Liver Flukes

Question 1

Diphyllobothrium latum

Answer 1

Liver flukes
-CESTODE = TAPEWORM (largest!)
•Flat, segmented (proglotid-filled w/ eggs–>gravid proglottids)
•Head = scolex → attachment via suckers or hooks
•No digestive system
•Hermaphrodites
** Tropism = small intestines
Hosts
•freshwater crustacean (1st intermediate host-completes life cycle)
•Fish that eats crustacean (2nd intermediate host-completes life cycle)
•Fish-eating mammal (definitive host-where sexual reproduction occurs)
Sx & diagnosis
•Injury = steal nutrients, excrete waste, mechanical blockage of lg intestine, discharge fertilized eggs (proglotids) in feces
•Infective stage: larvae on fish
•*Diagnostic stage: eggs in feces

Question 2

Enterobius vermicularis

Answer 2

Liver flukes
•Nematodes=roundworms
•"pinworm"
•Nonsegmented, tapered at both ends
•complete digestive system
•separate sexes
•causes *enterobiasis
•Infx more frequent in school-age or preschool-age and in crowded conditions
•More common in temperate than tropical countries
•Most common helminth infx in US
•*tropism fro mouth, colon, anus
Hosts
•Humans (intermediate and definitive host)
Sx
•Most common symptom *anal pruritus
Dx
•I.D. eggs in perianal area, *scotch tape test
•*Infective stage: eggs
•*Diagnostic stage: eggs

Question 3

Opisthorchis (clonorchis) sinensis

Answer 3

Liver flukes
•Trematodes = flukes
•Unsegmented, leaf shape
•2 suckers for attachment
•Hermaphrodites
-class 1 carcinogen
•endemic in Asia
•eggs have *operculum=hatch
•transmission occurs by ingestion of *metacercariae in fish
** Tropism = liver, bile duct (occasionally gb, pancreatic duct)
Hosts
-freshwater snail (1st intermediate host)
-fish (2nd intermediate host)
-carnivores (definitive host)
SX
•Many = asymptomatic
•Compromise fx important organs by obstruction, secondary bacterial infection, and carcinomatous changes
•Abdominal pain & nausea
•Jaundice in severe infections
•*cholangocarcinoma
•*Inf. stage: metacercaria in fish
•*Diagnostic stage: eggs in feces
TX
•Praziquantel / albendazole
Prevention
•Completely cook fish
•Freeze for 7 das
•Control of sewage and waste