Ascaris lumbricoides- Habitat and External Morphology


Ascaris lumbricoides is a parasitic worm that belongs to the phylum Nematoda, the class Chromadorea, the order Ascaridida, and the family Ascarididae . It is the most common and largest intestinal nematode that infects humans, especially children . It can grow up to 40 cm in length and 6 mm in diameter . It has a cylindrical, elongated, and tapered body with a pseudocoelom, a mouth with three lips, and a cuticle with transverse striations . It shows sexual dimorphism, meaning that males and females have different features. Males are smaller than females and have a curved tail with copulatory spicules, while females have a straight tail and a vulva near the anterior end .

Ascaris lumbricoides causes ascariasis, a disease characterized by abdominal discomfort, malnutrition, growth retardation, intestinal obstruction, and sometimes respiratory complications . The infection occurs through the fecal-oral route, when humans ingest eggs that are shed in the feces of infected individuals and contaminate soil, water, or food . The eggs hatch in the small intestine and release larvae that migrate through the blood vessels to the lungs, where they break into the alveoli and ascend to the trachea. The larvae are then swallowed again and reach the small intestine, where they mature into adult worms and reproduce . The life cycle takes about two to three months to complete.

Ascaris lumbricoides is widely distributed in tropical and subtropical regions of the world, where sanitation and hygiene are poor. It is estimated that 807 million to 1.2 billion people are infected with this worm worldwide. It can also infect pigs and other animals, and some studies suggest that Ascaris lumbricoides and Ascaris suum (pig roundworm) are the same species. Ascariasis can be treated with anthelmintic drugs that kill or expel the worms from the body. Prevention measures include improving sanitation, washing hands and food before eating, boiling or filtering water, and deworming programs for children.