Food borne trematodes

• Food-borne trematodes in humans include:

  • Liver flukes: Clonorchis sinensis, Opisthorchis viverrini, Opisthorchis felineus, Fasciola hepatica, Fasciola gigantica
  • Lung flukes: Paragonimus spp.
  • Intestinal flukes: Fasciolopsis buski, Echinostoma revolutum, Metagonimus yokogawai
• Species and number of infected people (in million):

  • Clonorchis sinensis: 15 (13 in PRC)
  • Paragonimus spp.: 22
  • Opisthorchis viverrini: 9
  • Opisthorchis felineus: 1.5
  • Fasciola hepatica: 2.6
  • Intestinal flukes (F. buski, Echinostoma spp., Metagonimus spp.): 40-50
• Liver flukes in humans:

  • Opisthorchis viverrini
  • Opisthorchis felineus
  • Clonorchis sinensis
  • Fasciola hepatica
• Life cycle of liver flukes (O. viverrini, O. felineus, C. sinensis):

  • DH: fish-eating carnivores and humans in Asia
  • Adults (5-20 mm) localized in bile ducts of liver, gall bladder
  • Two intermediate hosts: 1st IMH snail (Bithynia), 2nd IMH fish (Cyprinidae)
  • Source of infection: fish (raw, undercooked, dried)
• Diagnosis of clonorchiasis and opisthorchiasis:

  • Indirect diagnosis (serology) available
• Cancerogenic effect of liver flukes:

  • O. viverrini and C. sinensis classified as Group 1 carcinogens
  • Cholangiocarcinoma - cancer of bile ducts
• Fasciolosis in humans:

  • F. hepatica and F. gigantica cause fasciolosis
  • 2.6 million people infected, 180 million at risk
  • Plant-borne disease
• Lung flukes - Paragonimus spp.:

  • Adults 7-16 x 4-6 mm, localized in lungs
  • DH: humans and carnivores
  • 1st IMH snails (Antemelania sp., Planorbidae), 2nd IMH mountain crab (Sundathelphusa philippina), crayfish
  • Wild boar as paratenic host
• Intestinal flukes:

  • Fasciolopsis buski = fasciolopsiasis
  • Metagonimus yokogawai = metagonimiasis
  • Echinostoma revolutum = echinostomiasis
  • Heterophyes heterophyes
• To remember:

  • Liver and lung flukes are foodborne in humans (fish, crustaceans, plants)
  • Easy treatment (praziquantel) but irreversible changes in the liver
  • Opisthorchis and Clonorchis are cancerogenic
  • Best prevention is based on education