Table of contents:
- Fluke class
- What is a liver fluke
- Development cycle of the hepatic fluke
- Liver fluke life cycle
- Internal structure of the hepatic fluke
- Hepatic fluke intermediate host
- Liver fluke Miracidium
- Diagnostics of the hepatic fluke
- Ways of infection by the hepatic fluke
- Hepatic fluke - affected human organs
- Prevention of hepatic fluke
Video: Hepatic Fluke: Signs, Symptoms, And Treatments
The liver fluke is one of the most well-known parasites. Another name for this parasite is cat fluke. The hepatic fluke has a complex life cycle and is characterized by frequent host changes. Fluke can parasitize not only in human organs, but also in fish and herbivores, which act as a secondary host. The fluke class includes about 4,000 species that parasitize the internal organs of humans and various animals.
The content of the article:
- 1 Class flukes
- 2 What is a liver fluke
- 3 Development cycle of the hepatic fluke
- 4 Life cycle of the liver fluke
- 5 Internal structure of the hepatic fluke
- 6 Intermediate host of hepatic fluke
- 7 Hepatic Fluke Miracidium
- 8 Diagnosis of hepatic fluke
- 9 Ways of hepatic fluke infection
- 10 Liver fluke - affected human organs
- 11 Prevention of hepatic fluke
A representative of the class is the hepatic fluke living in the liver of cattle. It has oral and abdominal suction cups. With their help, the worm is kept inside the host's liver. The fluke feeds on blood, sucking it through an oral suction cup.
Once in the water, microscopic larvae with cilia develop from the eggs. They penetrate into the body of a small pond snail, in which they grow, reproduce, and tail larvae appear.
Hepatic fluke. Living in the liver leads to the destruction of the walls of the bile ducts, sometimes parasites clog them. In addition, metabolic products of the parasite have a harmful effect on the host organism, in which the fluke lives. The life cycle of the parasite is very complex. Fertilized eggs are released through the intestines of the host to the outside.
These larvae leave the mollusk, actively swim in the water, then attach to plants, discard their tail, become covered with a thick shell - a cyst is formed. With grass or water, the cyst enters the intestines of the cow, where an adult worm develops from it. A person can become infected with liver flukes if they drink water from a dirty reservoir.
Another parasite that can infect humans and mammals (dogs, cats, wolves, etc.) is the feline fluke.
Unlike the hepatic fluke, its life cycle takes place with the participation of two intermediate hosts: the freshwater gastropod mollusk - bitinia - and freshwater cyprinids. A person or animal becomes infected with a feline fluke when they eat raw, insufficiently salted or boiled (fried) fish.
What is a liver fluke
A dangerous parasite that affects the liver and causes fascioliasis is the hepatic fluke. Consider its life cycle, ways of infection and methods of destruction.
Helminth is a parasitic form of flukes that live in the organs of vertebrates (animals, humans) and invertebrates. Another name for the parasite is the cat fluke, since the cat is the most suitable host for the worm.
The adult infects humans and cattle.
The fluke has a leaf-shaped body and reaches a size of 3-5 cm. It can get into the organs of herbivores and fish, which act as a secondary host.
The main characteristics of the parasite:
- there is a special cover on the body that protects it from being digested by the host's juices;
- many attachment organs: hooks, suction cups and others;
- simple structure of the digestive system;
- high fertility and asexual reproduction;
- regressive development of the sense organs and the nervous system.
The parasite is characterized by a complex life cycle with transformations and frequent changes of hosts. This leads to its resettlement and protects the main carrier from excessive overpopulation and death. Most often, human infection occurs when drinking unboiled or untreated water.
Development cycle of the hepatic fluke
In the course of their existence, these helminths go through several stages.
