Human Ascarids: the life cycle of development

Ascariasis (a disease of "dirty hands") is a parasitic pathology, which is caused by roundworms - ascarids. People of any age and sex are affected, but children are more likely to suffer. You can get infected if you use uncleaned water, contaminated fruits and vegetables, if you violate the rules of personal hygiene. For treatment, anthelmintic therapy is necessary. Let us examine in detail the life cycle of the development of ascarids.

• What type of ascaris is
• Sequence of life processes
• How the ascarids multiply
• What feeds the parasite
• Atypical course of ascariasis

What type of ascaris is

Helminth is the largest representative of the family of nematodes (roundworms). The peculiarity of ascarids is the absence of intermediate hosts, they parasitize in one organism. The main habitat of the helminth is the small intestine. The outer structure of the ascarids resembles earthworms. They have a round body with pointed ends, covered with a protective shell. The length of the female is about 40 cm, the male is 25 cm. A female specimen per day is capable of producing more than 200 thousand. eggs. The lifetime of ascarids is 1.5 - 2 years, but if hygiene is not observed, the disease can be prolonged for a long time.

Sequence of life processes

Brief development scheme: egg - larva - adult worm. Let's consider each stage in detail.

Egg

Eggs are excreted with human feces into the environment, they are covered with a firm capsule. In soil and water can be maintained for a long time (10-12 years), due to the presence of a multilayered protective shell. Well tolerate low temperatures, mechanical effects, chemical water treatment. Dying at high temperatures, drought.

In favorable conditions (temperature 22-25 degrees above zero, high humidity), the larva begins to develop within 17-20 days. The next stage comes when the person swallows an egg with food and water. Contribute to this dirty hands, especially in children. Then the egg moves along the digestive tract. In the small intestine its shell dissolves under the action of enzymes and a young larva emerges.

Larva

To further develop the helminth, oxygen is required. At the end, the larva has an acute hook-shaped process, which damages the intestinal mucosa and exposes the blood vessels. It also produces an enzyme called hyaluronidase, which destroys the wall of the vessel. This allows the larva to penetrate into the venous bed, after which its migration begins in the human body. It corresponds to the incubation period (up to 2 weeks).

Stages of migration

Venous blood carries the larva to the portal vein, and then to the following organs:

• liver;
• the lower vena cava;
• right heart;
• pulmonary trunk;
• the pulmonary artery;
• lungs.

In the presence of oxygen, the larva lives in the lungs for about 10 days, develops and grows. After reaching a certain size, it rises in the ciliated epithelium of the respiratory system. Once in the trachea and larynx, the larva (adult) irritates the cough receptors.

During this period, patients can seek help from a polyclinic with complaints of dry coughing attacks, a feeling of perspiration in the throat. On the roentgenogram, areas of hemorrhage in the lung tissue are visible, and anemia is determined in the general blood test.

During the cough, the larva enters the oral cavity and swallows, again reaching the small intestine. During migration, nonspecific symptoms may occur-abdominal pain, icterus of the skin, hemoptysis, and others.

Adult specimen

In the small intestine an adult worm is formed from the larva. Round helminths are more often than sex. The life of an adult roundworm in the human body can last a long time, but on average is 1.5 years. When outward, a mature individual dies from excess oxygen.

How the ascarids multiply

The male attaches itself to the female and fertilizes it. In one clutch there may be several hundred thousand eggs. Simultaneously, the female can carry eggs of different stages of development. Then they go out with feces.

What feeds the parasite

In the process of its development and reproduction, the worm receives nutrients from blood serum. As he grows up, he feeds on red blood cells (erythrocytes) that contain oxygen. The worm robbed the host's body, taking away vitamins and other useful elements from it. A person can feel weakness, decrease in working capacity, irritability, apathy, weakening of immunity.

Important! There is an erroneous opinion that the ascaris itself leaves the body after the end of its life cycle! Circulating through the circulatory system, the larva can damage other organs and systems, causing myocarditis, pneumonia, mechanical jaundice, intestinal bleeding.

Atypical course of ascariasis

The life cycle can be interrupted:

1. At the liver level, where the larvae settle and die.
2. When migrating from the lower respiratory tract to the upper ones, when the larvae go into the environment with a cough and do not swallow.

To minimize the risk of infection, you must follow the rules of personal hygiene, wash vegetables and fruits, drink purified water.