Roundworms in humans grow up to 35-40 cm. The larger ones are females. It is extremely rare for a male to reach this size. Its maximum length is 25-28 cm. The size of the roundworm depends on the age of the parasite, which can live in the human body for 3-4 years. There are also distinctive structural features of floors. Males have a curved tail tip that points toward the abdomen.
The main habitat is the small intestine. Ascaris has a characteristic feature - a smooth body surface. Sexually mature individuals are in constant motion - against the direction of peristalsis and movement of feces. They cannot attach to the walls of internal organs.
What to do in such a situation? To get started, we recommend reading this article. This article describes in detail methods of controlling parasites. We also recommend that you consult a specialist. Read the article >>>
The process of infection with roundworms
The main distributor of roundworms are people themselves. The feces of a person infected with helminthic infestation contain parasite eggs. They can survive outside the human body for 2-3 years.
If there is contact with the ground, the parasites acquire favorable “soil” for the development of human roundworm, ready to re-infect humans. The pattern of development of roundworm from an egg occurs in stages, during warm periods of the year. Therefore, signs of ascariasis in adults and children are observed more often from April to October.
The full development cycle of human roundworm begins with the egg phase. Some of them are fertilized. To begin their active growth, they need to go through certain stages of ripening in the soil. This is accompanied by air humidity of 4-8%, temperature of 14-37˚C, as well as a constant flow of oxygen.
A feature of the development of the parasite is its resistance to sudden cold snaps. If the air temperature drops during the ripening process, the helminths will not die. The roundworm's life cycle is suspended. In this state, eggs can remain for up to 8 years.
The development of roundworm to maturity occurs in the human body itself.
She can get there in one of the following ways:
- through body contact with the soil;
- eating poorly washed vegetables, berries or fruits;
- drinking tap water;
- with the consumption of meat and fish dishes that have undergone insufficient heat treatment.
Once in the body, the life cycle of the human roundworm moves on to the next stage of its own development. There are two of them - intestinal and migratory.
The migration cycle of roundworm development occurs through the circulatory system. The larvae are transported through the bloodstream to the liver, then to the heart and lungs. After this, they enter the throat. And this is again a direct path to the intestines. A secondary ingestion of the larva occurs, which, once in the intestine, develops into a sexually mature individual.
It takes up to 2.5-3 months for a sexually mature individual to mature. The development of the human roundworm occurs throughout its life. The average lifespan of an individual is 1-2 years. When it dies, the roundworm parasite leaves the intestines along with the feces. But self-healing occurs very rarely. Most often, more than one individual parasitizes the intestines. There is also a risk that a person will become infected with ascariasis again. No one is protected from such a “cycle”.
Internal structure of the body of a roundworm
Digestive system
The mouth opening is located at the anterior end of the body and is surrounded by lips. The anterior part of the intestine, the pharynx, has dense muscular walls. Free-living nematodes feed on bacteria, algae, and organic debris - detritus. Some have cuticle outgrowths in the throat - peculiar teeth. With their help, nematodes pierce the integument of animals and plants.
Body cavity
Previously, nutrients were distributed throughout the body by a branched intestine. Now that the intestine has turned into a straight tube, this function has been taken over by the body cavity - the fluid-filled space between the skin-muscular sac and the intestine.
The liquid is not cells; it would leak out if it were not packaged in an impenetrable elastic cover. This cover is formed by a layer of ectoderm cells and covered with cuticle - a durable film. The cuticle not only protects against mechanical damage and toxic substances, but also restrains the pressure of the cavity fluid.
As a result, the body cavity, surrounded by a cuticle and filled with liquid, acquires the elasticity of an inflated ball and forms a hydroskeleton. It is the hydroskeleton that gives roundworms their characteristic shape and serves as a support for muscles. Their muscles are only longitudinal. They are located inside the cavity, along the walls of the body. By contracting alternately the dorsal and abdominal muscles, the worm bends and moves forward, lying on one side.
Gas exchange and metabolism
In free-living roundworms, gas exchange (oxygen consumption and carbon dioxide release) occurs through the integument of the body. In parasitic nematodes, the energy necessary for life is released due to the breakdown of organic matter accumulated in the body - glycogen. Due to the absence of a circulatory system, nutrients and waste products in the body are carried by the fluid of the primary body cavity.
