Broad lenticles: symptoms and prevention

The largest helminth that can parasitize humans and animals is the broad tapeworm (Diphyllobothrium latum or Dibothriocephalus latus): its adult can grow up to 12 meters in length.

The biological systematics of the broad tapeworm classifies it as a flatworm, a tapeworm (cestodes) class, and a pseudophyllid order - tapeworms.

This parasite can be considered a long-liver, because sometimes it lives for two or three decades.

Structure and life cycle of the broad tapeworm

The structure of the broad tapeworm is typical for cestodes, whose body (strobilus) has the form of a flat band consisting of segments. However, in the broad tapeworm, the transverse size of mature segments of the strobila can be up to 10-15 mm, and their length, as a rule, does not exceed 3 mm.

The head or scolex of the broad tapeworm has the shape of a strongly elongated oval about 3-4 mm long and is equipped with a pair of bothria - slit-like depressions with the help of which the worm attaches to the intestinal wall of the host (human, cat, dog, etc.).

Behind the scolex is the neck, a growth zone where new segments of the broad tapeworm (proglottids) are constantly formed, and as they move from the neck to the back of the body, the width of the segments increases. One tapeworm can have up to three thousand segments.

Each segment is covered with a dense cuticle, which has microtrichia - villous outgrowths, with which the cestode more tightly attaches to the microvilli of the intestinal mucosa and thus feeds by pinocytosis - sucking out the substances it needs with its whole body. The broad tapeworm does not need oxygen, so it does not have a respiratory or circulatory system. And it excretes its waste products through the protonephridial tract - through a system of tubules. Moreover, each proglottid has such a system.

And each segment has an autonomous hermaphroditic reproductive system with a full set of transforming reproductive organs. As a result of its functioning, a uterus (in the form of a rosette with an opening) is formed inside the segment, containing the eggs of the broad tapeworm - ellipsoid or oval in shape, 40-65 microns in size. At one end of the egg there is a lid, and inside a spherical larva matures - a coracidium (or oncosphere) with a shell and hooks. This is the first larval stage of the worm.

The definitive or final host of the broad tapeworm is humans, as well as fish-eating predators, in whose small intestine the helminths develop to sexual maturity and begin to reproduce.

The life cycle of the broad tapeworm lasts about six months and begins when mature proglottids release eggs and eventually break away from the scolex. From the large intestine, the eggs (along with feces) exit.

The coracidium emerges from the shell only when the egg is in an aquatic environment (at +15-18°C), where it matures within 1-2 weeks and opens the lid. The mobile coracidium floats in the water and serves as food for the Cyclops crustacean that lives in water bodies. And this is the first intermediate host of the broad tapeworm. In the body of the cyclops, the coracidium penetrates all tissues through the intestines, and there, in 15-20 days, the broad tapeworm finna is formed - a worm-like procercoid no more than 0.5 mm in size.

The second intermediate host of the broad tapeworm, which parasitologists call auxiliary, is a fish that eats cyclops crustaceans. Having penetrated from the stomach into all the organs and muscle fibers of the fish, the procercoids grow for some time and then move on to the next stage - the plerocercoid of the broad tapeworm (sparganum), which is a white oblong larva measuring 10-25 mm with a scolex buried inside. This stage of the parasite is invasive.

Most parasitologists admit that the broad tapeworm has a third intermediate host, since people usually do not eat small raw fish. Therefore, if a predatory fish - perch, pike, pike perch, trout or salmon - catches and eats a small fish with plerocercoids, the larvae again penetrate the intestines and migrate in the flesh of a large fish.

The routes of infection with broad tapeworm are oral, through eating poorly cooked or fried fish infected with the parasite's larvae - not only freshwater, but also some types of sea fish. You can become infected after eating lightly salted caviar, lightly salted or raw fish. In particular, Canadian doctors warn about the potential threat of broad tapeworm infestation when eating such popular raw fish dishes as carpaccio, tartare and ceviche.

It is not necessary to exclude the possibility of infection through the contact of particles of feces of infected hosts of the parasite (humans and animals) with other food, as well as untreated wastewater.

The incubation period – from the moment the plerocercoid larva enters the body until the appearance of symptoms of infection – lasts from one to three months.

Symptoms of broad tapeworm

As noted by infectious disease doctors, the symptoms of the broad tapeworm may often not have a pronounced clinical picture. Typical gastrointestinal signs of infection with the broad tapeworm - diphyllobothriasis - are nausea, epigastric pain, alternating diarrhea and constipation, changes in appetite, and weight loss. Headaches and general weakness are possible.

