The biological characteristics of roundworms in eighth grade are as follows:

Ascaris is an animal of the order Ascaridae and is the largest parasitic nematode in the human intestine. The adult body is slightly pink or yellowish, with horizontal stripes on the body surface, and the male tail is often curled.

1. Introduction

Human ascariasis is a common parasitic disease caused by roundworms parasitizing in the human small intestine. The incidence rate is relatively high in children. Adult roundworms are cylindrical, like earthworms; eggs are oval, and the surface of the egg shell is often attached with a rough and uneven protein film, which is brown due to bile staining.

2. Life history

1. Adult worms parasitize in the small intestine, mostly in the jejunum, and feed on semi-digested food. After mating between male and female adults, the female lays eggs, which are excreted in the feces and pollute the environment.

2. The fertilized eggs will develop into first-stage larvae after 2 weeks under shade, moisture, sufficient oxygen and suitable temperature (21~30℃). After another week, the eggs will After the first molt, they develop into infectious eggs

3. Pathological changes

1. X-ray examination of the lungs of some patients in the pathogenic stage of larvae shows infiltrative lesions, often with lesions There is migration phenomenon; during the pathogenic stage of adult worms, they can damage the intestinal mucosa, cause urticaria, skin itching, angioedema, conjunctivitis, purulent cholangitis, cholecystitis, and even bile duct necrosis, perforation, intestinal volvulus and intestinal necrosis.

2. The migration, development and molting of roundworm larvae in the body can also cause Loffler`s syndrome. Clinically, the symptoms are pulmonary inflammation.

3. Accompanied by systemic manifestations: patients have fever, cough, asthma, bloody sputum and an increased proportion of eosinophils in the blood. X-ray examination shows infiltrative lesions. In severe infections, pulmonary edema and pulmonary hemorrhage may occur. wait. Usually heals on its own within 1-2 weeks.

IV. Epidemiology

1. The distribution of roundworms is worldwide. About 1/4 of the world's population is infected with roundworms, mainly in temperate zones, tropics, economically underdeveloped and warm areas. The epidemic is more widespread in countries or regions with damp and poor sanitation conditions.

2. The infection rate of roundworms in rural areas is higher than that in cities; children are higher than adults. The infection rate among rural people in most areas of my country is still as high as 60% to 90%.