The reproductive system of the human roundworm. Roundworm

Ascaris belongs to the type of roundworms, or nematodes, and has all the features of the internal structure that are characteristic of this group of invertebrates:

• primary body cavity;
• the presence of longitudinal muscles and cuticles;
• the nervous system, represented by the peripharyngeal ring and six nerve trunks;
• lack of respiratory and circulatory systems;
• dichotomy.

body cavity

Ascaris has a primary cavity, or pseudocoel, filled with a clear liquid. It differs from the secondary one in the absence of an epithelial lining. Inside are the organs of digestion and reproduction.

The body cavity performs many functions:

Thus, the primary body cavity has the function of a hydroskeleton and is involved in metabolic processes. It replaces the circulatory system that is missing in roundworms.

On a cross section, the integument of the roundworm looks like thin shell covering the entire body of the helminth.

In the musculoskeletal sac of roundworm, the muscles are represented only by longitudinal muscle fibers. That is why the roundworm cannot straighten its body, as earthworms do.

Digestive system

The digestive organs of ascaris are divided into three sections: the anterior, middle and hindgut. The first two are ectodermal in origin, the latter is formed from the endoderm. The intestine of the helminth is in the form of a hollow tube, suction nutrients occurs in the midgut.

Nervous system

Nervous system roundworms is arranged simply. The only ganglion, or ganglion, has an annular shape and is located at the anterior end of the body of the helminth. Six nerve trunks depart from it, which are responsible for the sensitivity and movement of the worms.

Nematodes have no receptors, except for tactile tubercles on the surface of the pharynx. It lives inside the human body, where there are very few external stimuli, so it does not need complex sensory organs to survive.

Breath

Ascaris is an anaerobic organism that does not need oxygen. She has no respiratory organs. This is an important adaptation to a parasitic lifestyle, since the human intestine contains little air.

The color of this helminth is reddish, after death the color changes to white with a yellow tint. The body is spindle-shaped, elongated, gradually tapering towards pointed ends. It consists of a cuticle - the outer shell, and a cavity. The cuticle consists of ten balls of epithelium. Its main task is to protect the worm from the chemical effects of the host's digestive enzymes, toxic substances, and mechanical damage.

The digestive system begins with the mouth, which is surrounded by three sensitive papilloma lips. Food through the mouth enters the tubular intestine, where all the nutrients are absorbed. Undigested residues are excreted by the anus, which is located at the end of the body.

The body cavity of the roundworm is a kind of ectoderm bag filled with liquid. It is very strong, resilient and has the role of support for the muscles. The muscles are longitudinal, separated from each other by the hypodermis and located along the walls of the body. Such a special structure of the musculature does not allow the worm to shorten or lengthen, therefore, to advance, the worm bends, staying on its side.

The nervous system is expressed by a peripharyngeal ring and nerve trunks that run along the entire body of the worm.

Organs of attachment of the human roundworm are absent. The worms are constantly moving towards the feces, due to which they are retained in the intestines.

Roundworm eggs begin their development after entering the soil along with feces. The maturation of the larvae in the egg should be facilitated by access to oxygen, as well as the optimal air temperature - up to 25 degrees Celsius. The larvae enter the human body along with unwashed vegetables, fruits and garden greens. People who work in vegetable gardens, greenhouses, orchards, as well as children, suffer the most from roundworm infection.

Ways of transmission and infection of ascariasis

Transmission of ascariasis occurs from person to person. But it is impossible to get sick from contact with the patient. This is evidenced by life cycle human roundworm. Helminth eggs can only be infectious if they have matured in the ground. They also need a certain temperature and humidity for their development. Temperatures above 50 degrees and below 30 degrees Celsius are fatal for roundworm eggs.

Ascariasis disease occurs in countries where a warm and humid climate prevails. In polar regions or deserts, helminths cannot reproduce and survive due to unacceptable climatic conditions for them.

The cycle of development of the human roundworm contains two stages.

Migration stage

Upon entering the small intestine, the larvae are released from the shell. Their size is 0.2 mm. With the help of hook-shaped processes, they pierce the intestinal mucosa and penetrate into the blood.

Moving across circulatory system, the larvae move into the human organs (heart, liver), after which they go to the lungs. In the alveoli, the larvae pass through two stages of molting. Their size becomes already 1.4 mm. To continue to develop, the larva has to move towards the larynx, passing through the bronchi and trachea.

