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In most body tissues and organs - most hosts
Third stage larvae larvae in bile duct (eratically)
Adult flukes are visible to the naked eye, although some are very minute.
Large flukes parasitic in the bile ducts and intestines of mammals, especially ingulates, with a broad, leaf-shape body and usually a spiny cuticle. The anterior and ventral suckers are close together.
Liver, bile-duck and gall bladder of cattle and sheep primarily; also, may infect goat swine, dogs, deer, and man.
The eggs pass by way of the bile duck into the intestine and hence are expelled in the feces. Eggs hatch in water (time of development depends on the temperature, i.e., at 260 C). Eggs hatch approimately in 9 days and miracidia enter an aquatic snail (species varies with country, North America-various species of Calba spp., Fossaria modicella, sp. and Pseudosuccinea columella first intermediate host. Within the snail their are both sporocyst and rediae and sometimes daughte redia. The cercariae settle on vegetation and encyst. The encystment thus marks the metacercarial stage.
The eggs, young stages in the snail, and metacercariae may survive the winters, thus pastures may remain contaminated into the next seasons. The most important resistant stage is the metacercaria. It can survive for long periods of time on moist vegetation and even fora few weeks on dried hay. If the hay is not properly cured it can survive and remain infective for a variable period of time.
Infection of the definitive host is established by eating plants with encysted metacercariae. In the duodenum the metacercariae escape from the cyst and burrow into the intestinal wall. Most of the flukes reach the liver by passing directly through the intestinal wall through the peritoneal cavity nd eventually penetrate directly through the liver capsule. Some may reach the liver by the blood stream and others by crawling up through the bile duct.
In the liver they wander through the perenchyma for a month or more, growing during this time. Eventually they reach the bile duct where they become mature. From initial infection to mature flukes takes 2 to 3 months. The entire life cycle may require up to 5 months under optimum conditions. Adults may live up to 11 years.
Extensive damage is done to the liver during fluke migration. In heavy infections, cirrhosis of the liver occurs. Dystrophic calification with cartilagenous mataplasia may occur in long standing cases. Secondary bacterial iniasion may occur. In sheep Clostridum novyi is frequently associated with F. hepatica. This condition is called "black disease".
In such cases there will be necrotic foci containing sanguineous exudate and the bacteria.
Chronic cholangitis in which the bile duct becomes greatly thickened is caused by the irritation from the cuticular spines of the parasite.
Cattle-more of a chronic disease. The most consistent sign is digestive disturbance. One sign associated with this is marked signs of liver fluke infection; becoming very emaciated and depressed followed by prostration. Other animals, particularly older, may show anemia and a few bits of information may help one suspect the possibility of Fasciola in animals showing above signs. First, geotraphical location. Heavy fluke infections occur more in wet areas at low altitudes, especially coastal areas. Some of the snail hosts have very wide distribution but would be found in abundance only in pastures that are marshy or boggy most of the year. This type of farm then might be a good suspect.
Another clue may be the number of animals involved. If the pasture were infected with the metacercariae then one would expect a number of animals to be infected, but, of course, the degree of infection would vary. Consequently, the clinical manifestation would vary within limits of the signs associated with liver disturbance.
Sheep-Since Closttridium novyi is often present in liver lesions, the clinical picture usually is one of a more acute nature. In addition to signs associated with Fasciola other symtoms may be noted resulting from alterations elicited by C. novyi. Due to the fact that this organism produces many toxins, including a hemolytic one, acutely infected animals exhibit blood stained froth from the nostrils and bloody discharge from the anus, much the same as seen in a case of anthrax. A much more marked anemia develops than is seen with liver fluke alone and there will be an elevated temperature.
Early in the course of infection the animal may show a tendency to fatten either from increased bile flow (before bile stasis from fluke blockage) resulting in better ssimilation of fat or retention of fluid due to anemia. Muscular weakness appears about this time. The signs are more apparent when animals goes off feed and pale mucus membranes and obvious edema develops. The skin feels dry and doughy and the wool is dry and brittle coming our in patches. As the disease progresses, the animal becomes very debilitated and emaciated. The animal may die. If the animal does not die, most of the flukes die in about 9 months; however, a few many survive for upto 5 years.
The surviving sheep will gradually recover, but the wool will have a "break" in the part grown during illness.
Finding fluke egg by a concentration or sedimentation technique. The eggs of Fasciloa and Paramphistoma ( a ruminal trematode of ruminants) fail within the same size range (130-150 by 63-90 microns). Differentiation of these two eggs is based on the clinical signs. Clinical signs have not been associated with adult Paramphistoma. In areas where both are present, the use of 1% methytene green to sediment may be used (eggs of Fasciola are amber where as those of the rumen flukes appear silver).
No drug is appreciably effective against young flukes; i.e. less than 4 weeks old. Hexachlorethane is considered an effective treatment against older worms. Hexachlorethan is no longer used in U.S.A. Albendazole at 7.5-15 mg per kg has been approves in some states, and is the best drug available.