In some cases, intestinal obstruction occurs, limbs go numb, cramps occur, and the tongue feels sore and burns (especially after salty and sour foods).

Also characteristic of diphyllobothriasis is the development of so-called pernicious anemia, associated with the presence of a broad tapeworm of significant size in the small intestine. On the one hand, this reduces the absorption of cyanocobalamin (vitamin B12) coming with food, and on the other hand, damage to the intestinal walls by the parasite disrupts the production of this vitamin by intestinal bacteria. In addition, as it turned out, this vitamin is absorbed by the parasite itself.

Since B12 ensures many processes in our body, including the metabolism of nutrients and the formation of red blood cells, its deficiency can lead to constant weakness and dizziness, pale skin and decreased tactile sensitivity, swelling of soft tissues and increased heart rate, impaired blood clotting, redness and cracks in the mucous membrane of the tongue (glossitis), loss of taste and difficulty swallowing. There may be seizures similar to epileptic seizures.

On the blood side, the ESR may accelerate and the bilirubin content may increase. At the same time, the number of erythrocytes and the hemoglobin level in the blood may be normal, but macromegalocytosis is noted - an increase in the size of red blood cells.

In addition, an allergy to the waste products of the helminth may develop, which is expressed in blood eosinophilia - an increase in the level of eosinophilic leukocytes, which are produced by the bone marrow to protect the body from foreign proteins.

Diagnosis and treatment of broad tapeworm

Diagnosis of broad tapeworm includes: examination of the patient and collection of anamnesis; general stool analysis (coprogram); clinical blood test. Gastric juice analysis for gastromucoprotein may be required.

Treatment of broad tapeworm is carried out by taking drugs such as Phenasal or Biltricid orally.

For diphyllobothriasis, the daily dose of the antihelminthic drug Fenasal in tablets of 0.25 g (other trade names of the drug are Niclosamide, Yomesan, Biomesan, Cestocide, Gelmiantin, Lintex, etc.) is taken at one time (in the morning on an empty stomach or 4 hours after dinner, at night); before taking the drug, you should drink half a teaspoon of baking soda. The standard dose for adults and children over 12 years old is 8-12 tablets, for children 5-12 years old - 6 tablets, 2-5 years - 4 tablets, under 2 years - 2 tablets. The tablets must be crushed into powder or simply chewed well. You can eat 3-4 hours after taking the tablets, the food should be light and preferably in liquid or semi-liquid form. A month after treatment, you must pass a stool test for the presence of tapeworm eggs or larvae. Phenasal is contraindicated in cases of anemia, stomach ulcers and pregnancy.

Treatment with Biltricid (other trade names - Praziquantel, Biltride, Cesol, Cestox, Cystricide, Azinox) is effective due to the paralyzing effect of praziquantel on the helminth's body, leading to its death. The drug is available in tablets of 0.6 g and is prescribed orally at 0.04 g per kilogram of body weight - once a day (during meals, with water).

Taking Biltricid may cause abdominal discomfort, nausea, vomiting, diarrhea (with blood), dizziness and headache, fever, increased drowsiness, urticaria, convulsions. The active substance of this drug has a destructive effect on the cells of the pancreas and liver, and can lead to the development of toxic hepatitis and liver cirrhosis. It is not used to treat children under 4 years of age and pregnant women.

Often, treatment of broad tapeworm at home is carried out with raw pumpkin seeds, which are recommended to be peeled, crushed and eaten on an empty stomach. Adults need to eat 200-300 g of seeds prepared in this way per day, children - up to 100 g. However, before this, you should also prepare your intestines: two days before taking a "dose" of seeds, you need to clean it out with an enema at night, and the next day take a saline laxative.

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Prevention of broad tapeworm

Since humans cannot destroy this parasite in nature (especially considering the volumes of discharge and the quality of wastewater treatment), the only possible prevention of the broad tapeworm is to cook the fish properly. First of all, it is its heat treatment of sufficient duration and temperature: the plerocercoid larvae cannot withstand a temperature of +60°C and above and die after 20-25 minutes. It is also necessary to salt the fish properly (with a salt concentration of 10%) and freeze it (at -15-10°C).

According to WHO estimates, the broad tapeworm is a parasite in the intestines of almost 15 million people worldwide, especially among residents of those countries where a lot of fish is consumed.