Digenean Trematodes: Morphology, Life Cycles, and Schistosomiasis

What is the general morphology of Platyhelminthes?

Typically bilaterally symmetrical and lack a body cavity (acoelomates), with no skeletal, circulatory, or respiratory systems.

What type of nervous system do Platyhelminthes have?

A centralized nervous system consisting of a brain and a nerve cord, with light-sensitive eyespots.

Describe the digestive system of Platyhelminthes.

They have a two-way digestive system where food is ingested and waste is expelled through the pharynx.

What are flame cells?

Specialized excretory cells in Platyhelminthes that function like kidneys to remove waste materials.

What does it mean for Trematoda to be hermaphroditic?

They possess both male and female reproductive organs, structures, or tissues.

What are the two groups included in the subclass Digenea?

Digenea and Aspidobothrea.

What is the definitive host (DH) in the life cycle of Digenean trematodes?

A vertebrate where sexual reproduction of the parasite occurs.

What is the first intermediate host (1st IH) in the life cycle of Digenean trematodes?

A mollusk where the parasite reproduces asexually.

What are the three types of suckers found in Trematodes?

Monostome, Amphistome, and Distome.

What is the function of the tegument in Trematodes?

To protect the parasite, evade the host immune system, absorb nutrients, and control motility.

Describe the general life cycle stages of Trematodes.

Egg, Miracidium, Primary sporocyst, Redia, Cercaria, Metacercaria, Adult stage.

What is the primary host for Alaria americana?

Canids, which are found in the small intestines.

What disease is caused by Schistosoma?

Schistosomiasis, also known as bilharziasis or snail fever.

What are the three species of Schistosoma that infect humans?

S. mansoni, S. haematobium, and S. japonicum.

What is the role of the snail in the life cycle of Schistosoma?

It serves as the first intermediate host (1st IH) where the parasite undergoes asexual reproduction.

What are the phases of disease associated with Schistosoma infection?

Migration phase, Acute phase, and Chronic phase.

What is the treatment for Schistosomiasis?

Praziquantel, which disrupts the integrity of the tegument.

What is the significance of the gynaecophoric canal in Schistosoma?

It allows the female to be held in the male's canal for mating.

What is the primary reservoir host for Schistosoma?

Primates.

What is the common name for the condition caused by S. haematobium?

Urinary schistosomiasis.

What are pseudotubercles in the context of Schistosoma pathology?

They are formations resulting from chronic infection, causing complications like cirrhosis and ascites.

What is the role of population-based chemotherapy in controlling Schistosomiasis?

It involves drug administration to infected individuals to reduce the prevalence of the disease.

How does the cercaria of Schistosoma enter the human body?

By penetrating human skin after being released from the snail host.

What is the typical lifespan of adult Schistosoma in the human body?

20-30 years.

What type of immune response is associated with Schistosoma infections?

Concomitant immunity and immunopathology, leading to various complications.

What is the significance of the eggs of Schistosoma in diagnosis?

They can be found in feces or urine, indicating infection.

What is the ecological role of molluscicides in controlling Schistosomiasis?

They help reduce the population of snail hosts that transmit the disease.