Development Stages Of The Hepatic Fluke

2024 Author: Josephine Shorter | [email protected]. Last modified: 2023-12-16 21:43

Development stages of the hepatic fluke

Hepatic fluke is a parasitic worm that lives in humans or animals, affecting the liver and bile ducts. The liver fluke is widespread throughout the world and causes a disease called fascioliasis. Most often, the worm parasitizes in the body of cattle and small-horned livestock, although massive and sporadic outbreaks of invasion among humans are known. Actual incidence data varies widely. According to various sources, the total number of people infected with fascioliasis ranges from 2.5-17 million people worldwide. In Russia, the liver fluke is widespread among animals, especially in those areas where there are swampy pastures. The parasite is rare in humans.

The hepatic fluke is a trematode with a flat, leaf-shaped body; two suckers are located on its head. It is with the help of these suckers that the parasite is kept in the body of its permanent host. An adult worm can be up to 30 mm long and 12 mm wide. The developmental stages of the hepatic fluke are as follows:

Content:

• Marita stage of the liver fluke
• Larval stage of hepatic fluke - miracidium
• Hepatic fluke sporocyst stage
• Liver fluke larva - redia
• Circaria stage of the hepatic fluke
• Stage of adolescaria (metacercaria) of the hepatic fluke

Marita stage of the liver fluke

Marita is the mature stage of the worm, when the parasite has the ability to release eggs into the external environment. The worm is hermaphrodite. The body of the marita is shaped like a flattened leaf. The sucker mouth is at the front end of the body. There is another sucker on the abdominal part of the worm's body. With its help, the parasite is attached to the internal organs of the host. Marita reproduces eggs on her own, as she is a hermaphrodite. These eggs come out in the faeces. In order for the egg to continue its development and pass into the larval stage, it needs to get into the water.

Larval stage of hepatic fluke - miracidium

Miracidium comes out of the egg. The larva has an oval oblong shape, its body is covered with cilia. On the front of the miracidium are two eyes and excretory organs. The posterior end of the body is retracted under the germ cells, which will further allow the parasite to multiply. With the help of cilia, miracidia are able to actively move in water and look for an intermediate host (freshwater mollusk). After the mollusk is found, the larva will invade its body.

Hepatic fluke sporocyst stage

Once in the body of the mollusk, miracidium passes into the next stage - the saccular sporocyst. Inside the sporocyst, new larvae begin to mature from germ cells. This stage of the liver fluke is called redia.

Liver fluke larva - redia

At this time, the body of the parasite lengthens, a pharynx appears, the intestines, excretory and nervous systems are born. Each sporocyst of the hepatic fluke can contain from 8 to 100 redia, depending on the specific type of parasite. When redia ripens, they emerge from the sporocyst and penetrate the tissues of the mollusc. Inside each redia there are germ cells that allow the liver fluke to move to the next stage.

Circaria stage of the hepatic fluke

At this time, the liver fluke larva acquires a tail and two suckers. In cercariae, the excretory system has already been formed and the rudiments of the reproductive system appear. The cercarium leaves the redia shell, and then the body of the intermediate host, perforating it. For this she has a sharp stylet or a bunch of spines. In this state, the larva can move freely in the water. It attaches itself to an object and remains on it, waiting for a permanent owner. Most often, aquatic plants become such objects.

Stage of adolescaria (metacercaria) of the hepatic fluke

This is the final larval stage of the hepatic fluke. In this form, the parasite is ready to penetrate the body of an animal or human. Inside the organism of a permanent host, the metacercariae turns into marita.

The life cycle of the liver fluke is quite complex, so most of the larvae die without turning into a sexually mature individual. The parasite's life can be interrupted at the egg stage if it does not get into the water or does not find the desired type of mollusc. However, the worms did not become extinct and continue to reproduce, which is explained by compensatory mechanisms. First, they have a very well-developed reproductive system. An adult marita is capable of producing tens of thousands of eggs. Second, each sporocyst contains up to 100 redia, and each redia can reproduce more than 20 cercariae. As a result, from one parasite, up to 200 thousand new liver flukes can appear.

Animals become infected most often when eating grass from flooded meadows, or while drinking water from open stagnant reservoirs. A person will be infected only if he swallows a larva in the adolescaria stage. Other stages of the hepatic fluke are not dangerous for him. In order to prevent the possibility of infection, you should thoroughly wash vegetables and fruits that are eaten raw, and also do not drink water that has not undergone the necessary processing.

Once in the human or animal organism, adolescaria penetrates the liver and bile ducts, attaches there and begins to reproduce offspring. With their suckers and spines, parasites destroy the liver tissue, which leads to its increase in size, to the appearance of tubercles. This, in turn, contributes to the formation of cirrhosis. If the bile ducts are blocked, then the person develops jaundice.

Author of the article: Danilova Tatyana Vyacheslavovna | Infectionist

Education: in 2008 received a diploma in the specialty "General Medicine (General Medicine)" at the Russian Research Medical University named after NI Pirogov. Immediately passed an internship and received a diploma of a therapist.