Ascariasis occurs when a type of roundworm known as Ascaris lumbricoides infects the small intestine.
Though common across the globe, the Centers for Disease Control and Prevention (CDC) state that ascariasis is not common in the United States.
Read on to learn more about the causes, symptoms, treatment, and outlook for an ascariasis infection.
Ascariasis is a common infection in developing countries that lack widespread, modern sanitation.
A roundworm called Ascaris lumbricoides infects a person's small intestine and acts as a parasite, getting nutrients from its host's intestinal tract.
Ascaris lumbricoides, along with whipworm and hookworm, is a type of parasite known as a soil-transmitted helminth (STH).
The roundworm lays eggs, which then pass in the person's stool, or poop. It can spread when an infected person defecates near farmland or crops.
When people do not wash crops or cook them thoroughly, the roundworm can enter a new host, and start its life cycle again.
Many people with ascariasis do not experience any symptoms until the infection has become severe.
Ascariasis may not cause symptoms at first. However, as the infestation inside the small intestine grows, a person may start to notice symptoms, including:
- abdominal pain or discomfort
- loss of appetite
- worms visible in stool
- impaired growth in children
- weight loss
- irregular bowel movements
In more advanced infestations, the worms can travel to the lungs. If this occurs, a person may also experience symptoms, including:
- discomfort in the chest
- gagging cough
- bloody mucus
- shortness of breath
In rare cases, a person may experience a complication known as aspiration pneumonia.
If a person ingests the eggs of Ascaris lumbricoides, the roundworm will progress through its life cycle within the host's body.
The stages of a roundworm's life are as follows:
- Eggs hatch into larvae in the host's intestine.
- The larvae move through the body via the bloodstream to the lungs.
- The larvae will mature in the lungs before entering the throat.
- A person will either swallow or cough out the larvae.
- If swallowed, the larvae move into the intestine and mature into adult worms.
- A female worm will produce about 200,000 eggs per day.
- The eggs will leave the body in a person's stool.
Human feces can cause contamination if an infected person defecates near a farming field or water source, or if they use untreated feces as a fertilizer for crops.
A person can contract ascariasis by eating or drinking contaminated food or water, especially if they do not adequately wash the food or their hands.
Children may be contaminated by playing with soil or plants and putting their hands in their mouths.
Roundworms live in areas all across the world but are most common in subtropical and tropical settings.
They are also much more prevalent in parts of the world where sanitation is below modern standards.
Ascariasis is uncommon in the U.S., so the environmental risk factors are low.
Risk factors for developing ascariasis include:
- exposure to contaminated dirt
- visiting or living in a subtropical or tropical area
- an absence of modern sanitation
- a lack of proper feces disposal
- using contaminated feces as fertilizer for crops
The most common method of diagnosis involves a stool sample. Using a microscope, a doctor can look for the parasite's eggs in a person's stool.
It can be difficult for a doctor to diagnose early infestations, as the eggs may not be present.
A doctor may also order imaging tests to help them determine how many worms are inside the person and to locate them.
Some imaging techniques a doctor may use include:
A doctor will treat most cases of ascariasis with antiparasitic drugs. They may consider additional treatment options for severe infestations.
A doctor may not aim to cure the infestation but simply reduce the number of worms and eggs in a person to relieve their symptoms.
A doctor may suggest surgery to help remove large numbers of worms. Surgery is also a good option if the infestation blocks a portion of the intestine.
In most cases, ascariasis has mild or no symptoms and no further complications.
If the infestation becomes too large or severe, a person is at risk of complications.
Some complications include:
- A blockage in the ducts that connect to the liver or pancreas.
- A blockage in the intestine, causing pain and vomiting. This is a medical emergency.
- Stunted growth and nutritional deficiencies in children.
People living in places with modern sanitation have a very low risk of ascariasis. However, it is essential to wash food properly and wash hands after using the bathroom.
People should also wash any utensils and cooking surfaces after each use.
When visiting a region with a lack of sanitary facilities, a person should take the following precautions to help avoid infection:
- Observe and inspect food preparation spaces for cleanliness.
- Filter and boil water before drinking it.
- Wash hands with soap and hot water before handling food and eating.
- Avoid common bathing areas, especially if they appear unclean.
- Peel and cook any vegetables or fruit grown in unsanitary conditions.
- Ensure children clean their hands with soap and water after playing outside.
People can take steps to avoid ascariasis infections by practicing safe food handling techniques, using modern sanitation equipment, and avoiding travel to places where it is common.
A person may not realize they have ascariasis until the infestation becomes very large or severe. Once identified, a person can often expect a full recovery after treatment.