30 Questions
What is the life cycle of Alaria Americana (trematode in the family Diplostomatidae) involving the penetration of the 2nd intermediate host?
Penetrate the tadpoles and become infective mesocercariae.
Where do Alaria americana trematodes primarily live in carnivorous mammals?
Small intestines
What is the mode of infection for Fasciola hepatica in ruminants?
Consumes metacercaria in the environment
Which organ is affected by Fasciola hepatica, leading to a 'pipestem' appearance in chronic infections?
Liver
What is a common clinical sign associated with Fasciola hepatica infections in ruminants?
Anemia
Where do trematodes reside as adults, depending on the species?
All the above
What is the final and definitive host in the life cycle of trematodes?
Birds and mammals
In the life cycle of trematodes, what is the name of the stage that appears as a skin rash due to an allergic reaction in humans?
Cercaria
Which stage of trematodes' life cycle involves encystment in the environment or in a 2nd intermediate host?
Metacercaria
What is the name of the trematode genus commonly known as blood flukes?
Schistosoma
Which host might consume the metacercaria in the life cycle of trematodes?
Fish
Which of the following is a characteristic of trematodes (flukes)?
They are dorso-ventrally flattened with oral and ventral suckers
What is the primary clinical sign associated with chronic Fasciola hepatica infection?
Bottle jaw
What is the intermediate host for the life cycle of Fasciola hepatica?
Freshwater snail
Which of the following can be a definitive host for the trematode Alaria americana?
All the above
What is the main site of infection for the adult stage of Fasciola hepatica?
Bile ducts
Which of the following is a characteristic of trematodes (flukes)?
They are hermaphroditic but can cross reproduce
Which of the following is a definitive host for the trematode Alaria americana?
Mammal
What is the main route of migration for the larval stages of Fasciola hepatica?
They burrow through the intestinal lining and migrate to the liver
What is the final host for the liver fluke Fasciola hepatica?
Sheep and cattle
What is the role of the miracidium stage in the life cycle of trematodes?
It penetrates and infects the snail intermediate host
Which of the following is a characteristic feature of trematode eggs?
They have an operculum or lid-like structure
Which trematode species has been reported to have a high prevalence in domestic cats and dogs in Ecuador?
Amphimerus sp.
What is the term often used to describe the adult stage of trematodes?
Digenean
Which Class to flukes belong to?
Trematoda
What is the subclass of trematodes consisting of parasitic flatworms?
Digenea
How many suckers do adult digenean flukes typically have?
Two (one ventral and one oral)
Which group is the sister group to Digenea according to the text?
Aspidogastrea
How many species of Aspidogastrea have been described to date?
~80 species
Where are adult Digenea particularly common?
Digestive tract
Study Notes
Characteristics of Trematodes (Flukes)
- Dorso-ventrally flattened, leaf-like body shape
- Oral and ventral suckers for attachment and feeding
- Hermaphroditic but can cross-reproduce
- Large operculate eggs, diagnosis in sedimentation
Life Cycle of Trematodes
- 'Complex' life cycle with multiple hosts
- Adult: final and definitive host
- Egg: environment – miracidium
- Rediae: Intermediate host (snail)
- Cercaria: into environment again
- Metacercaria: 2nd IH; PH; or environment
- Young adult to adult: final and definitive host
- Final host consumes metacercaria in the 2nd IH or PH or in the environment
Fasciola hepatica (Liver Fluke/ Sheep Liver Fluke)
- Parasitic trematode of the class Trematoda, Phylum Platyhelminthes
- Infects the livers of various mammals, including humans
- Final host: ruminant
- Mode of infection: consumes metacercaria in the environment
- Location: liver, bile ducts
- Pathology: "pipestem" liver with chronic infection
- Clinical signs: anemia, bottle jaw
- Diagnosis: clinical signs + egg in feces (sedimentation) or fecal antigen test
- Intermediate host: snail
Other Facts about Trematodes
- Some species are found in water-associated birds, and ballyhoo are often found swimming very near the water surface
- Can infect carnivorous mammals, living in their small intestines as mature worms
- Some species have economic importance, but the group is of great interest to biologists due to their archaic characteristics
- Can cause swimmer's itch, also called cercarial dermatitis, which appears as a skin rash caused by an allergic reaction to certain parasites that infect some birds and mammals
Explore the parasitic relationships involving digeneans, trematodes, and their hosts, such as water-associated birds, tadpoles, frogs, snakes, and dogs. Learn about the life cycle of flukes like Cercaria and mesocercariae infecting different hosts.
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