What is ascariasis? This is a disease caused by ascaris worms that have entered the human body by the oral route. People all over the globe suffer from this disease, even in desert areas and in areas where there is permafrost. To understand the causes of this disease, you need to find out how the worms develop.
Sources of infection
The earth is polluted with human waste products and is the main source of infection with ascariasis. Before we find out what the causative agent of the disease is, consider the life cycle of roundworms. You can get infected with them through unwashed hands, fruits, berries, vegetables, especially greens. In addition, roundworm larvae are carried by various insects, in particular, flies from street latrines. It is almost impossible to directly infect a person from a person. There are some other ways of transmitting ascaris, here are the main ones:
- Water from sources that have contact with faecal contamination. Importantremember that water from underground is not a guarantee of purity.
- Children can become infected in nature, because roundworm larvae can be everywhere.
- Individual cases - transmission of infection through the placenta.
- Self-infection. There are cases when roundworm eggs ripen directly in the human body, and thus it is re-infected.
What is Ascaris?
Before studying the life cycle of the human roundworm, it is necessary to imagine what this helminthic parasite looks like. The living helminth has a pinkish spindle-shaped body. The dead worm will be whitish-yellow. The body length of the roundworm female can be from 25 to 40 cm, width - from 4 to 6 mm. Male length - 15-25 cm, width - 2-4 mm.
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 course of their life, these worms poison the body with various toxins and allergens. By products of metabolism and decay, they provoke diseases in humans, for example, liver inflammation or skin rashes. Adult roundworms are very sensitive to oxygen: it has a detrimental effect on them, therefore, when they enter the environment, they immediately die.
Characteristics of roundworms
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 wine of a cone, while in males it is curved in the shape of a hook. The genital organs of parasites consist of:
- Females from a pair of ovaries, the organ for hatching eggs, have 2 uterus, which pass into the external genital organ - the vagina.
- In males from the gonads - testes, vas deferens and ejaculatory canals, 2 spicules from 0.15 to 0.2 cm in length.
The digestive system of Ascaris consists of the oral cavity, a long cylindrical esophagus, an intestinal tube with an anus at the end. The life cycle of a human roundworm lasts about a year. These parasites are fertile. Up to 27 million eggs of varying degrees of maturity can be in the body of a female at the same time. In one day, roundworm is able to lay 240,000 pcs.
What is the difference between fertilized roundworm eggs and unfertilized ones?
Ascaris eggs that are fertilized are oval or spherical in shape. The sizes can be from 50-70 to 40-40 microns. The egg consists of a protective multi-layer shell. Outside, there is a protein membrane, it is bumpy and transparent as long as the egg is in the womb of the female. Then the roundworm development cycle continues. When the parasite egg enters the intestine, the shell becomes brown or dark yellow and loses its transparency. But the inside 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 quite difficult to diagnose eggs, they are deprived of the outer shell.
Unfertilized eggs also go through a certain cycle of development of the human roundworm, the scheme for getting them into the human body is no different from fertilized ones. Size variations vary. The outer shell is protein, has a rough structure with uneven, alternating teeth. Inside the egg is a yolk cell. When an unfertilized egg lacks an outer shell, it is very difficult to tell what it is, and one can easily confuse it with a plant cell.
Ascaris development cycle
Eggs are excreted in the stool from the human body and under favorable conditions can be stored for about 10 years. They are highly resistant to chemical water treatment, but are filtered and die when it is boiled. In order for the life cycle of roundworms to continue, it is necessary that the egg enters a certain stage, that is, it becomes invasive - infectious for humans. The larva should begin to develop in it. Its formation is facilitated by oxygen, which is not present 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 ripen within 2 weeks, otherwise the process can take several months. Eggs also die during 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 tolerate low temperatures well, and they are not afraid of frost.
Further development of roundworm
Ba mature egg contains a formed larva, which represents the appearance of a coiled worm. The life cycle of the roundworm begins by emerging from the eggs in the intestines. She makes a difficult migration path from a larva to a sexually mature individual capable of laying eggs. Below is the entire life cycle of the roundworm, the process diagram is as follows:
- The larvae penetrate the intestinal mucosa and then into the capillaries.
- A large vein that runs from the intestines to the liver enters the liver.
- Through the lower vein with blood - to the right side of the heart.
- Through the pulmonary artery - to the lungs.
- Further through the bronchi and trachea - into the pharynx and oral cavity. Here, roundworms are swallowed and redirected to the intestines.
Just when the larvae enter the intestines for the second time, they turn into adult roundworms.
Length of the migration period
In order for a mature individual to form from a larva, a certain period must pass. At this time, she 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 roundworms 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 migration period does not have to end in the intestines, the larvae can settle and subsequently die in the liver. If they enter the mouth, they can simply be spit out, especially if there is a lot of sputum. Sometimes ascaris is found in the ventricles of the heart, trachea,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 includes horse roundworm, the development cycle of which lasts about 2 months. The length of this parasite is about 40 cm. Only a certain type of helminth parasitizes in each animal species. For example, pig and human roundworms are very similar. But infecting a human with a swine parasite is almost impossible, and vice versa.
The main danger is that helminths adversely affect the human immune system. They penetrate into almost all organs and tissues, causing inflammation and all sorts 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!
