Lancet Fluke: Life Cycle And Structure, A Threat To Humans

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Lancet Fluke: Life Cycle And Structure, A Threat To Humans
Lancet Fluke: Life Cycle And Structure, A Threat To Humans

Video: Lancet Fluke: Life Cycle And Structure, A Threat To Humans

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The lanceolate fluke is a parasitic worm of the trematode class with a flat body and a complex development cycle. The complexity is due to the fact that it alternates several intermediate hosts, which are land snails and ants. He prefers the last owner in the form of farm animals. Other animals, such as dogs, bears, foxes, can also become infected. The lanceolate fluke also carries a serious threat to humans.


  • 1 The structure of the parasite
  • 2 Hosts
  • 3 Stages of life
  • 4 Vital activity of parasites
  • 5 Infection
  • 6 The fluke threat to humans
  • 7 Prevention

The structure of the parasite

The structure of the lanceolate fluke is very similar to other types of flukes. The size is from 0.5 cm. An adult can reach 1.2 cm. The body of the fluke is flat and oval, the width is 2.5 mm. The front end of the body has suction cups that sit next to each other. The structure of the eggs has typical features, having an oval shape and a hole at one end for the larva to enter.

Like other fluke species, this helminth leads a parasitic life - in particular, in the body of herbivorous domestic and wild animals. But this species has a wider range of hosts - for example, this parasite was found in the body of a deer, hare, all kinds of rodents, and a bear. Along with this, more than one thousand flukes can be found in the body of one animal. An adult is in the bile ducts of the liver.

The parasite is found in Asia, North America, Australia and throughout Europe.

The hosts

The lanceolate parasite has several intermediate hosts, the first of which are land snails. Various species of ants are considered the next host. But it is worth noting that species such as the red forest ant and the black garden ant cannot be the host of the parasite.

Life stages

The egg at the invasive stage of the lanceolate parasite is eaten by a snail. Further, the larva is encapsulated and the three-month development cycle of the lanceolate fluke begins. After this time, the snail, simultaneously with the release of mucus, leaves the cercaria in the habitat, after which it is absorbed by the next host - the ant. In his body, the larvae of the lanceolate fluke form a temporary form of existence, that is, a cyst.

The larva of the parasite changes the nervous system of the ant, and the insect is outside at night, and does not climb into the nest. This is done to increase the likelihood of the ant being consumed by herbivores.


Once in the body of a mammal, the larvae in the gastrointestinal tract crawl out of the cyst and make their way to the liver. There they become adult worms, after which the stage of ontogeny begins, the release of eggs begins.

Vital activity of parasites

The life cycle of the lanceolate fluke involves the formation of parasites in the body of the first and last two hosts. After the helminth egg has penetrated the body of the snail, the development of the cercaria larva can reach five months.

Once in the ant's body and getting rid of the tail, most of the larvae can stay in it for more than a year without killing the insect itself. The larvae make slits from the inside in order to penetrate from the enlarged part of the esophagus into the inner space of the body. Along with this, they fill up the cracks with their own secretions. This movement takes about two days.

In the final host, it may take about 7 weeks for the fluke larva to mature, and another month to start producing eggs.


Until now, science has no information about the lifespan of an adult inside the host. In addition, the period of time from the moment the parasite enters the body until the symptoms of the disease are detected is unknown.


Due to the specific period of the fluke's existence, people are extremely rarely infected, since the chances of eating an ant are small. As a rule, ruminants become infected, which subsequently become the final hosts. However, there is a possibility of infection with both other herbivores and humans. For example, in one of the incidents of human infection, an ant ended up in a bottle of water and in this way entered the body.

There are cases of mistaken infection. By eating the liver of animals that has not undergone the necessary heat treatment, eggs of worms can be found in feces in humans. However, they do not pose a threat, since they will disappear after refusal from the diet of this product.


The fluke threat to humans

In adults, flukes have special suckers, with the help of which they cling to the epithelium of the biliary tract, which leads to a disorder in the blood circulation of tissues, their inflammation and irritation, and subsequently necrosis occurs

However, lanceolate flukes are capable of exerting not only mechanical, but also toxic effects. In the human body, the parasite secretes products of its life processes, which causes metabolic disorders and severe allergic reactions.

Symptoms of infection include the following.

  1. Increased irritability, which is caused by a violation of the nervous system. If the infection becomes chronic, the person can become aggressive.
  2. The emergence of intermittent pain in the right hypochondrium.
  3. Vomiting, nausea.
  4. Icteric staining of tissues may appear.
  5. Bloating, diarrhea.
  6. Weight loss.

More severe stages may be accompanied by liver enlargement or inflammation. In a single case, when a hepatic fluke was infected, a skin rash was found.

With helminthic infection, an increased number of eosinophils will be shown in the blood test results, an increase in immunoglobulin E is noted.

The presence of fluke eggs in the feces indicates the accuracy of infection. But this diagnostic method is not effective in all cases, since there is a certain percentage of false infection. To begin with, you should delete the liver of animals from food, and then re-take the analysis. If the results indicate the presence of a disease, an accurate conclusion is drawn up.


It is important to wash fruits and vegetables thoroughly before eating them to avoid contamination. Only filtered water can be used for drinking. It is necessary to ensure that there are no ants on food.

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