What is the way of transferring ascaris eggs to humans?
Ascaris is a large worm that is spindle-shaped and pale pink in color. Ascaris refers to the roundworm nematodes that cause a disease in humans called ascariasis.
Ascaris can only be carried by humans; these worms do not parasitize any other living organisms. The route of transmission of ascaris eggs to a person is alimentary, that is, through the mouth, and the mechanism of infection is fecal-oral. Every day, an adult female roundworm is able to lay in the intestines up to 200-250 thousand new eggs, which, together with the feces of a sick person, go outside and enter the external environment. Adults live for a year, after which they die on their own from old age.
The way roundworm eggs are transmitted to humans
For infection with ascariasis to occur, the invasive larva must enter the human gastrointestinal tract.
Most often this happens in the following ways:
- When eating vegetables, fruits, herbs, berries that were poorly washed and worm eggs remained on them.
- Drinking drinking water that is contaminated with invasive Ascaris eggs. As a rule, all water supplied through the water supply system undergoes high-quality preliminary treatment. However, it is possible that the pipes may be damaged and ascaris larvae will get into them, along with the soil. It is no less dangerous to drink water from wells, open springs and other natural sources.
- Eggs can be introduced into the digestive tract if personal hygiene is not followed. This, first of all, concerns unwashed hands, on which larvae of worms may be present. Children are at high risk as they come into frequent contact with sand and earth, especially during the summer months. At the same time, the rules of personal hygiene by young children are not fully observed.
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All people engaged in agriculture, as well as gardeners, gardeners, and summer residents are at risk for ascaris infestation. This also includes workers of sewage treatment plants.
- Pets are often the source of infection. Parasites cannot live in their bodies, but they are able to attach to their fur while walking. After that, it will be enough to stroke your pet, do not wash your hands and start eating.
- Ascaris eggs can be carried by flies and cockroaches, seeding them with food.
Transmission of ascariasis most often occurs from May to October, if we consider the middle lane, and as for tropical countries, the risk of invasion remains there all year round.
After the invasive roundworm larva enters the gastrointestinal tract, gastric enzymes begin to act on it. Under their influence, the larva is released from its membrane and penetrates through the epithelial cover of the small intestine into the blood vessels.
Through the portal vein, the larvae enter the liver, then into the right heart, and then, through the small circle of blood circulation, into the lungs. There they penetrate the alveoli through the capillaries and stay in them for up to 7-10 days. Then, along the bronchial tree, in the process of coughing, the larvae are thrown into the larynx, where they are swallowed again with saliva and lowered into the intestines. In the small intestine, the larvae mature to mature individuals, which will reproduce new eggs. Together with feces, they go outside, fall into the soil and the cycle repeats.
The full cycle of transformation of the roundworm egg into a mature worm is about 3 months. After this time, the eggs of the parasites can be detected in the feces by laboratory means.
Development of larvae from eggs laid by roundworms occurs
The development of larvae from eggs laid by roundworms occurs in the soil. Eggs excreted with feces in one way or another fall into the ground, where they ripen.
The optimal conditions for this process are:
- Ambient temperature from +10 to +25 ° C Celsius.
- High soil moisture.
- Good soil aeration.
If all three of the above conditions are met, then after 2-3 weeks the eggs will mature and be ready for invasion. If the air temperature drops to -12 ° C, then the maturation of eggs slows down, they do not die, but they do not develop either. In addition, not all roundworm eggs contain larvae. Some of them turn out to be empty, which means that they cannot infect a person.
Ascaris eggs die at temperatures of -30 and below and +100 and above. They do not tolerate ultraviolet light and are prone to drying out. However, if the soil is moistened and there is enough oxygen in it, then they can maintain their viability for 6-7 years. Roundworms are widespread throughout the world, they cannot be found only in permafrost zones, in the highlands and in dry deserts.
The eggs are oval in shape and can be yellow or brown in color. The average egg size is 7 micrometers, so they can only be seen under a microscope. Each egg is covered with five protective shells that protect them from damage. It is thanks to such reliable protection that ascariasis is so widespread throughout the world.
Article author: Mochalov Pavel Alexandrovich | d. m. n. therapist
Education: Moscow Medical Institute. IM Sechenov, specialty - "General Medicine" in 1991, in 1993 "Occupational Diseases", in 1996 "Therapy".
