ASCARIS LUMBRICOIDES

ROUNDWORM (Ascaris lumbricoides)
Ascaris lumbricoides is one of the most common of the intestinal worms. It is a roundworm and infection with it is called Ascariasis. Children are more frequently and more heavily infected than adults because of their habit of putting all kinds of things into their mouths. If these objects are contaminated with ascaris eggs from human faeces the children swallow the eggs and thus become infected.
The round worm lives in the small intestines. The female lays as many as 200,000 eggs a day. These are passed in stool and develop in the soil. They are then transmitted as follows:

• Eggs passed out in stool are embryonated in stool before they are infective.
• The embryonated eggs are carried away from the contaminated place into houses by feet, foot wear or in dust by wind. They also can reach vegetables and fruits
• A child then eats and swallows food or fruits contaminated with eggs.
• The eggs hatch into larva in the intestinal canal.
• The larva penetrates the intestinal wall and reach the liver via the portal system.
• The larva is then carried to the lungs.
• In the lungs, they penetrate into the airway and pass via the bronchioli, bronchi, and trachea to the pharynx.
• They are coughed up and are swallowed a second time, thus returning to the intestinal tract.
• They then settle into the jejunum where they develop.
• In two months, they mature as adult worms and can live for about a year.

Fig. 15.1: Life Cycle of Ascaris lumbricoides

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