Blood Flukes (Schistosomes) - Characteristics and Life Cycle Overview
Learn about blood flukes (schistosomes) including their characteristics, life cycle stages such as miracidium, cercaria, and schistosomulae, and details about Schistosoma japonicum. Understand how these parasitic organisms infect hosts and reproduce, causing diseases like schistosomiasis.
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4. BLOOD FLUKES Characteristics Dioecious Males are shorter and stouter than females Lateral margins of males are folded ventrally to form a gynecophoral canal in which females are received Suckers are armed with delicate spines There is no muscular pharynx Eggs are non-operculated Eggs are fully embryonated when laid Embryonated eggs have a ciliated embryo called miracidium Cercariae have bifid tails There is no encysted metacerciarial stage Infective Stage: cercaria penetrating the unbroken skin
7. Schistosome Miracidium Hatches from the egg in slightly alkaline clean water with a temp. between 25 0C to 310C Free swimming cilated embryo liberated from the egg Photactic Infect snails Miracidium
9. Schistosome Cercaria Emerges from daughter sporocysts Escapes from the snail Has a body and a forked tail Infects man by skin penetration Cercaria
10. Schistosomulae Develops from cercaria after skin penetration Adapted to survive in serum or physiologic saline at 37 0C Enter the pleural cavity---diaphragm--- peritoneal space--- penetrate the liver to reach the intrahepatic portions of the portal vein Schistosomule
12. Schistosoma japonicum japonicum Primarily parasites of the portal vein and its branches Each female fluke deposits 500-2000 immature eggs/day Embryonation takes place within 10-12 days Eggs escape through ulcerations in the intestinal lumen and are passed out with the feces Schistosoma
14. Schistosoma japonicum japonicum Ova Ovoidal, rounded or pear-shaped Thin shell Pale yellow Curved hook or spine or lateral knob Laid in the multicellular stage and embryonte within 10-12 days Schistosoma
13. Symptoms and Signs (1) Initial phase: It is characterized by fever, dry cough (pneumonitis), urticaria due to adolescents migration. (2) Acute stage: The characteristics symptoms is dysentery. The patient may pass stool with blood, pus and mucus 5-10 times per day with a large number of eggs. Chill, fever, and malaise occur. (3) Chronic stage: Chief manifestation of the patients are interval diarrhea or dysentery. The patients experience fatigue, general condition and strength deteriorate, loss of weight and interest, retardation of both physical and mental growth in children. Spleen and liver enlargement, anemia, in women menopause, sterility and abortion may occur. This stage may last from several years to 20 years.
14. (4) Terminal stage: is characterized by portal vein hypertension syndrome, common saying, abdomen distention looks like a big drum, emaciation looks like a fire wood. Ascites, emaciation, varicosity, splenomegaly and anemia are commonly found. The patients die of secondary infection, upper digestive tract bleeding, hepatic coma. **Ectopic lesion: The damage to the central nervous system (brain,spinal) may cause paralysis (monoplegia, hemiplegia ). 18. Specific Treatment Infection Drug of Choice Adult Dose and Duration Blood Flukes S. mansoni, S. intercalatum, Praziquantel S.haematobium 20 mg/kg, 2 doses in 1 day . S. japonicum, S. mekongi Praziquantel 20 mg/kg, 3 doses in 1 day