The larva is annoying Airways and causes a cough that makes it easier to move around. The final point of migration is the intestines, in which the larva will turn into an adult worm.

Stage intestinal

In the intestine, the developing roundworm feeds on blood serum and continues to grow. Until the moment when the larva turns into an adult and begins to lay eggs, 80 days pass. The female helminth can reach 40 cm in length, which is almost twice as long as the male.

The human roundworm feeds on the blood of the patient, gradually absorbing useful substances from the small intestine. Therefore, the first symptom of roundworm infection is weakness and general malaise.

Often it is impossible to detect the presence of worms in the body in the first stages of the disease, since they do not manifest themselves in any way. The main symptoms can be noticed already when the infection of the lungs has occurred. They can be confused with signs of bronchitis or pneumonia due to their similarity.

List of the main symptoms of infection of the lungs with roundworms:

• Constant fatigue, loss of strength, weakness;
• sudden rise in body temperature. More often seen in children. Less common in adults;
• shortness of breath, shortness of breath;
• cough. May be dry or mucus. Frequent bouts of coughing in the morning;
• headache, dizziness, nausea, blurred vision;
• rapid weight loss and decreased appetite;
• skin rashes, allergic reactions;
• pain in the chest;

Symptoms of the presence of human roundworm in children on early stage may manifest as decreased appetite, prolonged cough, urticaria, itching, as well as nausea and vomiting. Often in children, the first sign of the disease is diarrhea, as well as enlarged lymph nodes.

In most cases, the child noticeably decreases activity, he becomes inattentive, refuses to eat. When the disease passes to the second stage, bloating and flatulence appear, the skin becomes pale, some of the symptoms worsen, the child loses weight. Roundworms reduce immunity, intoxication of the body begins.

With further reproduction of ascaris, signs of infection appear more and more. To the above symptoms are added muscle pain, strong sweating. It is also possible to observe high blood pressure and palpitations. When the reproduction of the worm develops into a mass one, a person may develop severe allergies and even anaphylactic shock. Pain in the stomach, vomiting, diarrhea - all these are signs of a very serious illness, in which the help of a specialist is required.

The first step in the diagnosis is to collect information about the symptoms that bother the patient. Further, using microscopy, the presence of helminth eggs in the feces is diagnosed. In photographs of a human roundworm in feces, the eggs look about the same as in the laboratory under a microscope.

The reasons why eggs were not found in the feces, but helminth disease is possible:

• The man was recently infected, and the female had not yet had time to lay her eggs;
• ascariasis in a patient in an extraintestinal form;
• eggs are absent only in the feces intended for analysis.

In such cases, other diagnostic methods are prescribed - a blood test, tomography, ultrasound, radiography.

Prevention of infection with human ascaris

The main rule for the prevention of infection with ascariasis is to prevent the entry of helminth eggs into the body. Personal hygiene is one of the most simple ways keep away the worms.

Personal hygiene as a fight against roundworm infection

• Timely cutting of nails;
• change of bed and underwear;
• washing fresh vegetables and fruits;
• proper heat treatment of meat and fish products;
• the use of gloves while working in the garden or garden;
• washing hands with soap or using antibacterial agents after walking outside;
• individual cutlery and personal hygiene products for each family member;
• frequent disinfection in common areas, wet cleaning;
• pet care, timely vaccination and deworming;

Even if all these rules are observed, no one is immune from the defeat of worms. You can become infected with ascariasis even while swimming in the lake, as there are usually a large number of helminth eggs in the water. Therefore, at the first suspicion of the possible presence of ascaris in the body, it is necessary to consult a doctor and carry out therapy. medicines according to the written prescription.

anthelmintic drugs in modern world There are many and in most cases improvement occurs after the first medication. Only a specialist can determine the necessary remedy, based on the severity of the disease, age, weight, and also the tendency to allergic reactions.

Depending on the stage, the drugs of first choice are different. For example, in the migration stage, agents based on mebendazole, levamisole or thiabendazole are used. They have a wide spectrum of action. In the intestinal phase - Piperazine, Mebendazole, Pirantel.

