Schistosoma

Definition

Schistosoma is a genus of parasitic flatworms, also known as blood flukes, that cause the tropical disease schistosomiasis. These trematode worms are responsible for significant morbidity and mortality in many parts of the world, particularly in developing countries.

5 Must Know Facts For Your Next Test

1. Schistosoma worms have a complex life cycle that involves both freshwater snails and human or animal hosts.
2. Infection occurs when people come into contact with water contaminated by Schistosoma cercariae, which can penetrate the skin.
3. The adult Schistosoma worms reside in the blood vessels, where they lay eggs that can become lodged in various organs, causing inflammation and tissue damage.
4. Chronic schistosomiasis can lead to severe complications, such as liver and spleen enlargement, bladder and intestinal lesions, and even bladder cancer.
5. Praziquantel is the primary drug used to treat schistosomiasis, targeting the adult Schistosoma worms and reducing the burden of infection.

Review Questions

• Describe the life cycle of Schistosoma and how it leads to human infection.
  • The Schistosoma life cycle involves an aquatic snail host and a human or animal host. The adult worms lay eggs that are released into the environment through urine or feces. These eggs hatch into free-swimming larvae called cercariae, which can penetrate human skin upon contact with contaminated water. The cercariae then develop into adult worms that reside in the blood vessels, where they continue the cycle by laying more eggs, leading to the chronic health issues associated with schistosomiasis.
• Explain the pathological effects of Schistosoma infection and the major complications of schistosomiasis.
  • Schistosoma infection can lead to significant tissue damage and organ dysfunction due to the adult worms' residence in the blood vessels and the immune system's response to the eggs. The eggs can become lodged in various organs, such as the liver, spleen, bladder, and intestines, causing inflammation, fibrosis, and granuloma formation. This can result in complications like liver and spleen enlargement, bladder and intestinal lesions, and an increased risk of bladder cancer. The chronic nature of schistosomiasis and the cumulative damage caused by the parasite contribute to the significant morbidity and mortality associated with this disease.
• Discuss the role of praziquantel in the treatment of schistosomiasis and how it relates to the Schistosoma life cycle and pathogenesis.
  • Praziquantel is the primary drug used to treat schistosomiasis, as it is effective against the adult Schistosoma worms. By targeting the adult parasites, praziquantel helps to reduce the burden of infection and the associated pathological effects. This is particularly important because the adult worms are responsible for the continuous production of eggs, which are the primary drivers of the chronic health issues seen in schistosomiasis. By disrupting the Schistosoma life cycle and decreasing the number of adult worms, praziquantel can help to alleviate the tissue damage and organ dysfunction caused by the parasite's presence and the immune system's response to the eggs.

Related terms

Schistosomiasis: A disease caused by parasitic Schistosoma worms, which is prevalent in tropical and subtropical regions and can lead to chronic, debilitating health issues.

Trematoda: The class of parasitic flatworms that includes the Schistosoma genus, characterized by a complex life cycle involving both aquatic snail and human or animal hosts.

Cercariae: The free-swimming larval stage of Schistosoma worms that can penetrate human skin and develop into the adult parasites.