Trematodes (flatworms) Notes


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Clonorchis sinensis

Paragonimus westermani


NOTES NOTES TREMATODES (FLATWORMS) GENERALLY, WHAT ARE THEY? PATHOLOGY & CAUSES ▪ AKA flukes; parasitic flatworm; infects internal organs ▪ Phylum: Platyhelminthes Characteristics ▪ Adult morphology: flattened oval/elongated ▪ Structures ▫ Tegmentum (outer body covering) ▫ Ventral, oral suckers ▫ Pharynx → esophagus → caeca ▫ Testes, uterus/ovary (hermaphrodites) ▪ Eggs generally operculated (lidded); except schistosomes ▪ Obligate parasites of mollusks, vertebrates Development 1.Egg 2.Miracidium (ciliated, lacks mouth; infects first intermediate host) 3.Sporocyst (elongated sac, produces rediae) 4.Redia (larval stage with oral sucker) 5.Cercaria (larval stage; may be infectant) 6. Metacercaria (encysted cercaria) 7.Adult SIGNS & SYMPTOMS ▪ See individual trematodes 570 OSMOSIS.ORG DIAGNOSIS DIAGNOSTIC IMAGING ▪ Medical imaging (e.g. ultrasound, CT scan, MRI) LAB RESULTS ▪ E.g. blood tests ▪ Direct microscopy OTHER DIAGNOSTICS ▪ Serologic tests TREATMENT MEDICATIONS ▪ Anthelmintic
Chapter 102 Trematodes (Flatworms) CLONORCHIS SINENSIS PATHOLOGY & CAUSES ▪ Parasitic fluke; invasion of biliary tree → liver infection ▪ AKA Chinese liver fluke ▪ Morphology ▫ Adult: flat, elongated body; 25 x 5mm ▫ Egg: oval-shaped; 30 x 15μm ▪ Intermediate hosts ▫ First: freshwater snail (e.g. Parafossarulus manchouricus) ▫ Second: freshwater fish/shrimp ▪ Reservoirs: cats, dogs ▪ Transmission ▫ Ingestion of raw/undercooked fish/ shrimp ▪ Infectious form: metacercariae ▫ Ingestion of metacercariae → excyst in duodenum → migration to biliary tract → inflammation, epithelial hyperplasia ▪ Endemic to Eastern Asia (e.g. China, Japan, Philippines, Vietnam) RISK FACTORS ▪ Recent travel to endemic areas ▪ Consumption of raw/undercooked fish/ shrimp COMPLICATIONS ▪ Pancreatitis, cholangitis, liver abscesses, cholangiocarcinoma DIAGNOSIS DIAGNOSTIC IMAGING Ultrasound, CT scan, MRI ▪ Enlarged gallbladder, hepatomegaly, bile duct inflammation, dilated/thickened intrahepatic bile ducts Endoscopy ▪ Visualization of adult organisms LAB RESULTS ▪ Acute infection ▫ Eosinophilia, ↑ IgE ▪ Chronic infection ▫ ↑ alkaline phosphatase, ↑ bilirubin ▪ Direct microscopy ▫ Detection of Clonorchis eggs in stool samples ▫ Formalin ethyl-acetate concentration technique (FECT) → parasite separation from faeces ▪ Serologic tests ▫ E.g. ELISA ▪ Polymerase chain reaction (PCR) TREATMENT MEDICATIONS ▪ Anthelmintic (e.g. praziquantel) SIGNS & SYMPTOMS ▪ Mostly asymptomatic ▪ Acute infection: fatigue, right upper quadrant abdominal pain, indigestion, diarrhea, flatulence ▪ Chronic infection: fatigue, weight loss, abdominal discomfort, diarrhea, dyspepsia, jaundice (severe cases) Figure 102.1 An adult Clonorchis sinensis worm. OSMOSIS.ORG 571
PARAGONIMUS WESTERMANI PATHOLOGY & CAUSES SIGNS & SYMPTOMS ▪ Parasitic flatworm; causes pulmonary paragonimiasis ▪ AKA Japanese lung fluke ▪ Morphology ▫ Adult: oval-shaped body with spines; 15 x 8mm ▫ Egg: oval-shaped, thick shell; 100 x 55μm ▪ Intermediate hosts ▫ First: freshwater snails (e.g. Semisulcospira spp.) ▫ Second: crustaceans (e.g. crabs, crayfish) ▪ Transmission ▫ Ingestion of raw/undercooked crustaceans (e.g. crab, crayfish) ▪ Infectious form: metacercariae ▫ Ingestion of metacercariae → excyst in duodenum → penetration of peritoneal wall → migration to lungs → encapsulate, mature → inflammation, fibrosis ▪ Endemic to Eastern Asia (e.g. China, Japan, Philippines, Vietnam) Pulmonary ▪ Early infection ▫ Systemic: fever, malaise ▫ Pulmonary: dyspnea, cough, pleuritic pain ▫ Gastrointestinal: diarrhea, epigastric pain ▪ Late infection ▫ Malaise ▫ Recurrent, chocolate-colored hemoptysis RISK FACTORS X-ray, CT scan, MRI ▪ Brain ▫ Skull X-ray: soap-bubble calcifications; calcified cysts ▫ CT/MRI: grape clusters; conglomerated, cystic lesions ▪ Lungs ▫ Pleural effusion, parenchymal cysts/ nodules, cavitary lesions, parasite migration tracts ▪ Poor sanitary conditions ▪ Seafood consumption in endemic areas COMPLICATIONS ▪ Meningitis, encephalitis, seizures 572 OSMOSIS.ORG Extrapulmonary ▪ Cerebral: headache, fever, vomiting, seizures, papilledema, paresis/paresthesias, visual disturbances (e.g. diplopia) ▪ Abdominal: nausea/vomiting, hematoquezia (bloody stool), pain, hematuria ▪ Subcutaneous: tender, firm, painless, mobile nodules DIAGNOSIS DIAGNOSTIC IMAGING