After taking medications, it is recommended to take enterosorbents - to remove toxic substances from the body. And for the speedy recovery of health, it is recommended to take a vitamin-mineral complex, as well as enzyme preparations prescribed by the attending physician.

According to statistics, every fourth inhabitant of our planet suffers from ascariasis. The disease occurs in both children and adults. Detecting roundworm is not so easy, because of its movement up the intestines. As a diagnosis, ovohelminthoscopy is used to detect worm eggs in the feces.

What is the human roundworm

Picking up a magnifying glass, it is possible to examine the mouth opening of the worm.

All nematode worms have a mouth surrounded by three lips. In the female, the tubes of the reproductive system can be seen through the thin skin. The live worm is very active.

From the anterior and posterior ends, the body of the worm is narrowed. When cross-sectioned, it is seen that the body is round. The skin is made up of three layers. The first layer is the cuticle. The second is a layer of epithelial cells. The third layer is made up of muscles. All these three layers form the walls of the body or, in other words, the skin-muscular sac. Such a skin-muscular structure of the body allows the roundworm to actively move.

The internal structure of roundworm

Ascaris organ systems

Consider the main organ systems of the worm, which have their own characteristics. Inside the body are the digestive and reproductive systems.

Reproduction and development of human roundworm

Ascaris is a representative of geohelminths. In order for the larva to become a worm, it needs to get into the soil, and then into the host. Roundworms are dioecious worms. The reproductive system of the female is extremely productive. It stands out from 200 thousand eggs per day. She has two ovaries and two uteruses. The male has a long thread-like testis. After mating, he dies.

Helminth eggs enter the soil along with faeces. A fertilized egg, falling into the ground, goes through several stages of development. It is surrounded by several layers of protection. The egg matures in the soil. A suitable temperature range for this is 15-30̊ C. Most often, eggs are found on unwashed vegetables and plants. Optimum humidity is not lower than 8%.

Unlike the adult worm, the larva breathes oxygen. So with dirty hands, unprocessed vegetables and plants, as well as through unboiled water, the larva enters the human intestine. Gastric juice or hydrochloric acid destroy the protective shell of the larva, it begins to develop and migrate through the organ systems. At this stage, the larva needs oxygen from the lungs in order to become a sexually mature worm. And she finds him.

With its sharp end, it “perforates” the walls of the intestinal epithelium and enters the blood vessels.

Thus begins the migration path of roundworm through the human body to the lungs. With the bloodstream, it enters the chambers of the heart and reaches the human respiratory organs. Already a roundworm larva in the lungs of a person. "Traveling" through the capillaries, the larvae reach the alveoli and stay there for two weeks. From there, they enter the pharynx and move with saliva to the stomach. Finally, the larva enters the small intestine, and lives there for about a year if not treated. The process of appearance of an adult worm takes 2-3 weeks.

What harm does ascaris cause to the host's organs

Follow the rules of personal hygiene, do not be lazy to process food and boil water, such rules will help to avoid infection with helminths, in particular ascariasis.

The outer layer of the roundworm is made up of the hypodermis - in its structure it resembles epithelial cells, of which there are a significant number - ten layers that play a protective role and prevent damage to the individual itself and digestion by intestinal enzymes. Under the hypodermis is a layer of muscle fibers that allow the roundworm to actively move. Further under the muscle fibers is a cavity that is filled with fluid. This structure allows the worms to maintain a constant body shape and elasticity.

The excretory system of the roundworm is represented by two lateral canals that run along the body and correspond to the length of the body of the roundworm. Harmful undigested substances after the intestines enter the cavity filled with liquid, and then into these channels. Near the initial end of the roundworm body, excretory openings open, which correspond to the excretory organs.

The nervous system of the human roundworm is represented by neural tubes, which are located on the sides of the body, they have connecting elements. This is how the innervation of the sense organs and other internal organs. The sensory organs are very poorly developed - they are represented by bristles, which are the organs of touch.

The species of human roundworm that causes ascariasis is Ascaris lumbricoides, there may be differences only in the length of the individual between males and females.

