Ascaris lumbricoides is the most common helminth infection of humans, with an estimated 1 billion cases worldwide. Transmission usually occurs from hand to mouth. Ova are ingested from a contaminated environment; larva are released into stomach, penetrate the gut wall and enter the circulation, on reaching the lung, larva cross the alveoli and are transported to the trachea by coughing and muciliary function. They are swallowed and reach the small bowel, where they stay, developing into sexually active forms. Adult worms have an average lifespan of 1-2
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