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Ascaris is a large worm that has a spindle shape and a pale pink color. Ascaris is a roundworm nematode that causes a human disease called ascariasis.
Only a person can be a carrier of ascarids; these worms do not parasitize in any other living organisms. The way of transmission of roundworm eggs to humans is alimentary, that is, through the mouth, and the mechanism of infection is fecal-oral. Every day, an adult female Ascaris is able to lay up to 200-250 thousand new eggs in the intestines, which, together with the feces of a sick person, come out and enter the external environment. Adults live for a year, after which they die of old age on their own.
Way of transmission of roundworm eggs to humans
In order for infection with ascariasis to occur, it is necessary for the invasive larvae to enter the human gastrointestinal tract.
Most often this happens in the following ways:
While eating vegetables, fruits, herbs, berries that were poorly washed and worm eggs remained on them.
The use of drinking water that is contaminated with invasive ascaris eggs. As a rule, all water supplied through the water supply system undergoes high-quality pre-treatment. However, it is possible that the pipes may be damaged and, along with the soil, roundworm larvae will fall into them. It is no less dangerous to drink water from wells, from 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 worm larvae may be present. Children are at increased risk, as they often come into 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.
All people involved in agriculture, as well as gardeners, gardeners, and summer residents are at risk for ascaris invasion. This also includes wastewater treatment workers.
Domestic animals are often the source of infection. Parasites cannot live in their bodies, but they are able to attach themselves to their fur during a walk. After that, it will be enough to stroke your pet, do not wash your hands and start eating.
Ascaris eggs can carry flies and cockroaches, seeding food with them.
The 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 shell and penetrates through the epithelial cover of the small intestine into the blood vessels.
Through the portal vein, the larvae enter the liver, then to the right side of the heart, and then, through the pulmonary circulation, to the lungs. There they penetrate the capillaries into the alveoli and linger 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 again swallowed with saliva and lowered into the intestines. In the small intestine, the larvae mature into sexually mature individuals that will reproduce new eggs. Together with faeces, they go outside, fall into the soil and the cycle repeats.
The full cycle of turning an roundworm egg into a mature worm is about 3 months. After this time, parasite eggs can be detected in the stool by laboratory tests.
The 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 faeces in one way or another fall into the ground, where they mature.
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 ripen and will be ready for invasion. If the air temperature drops to -12 ° C, then the maturation of the eggs slows down, they do not die, but they do not develop either. In addition, not all roundworm eggs contain larvae. Some of them are empty, which means they cannot infect a person.
Ascaris eggs die at temperatures of -30 and below and +100 and above. They do not tolerate ultraviolet light, are prone to drying out. However, if the soil is moist and there is enough oxygen in it, then they can remain viable for 6-7 years. Roundworms are distributed 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 may 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.