A large nematode that parasitizes the human intestine; adult females measure 20–35 cm and males 15–30 cm【654651252155911†screenshot】.
Explanation
Ascaris lumbricoides is a large roundworm that parasitizes the human intestine. Adult females measure 20–35 cm and adult males 15–30 cm【654651252155911†screenshot】. Eggs excreted in feces become infective in warm, moist soil after 18 days to several weeks【654651252155911†screenshot】. Humans acquire infection by ingesting these embryonated eggs, often through contaminated produce or soil. Larvae hatch in the small intestine, penetrate the intestinal wall, migrate via the bloodstream to the lungs, ascend the airway and are swallowed, returning to the gut where they mature. Heavy infections may cause abdominal pain, intestinal obstruction, malnutrition and growth delay【654218675510731†L77-L175】. Pulmonary migration can lead to cough, wheezing and eosinophilia.
Clinical features and life cycle details
Ascaris lumbricoides is globally distributed, with highest prevalence in tropical and subtropical regions lacking sanitation. Adult worms are cylindrical with tapered ends and a creamy colour; females are larger than males, which have a curved posterior end. Ascaris suum, a similar species infecting pigs, may also infect humans, and hybrids have been identified【654651252155911†screenshot】. Each female produces hundreds of thousands of eggs daily; these eggs are resilient and can survive harsh environmental conditions. Diagnosis is usually made by identifying eggs in stool or visualising adult worms. Prevention relies on improved sanitation, handwashing and proper disposal of human waste. Treatment uses anthelmintic drugs such as albendazole, mebendazole or pyrantel pamoate, often delivered through mass deworming programs in endemic areas.
Ascaris infection can impair nutrient absorption and contribute to stunting. Migrating larvae may cause hepatic or pulmonary complications, and adult worms occasionally enter the biliary tree or pancreas, causing obstruction. Effective control of this parasite is important in efforts to eliminate soil‑transmitted helminthiases worldwide.
Related Terms: Roundworm, Helminth, Nematode, Ascariasis, Parasite