: Santonin three to five grains, calomel five to eight grains. This is sufficient for one hundred pounds weight. If the pigs are small and it requires two or three to weigh one hundred pounds, the large dose should be given. If the hogs weigh one hundred pounds or more, they should receive the small dose. The drove should be divided into lots of ten or fifteen hogs each. The drugs should be mixed and divided into the same number of powders as there are lots of hogs. Ground feed is placed in the trough, dampened with milk, or water and the powder sprinkled evenly over it. The hogs are then allowed to eat the feed. It is best to dose them in the morning after they have been off feed for ten or twelve hours.
VERMINOUS BRONCHITIS IN CALVES.--The lung worms of cattle, _Strongylus micrurus_ and _Strongylus pulmonaris_, may cause heavy losses in calves and yearlings. Older cattle may harbor these parasites, but they do not seem to be inconvenienced by them. The _S. micrurus_ is from 1 to 3 inches (25 to 75 mm.) long. The _S. pulmonaris_ is smaller. It is from 0.4 to 1.3 inches (10 to 35 mm.) long. They are found in the trachea and small bronchial tubes, where they are mixed with mucous secretions from the inflamed lining membrane of the bronchial tubes.
Wet seasons and low, wet pastures are said to favor the development of lung worms. Their life history is not fully understood. They do not persist generation after generation in the air passages of an animal, but the eggs and embryos are expelled and live for a time outside of the animal, when they may again become parasites of another or the same host.
_The symptoms_ are the same as occur in bronchitis and pneumonia. Calves and yearlings are the only animals in the herd that may show symptoms of the disease. The air passages become irritated and inflamed, and the calf shows a slight cough. As the inflammation increases and the worms and mucous secretions plug up the small bronchial tubes, the coughing spells become more severe and rattling, wheezing sounds may be heard on auscultating the lungs. The calf finally loses its appetite, becomes emaciated and weak, and wanders off alone. It is usually found lying down and shows labored breathing that is occasionally interrupted by paroxysmal coughing. The death rate in poorly-cared-for herds is heavy.
VERMINOUS BRONCHITIS AND PNEUMONIA OF SHEEP.--The two lung worms of sheep are the _Strongylus filaria_ and Strongylus_ rufescens_. The former is from 1.3 to 3 inches (33 to 80 mm.) long, and the latter from 0.6 to 1 inch (16 to 25 mm.) long. The _S. filaria_ is thread-like and the _S. refuscens_ hair-like in appearance. For this reason they are termed thread and hair lung-worms. The thread-worm is found in the trachea and the larger bronchial tubes, and the hair-worm in the most minute as well as the larger bronchioli.
This disease is most common in wet seasons. Undrained pastures and ponds are said to favor the spread of the disease. Permanent pastures favor the reinfection of the flock from year to year. The eggs and embryos are expelled in coughing, and live for a time in the pastures, pens and houses.
The sheep become infected through the dust, drinking water or feed.
_The symptoms of verminous bronchitis_ and pneumonia are quite characteristic. Lambs suffer most from these diseases. A number of animals in the flock are affected. Coughing, rapid and labored breathing, loss of appetite, emaciation and weakness are the usual symptoms noticed. When a paroxysm of coughing occurs, considerable mucus is expelled. An examination of the expectorations may result in finding a few lung worms. In poorly-cared-for flocks, and when complicated by stomach and intestinal worms, the death rate is usually heavy.
_The treatment_ of lung-worm diseases in lambs and calves is largely preventive. We should use every possible precaution against introducing the infection into the herd or flock. It is not advisable to bring animals from an infected herd onto the premises, without subjecting them to a careful examination and a long quarantine before allowing them to stable or pasture with the other animals. Calves or lambs that show marked symptoms of disease should be given comfortable quarters, and special care and feeding.
The entire herd or flock must be given the best care and ration possible.
This is the only satisfactory method of treatment. Changing the pasture or lot frequently may help in ridding the premises of the infection.
VERMINOUS BRONCHITIS IN HOGS.--The lung worm, _Strongylus paradoxus_, is a common parasite of young hogs. It is from 0.6 to 1.6 inches (16 to 40 mm.) long. When the infection is light, the worms are found mostly in the bronchial tubes of the margin and apex of the lung.
Infection with this parasite does not depend on the humidity of the soil, or low, wet pastures containing ponds. Probably dusty quarters are responsible in large degree for this disease.