Schistosoma | Schistosomiasis | Blood Flukes | Schistosoma mansoni, haematobium & japonicum

Summary

This educational video explores Schistosoma, also known as blood flukes, which cause schistosomiasis. It covers the three main species—S. mansoni, S. japonicum, and S. haematobium—detailing their morphology, life cycle, transmission, and clinical impact. The video explains how humans become infected through skin penetration by cercariae, the role of freshwater snails as intermediate hosts, and how adult flukes reside in veins to lay eggs that cause granulomas and tissue damage. It also discusses epidemiology, acute and chronic symptoms, laboratory diagnosis, treatment with praziquantel, and preventive measures such as sanitation and snail control, offering a comprehensive overview of this parasitic infection.

Takeaways

• 😀 Chistosoma is a parasitic blood fluke responsible for causing schistosomiasis, existing as separate male and female organisms that live attached to each other.
• 😀 Schistosoma species are classified based on infection site: gastrointestinal (C. mansoni, C. japonicum) and urinary tract (C. haematobium).
• 😀 The life cycle of Schistosoma includes eggs, larval stages (miracidium, sporocyst, cercaria), and adult flukes.
• 😀 Morphological differences among species include egg shape and spine location: C. mansoni has a lateral spine, C. japonicum has a small lateral spine, and C. haematobium has a terminal spine.
• 😀 Humans are the definitive hosts while freshwater snails act as intermediate hosts for different Schistosoma species.
• 😀 Transmission occurs when free-swimming cercariae penetrate human skin, entering the bloodstream and maturing into adult flukes in veins of the liver, intestines, or bladder.
• 😀 Most pathologic effects are caused by eggs, inducing granulomas and fibrosis in target organs, potentially leading to portal hypertension, splenomegaly, gastrointestinal hemorrhage, or bladder carcinoma.
• 😀 Acute infection symptoms include itching, dermatitis, fever, chills, diarrhea, hepatosplenomegaly, and eosinophilia, while chronic infection can lead to severe organ damage.
• 😀 Diagnosis relies on microscopic identification of eggs in urine or stool; liver function tests are usually normal and eosinophilia may be present.
• 😀 Praziquantel is the treatment of choice for all Schistosoma species, while prevention involves proper sanitation, snail eradication, and avoiding swimming in endemic waters.
• 😀 Schistosoma can evade host immune defenses by coating themselves with host antigens, making immune recognition difficult.
• 😀 Epidemiologically, over 150 million people are affected worldwide, with species distribution varying by region: C. mansoni in Africa and Latin America, C. haematobium in Africa and the Middle East, and C. japonicum in Asia.

Q & A

What organism is responsible for causing schistosomiasis?

Schistosomiasis is caused by blood flukes of the genus Schistosoma, which exist as separate male and female worms.

Which species of Schistosoma infect the gastrointestinal tract and which infect the urinary tract?

Schistosoma mansoni and Schistosoma japonicum primarily infect the gastrointestinal tract, while Schistosoma haematobium infects the urinary tract.

How can the eggs of different Schistosoma species be distinguished under a microscope?

S. mansoni eggs have a large lateral spine, S. japonicum eggs have a small lateral spine, and S. haematobium eggs have a terminal spine.

What are the main stages in the life cycle of Schistosoma?

The life cycle includes egg, miracidium, sporocyst, cercaria, and adult fluke stages. Cercariae infect humans through skin penetration.

What is the role of freshwater snails in the life cycle of Schistosoma?

Freshwater snails act as intermediate hosts where miracidia develop into sporocysts and cercariae, which are then released into water to infect humans.

What clinical symptoms are seen during the acute stage of schistosomiasis?

Acute schistosomiasis presents with itching, dermatitis, fever, chills, diarrhea, lymphadenopathy, hepatosplenomegaly, and eosinophilia.

What are the long-term complications of chronic Schistosoma infection?

Chronic infections can cause gastrointestinal hemorrhage, hepatomegaly, splenomegaly, esophageal varices, hematuria, urinary tract infections, and bladder carcinoma depending on the species.

How do Schistosoma parasites evade the host immune system?

Schistosomes evade host defenses by coating themselves with host antigens, which reduces recognition by the immune system.

What is the treatment of choice for Schistosoma infections?

Praziquantel is the treatment of choice for all Schistosoma species, although acute infections may resolve spontaneously.

What preventive measures can reduce the risk of schistosomiasis?

Preventive measures include proper disposal of human waste, eradication of snail hosts, and avoiding swimming in endemic freshwater areas.

Which human organs are primarily affected by Schistosoma species?

S. mansoni and S. japonicum mainly affect mesenteric veins of the intestines and liver, while S. haematobium affects veins of the bladder.

What laboratory findings can help diagnose schistosomiasis?

Diagnosis relies on detecting characteristic eggs in stool or urine; blood tests may show moderate eosinophilia, while liver function tests are usually normal.