Trematodes (Fasciola and Heterophys) Lecture PDF
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Menoufia University
Dr. Mona Mohamed Fahem Saleh
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Summary
This lecture covers trematodes, specifically Fasciola and Heterophys, including their morphology, life cycle, diagnosis, treatment, and prevention. It discusses the diseases, geographical distribution, habitats, and definitive and intermediate hosts. The lecture also details the clinical picture, diagnosis, and treatment methods, covering both acute and chronic phases.
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Trematodes (Fasciola and Heterophys) by Dr. Mona Mohamed Fahem Saleh Lecturer of medical parasitology Faculty of medicine Menoufia university Fasciola gigantica and Fasciola hepatica Disease: Fascioliasis. Geographical distribution: wor...
Trematodes (Fasciola and Heterophys) by Dr. Mona Mohamed Fahem Saleh Lecturer of medical parasitology Faculty of medicine Menoufia university Fasciola gigantica and Fasciola hepatica Disease: Fascioliasis. Geographical distribution: worldwide, especially in tropical and subtropical countries. Habitat: Bile ducts of the liver and gall bladder. Definitive host: Herbivorous animals most commonly, sheep, cattle, goats, camels, and buffalo. Man can be occasionally infected. Intermediate host: Snails Lymnaea cailliaudi and Lymnaea truncatula. Morphology: Adult flukes: Size: 30 - 70 mm long by 8 - 15 mm wide. F. hepatica is smaller. Shape: Adult flukes are flattened and leaf-like. hermaphrodites (i.e., have both male and female sex organs), broader anteriorly, having an anterior cone and prominent shoulders. The worm has 2 suckers, oral and ventral. The tegument is armed with backwardly directed spines. Egg: (Diagnostic stage) Size: 150 x 90 um. Shape: ovoid. Shell: thin, operculated. Color: bile stained (yellowish brown). Content: embryonic cells (immature). Encysted metacercaria (Infective stage): Size: 0.25 mm diameter. Shape: spherical with a thick white cyst wall. Life Cycle: In the definitive host, adult worms live in the bile ducts, lay eggs that are carried with bile to reach the intestinal lumen and passed with stool outside the body. Eggs must reach water to complete the life cycle. Immature eggs embryonate in fresh water and the miracidium develops and emerges from the egg to infect the snail intermediate host. In the snail, the miracidium develops asexually sporocyst, redia and finally cercaria. The cercariae are shed out of the snail, lose their tail, and encyst on aquatic vegetation as encysted metacercaria Definitive hosts acquire the infection by eating contaminated vegetation with metacercaria. After ingestion, the cyst wall of metacercaria is destroyed during mastication and by the enzymatic activity of the intestinal environment. The emerging juvenile flukes penetrate the intestine and migrate through the abdominal cavity and penetrate the Glisson’s capsule to reach the liver. In the liver, it enters its final habitat, the bile ducts, and matures into adults. Clinical picture: The clinical course of human fascioliasis can be divided into two phases: acute and chronic. Acute phase: patients may develop symptoms like prolonged febrile illness, anorexia, right upper quadrant abdominal pain, gastrointestinal disturbances, urticaria and weight loss. Ascites, hepatomegaly, splenomegaly, and anemia also occur. Chronic phase: patients may develop symptoms of biliary obstruction such as biliary colic, epigastric pain, jaundice, and right upper quadrant abdominal tenderness. In severe cases, migrating parasites may erode into blood vessels, causing huge, life-threatening subcapsular liver hematomas. Young children are especially susceptible to the disastrous long-term complications associated with malnutrition and anemia such as stunting and poor neurocognitive maturation Ectopic Infection: is not frequent, but can occur in peritoneal cavity, intestinal wall, lungs, subcutaneous tissue. Diagnosis: Clinical: history and clinical manifestations Laboratory: There is no gold standard test to diagnose fascioliasis. A. Stool examination: detecting parasitic eggs is confirmatory B. Serological tests: for antibody and antigen detection are of value during the migratory stage of the worms and ectopic infection. C. Eosinophilia. D. Ultrasound and CT. E. Molecular diagnosis: A nested-PCR was developed for detection of parasitic DNA in human stool and urine samples. Treatment: Biothionol: 30 -50 mg/kg on alternate days for 10 to 15 doses. Triclabendazole: 10 mg/kg in two doses separated for 12 to 24 hours. Nitazoxanide: is a good alternative in case of triclabendazole failure especially in the chronic stage of infection. It is given as 500 mg twice a day for 7 days in adults. Metronidazole: 1.5 g/day for 3 weeks is an effective treatment for adults and can be applied for treatment of fascioliasis in children. Prevention and control: Anthelmintic Therapy: Prophylactic anthelminthic therapy is given to the animal host. Mass drug administration to decrease the prevalence of fascioliasis in human especially in high burden countries Health education. Snail control. Intestinal Fluke Heterophyes heterophyes Geographical distribution:Fish-eating countries. Habitat: Small intestine. Definitive Host: Man- & fish-eating animals (dogs & cats). Intermediate Host: 1st intermediate host: Pirenella conica snail. 2nd intermediate host: boury & bolty fish. Infective stage: Encysted metacercaria Diagnostic stage: Egg Morphology: Adult worms: Pear-shaped, gray, and have a broadly rounded posterior end in addition to an oral and ventral sucker, contains a third sucker, the genital sucker, surrounding the genital pore. Egg: Size: 30 μm ×15 μm. Shape: oval. Shell: thick double walled with operculum & posterior knob. Color: brownish yellow. Content: miracidium (mature). Cercaria:- Formed of body and membranous tail (lophocercous cercaria). Body contains oral and ventral suckers, primitive gut, 2dark eye spots and 7 pairs of penetrating glands Life cycle: Adults live in between the intestinal villi (habitat) of the definitive host. Mature eggs pass with stool. In water eggs don’t hatch, they are ingested by 1st intermediate host (Pirenella conica). Egg hatches inside the snail and the miracidium is liberated. Miracidium changes into sporocyst → redia → cercaria. Cercaria comes out of the snail. Cercaria swims in water until they find the 2nd intermediate host (boury & bolty fish). Cercaria penetrates the skin of fish leaving the tail outside and become encysted metacercaria under scales, gills, or inside fish muscles then it becomes infective after 2-3 weeks. Man and fish-eating animals are infected by eating raw, undercooked, or under-salted fish (feseekh) for less than 10 days containing encysted metacercaria (the infective stage). In the small intestine metacercaria is liberated and lodged in between villi and mature into adult in 3 weeks ⮚ Clinical Picture: Name of the Disease: Heterophyiasis. Clinical manifestations: Most infections are asymptomatic or accompanied by mild intestinal discomfort, which may include mucous diarrhoea, colicky pains, intermittent neurasthenia, and lethargy. Symptoms are more frequent in heavy infections, but they subside spontaneously after one month, although the flukes remain. Upon further infection, symptoms may recur, giving rise to occasional episodes of diarrhoea in endemic areas. Diagnosis: Clinical: History of eating undercooked or under-salted fish. Symptoms and signs. Laboratory: Direct Microscopic examination: The diagnosis is suggested by detecting the characteristic eggs in the stool ⮚ Treatment: Praziquantel is the drug of choice. A single dose of 10–20 mg/kg is highly effective. Prevention and control: Treatment of patients and infected animals. Proper cooking of fish and salting not less than 10 days. Snail control. Health education: The life cycle could be disrupted by improved sanitary conditions and educational information about proper sewage disposal away from ponds or lakes where the intermediate hosts reside.