Ascariasis

What is Ascariasis?

Ascariasis is a parasitic infection caused by the roundworm or Ascaris lumbricoides. The roundworm is the largest intestinal parasite and can reach up to 40 cm in length. The infection is common in regions with poor sanitation, particularly in poorer countries in the tropics and subtropics.

The worms live in the intestine of man, but can move to other parts. The larvae migrate to the lungs. The infestation can contribute significantly to malnutrition & diminished work capacity, though it is usually not fatal.

What are the Causes of Ascariasis?

Ascariasis occurs due to ingestion of eggs of the roundworms. This may occur due to:

• Ingestion of raw vegetables contaminated with ascaris eggs
• Improper disposal of human feces
• Drinking of unhygienic water
• Use of contaminated human feces as fertilizer

Life cycle of Ascaris Lumbricoides

Ascaris lumbricoides or round worm passes most of its life in man, and some part in the soil.

• Adult worms live in the jejunum part of small intestine in man. Each female worm produces 2, 40,000 eggs per day, which are passed out with the feces.
• In areas of open defecation, the eggs are passed in the soil. These eggs are not immediately infective to man. In 10-40 days, a rhabditiform larva is formed within each egg shell. The eggs which contain "rhabditiform larvae" or "embryonated eggs" are infective to man.
• Man acquires the infection through ingestion of food, drink or raw vegetables contaminated with eggs containing rhabditiform larvae (embryonated eggs). The eggs move into the small intestine where they hatch.
• The larvae that emerge from the eggs then burrow through the mucous membrane of small intestine and are carried by blood to the liver, where they remain for 3-4 days.
• Then they move through the blood to the right side of the heart. From there, the blood carries them to the lungs.
• From the alveoli or air sacs of the lung, the larvae crawl up the bronchi & trachea (wind pipe) and up into larynx and pharynx, from where they are swallowed.
• They pass down the esophagus (food pipe) to the stomach & remain in the small intestine. They attain sexual maturity; the pregnant female Ascaris discharges eggs in the stool & the life cycle is repeated.

What are the Symptoms & Signs of Ascariasis?

Roundworms may be present in the body and yet not cause any symptoms. Symptoms occur due to migrating larvae that cause inflammation in the lungs, or due to adult worms.

Effects due to adult worms are as follows:

• Loss of appetite
• Malnutrition may occur
• Heavy infection may cause intestinal obstruction
• Worms may be vomited out or may come out through mouth or nose.
• From the throat, worm may enter the middle ear through the Eustachian tube.
• Sometimes worms may enter into the trachea (wind pipe) & cause respiratory obstruction.
• Release of toxic body fluid (ascaron) of the worm may lead to allergic manifestations.
• Abdominal pain

Effects due to migrating larvae are as follows:

• Irritating cough
• Burning behind the breastbone
• Symptoms worsened by coughing or deep inspiration.
• Fever
• Breathlessness
• Sputum may sometimes contain blood.

Complications of ascariasis are usually due to obstruction caused by the worms in the intestines or as they move into other parts of the body. They include:

• Intestinal obstruction, which can further result in perforation, intussusceptions or volvulus
• Obstruction to the biliary tree of the gallbladder, resulting in biliary colic, cholecystitis, cholangitis, pancreatitis or liver abscess

How is Ascariasis Diagnosed?

Ascariasis is diagnosed with the following tests:

• Stool examination: Both adult worms as well as eggs can be demonstrated in the stool sample. Eggs can be demonstrated by direct microscopic examination of stool specimen.
• Demonstration of the adult worms: Adult worms may be passed out through anus (in stool), mouth, nose and rarely through ear. A barium meal can also be used to demonstrate worms in small intestine. In this test, a small amount of barium is ingested, and x-rays are taken as it passes through the digestive tract.
• Demonstration of larvae: The larvae may be detected in the sputum during the stage of migration to lungs.
• Blood tests: Antibodies against Ascaris lumbricoides can be detected through blood tests. An increase in the number of white blood cells called eosinophils may also be present.

• Chest x-ray may reveal evidence of a type of pneumonia called eosinophilic pneumonia, also called Loffler's syndrome.

How is Ascariasis Treated?

Any one of the following anti-helminthic drugs can be used in the treatment of ascariasis:

• Ivermectin
• Albendazole - single dose 400 mg once
• Mebendazole - 100 mg twice daily for 3 days

The above medications are contraindicated in pregnancy

• Pyrantel pamoate - single dose ( safe in pregnancy)
• Partial intestinal obstruction should be managed with nasogastric suction, IV fluid administration & instillation of piperazine through nasogastric tube.
• Complete intestinal obstruction & its complications require immediate surgical intervention.

Prevention of Ascariasis

Ascariasis can be prevented by:

• Proper disposal of human feces.
• Wash raw fruits and vegetables thoroughly to remove pesticides.
• Drinking purified water

References:

1. Harrison�s principles of internal medicine - 19^th edition.
2. C P Baweja medical parasitology � 3^rd edition.

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