Session 18 Fasciola hepatica & Fasciolopsis buski PDF

Session 18: LIVER FLUKES Fasciola hepatica Common name: Sheep liver fluke LCP 310 KIUT  Introduction Fasciola hepatica is the largest and most common liver fluke found in humans, but its primary host is the sheep and to a less extent, cattle....

Session 18: LIVER FLUKES Fasciola hepatica Common name: Sheep liver fluke LCP 310 KIUT  Introduction Fasciola hepatica is the largest and most common liver fluke found in humans, but its primary host is the sheep and to a less extent, cattle. Fasciola hepatica inhabit the human biliary tract. It causes the economically-important disease, ‘liver rot’, in sheep.  Habitat Adult: Resides in the liver and biliary passages of the man. Eggs: Are shed in feces. Miracidium, sporocyst and redia: In the tissues of first intermediate host, snails of the genus Lymnaea. Cercariae: In the water and encysted on aquatic vegetation or blades of grass. Metacercariae: In aquatic vegetation (watercress)  Epidemiology and Geographical distribution It is worldwide in distribution, being found mainly in sheep-rearing areas. Human infections have been reported from many areas of the world and are of considerable importance in parts of South America. A minimum of 350,000 human infections is estimated for the highlands of Bolivia, Peru In other South American countries human infections are sporadic, though the disease is prevalent in Uruguay, Argentina, and Chile. In Cuba, southern France, and Algeria, human infections are common.  Pathogenesis and Clinical Features The definitive host, sheep and man, get infection by ingestion of metacerceriae encysted on aquatic vegetation. The metacercariae excyst in the duodenum of the definitive host and pierce the gut wall to enter the peritoneal cavity. They penetrate the Glisson’s capsule, traverse the liver parenchyma, and reach the biliary passages, where they mature into the adult worms.  Pathogenesis and Clinical Features… In traversing the liver tissue, it causes parenchymal injury and severe inflammatory response. Some larvae penetrate right through the liver and diaphragm ending up in the lung. In acute phase during the migration of the larva, patients present with fever, right upper quadrant pain, eosinophilia, and tender hepatomegaly. The symptoms subside as parasites reach their final destination.  Pathogenesis and Clinical Features… In chronic phase, patients may develop biliary obstruction, biliary cirrhosis, obstructive jaundice, cholelithiasis, and anemia. No association to hepatic malignancy has been ascribed to fascioliasis. Occasionally, ingestion of raw liver of infected sheep results in a condition called halzoun (meaning suffocation). When attached in the pharyngeal mucosa, may cause edematous congestion of the pharynx and surrounding areas, leading to dyspnea, acute dysphagia, deafness, and rarely, asphyxiation.  Diagnosis Demonstration of operculated eggs in feces or aspirated bile from duodenum is the best method of diagnosis. Eggs of F. hepatica and F. buski are indistiguishable.  Diagnosis... Blood Picture to reeveals eosinophilia. Serological tests such as immunofluorescence, ELISA, complement fixation and immunoelectrophoresis are helpful in lightly-infected individuals. ELISA becomes positive within 2 weeks of infection and is negative after treatment. Imaging: USG, CT scan, Endoscopic Retrograde Choangiopancreatography (ERCP) and percutaneous cholangiography may be helpful in diagnosis.  Treatment Oral triclabendazole (10 mg/kg once) is the treatment of choice. Alternative drug is bithionol (30–50 mg for 10–15 days) Prednisolone at a dose of 10–20 mg/kg is used to control toxemia.  Prevention and Control Fascioliasis can be prevented by; Health education Preventing pollution of water courses with sheep, cattle, and human feces Proper disinfection of watercresses and other water vegetations before consumption.  Prevention and Control… Host Control By eradicating & destroying snails using Molluscicides Biological control Introduction of competitor snail species which will compete with unwanted snails in a given habitat or other predators which will eat the snails. Genetic manipulation of snail vectors Removing vegetation from locally used water places or flooding swamps.  Intestinal fluke: Fasciolopsis buski Common name: Giant intestinal fluke LCP 310 KIUT  Geographical distribution It is a common parasite of man and pigs in China and in South- east Asian countries. In India it occurs in Assam and Bengal.  Habitat Adult worm: Lives in the duodenum or jejunum of pigs and man, but in heavy infestations can also be found in the stomach and lower regions of the intestine. Eggs: In passed in feces Miracidium, sporocyst, redia and Cercariae: In the tissues of first intermediate host, snails of the genus Segmentina and Hippeutis. Metacercariae: The cercariae are released from the snail and encyst as metacercariae in aquatic plants such as water chestnut, watercress, water caltrop, lotus, bamboo, and other edible plants.  