Medical Helminthology Parasitology PDF

Trematode LECTURE (2) Medical helminthology 1  Trematode  The science dealing with helminths (worms) of man. Flat worms Round worms...

Trematode LECTURE (2) Medical helminthology 1  Trematode  The science dealing with helminths (worms) of man. Flat worms Round worms 2  Trematode 1. Flattened dorsoventrally (leaf like) except Schistosoma → has rounded female. 2. Has no body cavity 3. Unsegmented 4. Bilaterally symmetrical 5. Organs of fixation: a) Oral sucker: at the anterior end surrounding the mouth. b) Ventral sucker: in the ventral surface c) Genital sucker: sometimes present d) Spines cover the cuticle and help fixation. 6. Digestive system: a) Mouth at the anterior end b) Esophagus having a muscular pharynx c) Two intestinal caeca end blindly at the posterior end 7. Hermaphrodites (each adult parasite contains both male and female sex organs) except Schistosoma (unisexual, separate sex, male or female parasite). 3  Trematode  Inhabits Man (definitive host) and animal (reservoir host).  It can be classified according to its habitat into: 1. Intestinal flukes: inhabit small intestine. 2. Lung flukes: inhabit lung alveoli. ❶ Adult 3. Liver flukes: inhabit liver and biliary tract. 4. Blood flukes: inhabit mesenteric veins (intestinal schistosomiasis) or pelvic and vesical venous plexus (urinary schistosomiasis).  Trematoda eggs are operculated, except Schistosoma egg No operculum Has a spine.  Egg reaches water where it hatches into miracidium ❷ Egg ❸ Miracidium  A Pyriform ciliated organism 4  Trematode  The miracidium develops into sporocyst, a sac-like organism full Snail of germinal cells which develop into rediae. ❹ (intermediate  The redia develops into daughter rediae and cercariae host)  Cercariae leaves the snail  Schistosoma has no redia.  Has a body and a tail  1. Simple tail (leptocercous cercaria). 2. Membrane along its tail (lophocercous cercaria). 3. Tail as a knob (microcercous cercaria). 4. Forked tail (furcocercous cercaria) as in Schistosoma. ❺ Cercaria  The cercaia loses its tail and secretes a cyst wall to become Encysted encysted metacercaria. ❻ metacercaria  Schistosoma has no encysted metacercaria  Adult → egg → miracidium → sporocyst → redia → cercaria → encysted metacercaria.  Except Schistosoma (Adult → egg → miracidium → sporocyst → cercaria).  Thus, the infective stage of trematodes is encysted metacercaria, except Schistosoma in which the infective stage is furcocercous cercaria. 5  Trematode ❶ Ingestion  of contaminated food or drink with encysted metacercaria Skin  by furcocercus cercaria in Schistosoma ❷ penetration 6  Trematode The clinical presentations differ according to the habitat of adult parasites and the affected organ. 1. Abdominal colic. 2. Diarrhea. Intestinal 3. Vomiting. ❶ flukes 4. Loss of appetite, loss of weight. 5. Vitamins deficiencies.  Prolonged fever  Right hypochondrium pain Hepatobiliary ❷ trematodes  Jaundice  Hepatomegaly.  Chest pain, cough, dyspnea (difficult breathing), hemoptysis Lung ❸ trematodes (coughing of blood), respiratory failure.  Intestinal Schistosomiasis:  Dysentery with blood and mucous in stool.  It may be complicated with portal hypertension, esophageal varices in which there are a. Haematemesis (vomiting of blood) b. Melena (black stool due to presence of blood in stool). Blood flukes ❹ (Schistosoma)  Urinary Schistosomiasis:  Terminal haematuria (bloody urine), dysuria and frequency.  It may be complicated with cancer bladder. 7  Trematode A). Clinical b). Laboratory:  To detect the characteristic eggs 1. In intestinal or hepatobiliary helminths: stool or duodenal aspirate help in diagnosis. 2. Pulmonary helminths: sputum or stool examination 3. Urinary helminths: urine examination Microscopic ❶ examination ❷ Imaging  X-Ray, US on affected organs. ❸ Serology  Detect antibodies in serum  Sigmoidoscopy or ❹ Endoscopy  Cystoscopy. Histo- ❺ pathological diagnosis Most of trematodes respond to Praziquantel. 8