Excretory system
The excretory system consists of two lateral blindly closed channels. They open outward with an excretory opening on the ventral side of the front of the body. The walls of the canals are formed by one or several very long cells (their length can reach 40 cm). Harmful substances formed in the body enter the cavity fluid, then into the channels of the excretory system and are eliminated.
Nervous system
The nervous system of nematodes is represented by longitudinal nerve trunks connected by annular bridges. Nerves extend from them to the muscles and sensory organs.
Sense organs
The sense organs of roundworms, especially parasitic species, are very poorly developed. On the front of the body there are setae that serve as organs of touch and olfactory pits. Some free-living creatures have primitive eyes.
Reproduction
Nematodes are dioecious animals. The genital organs have the shape of tubes: in females they are paired, in males they are unpaired. Females have paired ovaries and oviducts, one uterus and a genital opening that opens on the ventral side of the body.
The male has one filamentous testis, gradually turning into a larger vas deferens. It flows into the hindgut just before the anus. The male has retractable cuticular needles, with the help of which he introduces sperm into the female’s genital opening.
Every day, one female human roundworm is capable of producing 200,000 eggs. The eggs are covered with a dense shell that protects them from the effects of unfavorable factors (drying, etc.). The crushing of the egg and the development of the larva lasts about a month and can only occur in a humid environment with a sufficient amount of oxygen.
Life cycle stages
Adult worms live in the lumen of the small intestine. Their lifespan ranges from 10 months to two years, after which they, or rather their remains, are excreted in the feces. The eggs of any roundworm (not just human ones) leave the body of the final host along with the feces. If during the course of the infection only a female lives in the body, then her eggs are infertile, and if only males, then the eggs do not come out at all.
Initially, fertilized eggs do not pose a threat, since they are still immature, and therefore non-invasive (non-contagious). First, the larvae should mature in them within about two weeks in the presence of a sufficiently warm and humid environment. During this process, the embryo goes through several stages: morula, gastrula, tadpole, larva. After this, the egg must be swallowed by the future owner, which usually happens along with contaminated food or water.
The entire life cycle of development of the human roundworm in the host’s body can be divided into two global stages:
- stage of helminth migration;
- intestinal stage.
Migration stage
Once in the lumen of the human intestine, the larvae are released from the protective shell and become about 0.2 mm long. The implementation of this process occurs due to the release of its own enzymes that can dissolve the outer coating. The presence of a special uncinate process makes it possible to firmly attach to the mucous membrane of the small intestine, after which the larvae pierce it and enter the bloodstream. Studies have also shown that migration is facilitated by the release of an enzyme related to hyaluronidases, which dissolves vascular tissue.
The penetration of roundworm larvae into the bloodstream causes their spread throughout the body. One of the first target organs is the liver. Then, after migrating to the heart, they enter the pulmonary circulation (pulmonary), thanks to which they reach the lungs. The larvae need oxygen to fully mature. Unlike mature worms, which this gas kills and this is one of the treatment methods.
In the alveoli of the lungs, the last two molting processes take place over the course of about 10 days, due to which each larva reaches 1.4 mm in length. Then they travel along the ciliated epithelium that lines the human respiratory tract, through the bronchi and trachea to the larynx, to be swallowed again. During this period, a cough may be observed as a response to irritation.
The larva thus returns to the small intestine, where it grows until it becomes an adult. But this is already the intestinal stage.
This complex process of helminth maturation is an integral part of their life. The duration of the migration phase for ascariasis is on average 14-15 days.
Intestinal stage
The main parameter characterizing this stage is the maturation of roundworm larvae and their transformation into an adult. At the same time, the worms reach impressive sizes - females become up to 40 cm long with a diameter of 5 mm, and males - 25 cm and 3 mm, respectively.
They then live, mate and lay eggs inside the intestines for up to 1.5 years.
The duration of the disease is due to constant self-infection. Since reproduction within the host is not possible for roundworms, as is the case for most other worms. Considering this factor, a person may suffer from ascariasis for several years.
From the moment an roundworm egg enters the human body until the first egg laying by an adult female, an average of 80 days pass.
In the initial period of its development and maturation, the immature roundworm feeds by absorbing human blood serum. During its maturation, red blood cells become the source of nutrients for the parasite.
