Ascariasis: causes, symptoms and treatment - medical - 2023



Symptoms such as severe stomach pain, shortness of breath, vomiting, or foreign bodies in the stool can be signs of ascariasis. This pathology is the most common helminth infection worldwide, and its prevalence is higher in tropical regions, especially in low-income countries with inadequate sanitary conditions.

Due to the wide range of distribution that the causative pathogen presents and its close relationship with humans (the first records of this disease date from Roman times), it is essential to know its infective dynamics. Here we show you everything you need to know about ascariasis and Ascaris lumbricoides, its causative agent.

Ascariasis: a fascinating pathology

Ascariasis is the name given to the disease caused by small helminths of the genus Ascaris. This group comprises both Ascaris lumbricoides like Ascaris suum, which are specialized in parasitizing humans and pigs respectively. Although both species can generate a clinical picture in humans, we will focus on Ascaris lumbricoides, due to its higher prevalence, epidemiological relevance and because the human being is its natural host.

Knowing the pathogen

Ascaris lumbricoides it's a worm-shaped endoparasitic nematode. The adult individual measures 15 to 35 centimeters in general, with the females being the largest. Unlike tapeworms and other digestive tract parasites, they never adhere to the intestinal mucosa of the host, so they do not require specific suction cups or buccal hooks. Instead, in the cephalic region they present three thick lips. In addition to the difference in size, males are distinguished from females by having copulatory hooks at their rear end.

It is interesting to know that Ascaris lumbricoides Y Ascaris suum they are morphologically indistinguishable. They only differ by 4% in their mitochondrial genome, indicating a very close phylogenetic relationship. Therefore, although both species are highly specialized in their hosts, A. lumbricoides Y A. suum they can cause ascariasis in humans and pigs indistinctly on certain occasions.

A life cycle of vertigo

These parasitic nematodes have a sophisticated life cycle that has evolved in order to infect as many hosts as possible. Here's a summary of it:

  • Adults live in the lumen of the human small intestine, and females can lay up to 200,000 eggs a day.
  • These microscopic-sized oval-shaped eggs are expelled with the feces into the environment.
  • The larvae develop within the egg in the environment to an L3 stage in approximately 18 days.
  • When these eggs are ingested by the host, the larvae hatch and go to the small intestine.
  • Incredible as it may seem, these larvae burrow into intestinal tissue and travel through the circulatory system to the lungs.
  • Later, they ascend through the bronchial tree to the throat and are swallowed again to reach the small intestine, where they become adults.

This entire process of travel through the human body may seem complex, but the truth is that it is necessary for the larva to reach the adult stage. From when they hatch from the egg until they return to the small intestine after their journey through the pulmonary circuit, it can take up to 14 days. From day 24, these nematodes reach sexual maturity in the intestine and begin to lay eggs that will be expelled with the feces. These adult stage parasites can live up to a year in the intestine if they are not expelled.

Clinical considerations

Although it is surprising to us after everything we have read so far, ascariasis does not usually present severe symptoms associated. In addition, there are certain risk groups for the disease and various clinical considerations to take into account when we talk about it.

  • We recommend you read: "The 6 most common parasites (and the diseases they cause)"

Disease epidemiology

As we have previously anticipated, ascariasis is one of the most common diseases caused by an intestinal pathogen in the world. A parameter that expresses the number of years lost due to a specific disease (DALYs, Disability-Adjusted life year) underlines its importance, since its accumulated loss amounts to 10.5 million. It is estimated that more than 120 million cases are diagnosed annually, with more than a billion people affected by Ascaris globally.

In addition to these astronomical figures, ascariasis presents other epidemiological patterns of great interest. For example, various studies have highlighted that there appears to be a gender and socioeconomic status bias associated with the disease. In low-income countries, it is the poorest people who often come into contact with human fecal matter, especially women, who are mostly responsible for the care and cleaning of newborns.


As we have mentioned previously, most cases of ascariasis are asymptomatic. About 8 to 15% of those infected have associated morbidity. Some of the symptoms are as follows:

  • Cough and shortness of breath, due to the migration of the larvae through the respiratory system.
  • Stomach pain, due to the presence of adults in the gastrointestinal tract.
  • Abdominal bloating and general malaise.
  • Low fever

One of the most striking characteristics of this parasite is that can lead to malnutrition in infants in the long term. Several studies have shown that children free of Ascaris They had a lower lactose intolerance, better assimilation of vitamins A and C, amount of albumin and general growth than the parasitized. Furthermore, a significant increase in weight and growth of infected children was observed after treatment.

As unpleasant as the idea is, hosts with a high parasite load can show intestinal plugging, due to the disproportionate presence of these nematodes in the digestive tract. In these cases it is essential to resort to surgery.

Prevention and treatment

Treatment is based on the application of anthelmintics as soon as the disease is identified (either by the expulsion of adults in the stool or by observing eggs in a stool culture). Medications such as albendazole and mebendazole are often used, which take effect in approximately three days. The disease remits quickly, and the prognosis is positive in most cases, since the anthelmintics mentioned appear to be very effective and have very few side effects.

As is the case with most infections caused by intestinal parasites, the best prevention against ascariasis is proper hygiene. For this, the CDC (Centers for Disease Control and Prevention) collects the following measures, especially applicable to areas where the prevalence of the disease is high. It is recommended:

  • Do not defecate outside the assigned places and have a correct waste system.
  • Wash hands with soap after coming into contact with possibly contaminated soil, pigs or other possible sources of infection.
  • Teach children (the group most prone to contracting the disease) to have hygienic habits during games and interactions.

All these preventive measures may be obvious when read by a person who has grown up in a high-income country, but we cannot forget that these types of diseases occur, above all, in isolated communities with low budgets and poor infrastructure.


As we have seen, Ascaris lumbricoides It is a nematode that has a fascinating life cycle, but which in turn generates a disease in humans known as ascariasis. This usually has no symptoms, but in some cases it can become severe, causing widespread malnutrition or intestinal blockages that occur with different severity.

For this reason, it is essential not to lose sight of the importance of a correct sanitation of the environment to prevent this type of pathology. Unlike viruses and bacteria, these parasites do not travel in airborne particles, nor can they be inhaled or transmitted by direct contact. They only have one way of entry. And this is the host's mouth.