The stages of development of the hepatic fluke have a certain sequence:
- the first larval stage is miracidium, which emerges from the egg and floats in the water until it penetrates the body of the mollusk;
- after this introduction, a sporocyst is formed, which begins to multiply by parthenogenesis;
- the further stage of the life cycle of the larvae of these helminths is redia, in the structure of which there are already rudiments of organ systems. Also in their body there are germ cells, from which a new larval form - cercariae - is parthenogenetically derived;
- a feature of the structure of the cercaria is the presence of a brain, an eye and a powerful tail, which gives it freedom of movement. At this stage, the larva emerges from the mollusk, trying to get out of the water faster;
- Cercaria on land transforms into a cyst, losing its tail, and attaches to coastal plants. This stage is called adolescaria. So the fluke can stay for a very long time until it enters the body of a person or an animal that feeds on grass;
- after the successful introduction of the larva into the host's body, it transforms into a sexually mature individual - marita. At this stage, eggs are laid by the trematode (thousands of eggs per day!), Then they are excreted together with feces into the external environment. If they get into the water, the helminth development cycle repeats.
Liver fluke life cycle
Fasciola is characterized by frequent transformations and host changes. The life cycle of the hepatic fluke is represented by the following chain: final host; egg; miracidium; intermediate host (pond snail mollusk); sporocyst; maternal redia; daughter redia (cysts); cercarium; adolescarium; adolescaria in the external environment.
The hepatic fluke begins to develop from the egg, from which the miracidium emerges. The larva has a nerve ganglion, excretory organs, and a light-sensitive ocellus. In the back are the germ cells. The front of the body has a gland that produces an enzyme that dissolves living tissue and penetrates the intermediate carrier.
Hepatic fluke. The parasite is covered with cilia and actively moves in the aquatic environment. It feeds on substances accumulated in the egg. At the next stage of its life cycle, the hepatic fluke transforms into a sporocyst. This larva looks like a shapeless sac without organs, excretory and nervous systems.
At this stage, reproduction occurs without fertilization with the help of germ cells. The sporocyst bursts and redia emerge from it, which parasitize in the same carrier. Redia have a number of formed organs: mouth, digestive tube and pharynx, opening for eggs.
Each cyst contains germ cells, from which the next larval generation is formed - cercariae. The cercarium has suction cups, intestines, excretory and nervous systems. The larva has a long, muscular tail. Cercarium emerges from the mollusk and moves in water.
Free-floating cercariae are attached to the stems of plants and objects in the water, becoming covered with a shell. This stage is called adolescaria. The future fluke has a spherical shape.
If the larva is swallowed by an animal from among the final hosts, then the fasciola membrane dissolves in the intestines of the host and the helminth enters the liver, where it develops to a sexually mature state. The invasion of animals occurs when eating grass in flooded meadows and when drinking water from contaminated water bodies. People are infected through contaminated vegetables.
Internal structure of the hepatic fluke
The human causative agent of fasciola can be both fasciola vulgaris and giant. Both have a specific and almost identical structure and functioning, which is due to their parasitic lifestyle. Consider the internal structure of the hepatic fluke.
The parasite has a leaf-shaped body, 2-7 cm in size and grayish-yellow in color. It lives in the bile ducts, liver and pancreas of vertebrates. With the help of the oral and abdominal suction cups, it is attached and held on the walls of the ducts.
Fluke is characterized by simplification and specialization in the structure of some organs. This is due to her parasitic lifestyle.
As a specialization, suckers, thorns and other formations on the body of the worm, powerfully developed genitals and several complex life cycles act. Morphological simplification is expressed by the absence of sense organs in sexually mature individuals, which act as endoparasites
The main systems of life of the worm:
- digestive - the mouth opening is connected to the muscular pharynx (sucking apparatus). For the pharynx there is a branched esophagus and blindly ending intestines;
- nervous - represents the periopharyngeal nerve ring, from which three pairs of nerve trunks depart (the lateral ones are most developed). The nerve trunks are connected by jumpers, which makes them look like a lattice;
- excretory - developed protonephridia in the depths of the parenchyma. Thermal cells have channels with cilia, which select tissue fluid and dissimilation products from the parenchyma. The cilia move the fluid through the channels and excretory pores, removing it from the body;
- sexual - the helminth is a hermaphrodite. The male reproductive system is represented by a pair of testes, two vas deferens, which merge into the ejaculatory canal and cirrus. The female reproductive system is more complex: the ovary, vitelline cells, seminal receptacle, ootype (fertilization and formation of eggs occurs in it), uterus and genital opening. In some species, fertilization takes place in the seminal receptacle. In most cases, insemination is cross, but there are cases of self-insemination.
