trematodes

• trematodes are commonly known as flukes (tramatoda or digenea)
• may be hermaphroditic or dioecious (seperate sexes)

  • most are hermaphroditic except schistoma spp. (blood fluke)
• have a digestive tract and two musuclar sucker: oral type (beginning of incomplete digestive system) and ventral sucker (attachment)
• lid-like structure (operculum) is present in the eggs of fasciolopsis and fasciola
• humans never serve as intermediate host for flukes

  • mollusk (snail and clams) - asexual reproduction
  • second intermediate host vary depends on the parasite
  • sexual reproduction occurs in human - occur through ingestion of raw second intermediate host
• skin penetration of infective larvae is the major transmission for blood fluke
• blood-dwelling flukes: schistosoma spp

  • associated with human disease: s. mansoni, s. japonicum, s. haematombium
  • dioecious, known as romatic parasites
  • female worms are larger than male worms
  • found in fresh water contaminated with fece or urine of infected human
  • egg develop into miracidium once its in the water > locate a snail > transform into cercariae
  • infection acquired through skin penetration
• • s. japonicum and s. mansoni: enters vein surrouding intestinal tract
  • s. haemotobium localize in veins surrounding urinary bladder
• diseases of schistosomiasis

  • asymtomatic infection
  • early acute infection - pruritic papules (swimmer's itch / clam digger's icth)
  • katayama fever - associated with s. japonicum, may cause death ((internal bleeding from ruptured esophageal varices)
  • associated condition - development of nephrotic syndrome in s. japanicum (liver cancer) and s. haematobium (cancer of urinary bladder)
• recommended drug for schistosoma: praziquantel

  • s. mansoni: oxamniquine
• tissue-dwelling flukes

  • clonorchis sinesis (asian / chinese liver fluke)
  • fasciola hepatica (sheep liver fluke)
  • paragonimus westermani (oriental lung fluke)
  • fasciolopsis buski (large intestinal fluke)
• clonorchis sinesis (asian / chinese liver fluke)

  • morphologic stages: egg (shoulder), larva, adult
  • first intermediate host: freshwater snail
  • second intermediate host: freshwater fish
  • egg contains developed miracidium that is released once in contact with fresh water
  • acquired through ingestion of raw or undercooked freshwater fish contaning infective metacercariae
  • inhabits bile duct (higher risk of developing cholongiaocarcinoma - cancer of bilde ducts)
  • drug of choice is praziquantel
  • alternative drug is albendazole
• fasciola hepatica (sheep liver fluke)

  • first intermediate host: snail white
  • second intermediate host: edible aquatic plants (kangkong and watercress)
  • acquired through ingesting raw edible aquatic plants / drinking water contaminated by metacercariae
  • excyst in duodenum or jejunum > releases young flukes > wander viscera until liver capsule > enter bile duct where they mature
  • humans are accidental host
  • treatment of choice is dichlorophenol (bithionol)
  • alternate drug is triclabendazole
• paragonimus westermani (oriental lung fluck)

  • first intermediate host: snail
  • second intermediate host: crab / crayfish
  • acquired through ingestion of raw or undercooked crabs or crayfish contaning infected encysted metacercaria
  • excyst in small intestine > intestinal wall > peritoneal cavity > diaphragm > lung parenchyma where they mature > enter brochioles > coughed up / swallow
  • may mimic pulmonary tuberculosis
  • immature flukes migrate to brain, leading cerebral paragonimiasis
  • drug of choice is praziquantel
  • alternative is bithionol
• fasciolopsis buski (large intestinal fluke)

  • ingestion of raw or inadequately cooked aquatic vegetation that carries encysted metacercarieae
  • excysts in duodenum > attaches to intestinal wall until maturity > released with feces into water
  • reservoir host: pigs and dogs
  • ulceration may occur (duodenal ulcer)
  • drug of choice is praziquantel