Intestinal ascariasis

Ascariasis is the most common intestinal parasitic disease. The source of infection is patients and carriers of Ascaris lumbricoides. A large number of eggs are excreted with the patient's feces, contaminating vegetables and soil. Under suitable temperature and humidity, they develop into mature eggs in about 2 weeks. Mature eggs enter the stomach through the mouth, most are killed by gastric acid, and a few enter the small intestine to hatch and develop into larvae. The larvae penetrate the intestinal mucosa, enter the portal vein, liver, and inferior vena cava via lymphatic vessels or capillaries, and reach the lungs; after molting in the lungs, they form larvae about 1 mm in size. The larvae pass through the capillaries, alveoli, bronchi, and trachea to the pharynx, and are then swallowed into the stomach again, constituting Ascaris larva migrans. After reaching the small intestine, the larvae develop into adult worms. It takes about 75 days from swallowing eggs to adult worm maturation, and the survival period in the small intestine is about 1-2 years.