Hepatic fluke intermediate host
As soon as the larvae enter the body of the final host, and this can be an animal or a person, they continue their development to sexually mature individuals. An acceptable environment for the survival of the offspring of the parasite is animal and human excrement. With them, the eggs of the worm fall into water bodies, repeating their life cycle. This stage is called aledoscaria.
The worm can exist in an aquatic or humid environment for a long period of time, retaining its viability.
The pond snail is the intermediate host of the liver fluke. The larva of the parasite is introduced into the body of the snail, where it lives and develops at its expense. An already grown individual leaves its carrier, and is attached with the help of suckers and thorns on the body to the stems of aquatic and coastal plants. At this stage, the helminth is covered with a protective shell - a shell.
Liver fluke Miracidium
The egg of fasciola begins to develop only after getting into the water, where, under favorable conditions, after 25-30 days, a larva emerges from it - miracidium. Miracidium has a nerve ganglion, a light-sensitive organ "eye", organs of excretion. In the back of it are the germ cells.
The anterior end of the body is equipped with a gland that produces an enzyme capable of dissolving living tissues upon penetration into an intermediate host. Miracidium is covered with cilia, thanks to which it actively floats in the water. He does not feed, but exists due to the nutrients accumulated in the egg.
Hepatic fluke. Inside the body of miracidium there are special germ cells capable of parthenogenetic development. Miracidium is actively introduced into the body of the intermediate host of the small pond squirrel. In the body of the mollusk, miracidium sheds the cilia and penetrates the host's liver.
Further, the parasite turns into the next larval stage - sporocyst. Sporocysts resemble a shapeless sac, devoid of any organs, including the nervous and excretory systems. This larval stage is capable of reproduction.
In the sporocyst, a new larval generation, redia, develops parthenogenetically (i.e., without fertilization) from germ cells. The sporocyst bursts, and the redia emerge from it, but continue to parasitize in the same host.
A number of organs are already forming in redia: the mouth, pharynx, digestive tube, and an opening for the emergence of individuals of the new generation. Inside the redia, the next larval generation, cercariae, is also parthenogenetically formed from the germ cells.
In the body of the cercaria, many organs characteristic of the marita are developed. It has suction cups, intestines, nervous and excretory systems, but unlike the adult form, it is equipped with a long, muscular tail, which provides forward movement. The cercarium leaves the mollusk and actively moves in the water.
Further, free-floating cercariae are attached to some object, for example, plant stems, and are covered with a shell. In this larval stage, called adolescaria, the fasciola is spherical. If the adolexaria is swallowed by an animal from among those that are the final hosts of the fasciola, then the membrane dissolves in the intestine of the host and the parasite enters the liver, where it reaches a sexually mature state.
Hepatic fluke. Thus, in the life cycle of fasciola, miracidium serves as an invasive (i.e., capable of infecting) stage for the intermediate host. For the final owner, this stage is adolescaria.
Livestock is most often infested by eating grass in flooded meadows and by drinking water from reservoirs where adolescaria may be found. People usually become infected through vegetables (most often lettuce), which are poured with water from reservoirs containing adolescaria.
It is interesting to note that there is a free-living stage in the life cycle of fasciola - miracidium, which is morphologically similar to ciliary worms, which serves as one of the proofs of the origin of flukes from ciliary worms.
Diagnostics of the hepatic fluke
Based on the presence of fluke eggs in the feces, the liver fluke is diagnosed. The parasite can be found in healthy people after drinking contaminated water or food. Eggs begin to be excreted 3-4 months after infection.
In the acute stage of fascioliasis, the diagnosis is made on the basis of painful symptoms.