Ascariasis is one of the most common parasitic diseases
There is an opinion that after the end of the life cycle, helminths independently leave the human body. This statement is wrong. Such migration paths of roundworms determine their uniform distribution throughout the body. Therefore, the appearance of combined inflammatory processes in the gastrointestinal tract, heart, and lungs is not accidental. Among the main clinical manifestations of ascariasis are myocarditis, pneumonia, bronchitis, jaundice, and gastrointestinal bleeding.
External structure
The body of roundworms is gradually narrowed towards the anterior and posterior ends, almost round in cross section, non-segmented. The outside of the body is covered with a cuticle; underneath it lies a layer of epithelial cells. Below are the muscles - four longitudinal single-layer ribbons. This structure allows roundworms to crawl by bending their body. The cuticle, epithelial cells and muscles form the skin-muscle sac (body wall). Between it and the intestine is the primary body cavity. It is filled with liquid, which, due to pressure, maintains a constant body shape, promotes the distribution of nutrients throughout the animal’s body, and the movement of decay products to the excretory organs.
These animals were the first to learn to burrow into soil or other substrate rich in food, such as plant tissue. Thus, they found not only a new habitat with its food supplies, but also shelter from predators - large eyelash worms.
With such a life, the mouth of roundworms is located strictly at the front end of the body. Pressure inside the hydroskeleton makes it difficult to swallow food. Therefore, their muscular pharynx acts like a pump with valves: it sucks in food and then forcefully pushes it into the intestine.
The external similarity of roundworms is due to the fact that, despite their widespread distribution, they all live in a similar environment - in a nutrient substrate. In bottom silt and soil, this “soup” is made up of the remains of organisms, along with bacteria and protozoa, and in plants and animals - the nutrients of their bodies. The main difficulty in these conditions is caustic chemicals. But the cuticle reliably protects against them. Some species can even survive in vinegar.
Maturation of roundworm eggs
The maturation of helminth eggs is influenced by several factors that should be familiarized with in advance.
Temperature
The rate of egg maturation directly depends on the ambient temperature. Indicators of about 20-25 degrees are considered optimal. In such conditions, worms are able to grow within 10-15 days. However, they also develop at temperatures of 5-10 degrees. With such indicators, the duration of their maturation increases to 30 days.
Soil moisture
Also, the duration of development of roundworm is affected by the level of soil moisture. In the summer, well-moistened soil promotes the maturation of eggs, since low humidity can lead to their death. In spring, when the air temperature is below 30 degrees, eggs develop well even in average humidity.
Oxygen access
The amount of oxygen in the soil can also affect the ripening process. In soils that are saturated with oxygen, the development of roundworm slows down. Their eggs develop better in dense soil with poor air permeability.
Nervous system
Its structure is also primitive. The nervous system of the parasite consists of one ganglion node represented by a peripharyngeal ring. It is located in the head part of the helminth. Dorsal and abdominal nerve bundles extend from it along the body. Their functions include organizing muscular control during movement and the presence of sensitivity.
Roundworms have practically no receptors. There are only papillomas, which are tactile bumps. They are located near the oral cavity.
Parasites also have no other sensitive formations. They have atrophied because the digestive environment of the human intestine does not contain any physical irritants.
Harm from roundworms
Adult roundworms can cause intestinal blockage, damage, and indigestion.
The waste products of roundworms are poisonous, which leads to poisoning of the body, which manifests itself through a rise in temperature, vomiting, irregular heartbeat, etc.
Ascaris larvae migrating with the bloodstream can damage internal organs (liver, pancreas); when the larvae pass through the walls of the lungs, blood may appear when coughing.
Clinical picture and symptoms
Ascariasis may not show any symptoms for a long period of time. The presence of signs of the disease depends on the individual sensitivity of the body and the severity of the invasion.
However, the parasite causes significant damage to organs as it migrates and grows in the small intestine. Main clinical features:
- Lung damage and hypersensitivity. During the migration stage, the patient may have an allergic reaction to the worm larvae. This may include a continuous cough, difficulty breathing and an increase in body temperature. Sometimes skin rashes appear.
- Intestinal disorder. Thus, the activity of the parasite in the small intestine can cause digestive disorders, anorexia, nausea and diarrhea. Impaired absorption of nutrients in the intestines provokes hypovitaminosis and mineral deficiency. Most often, patients have a deficiency of vitamins A and C.