Carbon tetrachloride and several new drugs (notably, substituted salicylandilides and halogenated phenols) are used extensively in many foreign countries. Deamphenethide, Nitroxymil, oxclozanide rafoxanibe, and Tricleabendazole fall int this same category. The time of treatment should be scheduled so as to take advantage of the weakest point of the flukes ' life cycle. In the Southeast this time would probably be in the Spring and Fall. In the Gulf Coast region snail activity is hihest during mild wet winter and Spring. Treatment should be in late spring at onset of dry season when snail goes into soil of becomes inactive and again in fall before onset o the wet season.
Even if all flukes could be removed by therapy, reinfection is continuous in some parts of th country. Idealy, keeping animals off of wet, boggy, pastures harboring the snails would be a most effective control measure. Unfortunately this is not possible. Fencing off ponds and lakes (particularly those with a lot of vegetation around the edges) and pastures which have standing water on them most of the year should be done when approach is not feasible then an attempt to kill snails may be advantageous. Copper sulfate kills snails, miracidia and cercariae, but it does not kill eggs or metacercaria. It also kills other fanuna including fish. For lakes, ponds, and streams 1 part copper-sulfate to 5 million parts of water repeated every 2 or 3 months (this level kills fish). Pasture treatment recommended levels are 1-2% copper sulfate mixed with 4-8 parts sand. Of this mixture broadcast 10-30 pounds per acre.
Stock should not be grazed on treated pasture until after rain-fall.
Liver (encysted) of deer; natural host. Cattle, sheep and horses may severe as hosts.
Very similar to F. hepatica.
This fluke become encysted in the liver of deer and cattle, hence there is very little pathological change when this fluke infects these hosts. The major findings would be a large fibrous cysts appears normal. In sheep the fluke does not encysts so that it continues to wander around the liver destroying the parenchyma. Actually 2 or 3 flukes can kill its host.
In the deer, even harboring 50 or more of these large fluke there are no obvious clinical signs. However, the cyst wall is thin enough for the eggs to escape, but in cattle the wall is so fibrous and thick that the eggs cannot contaminate an area. Neither are there clinical signs in cattle, In sheep the only sign given in the references is that a few flukes will kill.
Same as F. Hepatica
Similar to F. hepatica. ?
Occurs in small intestine of man and pig in the southeastern parts of Asia. Particularly China (not in USA)
Small or medium sized flukes parasitic in the biliary and pancreatic ducts of amphibia, reptiles, birds and mammals. The body is flattened and elongate. The cuticle often lacks spines. The suckers are not far apart. The testes are situated not far behind the ventral sucker and the ovary is usually behind them.
Biliary tract of sheep (most often). Cattle, goats horse swine, dogs, and man serve as hosts. Distributed thorughout the world, however, in the U.S. the geographical distribution is rather limited at present. The fluke was first reported from New York State. Since then it has been found in Pennsylvania and some of the New England States.
The potential existgs of it spreading and all practicing veterinarians in the East should be on the alert.
This fluke is slender more transparent and much smaller than F. hepatica.
The intermediate hosts in Europe are different from those in the U.S. Here is probably a case of a parasite adapting to another host when its natural hosts were not available. In the U.S. the first intermediate host is terrestrial snails. Cercariae are shed in slime balls which are then ingested by the black ants (Formica fusca) where it encysts to become the metacercariae. Infection is established in the definitive host when the infected ants are ingested. Since both intermediatge hosts have wide geographical distribution the spreading of this fluke into other areas is always a potential threat.
Enlargement of biliary ducts with a subsequent portal cirrhosis and hyperthrophy of biliary epithelium. In experimental studies on infected cattle a complete depletion of glycogen reserves, higher lipid content and increased lipofuschin deposition in the depatic cells. Greater mucin production, but no calicification was shown to occur. There was also a predominance of collagen in the connective tissue surrounding the site of infection.
Symptoms apparently are not observed unless there are large numbers of worms. However, such an occurrence is not uncommon. When signs do occur they would be very similar to those of animals infected with F. hepatica.
Eggs easiest found by a sedimentation-concentration technique. In a large animal showing signs of a liver fluke infection the finding of a fluke egg would help confirm D. dentriticum. The eggs measure 36-45 by 22-30 microns and are much smaller than F. hepatica (130-150 by 63-90 with miracidium).
Same as F. hepatica
Since terestrial snails are the intermediate hosts some knowledge about their habits can help reduce the snail population on a pasture without treating. Although, terrestrial snails are found outside of stream, environment as beneath loose stone, logs, and debris such as fertilizer bags, burlap bags, boards, etc., maintains enough moisture for their activity in this part of the country. Keeping the pasture free of such dibris reduces the snail population drastically.
What other larval forms may be observed in the liver of the above hosts?.