Life cycle of human roundworm

Ascaris has a very long life cycle, a feature of which is a change in the location of the individual in the human body. The routes of infection by worms from the Nematode class are the fecal-oral route. The human roundworm belongs to the geohelminths, because one of its development cycles is in the ground. Thus, infection occurs during the ingestion of roundworm eggs. Ways of infection can be the following:

1. dirty hands - children are at greater risk due to the fact that they constantly play in the sandbox and eggs can be stored under the nails;
2. dirty unwashed vegetables and fruits - during ripening, eggs from the ground can fall on vegetables and berries;
3. after animals that have roundworm eggs on their hair - they can be peddlers;
4. with unboiled water, which has roundworm eggs;
5. poorly thermally processed food that does not allow killing eggs or roundworm larvae.

Diagnosis should begin with a careful history taking. Ascaris, being in the human body for a long time, contributes to the development of symptoms of intoxication, as well as dyspeptic disorders. Therefore, this disease will be accompanied by complaints of poor appetite, rumbling in the stomach, weight loss, nausea in the morning. When it comes to children, then it is clear that the child is thin, small, pale. Characteristic features ascariasis, like any other helminthiasis, is the grinding of teeth at night during sleep. If such symptoms are observed for at least the last few months, then you should think about helminthiasis.

If the larvae of the human roundworm enter the liver and lungs during migration, then nonspecific symptoms may occur with a violation of the intrahepatic outflow of bile. At the same time, an informative method for identifying the cause of this pathology is ultrasound. On ultrasound in the liver, anechoic foci are determined, which have clear edges and a rounded shape. Also, such changes can be determined in the lungs, which makes it possible to suspect the presence of roundworm larvae.

Many of the helminths can cause similar symptoms as roundworms, so it is necessary to carry out differential diagnosis. First of all, it is necessary to differentiate ascariasis and bovine tapeworm.

Although the principles of treatment for different types helminthiases are similar, but there are differences, so it is necessary to accurately differentiate the pathogen.

Treatment and prevention of invasion of human roundworm

Treatment of any helminthic invasion should be carried out only in combination with other means that prepare the gastrointestinal tract for deworming. Therefore, it is necessary to start with a diet that cleanses the intestines. It is necessary for the duration of treatment to completely limit sweet, starchy foods. It is necessary to eat cereals and cooked vegetables that stimulate intestinal motility. After that, it is desirable to conduct a course of carrying therapy. For this, it is necessary to conduct a single course with the use of laxatives. It is better to take herbal preparations with a carrying effect. These include "Senadexin" - a carrier-based remedy based on the leaves of the hay - a plant with a laxative effect. After such a course of cleansing therapy, they proceed to the treatment of the helminthic invasion itself. Anthelmintic drugs are used.

1. Pirantel- This is an antihelminthic drug that has an effect on human roundworm by depolarizing the membranes of the muscle cells of worms, which contributes to the death of mature forms of roundworm. The drug is available in the form of tablets and suspensions. The dosage of the drug for children is 250 milligrams up to six years old, and over six years old - 500 milligrams. For adults in the treatment of ascaris, a dose of one gram is recommended, that is, four tablets per dose. Possible side effects from the digestive system in the form of diarrhea, abdominal pain, nausea, as well as changes in the nervous activity in the form of dizziness, drowsiness, irritability, paresthesia.
2. Wormil is an anthelmintic drug active substance which is albendazole. The mechanism of action of the drug is to disrupt the metabolism of roundworm cells. The advantage of this tool is that albendazole acts both on the intestinal form, that is, on an adult, and on larvae and eggs. The drug is available in the form of chewable tablets and suspensions. The dosage of the drug is one tablet at a dose of 400 milligrams once a day, the course of treatment is three days. Possible side effects of the drug in the form of drowsiness, dizziness, decreased performance, as well as dyspeptic symptoms.

Prevention of infection with human ascaris can be specific and non-specific. Specific prophylaxis is the use of anthelmintic drugs that have activity against ascaris with a prophylactic purpose. For this, it is necessary to take anthelmintic drugs twice a year, for children half the doses of the therapeutic ones can be recommended. You can use any anthelmintic drugs - mebendazole, albendazole, Pirantel.

Non-specific prophylaxis should be used by all people, especially children should be monitored. Before eating, be sure to wash your hands, fruits and vegetables should also be washed before eating. As for water and food, for children better water do not drink raw, and give food to sufficient heat treatment. For good digestion and reduce the possibility of roundworm invasion, proper nutrition is necessary, which increases local immunity and anthelmintic capabilities of the intestine.

