Large Intestinal Roundworm
Physiology and Structure:
- A. lumbricoides are large (20cm to 35cm long), pink worms.
- The egg releases a larval worm which penetrates the duodenal wall and enters the bloodstream which is then carried to the liver and heart and finally into the pulmonary circulation.
- In the lungs, they break free and start to molt.
- The larvae would be coughed up, swallowed and returned to the small intestine. This process takes around 3 weeks.
- The worms mature in the small intestine.
- Up to 200,000 eggs can be produced in a day.
- Fertilized eggs become infectious after 2 weeks of exposure to soil.
Lifecycle of Ascaris lumbricoides
- Infections caused by the ingestion of a few eggs may produce no symptoms.
- The ingestion of a single adult worm may be dangerous as it is able to travel into the bile duct and liver and destroy tissue.
- Infections with many larvae would produce pneumonitis,similar to an asthma attack, when larvae migrate to the lungs.
- Prolonged exposure would cause eosinophilia and oxygen desaturation.
- Worms tangled in the intestines would cause obstruction, perforation and occulsion of the appendix.
- Victims would also experience symptoms like abdominal tenderness, fever, distention and vomiting.
Treatment, Prevention and Control
- Treatment of symptomatic infection with mebendazole is effective.
- Patients who have mixed infection in the stool have to be treated for ascariasis to prevent the migration of worms and intestinal perforation.
- Sanitary facilities should be maintained to prevent contamination of the soil with human feces.
- Practice of using human feces as fertilizer should be avoided.