16.6.1 PROTOZOA
1. Entamoeba histolytica - amoeba - seen liver of dog man
16.6.2 TREMATODES
1. Orphisthclonorchis orchis sinensis- " Oriental or chinese liver fluke" medium size - found in bile duct, gall bladder of man, dog, cat posteriorily and have thick dark brown wall- withmiricidium when laid, operculum fits into a prominent rim of the shell.
Life Cycle
Snail and fish are involved.
Pathogenesis
Catarrhal choleocystitis, papillomatous or even adenomatous proliferation of the bile duct epithelium- liver cirrhosis.
Prevention
Thorough cooking of fish/treat night-soil with ammonium sulfate to kill fluke eggs, has been rcommended.
2. O. tenuicollis
Similar to above species-In dog, fox, and pig of Europe, Asia Canada Produce marked fibrosis. Several cases of carcinoma of the liver and pancreas of cat and man reported.
3. *Eurytrema pancreaticum"
Occurs in the pancreatic ducts and more rarely in the bile ducts and duodenum of sheep, goat, cattle (see Soulsby pp. 15-17) Eggs cause granulomata, fibrosis, atrophy in sheep, goat, and cattle.
4. *Eurytrema proyonis
Has been reported from the pancreatic ducts, gall bladder and bile ducts of cats, foxes and raccoons in the U.S. (New York, Maryland, Connecticut, Kentucky). The snail Meson thyroideus has been infected experimentally and it has been suggested that animals may become infected thru ingesting of snails.
5. *Platynosomum fastosum:
Occurs in the liver of cats in the southern States of the U.S. and elsewhere. It measures 4-8 by 1.5-22.5 mm. It causes a marked dilatation of the bile ducts and desquamation of the biliary epithelium. The liver may be markedly enlarged. Clinical signs included diarrhea, vomiting and icterus. "Lizzard poisoning" snails and lizzards intermediate host.
Family - Opisthorachiidae:
Small to medium-sized flukes, parasitic in the gall-bladder and bile ducts of reptiles, birds and mammals. Usually much flattened with translucent body, width is narrow at anterior. The suckers are weak and not far apart.The testes lie in the posterior part of the body; they are situated diagnonally and are spherical or lobed. The ovary is not far anterior to the testes.
6. Metorchis conjuctus
Host and Location:
Gall bladder and bile ducts of dog, cat, fox, man, and other fish eating mammals (mink and raccon). In North America this parasite in dogs is most prevalent in Canada; however, it has been reported from the New England states and South Carolina.
Life Cycle:
Aquatic snail is first intermediate host. Ingestion of raw, infected fish completes the life cycle. Twenty-eight days is the time required for maturing of worm after ingestion.
Pathological Alterations:
Liver enlarged and turgid; gall bladder and ducts distended. Microscopic changes of liver are marked cirrhosis and proliferation of the bile ducts. In prolonged cases kidney will show acute nephritis and cardiac musculature exhibitis a degeneration or myofibrils.
Clinical Manifestation:
Gradual debilitation accompanied by ascites, increased heart rate with weak pulse. Jaundice if enough bile stasis.
Treatment:
Hetol in the current drug of choice for use in man for related parasite, Opisthorchis.
Opisthochis (clonochis) sinesis and O. viverrini are important related parasites of man in the Orient.
7. Histomonas meleagridis - Histomonad-Protozoa - In liver of poultry.
8. Trichomonas gallinarium - trichomonad - Protozoa.
16.6.3 PERITONEAL CAVITY AND PERITONEUM
- 1. Taenia hydatigena larvae (Cysticercus Tenuicollis) - In peritoneum sheep cyst tapeworm.
- Sheep, goat, cattle, swine, deer, moose, etc (See intestine of Dogs).
- 2. Echinococcus granulosus larve-Hydatic cyst perioneum of same host as above. (See intestine of Dog cat.)
- 3. Setaria equina - peritoneal worm - to 15 cm (Equine) In peritoneal cavity, tunical vaginalis, testes, pleural cavity, lungs, eyes (eratically). Adults reached in 8-10 months - produce only slight fibrinous peritonitis, though no lesions are observed most of the time Aldersserve as TH.
- 4. Setaria cervi - Peritoneal worm - to 12 cm (Cattle, bison, deer antelope) similar to species in equine -are long. Thin worms usually observed peritonitis, though no lesions are observed most of the time.
- 5. Strongylus edentatus larvae - Toothless strongyle may be observed free or in nodules or under parietal peritoneum- Right flank near cecum and causing other lesions.
- 6. Strongylus equinus larvae - Three tooth strongyle may be associated with similar lesions as # 5 above.
- 7. Oesophagostomum spp larvae- Nodule worms. In omentum and peritoneum in nodules of ruminates and swine - see intestine.
Stephanurus dentatus adults and larvae - 45 mm - kidney worm of swine - In peritoneal cavity of swine -occasionally be seen in this location cattle. (accidentally (see urinary system).
Doctuophyma renal - Gain kidney worm - 1 meter - peritoneal cavity (erratically) (see blood vascular system).
