Cestodes (tapeworms) Notes

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Diphyllobothrium latum

Echinococcus granulosus (Hydatid disease)

NOTES NOTES CESTODES (TAPEWORMS) GENERALLY, WHAT ARE THEY? PATHOLOGY & CAUSES ▪ Human gastrointestinal tract parasites; AKA tapeworms ▫ Adult tapeworms live in intestines ▫ Larvae live in different tissue (brain, liver, eye, etc.) ▪ Tripartite body ▫ Head/scolex (contain suckers, hooks/ attachment organs) ▫ Thin neck ▫ Trunk (made of numerous proglottids) ▪ Hermaphroditic ▫ Each proglottid has male, female organs ▪ Transmission ▫ Egg/larvae-contaminated water/food ingestion RISK FACTORS ▪ ▪ ▪ ▪ ▪ Poor hygiene Low socioeconomic status Raw/undercooked fish/meat Livestock exposure Living/travelling in endemic areas COMPLICATIONS ▪ ▪ ▪ ▪ 338 OSMOSIS.ORG Cysticercosis (Taenia) Cyst rupture Intestinal obstruction Malabsorption → vitamin B12 deficiency → megaloblastic anemia SIGNS & SYMPTOMS ▪ Tapeworm species-dependent ▪ Can be asymptomatic, abdominal pain. nausea/vomiting, weight loss DIAGNOSIS DIAGNOSTIC IMAGING MRI, CT scan, ultrasound ▪ Cyst presence LAB RESULTS ▪ Microscopy ▫ Identify eggs/proglottids in stool ▪ Complete blood count (CBC), serology TREATMENT ▪ Tapeworm species-dependent MEDICATIONS ▪ Anthelmintics
Chapter 61 Cestodes (Tapeworms) DIPHYLLOBOTHRIUM LATUM osms.it/diphyllobothrium-latum PATHOLOGY & CAUSES ▪ AKA fish tapeworm ▪ Longest human-infecting tapeworm (4–15m/13–49ft) ▪ Causes diphyllobothriasis in humans ▪ Proglottids ▫ Width > length ▪ Competes for vitamin B12 → vitamin B12 deficiency CAUSES ▪ Raw/undercooked fish → larvae ingestion COMPLICATIONS ▪ Tapeworms → mechanical intestinal obstruction ▪ Malabsorption → weight loss ▪ Vitamin B12 deficiency → megaloblastic anemia SIGNS & SYMPTOMS ▪ Vitamin B12 deficiency ▫ Impaired oxygen delivery: fatigue, activity intolerance, pallor, compensatory mechanisms (↑ heart rate, bounding pulse) ▫ Neuronal demyelination: numbness, tingling, weakness ▪ Weight loss ▪ Abdominal pain DIAGNOSIS LAB RESULTS ▪ Megaloblastic anemia; e.g. increased mean corpuscular volume (MCV) ▪ Microscopy ▫ Identify eggs/proglottids in stool ▪ ↓ serum vitamin B12 TREATMENT MEDICATIONS ▪ Anthelmintics OSMOSIS.ORG 339
ECHINOCOCCUS GRANULOSUS (HYDATID DISEASE) osms.it/echinococcus-granulosus PATHOLOGY & CAUSES ▪ Parasitic infection caused by E. granulosus ▫ AKA echinococcosis ▪ Produce protoscoleces ▫ Juvenile scolex invaginated in cysts ▫ Tapeworm maturation in definitive host’s intestine ▪ Humans (incidental hosts); herbivores (intermediate hosts); canids (definitive hosts) CAUSES ▪ Viable parasite egg-containing food consumption RISK FACTORS ▪ Parasite/egg-contaminated food/water ingestion ▪ Close contact with infected animals Figure 61.2 The gross pathology of hydatid cysts excised from the lung. 340 OSMOSIS.ORG Figure 61.1 A scolex of the organism Echinococcus granulosus, the causative agent of hydatid disease. COMPLICATIONS ▪ Arise as cysts migrate, grow in size, rupture ▫ Liver: eosinophilia, pruritus, jaundice, urticaria, liver abscess, anaphylaxis ▫ Peritoneal cavity: peritonitis, pancreatitis ▫ Pleural space: abscess formation → pneumothorax/pleural effusion ▫ Bronchial tree: respiratory distress, hemoptysis ▫ Heart: cardiomegaly/pericardial effusion ▫ Kidney: glomerulonephritis ▪ Large cyst compression effect ▫ Heart: large cyst in liver → compression of right heart ▫ Cerebral/spinal cord (CNS): neurological deficits ▫ Liver/biliary tree cysts: obstructive jaundice/cholangitis; venous drainage obstruction → portal hypertension → Budd–Chiari syndrome (abdominal pain, ascites, hepatomegaly)
Chapter 61 Cestodes (Tapeworms) SIGNS & SYMPTOMS ▪ Initially asymptomatic ▪ Depend on affected organs ▫ Liver: right upper quadrant pain, hepatomegaly, nausea, vomiting ▫ Lungs: cough, chest pain, dyspnea, hemoptysis ▪ Other organs (rarely affected) ▫ Heart: jugular venous distention, dyspnea ▫ Musculoskeletal: diffuse pain, pathologic fractures ▫ Kidney: hematuria, flank pain ▫ CNS: headache, motor deficit, seizure, coma ▪ Puncture-aspiration-injection-reaspiration (PAIR) ▫ Ultrasound/CT scan-guided cyst puncture ▫ Aspirate cystic fluid ▫ Inject scolicidal solution ▫ Reaspirate cystic solution ▫ Repeat procedure until aspirate clears ▫ Fill cyst with isotonic saline DIAGNOSIS DIAGNOSTIC IMAGING Ultrasound/MRI/CT scan ▪ Cyst presence LAB RESULTS ▪ Enzyme-linked immunosorbent assay (ELISA) ▫ Echinococcal antigen detection in cystic fluid ▪ Indirect hemagglutination ▫ Echinococcal antigen detection ▪ Immunodiffusion/immunoelectrophoresis ▫ Echinococcal-specific antibody detection ▪ Biopsy/cyst aspiration Figure 61.3 A CT scan of the abdomen in the axial plane demonstrating a large hepatic hydatid cyst. The numerous daughter cysts are faintly visible. TREATMENT MEDICATIONS ▪ Albendazole/ mebendazole ▫ Uncomplicated cases Figure 61.4 A histological section through a hydatid cyst wall showing a typical laminated structure. SURGERY ▪ Complicated cases ▫ Rupture, vital structure compression, cysts with diameter > 10cm/3.94in OSMOSIS.ORG 341

Osmosis High-Yield Notes

This Osmosis High-Yield Note provides an overview of Cestodes (tapeworms) essentials. All Osmosis Notes are clearly laid-out and contain striking images, tables, and diagrams to help visual learners understand complex topics quickly and efficiently. Find more information about Cestodes (tapeworms) by visiting the associated Learn Page.