What is ascariasis? This is a disease caused by roundworm worms, ingested orally. This disease affects people around the globe, even in desert areas and in areas where permafrost is present. To understand the causes of this ailment, you need to find out how the worms develop.
Sources of infection
The earth is polluted by human waste products and is the main source of infection with ascariasis. Before you find out what the causative agent of the disease is, consider the life cycle of roundworm. You can get them through unwashed hands, fruits, berries, vegetables, first of all it concerns greens. In addition, roundworm larvae are carried by various insects, in particular flies from outdoor latrines. It is almost impossible to get infected directly from a person. There are some more ways to transfer roundworms, here are the main ones:
- Water from sources that come in contact with contaminants from feces. It is important to remember that water from underground is not a guarantee of purity.
- Children can become infected in nature, because roundworm larvae can be everywhere.
- Isolated cases - transmission of infection through the placenta.
- Autoinfection. There are cases when ascaris eggs ripen directly in the human body, and thereby it again becomes infected.
What is roundworm?
Before studying the development cycle of human roundworm, it is necessary to imagine what this helminthic parasite looks like. A living helminth has a body in the form of a pinkish spindle. A dead worm will be whitish yellow. The body length of a roundworm female can be from 25 to 40 cm, width - from 4 to 6 mm. The male is 15-25 cm long and 2-4 mm wide.
Sexually mature roundworms usually live in the human small intestine and feed on its contents. The life span of the parasite is about a year. In the process of their activity, these worms poison the body with various toxins and allergens. By the products of metabolism and decay, they provoke diseases in humans, for example, hepatic inflammation or skin rashes. Adult Ascaris are very sensitive to oxygen: it acts on them destructively, therefore, when they enter the environment, they immediately die.
Characteristic Ascaris
Females and males differ from each other not only in size, but also in the shape of the tail. In females, the tail is in the cone's fault, and in males, it is curved in the shape of a hook. The genitals of the parasites consist of:
- Females from a pair of ovaries, an organ for hatching eggs, have 2 uterus that pass into the external genitalia - the vagina.
- In males of the sex glands - the testes, ejaculatory and ejaculatory channels, 2 spicules from 0.15 to 0.2 cm in length.
The roundworm digestive system consists of an oral cavity, a long esophagus having a cylindrical shape, an intestinal tube with an anus at the end. The life cycle of human roundworm lasts about a year. These parasites are fertile. In the female’s body, up to 27 million eggs of varying degrees of maturity can simultaneously be found. In one day, roundworm can postpone 240,000 pcs.
What is the difference between fertilized Ascaris eggs and unfertilized eggs?
Ascaris eggs that are fertilized have an oval or spherical shape. Sizes can be from 50-70 to 40-40 microns. The egg consists of a protective multilayer shell. Outside is a protein membrane, it is tuberous and transparent until the egg is in the female’s womb. Then the cycle of development of roundworm continues. When a parasite egg enters the intestine, the membrane becomes brown or dark yellow in color and loses its transparency. But the inner part remains smooth and transparent, it protects the embryo from harmful chemical influences. Inside the egg is a cell that arose during a certain division, with a spherical shape and a granular base. Sometimes it is difficult to diagnose eggs, they are devoid of the outer shell.
Unfertilized eggs also go through a certain development cycle of human roundworm, the pattern of their entry into the human body is no different from fertilized ones. Size variations fluctuate. The outer shell is protein, has a rough structure with uneven, alternating teeth. Inside the egg is a yolk cell. When unfertilized eggs are devoid of the outer shell, it is very difficult to determine what it is, and you can easily confuse it with the plant cell.
Ascaris development cycle
Eggs are excreted with stool from the human body and, under favorable conditions, can last about 10 years. They have high resistance to chemical water treatment, but are filtered and die when it is boiled. In order for the ascaris life cycle to continue, it is necessary that the egg enter a certain stage, that is, it becomes invasive - contagious to humans. The larva should begin to develop in it. Its formation is promoted by oxygen, which is not in the intestines. Therefore, when the eggs enter the environment, they begin to grow rapidly, especially if the conditions are favorable. At a temperature of about 25 degrees Celsius, the eggs mature within 2 weeks, otherwise the process can take several months. Eggs die in drought, for example, in dry sand. Wet sand is the most favorable environment for the life cycle of human roundworm to continue successfully. Eggs can tolerate low temperatures well, and frosts are not afraid of them.
The further development of roundworm
A ripened egg contains a formed larva, which is a type of curled worm. The life cycle of ascaris begins, leaving the eggs in the intestine. It makes a difficult migration path from a larva to a mature individual capable of laying eggs. Below is the entire life cycle of roundworm, the process diagram is as follows:
- Larvae penetrate the intestinal mucosa, and then - into the capillaries.
- The large vein from the intestines to the liver enters the liver.
- On the lower vein with blood - to the right side of the heart.
- In the pulmonary artery into the lungs.
- Further through the bronchi and trachea - into the pharynx and oral cavity. Here roundworms are swallowed and again sent to the intestines.
It is when the larvae enter the intestines for the second time that they produce adult roundworms.
The duration of the migration period
In order for a sexually mature individual to form from the larva, a certain period must pass. At this time, she goes through the migration route 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 ascaris after 2.5 months continues with the fact that eggs appear in the excrement, but in some cases they can appear much earlier - after 3 weeks.
The migratory period does not have to end in the intestine, the larvae can settle and later die in the liver. When ingested, they can simply spit out, especially in the presence of profuse sputum. Sometimes ascaris is found in the ventricles of the heart, trachea, lungs.
In animals
Roundworms 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 includes horse roundworm, the development cycle of which lasts about 2 months. The length of this parasite is about 40 cm. In each animal species, only a certain type of helminths parasitizes. For example, pork and human roundworms are very similar. But infecting a person with a swine 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 inflammatory processes and all kinds of complications with their presence. Therefore, the prevention of ascariasis is very important. In case of infection, you should immediately contact a specialist. Do not self-medicate!