It's important to know!

Ascaris eggs are both a factor of infection and a subject of diagnosis. There are some salient features appearance Ascaris eggs, as well as some features of their resistance to environmental conditions, which allows you to take this into account in the diagnosis and prevention of ascariasis.

Invasion (infection) with ascaris leads to the disease - ascariasis, which is in second place in prevalence after enterobiasis (helminthiasis caused by pinworms).

The head end of the human roundworm is provided with three lips surrounding the mouth opening. In addition, the digestive system includes a long esophagus and a digestive tube with an anus at the end of the body. On the sides of the worm, longitudinal lines are clearly visible - the locations of the tubular excretory system. The nervous system of the nematode is represented by the pharyngeal ganglion, from which nerve trunks extend in all directions.

Roundworms are dioecious biological species, the structure of which has both internal and external distinctive features in females and males.

Human roundworm females are larger than males - their length reaches 40 cm, and their diameter is 6 mm. The body of a sexually mature female is elongated and ends in a conical point. In the anterior third of the body, there is a vulva that opens outwards and looks like an annular constriction. The anal opening is localized on the ventral part of the body closer to the terminal end.

The reproductive system in females is represented by paired tubes, consisting of two large uteruses, thin oviducts and filiform ovaries (right and left). Both uterus communicate with the vagina, which opens outward in the form of a genital opening on the abdominal surface. The maturation and development of human roundworm eggs occurs in the ovaries, the structural feature of which is a special core - rachis (rachis). Around the rachis germinal cells of ascaris ripen - oogonia, which, after fertilization by the spermatozoa of the male, reach the uterus and turn into eggs there.

The structure of the body of male roundworms

Male roundworms are smaller in size - up to 25 cm long and up to 4 mm in diameter. The end part of the body of males in the natural state is spirally bent to the ventral side. Closer to the tail, on the ventral side of the body, there is an anus and tactile organs - preanal and postanal papillae.

The reproductive system of male roundworms, unlike females, is represented by an unpaired tube, consisting of a filiform testis, a vas deferens larger in diameter, and an ejaculatory canal that opens into the cloaca (hindgut). Spicules - paired organs for fertilization of females - reach a size of 2 mm.

Features of the structure and development of human roundworm eggs

Due to high fecundity, up to 25 million eggs can be present in the body of the female at the same time, which she lays in batches of 200-250 thousand per day.

Together with the host's excrement, fertilized and unfertilized helminth eggs are excreted. To achieve an invasive (mature) state, they must enter the soil, and stay there at a certain temperature and humidity from one and a half to two weeks.

Fertilized eggs measuring 50 - 65 x 45 - 50 microns have an ovoid or spherical shape and are covered on top with several layers of the shell: tuberous outer, and smooth inner. This protective coating provides resistance to external influences and preservation of the viability of the embryo for a long period (up to 5 years or more!). Inside each of the helminth eggs contains a spherical fine-grained blastomere.

The outer protein shell of the roundworm egg, when it leaves the female's body into the human intestine, is stained with faeces in brown, making the eggs opaque. The inner shell contains several lipid layers and is designed to protect the developing roundworm embryo from destruction by chemical factors. Fat-dissolving substances are fatal to them - gasoline, hot sunlight, alcohols or ethers.

The role of larvae in the roundworm development cycle

The larvae are formed inside the eggs within 10 - 40 days in the presence of oxygen and in a humid environment. Outwardly, they resemble adults, but are significantly inferior to them in size. Their growth and development is accompanied by repeated molts with a change in the cuticle. When maturing, the larva becomes mobile and acquires an invasive ability (the ability to further development in the body of the host).

Ingestion of ascaris eggs by a person occurs when food or water contaminated with soil is consumed, however, the development of helminthic invasion is possible only if mature eggs enter the body of the host. In the intestine, roundworm eggs release larvae that can penetrate the intestinal wall into the surrounding blood capillaries.

Further, with the blood flow, the larvae freely migrate throughout the body, settling in the liver, lungs, brain and feeding on serum and blood cells. In typical cases, the larvae that have entered the lungs actively penetrate from the vessels into the alveoli, and then move with the help of the ciliated epithelium to the oropharynx, where they are reflexively swallowed along with sputum.