Parasitology Exam 2: Trematodes Flashcards
What is another name for trematodes?
Flukes
Describe trematodes as a whole.
Platyhelminth (flatworm)
Dorsoventrally flattened
Most are hermaphroditic
Transmitted by ingestion of metacercariae (tailless encysted larvae)
List in order, the 4 stages that most trematodes go through in their life cycle.
Egg –> miracidium (free swimming larva) –> redia (cylindrical larvae) –> cercariae (tailed larva) –> metacercariae (tailless larva)
Name the intestinal trematodes:
F. buski
H. heterophyes
M. yokogawai
Name the liver trematodes:
C. sinensis
F. hepatica
Name the blood/body fluid trematodes:
S. haematobium
S. japonicum
S. mansoni
Name the lung trematode:
P. westermani
Which eggs are indistinguishable from F. buski?
F. hepatica
What are the reservoir and definitive hosts of F. buski?
Reservoir: pigs, dogs, rabbits
Definitive host: pigs and humans
How is F. buski transmitted?
Ingestion of raw water chestnuts or caltrop contaminated with infected feces
What is the infective/diagnostic stage of F. buski?
Infective: ingestion of metacercariae on water chestnuts/plant
Diagnostic: eggs in feces
How is H. heterophyes transmitted?
Ingestion of raw, pickled, or inadequately cooked fish
What is the diagnostic/infective stage of H. heterophyes?
Infective: ingestion of metacercariae in undercooked fish
Diagnostic: eggs in stool
Which eggs are H. heterophyes’ eggs indistinguishable from?
M. yokogawai
What is the smallest human fluke?
M. yokogawai
What is the most common intestinal fluke infection in the far east?
M. yokogawai
How is M. yokogawai transmitted?
Ingestion of raw/undercooked fish
What is the intermediate hosts of M. yokogawai and H. heterophyes?
snails and freshwater fish
In which form are intestinal flukes accidentally ingested by humans?
Metacercariae
Which is the chinese liver fluke? Which is the sheep liver fluke?
C. sinensis = chinese liver fluke
F. hepatica = sheep liver fluke
Where do adult liver flukes live?
Biliary ducts
How to prevent liver fluke infections?
Ensure that fish and aquatic vegetation are properly cooked
What is the definitive and intermediate hosts of C. sinensis?
Definitive: humans
Intermediate: snails/fish
Describe the life cycle of C. sinensis.
- eggs ingested by snail
- cercariae leave snail and enter water
- cercariae penetrate fish
- metacercariae develop in fish
- undercooked fish consumed
- metacercariae encyst in the duodenum and travel to bile duct to mature into adults
What is notable about C. sinensis eggs?
HEAVILY shouldered operculum with a small knob at the end opposite of the operculum
Lab ID of C. sinensis
Eggs in feces
Describe the life cycle of F. hepatica
Miracidia invade a snail intermediate host
Metacercariae on aquatic vegetation
Humans ingest raw water chestnuts
Metacercariae encyst in duodenum and into the peritoneal cavity
Lab ID of F. hepatica
Eggs in feces
What is special about F. hepatica eggs?
Operculated
Indistinguishable from F. buski eggs
Not as heavily operculated as C. sinensis
Transmission of P. westermani?
Ingestion of uncooked crabs, crayfish, freshwater shrimp, mussels
Describe the life cycle of P. westermani
Adult worms encapsulated in the lungs produce eggs
Eggs coughed up and swallowed
Excreted in feces
Enter snail host
Enter crab/crayfish
Raw or undercooked crab/crayfish consumed
Lab ID of P. westermani
ID of eggs in stool or sputum
What is notable about eggs of P. westermani?
Operculated with shoulders
Thick-shelled on the end opposite of the operculum
What are Charcot-Leyden crystals?
Slender, pointed crystals made of an eosinophil protein that may be seen in sputum or lung tissue specimens of patients w/ parasitic infections
Associated with P. westermani
What is different about the blood/body fluid flukes from other flukes?
Adult schistosomes are NOT flattened
Separate male and female worms present (NOT hermaphroditic)
What organisms cause the disease schistosomiasis/bilharziasis/snail fever?
Schistosoma spp.
How are Schistosoma spp. transmitted?
Fecal/urine contamination of small bodies of water that favor the growth of snail hosts
What is different about the life cycle of Schistosoma from other flukes?
No encysted stage
Infective stage is cercaria
Which Schistosoma spp. causes urinary schistosomiasis?
S. haematobium
Which Schistosoma spp. causes hepatointestinal disease (enlarged spleen and liver)?
S. japonicum
Lab ID of Schistosoma spp.
ID of eggs in feces (S. japonicum/S. mansoni)
ID of eggs in urine (S. haematobium)
Differentiate the eggs between the Schistosoma spp.
S. haematobium egg: found in urine, terminal spine
S. japonicum egg: found in stool, with a small inconspicuous lateral spine
S. mansoni egg: LARGE lateral spine, found in stool
