Lancet-like trematode: life cycle, structure. Lancet-like trematode in humans: diagnosis, prevention

In nature, there are more than 7000 species of flat parasitic worms. A lancet-like trematode, or, as it is also called, a lancet-like fluke is one of them. It is distributed throughout all continents. Fortunately, this parasite inhabits a man rarely, but is very dangerous for domestic animals, as it causes serious illnesses in them, and sometimes even death. In the process of evolution, the worm has adapted to "dwell" in different hosts. Its development cycle is complex, but well-run. People must take a lot of effort to protect their animals and themselves from infection.

Lancet-like trematode. Morphological and physiological characteristics

This type of flukes belongs to the flat worms of trematodes. Its dimensions are relatively small - the body length is not more than 10 mm, and the width is 3 mm. Outwardly, the creature resembles a lancet, hence the name of the parasite. The adult formed worm (marita) is armed with two suckers - a larger abdominal and slightly smaller - oral. The body of the trematode is enclosed in a muscular-muscular sac. Muscles have three layers - outer annular, internal longitudinal and transverse. The body of the worm is flat, not divided into segments. Its internal organs are represented by the digestive, nervous, excretory and reproductive systems. Excretory and nervous - rather simple. The digestive system includes a mouth opening, pharynx, esophagus and intestine, two branches of which extend along the body along the sides and blindly terminate. Undigested food parasite leaves through the mouth opening. Lancet-like fluke structure of the reproductive system is quite complicated. It is represented by two testes with vas deferens, one round, a relatively small ovary, an oviduct, an ootype and a uterus that occupies about 2/3 of the body's volume.

Reproduction

According to the type of the device of the reproductive system, the lanceolate trematode refers to the hermaphrodites. Its reproduction occurs only in the final, third host. The seed of the sexually mature specimen of the worm along the vas deferens enters the cirrus (the ejaculatory organ), and then it moves into the copulatory (copulatory) organ. Ootype is a special chamber with a dense shell. It leads the ejaculatory duct of the male genital organs, duct of the oviduct, vitellaria and uterine canal. In ootype, fertilization of eggs takes place, covering them with vitelline elements and membranes. Formed eggs enter the uterus, where, moving to the uterine opening, they mature and go out into the body of the victim. Moving into her intestines, they are removed from the faeces into the environment.

Eggs

The lancet-like trematode, whose egg morphology is such that, at the time of its release, the larva (miracidia) is already fully formed in it, it needs several hosts. According to the shape of the egg, the parasite is oval, covered with very dense shells, with a lid on one end. Their sizes vary in length from 0,038 to 0,045 mm, and in width - from 0,022 to 0,03 mm. Color - from dark yellow to brown. The lancet-like trematode, like all parasitic worms, is extremely prolific. One individual is capable of producing up to a million eggs a week. They have two dense shells, after all, after getting into the environment, they have to wait for their first master, perhaps to survive a drought, showers, heat or cold.

First owner

The entire cycle of development of the lanceolate trematode proceeds on land. In the grass live snails and slugs, which with their rough, like a grater, the tongues remove plant tissues. Eggs of the worm come into the intestines of mollusks. There they hatch miracidia. Their body is partially covered with cilia, and on the head lump there is an education - stylet. With its help, each larva seeps through the walls of the intestine of the victim in the intervals between its organs, where it is released from the cilia and turns into a maternal sporocyst. It loses almost all organs, except for germ cells. Its purpose and purpose is to create as many daughter larvae as possible, so that the lanceolate trematode does not stop its genus. The life cycle of it depends on hundreds of accidents, because of the millions of eggs caught on the grass, only a negligible part finds the master. Reproduction occurs in a virgin manner (parthenogenesis). As a result, new larvae (redia) appear. They have a sip, with which they suck liquids out of the body of their host. In the future, cercariae are born from redias. With the help of their muscular system, they reach the lungs of the mollusk, where they glue together into spherical lumps covered with mucus. Sometimes they can count up to 400 individuals. The snail exhales them out of itself on the grass. There, the mucus hardens, protecting the cercaria from adverse effects.

The second owner

The cycle of development of the lanceolate trematode continues in ants that eat balls with larvae. Once in the intestines of the next victim, the mucus dissolves, and the cercariae form cysts with new larvae inside. This is metacercariae. It is believed that some cercariae in the body of the ant advance to its nerve ganglia, and by penetrating there, paralyze the insect when the temperature of the air decreases. This hypothesis is confirmed by the behavior of sick ants, which live as a warm day, as usual, and in the evening or in cloudy, cold weather, freeze on grass like paralyzed. Mammals (ungulates, hares, dogs and others), eating grass, swallow such immovable ants, and with them and the larvae of the parasite. Once in the body of the final host, the metacercaria migrate to its liver, where a young lanceolate trematode is formed from them. The life cycle of the parasite from this point is repeated.

Dicrocoliosis in animals

All animals that have eaten infected ants become ill with dicrocelia. In dogs, this happens when eating fodder, in which there are ants. Home pets become sluggish, exhausted, lagging behind in growth. Their mucous membranes become icteric. The result of the disease is cirrhosis of the liver or inflammation of the bile ducts.

Signs of the disease with dicrocelia in ungulates, for example, goats, sheep:

• oppression;
• Loss of hair, its dullness;
• Icterus of mucous membranes;
• Constipation or diarrhea;
• A coma (immobility with a neck turned on its side and closed eyes); The case of diseased livestock is quite high.

That's what a dangerous parasite is a lanceolate trematode. The structure and features of its eggs and larvae allow them to withstand ambient temperatures from +50 to -50 degrees. They die only in conditions when the above-mentioned indices of the temperature regime substantially increase. And they can live in feces for about a year.

Dicrocoliosis in humans

No matter how prolific the lanceolate trematode is, it rarely causes a disease in a person, because it requires penetration into the stomach of sick ants. When eating the liver of infected animals, a false infection occurs that does not require treatment. And, nevertheless, people suffer from dicrocoliosis. Infection occurs when ants fall on the standard human food (bread, vegetables, etc.), while eating unwashed meadow sorrel, putting into the mouth grass grasses on which there are ants, and so on. Symptoms of the disease:

• Discomfort and pain in the liver ;
• Diarrhea or constipation;
• weight loss;
• Icterus of mucous membranes.

Treatment

Lancet-like trematode parasitizes only in the liver and bile ducts. People are treated with drugs "Triklobendazol" and "Prazikvantel". Hospitalization is not required.

In the case of false dicrocelia, it is recommended that the meat of sick animals be eaten. Medicines in this case are not used.

Domestic ungulates are treated with "Politrem", "Panakur". Doses are assigned based on the weight of the animal. The medicine is mixed with the food and given in the morning. There are also drugs that are injected intramuscularly.

To treat dogs use "Geokshol", and for the normalization of the liver use the "Karsil" remedy.

Prevention

In animals, dicrocoliosis is severe and often ends in death. Part of the reason for this is that the signs of the disease are manifested when the concentration of the worm in the liver reaches high figures (for example, in sheep more than 10,000 individuals). Therefore, to prevent problems lanceolate trematode, prevention plays a decisive role. It consists in dehelminthization of animals. As for sheep and other ruminants, it is carried out at 1.5 years, at 3, 5 and 7 years. It is also necessary to monitor the condition of pastures, to eliminate the suspected habitat of mollusks - shrubs, stones. Dung on the fields should be disinfected by a biothermal method.

In humans, outbreaks of dicrocelia are most often observed in regions where it is customary to eat insects, and among them ants. Also in some countries, they are used in folk medicine. In order not to "catch" the fluke, a person must observe simple rules of hygiene.