Lancet Fluke - Life Cycle And How To Deal

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Lancet Fluke - Life Cycle And How To Deal
Lancet Fluke - Life Cycle And How To Deal

Video: Lancet Fluke - Life Cycle And How To Deal

Video: Lancet Fluke - Life Cycle And How To Deal
Video: Dicrocoelium dendriticum: The lancet liver fluke 2023, December

Caution: lanceolate fluke


  • 1 The structure of the lanceolate fluke and general information

    • 1.1 Micrograph of a lanceolate fluke
    • 1.2 The area of distribution of the parasite
  • 2 Life cycle of Dicrocoelium dendriticum

    2.1 Diagram of the life cycle of a lanceolate fluke

  • 3 Ways of infection with lanceolate fluke

    3.1 Sources of human invasion

  • 4 Prevention of lanceolate fluke infection
  • 5 Symptoms of parasite infestation

    • 5.1 Symptoms of human hepatic fluke infection
    • 5.2 Symptoms of hepatic fluke infection in animals
  • 6 Treatment of dicroceliosis and associated symptoms

    6.1 Liver of an animal infected with lanceolate fluke

  • 7 Frequency of infection

Lanceolate (hepatic) fluke or fluke (Latin Dicrocoelium dendriticum, D. lanceatum, D. lanceolatum) is a parasite characterized by a multi-stage development cycle. The hepatic fluke is potentially dangerous to humans - one of the developmental stages of this organism involves human invasion.

The parasite is classified as a liver fluke, although it also often settles in the gallbladder or ducts, less often in the intestines of the final host. Ruminants - cows, deer, sheep, goats, elks, giraffes and others - are most at risk of fluke infection. Less common are cases of infection of non-ruminant mammals, including humans.

The structure of the lanceolate fluke and general information


The structure of the lanceolate fluke

The lanceolate fluke belongs to the Dicrocoeliidae family of parasites, a class of flukes (flatworms). The body of an adult fluke has the shape of a highly elongated oval, about a centimeter long and 0.2-0.3 millimeters wide. The front part of the parasite's body is pointed and equipped with special suction cups around the mouth, with which it "sticks" to the organs of its victim. In the middle of the body of Dicrocoelium dendriticum there is an additional large abdominal sucker. The posterior end of the hepatic fluke larva is uniformly rounded. The eggs of the lanceolate fluke are rather large, rounded, up to half a millimeter in diameter and have an asymmetrical shape.

They have a peculiar lid, which facilitates the exit of the larva from the egg, and are colored dark brown. Like many parasites, the liver fluke has the most developed system in the body, the reproductive system.

Micrograph of a lanceolate fluke

The parasite was discovered in 1819 by the famous German natural scientist, one of the founders of helminthology, Karl Rudolfi. But the features of the life cycle of this organism remained unknown for a long time. The features of the development of Dicrocoelium dendriticum were studied and described in detail by the American Wendell Krul in the 50s of the twentieth century.

The area of distribution of the parasite

The lanceolate fluke is found almost everywhere on the planet. Its habitat includes:

  • Europe;
  • Asia;
  • North and South America;
  • Africa;
  • Australia.

Particularly attractive regions for this parasite are arid areas with alkaline acidity.

Life cycle of Dicrocoelium dendriticum


Life cycle of Dicrocoelium dendriticum

Like other trematodes, the life cycle of the fluke is characterized by a sequential change of at least three generations that require several hosts for their development.

For the first time, the developmental cycle of the hepatic fluke was established by Wendell Krul using the following example. The initial host of the parasite studied by Krul was the land snail, Cochlicopa lubrica. The mucus-coated globes that the snail sometimes spewed out of the mouth contained the eggs of the lanceolate fluke.

The next (intermediate) host of the fluke was the brown forest ants, Formica fusca, which, in turn, infected domestic sheep, which became the residual carrier of the lanceolate fluke.

