• Paltyheminthes
• class
  • cestoda (tapeworms)
  • trematoda (flukes)

• waterborn infections
  • obligate snail intermediate hosts
  • geographic dist. reflects snail loc.
• most are foodborne infection
  • second intermediate (after leave snail)
  • exception: schistosomiasis

• blind gut
• hermaphroditic
• fleshy
• oral sucker

• based on location in body
• intestinal (Fasciolopsis buski)
• liver
• lung
• blood (schistomiasis)

• Fascioliasis
• Clonorchiasis and Opisthorachiasis

• Clonorchis sinensis: China, Korea
• Opisthorchis viverrini: Thailand, Laus
• Opisthorchis felineus (West Siberia, Kazakhstan)

Transmission- uncooked fish

1. mettacecaria is ingested w/raw and undercooked fish
2. larvae hatch in small intestines
3. larvae enter bile ducts
4. adult matures and lives in bile duct
5. eggs in feces depositied in fresh water
6. eggs eaten by snail

• acute infection
  • fever
  • abdominal pain
  • hepatomegally
  • eosinophilia
  • eggs appearing in 3-4 weeks
• chronic infection- recurent ascending cholangitis and pancreatitis
• cholangiocarcinoma (exacerbated by nitrosoamines)

• praziquantel (except Fasciola hepatica and F. gigantica)
• interferes with calcium ion channels as surface of parasite causing tetany of parasite msucles

synergy with host antihelminth immune response

Schistosoma mansoni

Schistosoma japonicam

• geography- Africa, South America, Caribbean

Africa

Middle East

1. cercaria can penetrate skin directly (unlike others)
2. lose tail as they go into afferent ciruclation, now go by schistasomiya
3. mature in intrahepatic portal blood (male and female worms mate)
4. adults in blood vessels go out via urine or feces
5. miracidium hatches
6. peenetrates into snail
7. sporocyts in snail (2 gen)

They are not hemaphroditic

• form schistosome granuloma
  • trapped in wall of intestines, bladder, liver
  • this leads to inflammatory response
  • form granuloma

The pathology is from these trapped eggs.

• bloody diarrhea (blood vessels rupture)
• fibrosis, granulomas in intestines and liver

Stunts growth in children

1. penetrate skin
2. migrate to lungs, then to liver via blood stream
3. adults mate in liver
4. adults migrate to mesenterics
5. adults live in mesenteric venules
   • CNS damage
   • hepatosplenomegallly
   • Cor pulmonale
6. eggs enter small intestines
7. eggs lost via feces

• urinary granulomas
• hematuria
• obstructive uropathy
• renal failure
• squamous cell carcinoma of the bladder
• growth stunting

Mainly in Africa, Middle East

• mass tx of everyone
• age targeted mass treatment (school aged kids)
• selected age targeted mass tx- focus on individuals and community at great risk of disease
  • mass tx recommended by WHO where prevalance 50% or greater