The Cycle Of Development Of Roundworm In Humans And Transmission Routes

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The Cycle Of Development Of Roundworm In Humans And Transmission Routes
The Cycle Of Development Of Roundworm In Humans And Transmission Routes

Video: The Cycle Of Development Of Roundworm In Humans And Transmission Routes

Отличия серверных жестких дисков от десктопных
Video: Ascaris Lumbricoides lecture 2023, February
  • 1 What is Ascariasis?
  • 2 Life cycle
  • 3 Ways of infection
  • 4 Why are roundworms dangerous?

The human roundworm is a parasitic worm that lives in the small intestine of people of all ages. This is one of the most common forms of helminthiasis on our planet. This disease is most often found in countries with a tropical climate, because it is most suitable for this parasite. The development cycle of human roundworm is a rather complex process, which includes several stages, each of which has its own symptoms and certain consequences for the body. How are Ascaris infected? What are the ways of transferring ascaris eggs to humans? What do roundworms look like in humans? These and many other similar questions regarding this parasite are asked by people who care about their health, and it is very important to know the correct answers to them.

What is Ascariasis?

human roundworm
human roundworm

Ascariasis is a parasitic disease caused by ascaris. In this case, the person is both the source and the ultimate host of the parasite. The roundworm larva develops most of its life in the human body, spending only a little time in the surrounding world.

Developing countries are more likely to suffer from this disease than developed countries. This is due to lower quality sanitation, medical care, access to clean water and food. In a tropical climate, the parasite is more common, in a temperate climate there is a clear seasonality of the disease - most cases of treatment with ascariasis in them are recorded in the warm season.

Most of the symptoms of ascariasis are directly related to the various phases of migration of the parasite in the human body. These or those manifestations of ascariasis depend on the place where the helminth enters and the development of the disease. They usually affect the gastrointestinal tract, where adults are already localized, and the respiratory system, where the larval stage of the parasite passes.

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Ascaris itself rarely can be called a serious threat to human life. In most cases, these parasites only cause a number of minor and subtle disturbances in the functioning of the body, however, in children and adults with weakened immunity, this disease can cause the development of serious complications.

Life cycle

ascaris life cycle
ascaris life cycle

There are several stages in the development of roundworm. The best habitat for adults of this parasite is the human body. An adult female secretes up to a quarter of a million eggs per day in the intestines, which are excreted in the feces. The life cycle of the roundworm can be divided into the following stages:

  • Penetration of fertilized eggs of the parasite into the surrounding world. They are stable enough to be viable for a long time. The best place to store them is the soil - they can lie in it for years. With optimal humidity, temperature and the presence of an appropriate level of oxygen, larvae develop from the eggs in a few weeks.
  • The larva of the parasite is not particularly dangerous immediately after formation. It becomes ready to penetrate into the human body only after molting.
  • Once in the human digestive tract, the larva goes to the upper intestine. Here she finally hatches and reaches maturity. Further, the parasite easily enters the bloodstream through the pores in the intestinal walls due to its small size.
  • With the blood, the larvae pass the liver, then the inferior vena cava and through the right atrium reach the lungs. Sometimes some of the larvae settle in other organs as well.
  • Through the pulmonary capillaries, the parasite enters the alveoli, which make up the lung tissue. This site meets all the requirements for optimal larval development. After about a week and a half, the already sufficiently grown larvae rise from the small bronchioles along the paths of air movement to the trachea. Having reached the oral cavity, roundworms enter the intestines again.
  • Having entered the intestine for the second time, the larvae, due to their already large size, do not have the opportunity to penetrate through the pores into the blood, but they can actively move, which allows them to linger in this area. After about 3 months, the larva transforms into an adult parasite. If individuals of both sexes are present, they reproduce, their eggs are excreted in the feces, and the life cycle of the roundworm begins from the very beginning.

Infection routes

dirty vegetables and fruits
dirty vegetables and fruits

How to get infected with Ascaris? One of the most common ways of infection with ascaris is considered to be neglect of hygiene standards - with dirty, poorly washed hands, the risk of ascaris entering the human body increases. Given that the eggs of the parasite can remain in the soil for a long time, doctors identify the following factors that contribute to infection:

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  • Not properly treated water from natural and artificial reservoirs;
  • Dirty vegetables and fruits;
  • Dirty hands;
  • Not thermally processed food;
  • Unsanitary working conditions.

Given the methods of infection with this parasite, it is quite easily transmitted from person to person if standard hygiene measures are not followed.

Why are roundworms dangerous?

intestinal obstruction
intestinal obstruction

Usually, ascariasis does not pose a particular danger to human health. A considerable number of people live with these parasites without even knowing about their presence. But sometimes there are some complications arising from this disease. According to the results of statistical studies, roundworms are most dangerous for young children, pregnant women and people with chronic diseases - in any weakened body, ascariasis develops faster and more massively, which leads to serious damage.

Today, the most common complications of ascariasis are:

  • Bowel obstruction. It occurs when roundworms are tangled in a ball in the digestive system - a mechanical closure of the intestinal lumen is formed. Obstruction is also possible in case of damage to the nerves and muscles of the intestinal walls due to irritation due to the waste products of helminths.
  • Obstructive jaundice. When parasites migrate through the duodenum into the bile ducts, a violation of the outflow of bile may occur. Because of this, the level of bilirubin in the blood rises with the parallel appearance of problems with the absorption of fats, drowsiness, and headaches.
  • Acute pancreatitis. It is provoked when the parasite moves into the ducts of the pancreas.
  • Appendicitis. The connection between the ingress of ascaris into the appendix and the development of this disease has not been precisely established, but it was statistically revealed that appendicitis in people with ascariasis is observed much more often.
  • Peritonitis. Usually occurs in the absence of treatment for appendicitis, rupture of the intestinal wall, necrosis of the pancreas. More often, peritonitis is the final stage of most complications related to the abdominal cavity. The risk of death is extremely high.
  • Purulent cholangitis. Since adult ascaris individuals are able to reach the top of the gastrointestinal tract and end up in the biliary tract, jaundice in this case may not be enough. Damage to the mucous membrane sometimes leads to serious complications such as purulent cholangitis.
  • Liver abscess. It is also the result of damage to the mucous membrane by parasites and the penetration of various microbes there.
  • Pneumonia. The finding of ascaris larvae in the respiratory system can cause bacterial pneumonia, the cause of which cannot always be found, because the larvae are in the lungs for only 7-10 days.
  • Asphyxia. A fairly rare complication in ascariasis, caused by irritation of the mucous larvae and their migration into the oral cavity.
  • Atypical localization of ascaris. Also a rare complication, which is characterized by the ingress of parasite larvae into other organs. But there roundworms most often do not survive for a long time, causing a minimum of damage to the human body.

The risk of the above complications increases with repeated infection with roundworms, because they have to go through the entire development pattern in the body again. Increased physical activity of mature individuals is quite often the cause of many complications. It can be provoked by taking certain medications, fever, and concomitant intestinal infections.


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