Chapter 102 Trematodes (Flatworms) LAB RESULTS ▪ Eosinophilia, ↑ IgE ▪ Direct microscopy ▫ Detection of eggs in stool, sputum, bronchoalveolar lavage ▪ Serologic tests ▫ Enzyme-linked immunosorbent assay (ELISA), immunoblot TREATMENT MEDICATIONS ▪ Anthelmintic (e.g. praziquantel, triclabendazole) SCHISTOSOMES PATHOLOGY & CAUSES ▪ Blood flukes; parasitize mesenteric veins/ vesical venous plexus → gastrointestinal/ genitourinary tract infections ▪ AKA bilharziasis/snail fever ▪ Morphology ▫ Adult: elongated body, 1–2cm/0.39– 0.79in ▫ Eggs: not operculated ▪ Intermediate host ▫ Snails ▪ Transmission ▫ Contaminated freshwater contact ▪ Infectious form: cercariae ▫ Contact with cercariae in fresh water → skin penetration → schistosomulae → migration to liver through circulation → adult form → migration to mesenteric venules/vesical venous plexus → egg deposits → inflammation → fibrosis ▪ High-prevalence area is sub-Saharan Africa RISK FACTORS ▪ More common in individuals who are biologically male, rural areas ▪ Recent contact with fresh water bodies in endemic areas COMPLICATIONS ▪ Bacteremia, infertility, intestinal obstruction, nephrotic syndrome, renal failure, cardiomegaly, acute myelopathy Figure 102.2 A scanning electron micrograph of a S. japonicum flatworm. SIGNS & SYMPTOMS Acute infection ▪ Swimmer’s itch ▫ Pruritic papular/urticarial rash, esp. legs/ feet ▪ Acute schistosomiasis syndrome/Katayama fever ▫ Non-specific symptoms (fever, urticaria, chills, arthralgia, myalgia, headaches) ▫ Angioedema, dry cough, abdominal pain, diarrhea Chronic infection ▪ Intestinal: abdominal pain, poor appetite, diarrhea ▪ Hepatosplenic: hepatosplenomegaly, portal OSMOSIS.ORG 573
hypertension (e.g. collateral circulation, gastrointestinal bleeding, ascites) ▪ Pulmonary: dyspnea; pulmonary hypertension → cor pulmonale (enlarged right cardiac chambers) ▪ Urogenital: hematuria, pyuria, dysuria, increased urinary frequency ▪ Neuroschistosomiasis (acute myelopathy): seizures, sensory/motor impairment, cerebellar syndrome (incoordination) prednisone) ▪ Manageme pruritus (e.g. antihistamines) OTHER INTERVENTIONS ▪ Prevention ▫ Water sanitation programs ▫ Mass therapy ▫ Control of snails (e.g. molluscicides) DIAGNOSIS DIAGNOSTIC IMAGING Chest X-ray, CT scan, MRI, abdominal ultrasound ▪ Brain: contrast-enhancing infiltrates ▪ Bladder: wall irregularities/fibrosis ▪ Liver: widened periportal space, periportal fibrosis, collateral pathways ▪ Lungs: patchy infiltrates, miliary nodules ▪ Spinal cord: radicular thickening, intramyelinic lesions LAB RESULTS Figure 102.3 Calcified eggs of the flatworm Schistosoma japonicum in the submucosa of the colon of an individual previously treated for schistosomiasis. ▪ Bladder/rectum biopsy ▫ Egg-filled granulomas in mucosa ▪ Direct microscopy ▫ Detection of eggs in stool/urine samples ▫ Kato–Katz method (thick smear) ▫ FLOTAC stool concentration method ▪ Lab tests ▫ Acute infection: eosinophilia ▫ Chronic infections: anemia ▫ Portal hypertension: thrombocytopenia (splenic sequestration) ▫ Urogenital infection: hematuria/ leukocyturia in urinalysis ▪ Serologic testings ▫ E.g. ELISA, indirect hemagglutination TREATMENT MEDICATIONS ▪ Anthelmintic (e.g. praziquantel, oxamniquine) ▪ Corticosteroids (e.g. prednisolone, 574 OSMOSIS.ORG Figure 102.4 A CT scan of the abdomen and pelvis demonstrating calcification of the bladder secondary to schistosomiasis.
Chapter 102 Trematodes (Flatworms) OSMOSIS.ORG 575

Osmosis High-Yield Notes

This Osmosis High-Yield Note provides an overview of Trematodes (flatworms) 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 Trematodes (flatworms) by visiting the associated Learn Page.