Back to: MICROBIOLOGY 300 LEVEL
Welcome to class!
Hello, superstar! I’m thrilled to have you in class today. You’re doing so well on your learning journey, and I can’t wait to walk with you through another exciting topic in microbiology. Today, we’re talking about Trematodes, particularly Schistosoma and liver flukes. These flatworms may be tiny, but they cause some of the most significant parasitic diseases in Africa and other parts of the world. And guess what? You’ll understand them so well by the end of this class.
Trematodes: Schistosoma, Liver Flukes
Trematodes, also known as flukes, are flat, leaf-shaped parasitic worms. Unlike the roundworms and tapeworms we’ve discussed before, trematodes have suckers they use to attach to body tissues like the liver, intestines, and blood vessels.
These worms have complex life cycles that involve freshwater snails as intermediate hosts. The final host is usually a human or animal. Let’s now look at two important types: Schistosoma and liver flukes.
Schistosoma (Blood fluke)
This is the trematode responsible for schistosomiasis (bilharzia)—a major public health problem in Nigeria and other African countries.
The most common species affecting humans are Schistosoma haematobium, S. mansoni, and S. japonicum.
Infection occurs when a person wades or bathes in freshwater contaminated with free-swimming larvae released by snails.
These larvae, called cercariae, penetrate the skin and move into the blood vessels.
Symptoms:
At first, there may be itching or a rash at the entry site (called “swimmer’s itch”).
Later symptoms include blood in urine (especially in S. haematobium), abdominal pain, diarrhoea, and liver or spleen enlargement.
Long-term infection can lead to bladder damage, kidney failure, or liver disease.
It mostly affects people who have regular contact with rivers or lakes—like farmers, fishermen, and children who swim in open water.
Liver Flukes (Fasciola hepatica and others)
These trematodes mainly affect the liver and bile ducts.
Humans become infected by eating raw or undercooked aquatic plants, like waterleaf or watercress, that are contaminated with encysted larvae.
The larvae travel to the liver and mature into adult worms, causing fascioliasis.
Symptoms:
Fever, pain in the upper right abdomen, nausea, and tenderness over the liver.
In chronic cases, liver damage and bile duct inflammation can occur.
Imagine a child swimming in a river in a rural village in Osun State. The water looks clean, but small larvae from infected snails are hiding in it. The larvae enter the skin and travel silently in the blood. A few weeks later, the child starts passing red-coloured urine and feeling weak. That’s Schistosoma haematobium at work.
Now imagine someone eating a soup made with freshly harvested waterleaf from a stream without proper washing or cooking. The leaf may carry liver fluke larvae that end up in the bile ducts, slowly damaging the liver.
Summary
- Trematodes are flat, parasitic worms with suckers.
- Schistosoma causes schistosomiasis, spread through contact with contaminated freshwater.
- Liver flukes are caught by eating raw aquatic plants contaminated with larvae.
- Symptoms can affect the urinary system, liver, or intestines, depending on the species.
- Prevention includes avoiding freshwater swimming in endemic areas and ensuring aquatic plants are properly cooked.
Evaluation
- What type of worm is Schistosoma, and how is it transmitted?
- What symptoms are caused by S. haematobium?
- How do liver flukes enter the human body?
- Name two ways to prevent trematode infections.
- Which organ is mainly affected by liver flukes?
You’ve done something amazing today—learned how trematodes operate and how to protect yourself and others from them. Your knowledge is a gift to your community and your future as a health leader. Keep going strong, keep believing in your brilliance, and remember: Afrilearn is always with you. See you in the next exciting lesson!