Pathogenesis and Clinical features The pathogenesis of fasciolopsiasis is due to traumatic, mechanical, and toxic effects. Larvae that attach to the duodenal and jejunal mucosa cause local inflammation and ulceration, sometimes accompanied by hemorrhage. Intoxication and sensitization also account for clinical illness. In heavy infections, the adult worms cause partial obstruction of the bowel, malabsorption, protein-losing enteropathy, and impaired vit. B12 absorption.  Pathogenesis and Clinical features The initial symptoms are diarrhea and abdominal pain, at times suggestive of duodenal ulcer disease. Toxic and allergic symptoms appear usually as edema, ascites, anemia, prostration, and persistent diarrhea. Paralytic ileus is a rare complication.  Laboratory Diagnosis History of residence in endemic areas suggests the diagnosis, which is confirmed by demonstration of the egg in feces or of the worms after administration of a purgative or antihelminthic drug. Treatment Drug of choice is praziquantel. Hexylresorcinol and tetrachlorethylene have also been found useful.  Prevention Treatment of infected persons. Adequate washing of water vegetables, preferably in hot water. Preventing contamination of ponds and other waters with pig or human excreta. Sterilization of night soil before use as fertilizer. Control of snails.  LUNG FLUKES: Paragonimus Westermani Common name: Japanese lung fluke or Oriental lung fluke  Geographical distribution The parasite is endemic in the Far East—Japan, Korea, Taiwan, China, and south east asia—Sri Lanka and India, few parts of Africa – Nigeria, Cameroon, and Zaire. Cases have been reported from Assam, Bengal, Tamil Nadu, and Kerala. P. mexicanus is an important human pathogen in Central and South America.  Habitat The adult worm is found on the lung The mature worm can be released in two ways; In the feaces in case if it is swallowed In sputum as normal habitat The eggs are found in faeces & sputum when fresh passed, they are unsegmented yellow in colour operculated. The Larva Miracidium; When eggs hatch releases the miracidium which is seen in fresh water after 2-7 weeks which require snail as an intermediate host to develop. e.g. Mirania spp.  Habitat Miracidium; After release, miracidia swim searching for water snail where it develop to sporocyst. Sporocyst; The sporocyst develop more further to radiae in the snail Radiae; The radiae swims in water searching intermediate host crustacean snail in which it develop to cercaria larva. Cercariae; It develop more further to form metacercaria which is infective form to man and is the final development stage which occur in crabs or cray fish.  Pathogenesis and Clinical features Man acquires infection by eating undercooked crab or cray fish containing metacercariae. Unembryonated eggs escape into the bronchi and are coughed up and voided in sputum or swallowed and passed in feces. There is inflammatory reaction to the worms and their eggs that lead to peribronchial granulomatous lesions, cystic dilatation of the bronchi, abscesses, and pneumonitis. Patients present with cough, chest pain, and productive sputum with blood stained (Haemoptysis).  Pathogenesis and Clinical features… The viscous sputum is speckled with the golden-brown eggs. Occasionally, the hemoptysis may be profuse. Chronic cases may resemble pulmonary tuberculosis. Extrapulmonary Features The extrapulmonary clinical features vary with the site affected; In the abdominal type, there may be abdominal pain and diarrhea, intestinal ulceration - enteritis. Involvement of brain; The cerebral type resembles cysticercosis and may cause Jacksonian epilepsy. Glandular involvement causes fever and multiple abscesses.  Laboratory Diagnosis Demonstration of the eggs in sputum or feces provides definitive evidence. NB: when eggs are few in number in the sputum centrifugation should be done with addition of 1 – 2% NaOH.  Laboratory Diagnosis Serology; Complement fixation test (CFT) is positive only during and shortly after active infection, while the intradermal test remains positive for much longer periods. IHA and ELISA tests are highly sensitive they become negative within 3–4 months after successful treatment. Serology is of considerable importance in egg-negative cases and in cerebral paragonimiasis. Imaging Chest X-ray reveals abnormal shadows (nodular, cystic, ring, infiltrative) in the middle and lower lung field. CT scan of chest also helps in diagnosis of pulmonary lesions and cerebral lesions. 'Soap-bubble' like appearance may be seen in cerebral cysts. Paragonimus westermani Eggs  Treatment Praziquantel (25 mg/kg TDS for 1–2 days) is the drug of choice. Bithinol and Niclofolan are also effective in treatment. Prevention Adequate cooking of crabs and crayfish and washing the hands after preparing them for food. Treatment of infected persons. Disinfection of sputum and feces. Eradication of molluscan hosts.