Roundworm

Ascariasis is the most common intestinal parasitic disease. The source of infection is ascariasis and infection. A large number of worm eggs are discharged with the patient's feces, contaminating vegetables and soil. Under appropriate temperature and humidity, it develops into mature worm eggs after about 2 weeks. The mature eggs pass through the mouth to the stomach, most of them are killed by gastric acid, and a few enter the small intestine to hatch and develop into larvae. The larvae penetrate into the intestinal mucosa and reach the lungs through the lymphatic vessels or microvascular portal veins, liver, and inferior vena cava; the larvae form about 1 mm after peeling in the lungs. Larvae pass through the microvessels, rise through the alveoli, bronchi, and trachea to the pharynx, and then are swallowed into the stomach, which constitutes tadpole migration. The tadpoles developed into adult worms after reaching the small intestine. It takes about 75 days from swallowing the eggs to mature adults, and the survival time in the small intestine is about 1-2 years.