Most people infected with ascariasis have no symptoms. Moderate to heavy infestations cause various symptoms, depending on which part of your body is affected.

In the lungs

After you ingest the microscopic ascariasis eggs, they hatch in your small intestine and the larvae migrate through your bloodstream or lymphatic system into your lungs. At this stage, you may experience signs and symptoms similar to asthma or pneumonia, including:

• Persistent cough
• Shortness of breath
• Wheezing

After spending six to 10 days in the lungs, the larvae travel to your throat, where you cough them up and then swallow them.

In the intestines

The larvae mature into adult worms in your small intestine, and the adult worms typically live in the intestines until they die. In mild or moderate ascariasis, the intestinal infestation can cause:

• Vague abdominal pain
• Nausea and vomiting
• Diarrhea or bloody stools

If you have a large number of worms in your intestine, you might have:

• Severe abdominal pain
• Fatigue
• Vomiting
• Weight loss or malnutrition
• A worm in your vomit or stool

Ascariasis isn't spread directly from person to person. Instead, a person has to come into contact with soil mixed with human feces that contain ascariasis eggs or infected water. In many developing countries, human feces are used for fertilizer, or poor sanitary facilities allow human waste to mix with soil in yards, ditches and fields.

Small children often play in dirt, and infection can occur if they put their dirty fingers in their mouths. Unwashed fruits or vegetables grown in contaminated soil also can transmit the ascariasis eggs.

Life cycle of a worm

• Ingestion. The microscopic ascariasis eggs can't become infective without coming into contact with soil. People can accidentally ingest contaminated soil through hand-to-mouth contact or by eating uncooked fruits or vegetables that have been grown in contaminated soil.
• Migration. Larvae hatch from the eggs in your small intestine and then penetrate the intestinal wall to travel to your lungs via your bloodstream or lymphatic system. After maturing for about a week in your lungs, the larvae break into your airway and travel up your throat, where they're coughed up and swallowed.
• Maturation. Once back in the intestines, the parasites grow into male or female worms. Female worms can be more than 15 inches (40 centimeters) long and a little less than a quarter inch (6 millimeters) in diameter. Male worms are generally smaller.
• Reproduction. Male and female worms mate in the small intestine. Female worms can produce 200,000 eggs a day, which leave your body in your feces. The fertilized eggs must be in soil for at least 18 days before they become infective.

The whole process — from egg ingestion to egg deposits — takes about two or three months. Ascariasis worms can live inside you for a year or two.

Risk factors for ascariasis include:

• Age. Most people who have ascariasis are 10 years old or younger. Children in this age group may be at higher risk because they're more likely to play in dirt.
• Warm climate. In the United States, ascariasis is more common in the Southeast, but it's more prevalent in developing countries with warm temperatures year-round.
• Poor sanitation. Ascariasis is widespread in developing countries where human feces are allowed to mix with local soil.

Mild cases of ascariasis usually don't cause complications. If you have a heavy infestation, potentially dangerous complications may include:

• Slowed growth. Loss of appetite and poor absorption of digested foods put children with ascariasis at risk of not getting enough nutrition, which can slow growth.
• Intestinal blockage and perforation. In heavy ascariasis infestation, a mass of worms can block a portion of your intestine, causing severe abdominal cramping and vomiting. The blockage can even perforate the intestinal wall or appendix, causing internal bleeding (hemorrhage) or appendicitis.
• Duct blockages. In some cases, worms may block the narrow ducts of your liver or pancreas, causing severe pain.