Of course, the life cycle of Dicrocoelium dendriticum can involve infestation of many more species than snails, ants, and sheep. Later, the following infection sequence was established:

  1. The first host of the liver fluke is land snails of the Gastropoda class (Fruticicola fruticum, Cochlicopa lubrica, Zebrina, etc.) or some species of fish.
  2. The intermediate hosts of Dicrocoelium dendriticum are ants from the genus Formica (brown forest, red-cheeked, meadow steppe dart, etc.). The researchers note that some Formica ants are never infested (red wood ant and black garden ant).
  3. The residual host of the lanceolate fluke is mainly ruminant mammals, as well as hares, horses, pigs, man, monkey, donkey, camel, bear (less often).

The source of infection with lanceolate fluke eggs is the feces of the residual host of the parasite. So, the feces of a sick person or animal can contain up to several tens of thousands of sporocysts.


The eggs of the parasite are covered with a strong two-layer shell. This allows the fully formed larvae encapsulated inside them - miracidia - to perfectly tolerate unfavorable environmental conditions, for example, sudden changes in humidity and temperature, up to their absorption by the primary host. The eggs remain dormant until they enter the esophagus of snails or slugs along with the plants they eat. In the intestines of the snail, the larvae of the lanceolate fluke emerge from the eggs, transform and form another sporocyst.

After several months, the sporocyst matures and cercariae, a new generation of flukes, emerge from it. Cercariae penetrate into the lungs of the snails, where its mucus sticks together into a kind of balls. The snail spews these lumps of mucus with larvae from the respiratory tract into the environment, where they become infected by ants, eating grass.

An ant that has swallowed Dicrocoelium dendriticum cercariae becomes lethargic and passive. Usually, the spore of the fluke settles in the muscles or fatty tissues of the ant, where it absorbs nutrients and actively develops for several months. Further, having reached a certain stage of development, in 1-2 days, Dicrocoelium dendriticum migrates to the subpharyngeal nerve node of the ant.

Due to the damage to the nervous system of the ant by the larvae, when the ambient temperature drops to 10-12 degrees Celsius, it becomes paralyzed.

A sick ant does not go to sleep in an anthill, remains on the grass, as a result of which it can be eaten by large mammals, most often ruminants.

Interestingly, sick ants lead a normal life during the day. Further, the fluke cysts, falling into the esophagus of the final host, hatch and penetrate into its bile ducts and liver, where they finally mature and multiply, producing many new parasites.

Life cycle diagram of lanceolate fluke

The entire development cycle of the hepatic fluke can take more than a year. It is known that cercariae remain inside the snail for up to five months, and the development period of the larva in the ant's body depends on many factors and can be a year or more. Once in the body of the residual host, the parasites begin to lay eggs in 2-3 months, and the feces of the sick individual become infected.

Due to the peculiarities of the life cycle of Dicrocoelium dendriticum, humans are relatively rarely the main host of the lanceolate fluke. An ant is unlikely to be swallowed by humans with basic hygiene practices, while free-grazing animals are more susceptible to infection.

But once an infection has occurred, the parasite multiplies very quickly within its residual host. So, there are cases when about 500 thousand fluke larvae were found in the liver of one sheep.

Ways of infection with lanceolate fluke


Ways of infection with lanceolate fluke

Invasion of humans and other large mammals by the lanceolate fluke is possible when the parasite is in the metacercaria stage. When swallowed, under the action of gastric juice, the shell of the larva of the lanceolate fluke partially decomposes. Further, once in the duodenum, complete splitting of the membrane occurs, and the larva enters the bile ducts already released.

Sources of human invasion

  • Eating food or drink contaminated by ants;
  • Ingestion of grass or berries contaminated with sick ants into the esophagus;
  • Accidental ingestion of sick ants or snails.

Since lanceolate fluke cysts are extremely resistant to adverse conditions, they can retain their ability to live even after boiling for about 10 minutes.

