Ascariasis, Man

Pathology

Ascariasis is an infection with Ascaris lumbricoides , a large, lumen-dwelling nematode contracted by the ingestion of its larva via eggs (Ascaris/Fig. 1). The larvae penetrate the small intestine wall and migrate through the lymphatics and blood stream to the liver, and then to the lungs where they enter the alveoli. There they pause for at least 2–3 weeks and molt, giving rise to allergic bronchopneumonia in previously infected and sensitized individuals. Later, they wander up the bronchi and trachea, giving rise to bronchitis with bronchospasm, urticaria, and occasionally, larvae in the sputum. Most larvae are swallowed and grow to adulthood in the small intestine. The adult worms are up to 30 cm long and 4 mm wide, and give rise to mechanical problems because of their size and, especially in children to a severe nutritional drain, because of the worm number and mass. A temperature elevation to 39 °C, certain drugs, and some unknown influences may cause the worms to...