- Intestinal obstruction. A large mass of worms can completely obstruct the intestinal lumen, causing a serious complication. Symptoms of this condition include severe abdominal pain, vomiting and constipation.
- Infants experience prolonged colic. Possible consequences of obstruction include gangrene and perforation of the intestinal wall.
- Damage to the liver and pancreas. Signs associated with the migration of the worm in the digestive organs include abdominal pain, biliary colic, cholecystitis, jaundice, and even inflammation of the peritoneum (peritonitis). An extremely dangerous complication is liver abscess. Patients with pancreatitis due to the spread of larvae develop fever and diarrhea.
Other possible symptoms:
- Dyspnea.
- Feeling of discomfort in the chest.
- Presence of blood in expectorated mucus.
- Loss of appetite.
- Bloating.
- Disorders of physical and mental development in children.
Most signs of ascariasis are nonspecific, so diagnostic testing is required.
Treatment and prevention of human roundworm infestation
Treatment of any helminthic infestation 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 to completely limit sweet and starchy foods during treatment. It is necessary to eat cereals and cooked vegetables, which stimulate intestinal motility. After this, it is advisable to conduct a course of carrying therapy.
To do 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 portable remedy based on the leaves of senna - a plant with a laxative effect. After this course of cleansing therapy, they move on to treating the helminthic infestation itself. Antihelminthic drugs are used.
- Pyrantel is an anthelmintic drug that acts against human roundworm by depolarizing the membranes of muscle cells of worms, which contributes to the death of mature forms of roundworm. The drug is available in the form of tablets and suspension. 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 roundworms, 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 nervous activity in the form of dizziness, drowsiness, increased excitability, paresthesia.
- Vormil is an anthelmintic drug whose main active ingredient is albendazole. The mechanism of action of the drug is to disrupt the metabolism of roundworm cells. The advantage of this remedy is that albendazole acts both on the intestinal form, that is, on the adult, and on larvae and eggs. The drug is available in the form of chewable tablets and suspension. 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.
Release form
Prevention of infection with human roundworm can be specific and nonspecific. Specific prevention is the use of anthelmintic drugs that have activity against roundworms for prophylactic purposes. To do this, it is necessary to take anthelmintic drugs twice a year; for children, half the therapeutic doses can be recommended. You can use any anthelmintic drugs - mebendazole, albendazole, Pyrantel.
Nonspecific 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, it is better for children not to drink water raw, but to allow food to undergo sufficient heat treatment. For good digestion and reducing the possibility of roundworm infestation, proper nutrition is necessary, which increases local immunity and the anthelmintic capabilities of the intestines.
Stop fooling yourself
Before reading further, I will ask you 1 question. Are you familiar with this situation when a person has been treated for chronic diseases for years, but there are no results?
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Read further:
Where does the roundworm larva develop: stages of development of the human roundworm
Ascaris larva: development cycle, migration, what they look like and how to destroy
Intermediate host of roundworm and its life cycle of development in the body
Whether the roundworm is a closed circulatory system or not, description and structure of the human roundworm
Roundworms in cats: life cycle of the parasite and how to treat it
What is the excretory system of the human roundworm?
Diagnosis of ascariasis
The first stage of diagnosis is collecting information about the symptoms that bother the patient. Next, using microscopy, the presence of helminth eggs in the feces is diagnosed. In photographs of human roundworms in feces, the eggs look approximately the same as they do in the laboratory under a microscope.
The reasons why eggs were not found in the stool, but helminth disease is possible:
- The person was infected quite recently, and the female had not yet had time to lay eggs;
- ascariasis in a patient in an extraintestinal form;
- eggs are absent only in stool intended for analysis.
In such cases, other diagnostic methods are prescribed - blood tests, tomography, ultrasound, radiography.
Respiratory system
Worms live in an anaerobic environment. Where there is no free oxygen. Therefore, they do not need the respiratory organs present in individuals that are more developed. Their lack of a respiratory system is the result of a natural adaptation, since there is no air in the human intestines.
Metabolic processes occur due to cellular respiration. It is carried out as a result of glycolysis in the cell cytoplasm. This type of cellular respiration, in which there is no oxygen, is used by anaerobic organisms.