In the diagnostic process, the following methods are used:
- collecting anamnesis, that is, epidemiological data: bathing or drinking water from stagnant reservoirs, eating unwashed vegetables, fruits, as well as fish, meat or animal liver;
- clinical signs of pathology: early symptoms and signs of a chronic form of fascioliasis;
- laboratory tests depend on the stage of the disease. In the early phase, serological methods are used, that is, the study of blood for antibodies-ELISA, RNGA. With advanced stages, coproovoscopy or duodenoscopy is performed.
Based on the results of the diagnostic procedures performed, the doctor makes a final diagnosis and prescribes a helminth treatment regimen.
Ways of infection by the hepatic fluke
The causative agent of fascioliasis is promiscuous in the choice of hosts: it can develop in both animal and human bodies. The pathways of infection with the hepatic fluke are associated with its life cycle.
The parasite is a hermaphrodite, that is, at any stage of development, the larva can produce its own kind and in large quantities. Helminth develops in the external environment, since its larvae get there after birth. As a rule, these are bodies of water or wet areas. Worms attach to plants, entering the body of a new victim.
There are risk groups that have an increased chance of contracting fascioliasis:
- ethnic groups whose traditional cuisine includes dishes from raw meat and fish;
- hunters, fishermen and people working with the land or in nature;
- children playing with earth or sand, vacationing in camps located in nature;
- sellers in meat and fish stores.
The liver fluke enters the animal body with contaminated grass or water. A person becomes infected in the same way by eating dirty vegetables, fruits, herbs. Another source of infection is water with worm larvae. There are also known cases when fasciola was introduced into the human liver when eating insufficiently fried fish.
The routes of infection in humans and animals are similar.
Fluke eggs are not dangerous for humans. They can enter the body with water or food, but their further development in the human intestine is impossible. The larvae are excreted in excrement. But this is not the end of their life cycle.
The future helminth enters the sewer and develops to the next stage, getting into water bodies where animals eat them. Therefore, it is very important to use only purified water, thoroughly wash the products before use and heat them.
Hepatic fluke - affected human organs
Getting into the human digestive tract with food, helminths penetrate into the abdominal cavity, and then into the liver and bile ducts, where they attach to tissues. Having noticed the signs of a hepatic fluke, you cannot postpone a visit to the doctor! You need to know that these worms begin to suck out nutrients and actively parasitize in the body, causing severe damage to various internal organs.
Hepatic fluke. Fasciola hepatica (liver fluke) becomes the causative agent of fascioliasis, a disease that not only affects the liver and bile ducts, but also causes severe allergic reactions, even anaphylactic shock is possible.
Human organs affected by the hepatic fluke further (through the bloodstream) include the lungs, skin and even the mammary glands. With the prolonged presence of the parasite in the body, severe diseases of the gastrointestinal tract, blood vessels, heart, nervous system develop, and an oncological process may begin.
The first signs of a hepatic fluke are associated with the incubation period of the parasite's development.
Prevention of hepatic fluke
To minimize the risk of hepatic fluke infection, preventative recommendations must be followed.
Prevention of fascioliasis consists of the following rules:
- observance of cleanliness in everything. Washing hands after using the toilet and before every meal. It is necessary to thoroughly wash salad herbs, vegetables and fruits, if possible, pour over them with boiling water or blanch them before use;
- special attention should be paid to the heat treatment of products. Boil or stew fish caught from the pond, even if it is intended for pets (cats are carriers of fascioliasis). Do not eat raw meat or liver;
- exclude the use of unboiled or untreated water from stagnant reservoirs. Swimming in stagnant water is not recommended;
- regularly carry out anthelmintic treatment of pets. Observe sanitary and veterinary standards. It is also recommended to clean ponds and control molluscs (intermediate host of helminths) in water bodies.
The liver fluke is not the worst representative of flatworms, but since the ways of its infection are known, it is better to follow the rules of prevention. At the first symptoms or suspicion of invasion, it is necessary to contact an infectious disease specialist and a gastroenterologist.
Find out more:
- Biohelminths and geohelminths: symptoms and what they are
- Helminths in humans: signs, symptoms and treatment
- Helminth worms. What worms live in a person. Types of parasites