Trematodes: Phylum Platyhelminthes (PDF)

7-8 TREMATODES PHYLUM PLATYHELMINTHES All flukes appear flat and leaf-like except for Schistosomes (blood flukes) – elongated/cylindrical All are hermaphroditic (monoecious) except for Schistosomes – separate sexes (dioecious) All eggs are operculated except for Schistosomes – non-operculated LIFE C...

7-8 TREMATODES PHYLUM PLATYHELMINTHES All flukes appear flat and leaf-like except for Schistosomes (blood flukes) – elongated/cylindrical All are hermaphroditic (monoecious) except for Schistosomes – separate sexes (dioecious) All eggs are operculated except for Schistosomes – non-operculated LIFE CYCLE OF TREMATODES 1. EGG The life cycle begins with an egg, laid by the adult trematode in the definitive host's feces. 2. Miracidium SHORT-LIVED LARVA INFECTS 1ST INTERMEDIATE HOST (SNAILS) use cilia (hair-like structures) to swim and sensory organs to locate and penetrate the snail host. 3. SPOROCYST SAC-LIKE STAGE INSIDE THE 1ST INTERMEDIATE HOST reproduces asexually, producing daughter sporocysts or another larval stage called rediae. 4. Redia motile larvae with a mouth and digestive system can further reproduce asexually not present in all trematode species. 5. CERCARIA infective stage for the definitive host with tails for swimming or other adaptations for finding their next host may directly infect the definitive host or encyst 6. Metacercaria cercaria encysts on a second intermediate host dormant and infective to the definitive host 7. ADULT typically flattened, leaf-shaped equipped with suckers and hooks for attachment to the host's internal organs reproduce sexually within the definitive host infective stage for final host metacercaria cercaria - for schistosomes mode of transmission ingestion skin penetration - for schistosomes requres 2 intermediate hosts: 1st IH: snail 2nd ih: Fish, Crab, Plant, Snail, Ant requres 1 intermediate host: schistosomes (snail) Adults attach themselves to the host by means of 2 suckers: oral sucker ventral sucker (acetabulum) for Heterophyes heterophyes having 3 suckers genital sucker/gonotyle Mature when laid Immature when laid Schistosoma Heterophyes Opistorchis Clonorchis Paragonimus Echinostoma Fasciola Fasciolopsis OPERCULATED, UNEMBRYONATED EGGS OPERCULATED, EMBRYONATED EGGS NON-OPERCULATED, EMBRYONATED EGGS Fasciola Fasciolopsis Paragonimus Clonorchis Opistorchis Heterophyes schistosoma eggs operculated non-operculated Fish: Heterophyes heterophyes, Clonorchis sinensis, Opistorchis felineus Crab: paragonimus westermani Fasciola hepatica, Fasciola gigantica, Fasciolopsis Plant/Vegetation: buski Snail: Echinostoma ilocanum Ant: Dicrocoelium dendriticum, Eurytrema pancreaticum LIVER FLUKES 1. Fasciola hepatica Common Names: Sheep Liver Fluke/Temperate Liver Fluke causes sheep liver rot Prevalent in sheep raising countries Habitat: Biliary duct/passages of liver host 1st IH: Snail 2nd IH: Plant/Vegetation (e.g. kangkong, water spinach) final host: Sheep infective stage: metacercaria mot: Ingestion of 2nd ih Egg: large, operculated, unembryonated, yellowish brown egg resembling F. gigantica and F. buski egg Resembling Hen’s egg shape Adult: Cephalic cone, well-developed shoulder 2. Fasciola gigantica Common Name: Giant Liver Fluke/Tropical Liver Fluke Infects cattles in the Philippines Dominant species affecting cattle and water buffaloes in the Philippines Habitat: Biliary Passages of Liver host 1st IH: Snail 2nd IH: Plant/Vegetation (e.g. kangkong, water spinach) final host: cattle infective stage: metacercaria mot: Ingestion of 2nd ih Egg: Similar to F. hepatica egg Adult: Longer cephalic cone, less developed shoulder Almost same with F. hepatica but is bigger 3. Clonorchis sinensis Common Name: Chinese Liver Fluke/Oriental Liver Fluke Most important liver fluke of man