Step-by-Step Guide to the Liver Fluke Life Cycle for Students
Numerous parasites that live in the human body can lead to a number of diseases, which may range from mild to very life-threatening. Liver fluke, scientifically known as Fasciola hepatica are parasites that can live in the liver of living beings and can lead to liver fluke disease. This condition is also called Fascioliasis.
What do We Understand by Liver Fluke?
These are parasites that can be present in the livers of most mammals and they can lead to liver fluke disease. The parasite falls into the phylum Platyhelminthes. They can cause the disease by entering the liver and the bile duct. These parasites are usually seen around watery areas since the environmental conditions are ripe for them to lay eggs.
What are the Various Life Stages for Liver Fluke?
The liver fluke parasite goes through certain life stages. It is important to know this to understand the stage at which the infection can occur.
Stage 1- The Egg
Immature eggs are laid by the parasites in the bile duct and they are excreted out with the waste produced. Once they come into contact with water, these eggs can hatch and form larvae, which is known as miracidia.
Stage 2- Intermediate Host
In this stage, the parasite first infects a host that it uses only as an intermediary to get to its final host. For example, it can infect a snail and grow into bigger larvae, and once this is done they abandon the host’s body and move around independently. These develop and become bigger and then they are ready to move on to bigger hosts such as animals and human beings.
Step 3- Young Fluke
After stage 2 the small intestine wall is penetrated by the fluke parasite and it enters into the peritoneal cavity. Next, it directly comes in contact with the liver and it begins feeding on liver cells. The above phenomenon happens a few days after the host comes in contact with the parasite. The young flukes enter into the bile duct and transform into adult liver flukes after eating numerous liver cells.
Stage 4- Adult
It takes approximately three months for the transformation of the metacercariae into the adult liver fluke. The approximate length of an adult liver fluke is around 3 cm. An adult female liver fluke can lay 20,000 to 25,000 eggs per day in her last stage of pregnancy.
What are the Symptoms of Liver Fluke Infection?
There are various symptoms of liver fluke disease which are:
Acute abdominal pain
Fever
Vomiting
Nausea
Diarrhea
Hives
Malaise
Apart from the above-mentioned symptoms, there may be some other rare complications associated with heavy liver fluke infections which include the formation of stone, recurrent infections of the biliary system, and cholangiocarcinoma (bile duct cancer).
What are the Treatment Options for Liver Fluke Infection?
Medication or Surgery:
Liver flukes can be cured completely with the help of medication. The most common medication to treat liver fluke is triclabendazole. Generally, the drug is given in one or two doses orally and most people soundly respond to this treatment. Sometimes doctors prescribe a short course of corticosteroids for severe phases with acute symptoms. In very rare cases surgery is required for related long-term complications such as cholangitis (infection of the bile duct).
Alternative Treatments:
There are some alternative and unusual therapies for parasite infection. It is recommended to take goldenseal for parasitic infections, parasite cleanses, and colonic irrigation.
How to Get Relief from Liver Fluke Symptoms?
Acetaminophen (Tylenol) can be taken to get relief from abdominal pain and to reduce fever. Nausea and vomiting can be reduced by anti-nausea medications. But the root of the disease cannot be treated by these medications. Hence, diagnosing the liver fluke infection and commencing the treatment as early as possible is always suggested.
Are there Risk Factors for Liver Fluke Disease?
Yes, certain parts of the world see a greater occurrence of this disease compared to others. Usually, unsanitary and unhygienic conditions can cause this problem. While it may not be directly a communicable disease, family members of the patient can also get affected.
How is this Disease Diagnosed?
A stool sample is taken and eggs can be identified from that. This would mean that the parasite has moved to the bile duct. The enzyme-linked immunosorbent assay (ELISA) test can diagnose this disease very accurately.
Prevention:
For every disease, it is universally true that ‘prevention is better than cure. Everyone must be aware of the fact that liver fluke infection can easily be cured. The most effective and proper way to prevent a liver fluke infection is to ensure that freshwater fish and watercress are properly cooked before consuming them. People must avoid food and water that could potentially be contaminated with the parasites while traveling to areas with the least sanitation.
Presently there is no vaccine available to prevent liver fluke infections. Liver flukes are initially big, flat parasitic worms that are found in the liver, resulting in a disease known as fascioliasis. The parasites are mostly found in parts of Australia and the regions with several water bodies such as irrigation channels, slow-streaming rivers, and so on. It is quite a natural infection and can be cured completely with the help of medications. Generally, complications don’t arise due to liver fluke infection.
