Lancet Flute: Life Cycle

Nature has created various creatures, many of whom love to "live at someone else's expense," that is, they are parasites. The fluke concealed a riddle for scientists for a long time, but numerous studies have helped to uncover all the secrets of the trematodes. This article will describe in detail the lancet flukes: life cycle, morphology, developmental stages, human infection, methods of prevention and treatment.

lancet fluke

Description, structure

Trematodes, or flatworms, are parasitic in the hepatobiliary system of the host. They affect the tissues of the liver and gallbladder, causing helminth invasions. Dicrocoelium lanceatum is the cause of a disease called dicroceliosis. Both herbivorous mammals and humans are subject to it. The parasite got its name due to the similarity of a flat body with a surgical instrument of the same name - a lancet. A fluke called him because of the presence of suckers, which are located on the mouth and abdominal part of the worm. He strengthens them in the tissues of infected individuals.

The body of the parasite reaches sizes from 0.5 to 1.3 cm in length and 2-3 mm in width. Its upper part is occupied by the intestines, and the lower one - by the reproductive organs. The lancet flukes, whose body structure implies the presence of developed muscles, can move inside the wearer. Its outer shell is represented by a cuticle with a large number of suckers.

The small globular pharynx through which food is supplied is also a place for removal of undigested residues. It passes into the elongated esophagus, ending with a bifid intestine.


Lanceolate flukes, the structure of the reproductive organs of which is very difficult for such a primitive creature, refers to hermaphrodites. Its reproductive system consists of a large uterus located in the lower part of the body, a single ovary, an ootype, and paired testes with channels.

Worms can either connect for the exchange of male germ cells, or reproduce through parthenogenesis. This process takes place exclusively in the body of the final owner. The seed falls into the ootype - the copulatory organ. Fertilized eggs are covered with yolk elements and a dense protective sheath. Their development continues in a branched uterus.After the embryos mature, the material enters the body of the infected mammal and is released into the environment with a bowel movement.

lancet fluke life cycle morphology

The Mystery of the Parasite

For a long time, scientists could not reveal the secret of the parasite. They were deeply mistaken, thinking that the lancet flute has only two masters. The main carrier, inside which the flatworm developed, was considered to be herbivores and humans, and the intermediate stage was assigned to parasitism in the body of mollusks. Numerous studies have shown that the fluke has an additional hawker - an ant. Only with its help invasive penetration into the organism of mammals occurs.

The lancet flukes, whose life cycle consists of several stages, is a dangerous parasite. Adult worms lay eggs, subsequently passing through a series of metamorphoses, closing this chain of development with the participation of three carriers.

lancet fluke life cycle

First carrier

An adult worm can lay up to a million eggs per week. They are covered with a very strong shell. Inside are fully formed tiny larvae, called miracidia.A feature of the parasite called the lancet flukes is that the embryos do not leave their safe haven before penetrating into the body of the wearer. The shell helps protect against any adverse conditions - it saves the life of the larva even with temperature drops from + 50⁰C to -50⁰C.

Ground mollusks become the first owner of the fluke. Their mouthpiece resembles a grater, which scrubs off the upper plant tissue. So the helminth eggs get into the digestive tract of the cochlea. Miracidia become a time bomb - they come out of their shells through a special cover and transform into a sporocysts. The larva loses cilia, due to which it reached the victim's intestines, and begins to reproduce parthenogenesis numerous offspring - redia parasite lanceolate flukes. The invasive stage in the body of a snail is due to the peculiarities of the struggle for the owner, because only a small part of the miracidians will reach the carrier.

lancet structure

Redia are reborn into cercariae, which penetrate the cochlea's respiratory system, preparing to leave its body. They are glued together in a lump containing up to 500 individuals, and are released into the environment.

Change of master

Snail mucus is an additional protective barrier against adverse environmental conditions. It hardens on the leaves of plants and becomes a desirable prey of ants that absorb food along with cercariae. The latter eject the membrane in the intestinal tract of the host and transform into a cyst, producing a new generation of larvae.

The lancet flukes in the metacercarium stage can literally “take possession of the mind” of an ant. Some individuals penetrate into the brain like brain - ganglion. There they invade and cause insect paralysis. The host infected with the parasite radically changes its behavior after a day has passed. He stops returning to the anthill at sunset, but climbs onto the top of a blade of grass and freezes, squeezing it with a mouthpiece.

lancet fluke body structure

Infection of herbivores

Eating vegetation, herbivorous mammals absorb paralyzed ants, carrying within themselves a source of infection. Metatserkarii, hitting the body of the final owner, moves to the duodenum. There, he leaves the shell and migrates to the gall ducts and liver, transforming into an adult lanceolate flukes.And after 6 weeks, she will produce a new offspring, which will leave the carrier's body, closing the life cycle.

Symptoms of dicroceliosis in livestock, disease prevention, treatment

Affected mammals suffer from dicroceliosis. There is a sluggish and depressed state, depletion of the body, yellowness of the skin and sclera. These symptoms do not appear immediately. When a lancet flute reaches sexual maturity and enters the breeding season, its activity leads to blockage of the bile ducts. This causes damage to the hepatobiliary system, characterized by intestinal disorders, liver enlargement, cirrhosis.

As a preventive measure, it is recommended to drive livestock to pasture in the early morning and in the afternoon. In the late afternoon, infected ants begin to consolidate on the grass, which increases the risk of invasion. When signs of disease are detected, laboratory tests are conducted. If they confirm dicroceliosis of livestock, then veterinarians recommend the use of anthelmintic drugs: Getolin, Hexichol, Fenbendazole, Closantel.

lancet flukes invasive stage

Human dicroceliosis: ways of infection, symptoms, treatment

People rarely get infected with a parasite such as a lancet flute. The invasive stage for a person begins after an accidental hit of an infected ant in the digestive tract.

Like inside the body of herbivores, the metacercarium begins to migrate to the liver and bile ducts. There he reaches maturity and enters the breeding season. The activity of the trematode leads to disruption of the liver:

  • inflammation;
  • hepatitis;
  • necrosis;
  • cirrhosis;
  • cholangitis

Symptoms of human dicroceliosis are also intestinal disorders, pain in the liver, an overly depressed or agitated state.

lancet flukes invasive stage for humans

In the case of a false disease, the eggs of the parasite are found in the analyzes, but no human infection occurs. This happens when eating cattle liver, which has not undergone thorough heat treatment. With repeated laboratory tests, all analyzes return to normal, since the eggs of the parasite called the lancet flukes leave the body with the digested remnants of the infected product.

To avoid dicroceliosis, it is important to thoroughly wash and inspect the plant food to prevent ants from entering it.In case of suspicion, it is necessary to pass tests in 2-3 stages (in order to exclude a false disease) and conduct a course of treatment with anthelmintic drugs according to the scheme prescribed by the doctor.

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