Habitat: Bile duct/Gallbladder host 1st IH: Snail 2nd IH: fish final host: man infective stage: metacercaria mot: Ingestion of 2nd ih egg: Operculated, mature; eggs like an old-fashioned electric light bulb; pitcher-like appearance pathogenesis: 1. desquamation of epithelial cells 2. hyperplasia 3. adenomatous tissue formation 4. pancreatitis and 5. cholangiocarcinoma 4. Opistorchis felineus Common Name: Cat Liver Fluke/Siberia Liver Fluke Habitat: Liver, Bile passages of the liver host 1st IH: Snail 2nd IH: fish final host: cats accidental host: man infective stage: metacercaria mot: Ingestion of 2nd ih egg: Operculated, mature Clonorchis sinensis Opistorchis felineus Opistorchis viverrini Branched Slightly lobulated Deeply lobulated 5. Dicrocoelium dendriticum/lanceolata Common Name: Lanceolate/Lancet Fluke Cirrhosis/Fibrosis of the liver Habitat: Biliary passages of the liver host 1st IH: Snail (Mass of Cercaria: Slime ball/Germ ball) 2nd IH: Ants final host: Cattle/Sheep accidental host: man infective stage: metacercaria mot: Ingestion of 2nd ih egg: Brownish, thick-walled, operculated, embryonated adult: Lancet-shaped INTESTINAL FLUKES 1. Fasciolopsis buski Common Name: Giant Intestinal Fluke Largest fluke parasitizing man Habitat: Small Intestine host 1st IH: Snail 2nd IH: Plant/Vegetation (e.g. chestnuts, caltrop) final host: MAN Reservoir Hosts: Pigs, Dogs, Rabbits infective stage: metacercaria mot: Ingestion of 2nd ih EGG Operculated, immature indistinguishable from Fasciola eggs Echinostomids Characterized by horseshoe shaped collar of spines around their oral suckers reservoir hosts: rat 1. Echinostoma ilocanum Common Name: Garrison Fluke (discovered among Bilibid prisoners) Habitat: Small Intestine host 1st IH: Snail 2nd IH: SNAIL final host: MAN RESERVOIR host: RAT infective stage: metacercaria mot: Ingestion of 2nd ih egg: Operculated, immature germ ball egg Heterophyes Pathogenesis: excessive mucus production most common manifestations: peptic ulcer disease and acid peptic disease 1. Heterophyes heterophyes Common Name: Von Siebold's Fluke Teardrop-shaped fluke Smallest fluke of man/deadliest fluke Habitat: Small Intestine host 1st IH: Snail 2nd IH: fish final host: MAN RESERVOIR host: Dogs, cats, birds infective stage: metacercaria mot: Ingestion of 2nd ih egg: Operculated, mature resembles C. sinensis egg appears old-fashioned light bulb 2. Metagonimus yokogawai Habitat: Small Intestine host 1st IH: Snail 2nd IH: fish final host: MAN RESERVOIR host: Dogs, cats, birds infective stage: metacercaria mot: Ingestion of 2nd ih LUNG FLUKES 1. Paragonimus westermani Common Name: Oriental Lung Fluke Causing endemic hemoptysis TB-like symptoms Common in Sorsogon (endemic) Habitat: Lungs host 1st IH: Snail 2nd IH: Crabs, crayfish, lobster final host: MAN infective stage: metacercaria mot: Ingestion of 2nd ih EGG Operculated with shoulders; immature/unembryonated Opposite the operculum is an abopercular thickening Similar to Diphyllobothrium latum egg ADULT Resembles coffee bean PATHOGENESIS Causes granulomatous reaction that proceeds into fibrotic encapsulation Dry cough that processes into rust-colored sputum with foul-fish odor Cerebral involvement: most serious complication; causes jacksonian epilepsy LABORATORY DIAGNOSIS: Specimen: Sputum (added with 3% NaOH to improve recovery)/Stool Diagnosis is based on sputum and stool examination for characteristic eggs Charcot-Leyden crystals may be observed in sputum or lung tissue specimens PANCREATIC FLUKES 1. Eurytrema pancreaticum Common Name: Pancreatic Fluke Causing cholecystitis, pancreatitis Habitat: Pancreatic ducts host 1st IH: Snail 2nd IH: Ant, grasshopper, mantis, crickets final host: Sheep, cattle ACCIDENTAL Hosts: MAN infective stage: metacercaria EGG: Operculated, embryonated (mature)