trematodes

• Trematodes (Flukes)

  • Unsegmented, leaf-like
  • All are hermaphroditic except Schistosoma (dioecious)
  • All require two intermediate hosts except Schistosoma
  • The infective stage is metacercariae except for Schistosoma (cercariae)
  • The diagnostic stage is embryonated egg Except for Paragonimus, Fasciola, Fasciolopsis, and Echinostoma (unembryonated egg)
  • The first intermediate host is always a snail
  • The second intermediate host may be a fish, crustacean, another snail, or fresh water plants
  • The DOC is praziquantel except for Fasciola which is triclabendazole
• Schistosoma spp.

  Adult schistosomes exist as separate sexes
• Schistosoma spp.

  • Oriental blood fluke (S. japonicum)
  • Urinary blood fluke (S. haematobium)
  • Manson's blood fluke (S. mansoni)
• Definitive host for Schistosoma spp.

  Human
• Intermediate hosts for Schistosoma spp.

  Snail (Oncomelania hupensis quadrasi, Bulinus, Biomphalaria)
• Infective stage for Schistosoma spp.

  Cercariae
• Pathogenic stage for Schistosoma spp.

  Adult worm
• Diagnostic stage for Schistosoma spp.

  Ova
• Mode of transmission for Schistosoma spp.

  Cercarial skin penetration
• Main pathology for Schistosoma spp. is host granulomatous reaction to eggs
• Liver granulomas lead to presinusoidal obstruction, hepatomegaly and portal hypertension (S. japonicum, S. mansoni)
• Bladder granulomas lead to nodules, polypoid lesions, and ulcerations in the lumens of the ureter and bladder, which in turn causes urinary frequency, dysuria and end stream hematuria (S. haematobium)
• Diagnosis for Schistosoma spp.

  Kato-katz, Circumoval precipitin test (ovoid egg with small hook)
• Treatment for Schistosoma spp.

  Praziquantel
• Clonorchis sinensis

  Chinese liver fluke/Oriental liver fluke
• Definitive host for Clonorchis sinensis

  Human
• First intermediate host for Clonorchis sinensis

  Parafossarulus, Bulinus (snail)
• Second intermediate host for Clonorchis sinensis

  Cyprinidae (fish)
• Infective stage for Clonorchis sinensis

  Metacercariae
• Pathogenic stage for Clonorchis sinensis

  Adult worm
• Diagnostic stage for Clonorchis sinensis

  Ova
• Mode of transmission for Clonorchis sinensis

  Ingestion of undercooked/raw fish
• Clonorchiasis is mostly asymptomatic but may manifest as fever, Upper abdominal pain, anorexia, hepatomegaly, diarrhea, eosinophilia
• Chronic clonorchiasis can lead to hepatomegaly and Cholangiocarcinoma
• Diagnosis for Clonorchis sinensis

  DFS
• Treatment for Clonorchis sinensis

  Praziquantel
• Fasciola hepatica


  Sheep liver fluke
• Definitive hosts for Fasciola hepatica

  Sheep, Human
• First intermediate host for Fasciola hepatica

  Snail
• Second intermediate host for Fasciola hepatica

  Kangkong, watercress
• Infective stage for Fasciola hepatica


  Metacercariae
• Pathogenic stage for Fasciola hepatica

  Adult worm
• Diagnostic stage for Fasciola hepatica

  Ova
• Mode of transmission for Fasciola hepatica

  Ingestion of infected aquatic plants
• Acute or invasive phase of fascioliasis presents with a triad of high fever, hepatomegaly, marked eosinophilia
• Chronic or latent phase of fascioliasis involves adults in bile ducts leading to obstruction
• Halzoun/marrara is a syndrome of hemorrhagic nasopharyngitis and dysphagia due to ingestion of raw Fasciola adult-infected liver
• Diagnosis for Fasciola hepatica

  DFS
• Treatment for Fasciola hepatica

  Triclabendazole
• Paragonimus westermani

  Oriental lung fluke