FAQs on Liver Fluke Life Cycle: Stages, Diagram & Explanation
1. What is a liver fluke and how is it classified in the animal kingdom?
A liver fluke is a parasitic flatworm that primarily infects the liver and bile ducts of mammals. The most common species studied is Fasciola hepatica. Its scientific classification places it in the Kingdom Animalia, Phylum Platyhelminthes (flatworms), and Class Trematoda. These parasites are known for their complex, digenetic life cycles, which require more than one host to complete.
2. What are the primary and intermediate hosts in the liver fluke's life cycle?
The liver fluke's life cycle involves two essential hosts:
- Primary Host (Definitive Host): This is where the adult fluke lives and reproduces sexually. The primary hosts are typically herbivorous mammals like sheep, cattle, and goats. Humans can also serve as accidental primary hosts.
- Intermediate Host: This is where the parasite's larval stages develop and multiply asexually. For Fasciola hepatica, the intermediate host is a specific type of freshwater snail (e.g., from the family Lymnaeidae).
3. What are the main stages in the life cycle of the liver fluke?
The life cycle of the liver fluke, Fasciola hepatica, progresses through several distinct stages:
1. Egg: Adult flukes in the host's bile duct release eggs, which are excreted in the faeces.
2. Miracidium: In water, the eggs hatch into a free-swimming larva called the miracidium, which must find and penetrate a snail host.
3. Development in Snail: Inside the snail, the miracidium transforms into a sporocyst, then rediae, and finally cercariae, multiplying asexually at each step.
4. Cercaria: This motile larva leaves the snail and swims in the water.
5. Metacercaria: The cercaria attaches to aquatic vegetation, like watercress, and becomes an infective cyst called a metacercaria.
6. Infection of Primary Host: A mammal ingests the metacercaria by eating the contaminated plant. The cyst hatches in the intestine, and the young fluke migrates to the liver to mature.
4. How do humans get infected with liver fluke, and is the disease contagious?
Humans become infected by consuming the metacercariae stage of the parasite. This typically happens by eating raw or improperly cooked aquatic plants, such as watercress, that are contaminated with these cysts. Drinking contaminated water can also be a source of infection. The resulting disease, known as fasciolosis, is not contagious and cannot be transmitted directly from one person to another through contact.
5. What is the difference between the various larval stages of the liver fluke?
The liver fluke has several distinct larval stages, each with a specific form and function:
- Miracidium: A tiny, ciliated, free-swimming larva that hatches from the egg. Its only job is to locate and infect the snail host.
- Sporocyst: A simple, sac-like structure that develops inside the snail. It lacks a digestive system and reproduces asexually to create rediae.
- Redia: A more complex larva with a pharynx and gut. It also reproduces asexually inside the snail, producing either more rediae or the next stage, cercariae.
- Cercaria: A motile larva with a large body and a tail for swimming. It exits the snail to find aquatic vegetation.
- Metacercaria: A non-motile, dormant cyst formed by the cercaria on a plant. This is the infective stage for the primary host.
6. Why does the liver fluke require two hosts to complete its life cycle?
The two-host (digenetic) life cycle is a highly effective evolutionary strategy for survival and dispersal.
- The intermediate host (snail) acts as a safe environment for asexual multiplication. A single miracidium can produce thousands of infective cercariae, massively amplifying the parasite's numbers.
- The primary host (mammal) is where sexual reproduction occurs. This introduces genetic variation into the parasite population, which is crucial for adaptation. This strategy allows the parasite to bridge the gap between an aquatic larval environment and a terrestrial adult environment.
7. What are some key parasitic adaptations that help the liver fluke survive inside its host?
The liver fluke possesses several important adaptations for its parasitic mode of life:
- Protective Tegument: A thick outer body covering that protects it from the host's digestive juices and immune responses.
- Attachment Organs: It has powerful oral and ventral suckers that allow it to anchor itself firmly within the host's bile ducts.
- Anaerobic Respiration: The ability to respire without oxygen, which is essential for survival in the low-oxygen environment of the liver and bile ducts.
- High Fecundity: Adult flukes are hermaphroditic and produce an enormous number of eggs (up to 25,000 per day), increasing the probability that some offspring will successfully infect a new host.
8. What is fasciolosis and what are its main symptoms?
Fasciolosis is the disease caused by infection with the liver fluke, Fasciola hepatica. The symptoms vary based on the phase of infection:
- Acute Phase: This phase occurs as the immature flukes migrate through the liver tissue. It can cause fever, pain in the upper right abdomen, nausea, and an enlarged, tender liver.
- Chronic Phase: This phase begins when the adult flukes are established in the bile ducts. Symptoms can be milder and may include intermittent pain, jaundice, inflammation of the gallbladder, and blockage of the bile ducts, which can lead to serious liver damage over time if left untreated.
