Development and life cycle of ascarids

What is an ascariasis? This is a disease caused by worms ascarids, ingested in the human body. People suffer from this disease all over the globe, even in desert areas and in regions where permafrost is present. To understand the causes of this ailment, it is necessary to find out how the worms develop.

Sources of infection

The earth is polluted with the products of human life and is the main source of infection with ascariasis. Before you know what the causative agent is, consider the life cycle of ascarids. Infecting them can be through unwashed hands, fruits, berries, vegetables, especially green. In addition, ascarid larvae are transported by various insects, in particular, flies from street latrines. It is practically impossible to get a person directly from a person. There are still some ways of transferring ascarids, here are the main ones:

1. Water from sources that have contact with contamination from faeces. It is important to remember that the water from under the ground is not at all a guarantor of purity.
2. Children can become infected in nature, as the ascarid larvae can be everywhere.
3. Single cases - transmission of infection through the placenta.
4. Autoinfection. There are cases when the eggs of ascarids mature directly in the human body, and thereby it again infects it.

What is an Ascaris?

Before studying the cycle of human ascarid development, it is necessary to imagine what this helminthic parasite looks like. The living helminth has a body in the form of a spindle of a pinkish color. The dead worm will be whitish-yellow. The length of the female body of the roundworm can be from 25 to 40 cm, width - from 4 to 6 mm. The length of the male is 15-25 cm, width - 2-4 mm.

Sexually mature roundworms usually live in the small intestine of a person and feed on its contents. The life of the parasite is about a year. In the process of their life, these worms poison the body with various toxins and allergens. By the products of metabolism and decay they provoke diseases in a person, for example, hepatic inflammation or rashes on the skin. Adult individuals of ascarids are very sensitive to oxygen: it acts on them fatal, therefore, when they enter the environment, they immediately die.

Characteristics of ascarids

Female and male differ from each other not only in size, but also in the shape of the tail part. The females have a tail in the wine of the cone, while in the males they are curved in the shape of a hook. Sexual organs of parasites are:

1. In females from a pair of ovaries, an organ for the extraction of eggs, 2 queens, which pass into the external genital organ - the vagina.
2. In males from the genital glands - testes, seminal and ejaculatory ducts, 2 spicules from 0.15 to 0.2 cm in length.

The system of digestion of ascaris consists of the oral cavity, the long esophagus, which has a cylindrical shape, the intestinal tube with the anal opening at the end. The life cycle of a human roundworm lasts about a year. These parasites are fertile. In the body of the female, up to 27 million eggs of different degrees of maturity can simultaneously be present. For one day ascaris is able to postpone 240 000 pcs.

What is the difference between the fertilized eggs of ascarids from unfertilized eggs?

Eggs of ascarids, which are fertilized, have an oval or spherical shape. Dimensions can be from 50-70 to 40-40 microns. The egg consists of a protective multi-layered shell. The protein membrane is located outside, it is tuberous and transparent until the egg is in the womb of the female. Then the cycle of development of the roundworm continues. When the eggs of the parasite enter the intestine, the envelope becomes brown or dark yellow and loses its transparency. But the inner part remains smooth and transparent, it protects the embryo from harmful chemical influences. Inside the egg there is a cell that appeared during a certain division, with a spherical shape and a granular base. Sometimes it is difficult to diagnose eggs, they are deprived of an outer shell.

Unfertilized eggs also undergo a certain cycle of development of the human roundworm, the scheme of getting them into the human body does not differ from the fertilized ones. Variations in size fluctuate. The outer shell is protein, has a coarse structure with uneven, alternating teeth. Inside the egg is a yolk cell. When unfertilized eggs are devoid of an outer shell, it is very difficult to determine what it is, and it is easy to confuse it with a plant cell.

The cycle of development of ascarids

Eggs are allocated with a chair from the human body and under favorable conditions can last about 10 years. They have high resistance to chemical water purification, but are filtered and die by boiling. In order for the life cycle of ascarids to continue, it is necessary that the egg enter a certain stage, that is, it becomes invasive - infectious for humans. The larva should begin to develop in it. Its formation is promoted by oxygen, which is not present in the intestine. Therefore, when eggs enter the environment, they begin to grow intensively, especially if the conditions are favorable. At a temperature of about 25 degrees, eggs mature within 2 weeks, otherwise the process may take several months. Dying eggs and when drought, for example, in dry sand. Wet sand is the most favorable environment for the life cycle of the human roundworm to continue successfully. Eggs do not suffer a low temperature, and they are not afraid of frost.

The further way of development of the roundworm

The matured egg contains a formed larva, which represents the appearance of a curled worm. The life cycle of the ascaris begins by leaving eggs in the intestine. She makes a difficult migratory path from the larva to the sexually mature individual, capable of laying eggs. Below is the entire life cycle of the roundworm, the scheme of the process is as follows:

1. Larvae penetrate into the intestinal mucosa, and then into the capillaries.
2. By a large vein, going from the intestine to the liver, get into the liver.
3. On the lower vein with blood - in the right side of the heart.
4. By the pulmonary artery - into the lungs.
5. Further through the bronchi and trachea - into the pharynx and the oral cavity. Here, ascarids swallow and are sent back to the intestines.

Just when the larvae enter the intestine a second time, adult roundworms are obtained from them.

Duration of the migration period

In order to form a sexually mature specimen from the larva, a certain period must pass. At this time, it passes the migration path described above. It lasts about 2 weeks - this is the time of the larval stage. The migration period is a prerequisite for maturation. The life cycle of ascarids after 2.5 months continues in that eggs appear in the excrement, but in some cases they can appear much earlier - in 3 weeks.

The migratory period need not end in the intestine, the larvae may settle and subsequently die in the liver. When ingested they can simply spit out, especially if there is abundant sputum. Occasionally, ascarids are found in the ventricles of the heart, trachea, and lungs.

In animals

Ascarids can lead a parasitic lifestyle in almost all animals: horses, pigs, donkeys, calves, cats, dogs, chickens, geese, etc. The largest family of very large worms is a horse ascaris, whose development cycle lasts about 2 Months. The length of this parasite is about 40 cm. Only a certain type of helminths parasitize each species of animal. For example, pork and human roundworms are very similar. But human infection with a porcine parasite is almost impossible, and vice versa.

The main danger is that helminths adversely affect the human immune system. They penetrate almost all organs and tissues, causing by their presence inflammatory processes and all sorts of complications. Therefore, the prevention of ascaridosis is very important. In case of infection, you should immediately contact a specialist. Do not self-medicate!