Prevention of lanceolate fluke infection

  • Apply timely veterinary control and antihelminthic drugs in animal husbandry;
  • Keep ants away from human food;
  • Wash vegetables and fruits before eating;
  • Drink purified water;
  • Wash hands and utensils before eating.

Symptoms of parasite infestation

Infection with a liver fluke results in a complex liver disease called dicroceliosis in the host. But in the initial stages of infection, the disease is asymptomatic.

The presence of signs of dicroceliosis indicates a prolonged and intense invasion of a person or animal by Dicrocoelium dendriticum, when the parasite multiplies abundantly and migrates deep into the hepatic ducts, damaging the patient's intestines and liver tissue.

Symptoms of a hepatic fluke infection in humans

Typically, symptoms of a person's hepatic fluke infection coincide with signs of a general digestive disorder:

  • Nausea;
  • Vomiting;
  • Intestinal colic;
  • Pain in the right hypochondrium;
  • Bloating;
  • Diarrhea;
  • Increased body temperature;
  • Muscle pain;
  • Sweating.

In difficult cases of infection, a person suffers from general intoxication due to improper liver function and the production of toxins by parasites, tissue overgrowth of the bile ducts and enlargement of the liver due to their constant irritation can be observed, as well as:

  • Yellowing of the skin;
  • Cholecystitis;
  • Allergic reactions;
  • Lack of appetite;
  • Strong weight loss;
  • Anemia;
  • Exhaustion;
  • Cirrhosis.

Occasionally, those infected with hepatic flukes have a cough.

Since the parasite is attached to the tissues of the host's bile ducts with suckers located on the lower surface of his body, the ducts are damaged, and over time their necrosis occurs.

Symptoms of liver fluke infection in animals

In animals, the symptoms of worm infestation by the hepatic fluke are similar to the general symptoms observed in humans:

  • General weakness;
  • Lethargy;
  • Hair loss;
  • Yellowing of the sclera;
  • Lack of appetite;
  • Digestive disorders;
  • Dyspnea.

In addition to the lanceolate fluke, there is another parasite that causes dicroceliosis. This is Dicrocoelium Hospes, discovered in 1907 by another German helminthologist Arthur Loos.

Treatment of dicroceliosis and accompanying symptoms

Infection of a person with a hepatic fluke is diagnosed based on an extended blood test.


An increase in the level of eosinophils and an increase in immunoglobulin E, as well as bilirubin, may indicate the disease. Also, for diagnosis, an analysis of the patient's feces should be performed. Although, the presence of helminth eggs in the feces does not always indicate human infection.

There are cases when the eggs of the liver fluke were found in the stool of people who ate the liver of sick animals. At the same time, the person did not undergo invasion by the lanceolate fluke, since the larvae that entered his body were not at the appropriate stage of the life cycle. The results of duodenal intubation, namely, analysis of the duodenal fluid can also show the presence of nematodes in the human body.

Liver of an animal infected with lanceolate fluke

For the treatment of patients infected with lanceolate fluke, the following are used:

  • A diet that allows you to relieve the liver and gallbladder;
  • Anthelmintic drugs;
  • Drugs to support liver function;
  • Drugs that relieve intoxication.

Of the medicines, the antihelminthic medicines praziquantel and triclobendazole are prescribed to persons who have undergone infestation by the lanceolate fluke. The dose of the drug is 10 mg / kg of the patient's body weight.

If you suspect that a person is infected with a lanceolate fluke, you should go to the hospital. Treatment should be prescribed by a doctor, based on the general condition, age, complaints of the patient.

Infection frequency


Infection frequency

Despite the widespread prevalence of infection with lanceolate fluke among animals, cases of human infestation are rare. Most often, human infection with liver flukes occurs in poor regions of Africa (Ghana, Nigeria, Chad), in China, which is associated with inadequate sanitary and hygienic living conditions.

To a greater extent, the lanceolate fluke is dangerous for pets, because the infected animal becomes a source of the parasite's eggs, and also suffers from parasitism of the fluke inside it, which can lead to serious illness and even death of the animal.