Extent of spread
The infection of Ascaris Lumbricoides begins when an individual ingests the egg which can be present in food contaminated with its egg. As soon as the egg enters the digestive tract, it becomes a larva inside the small intestine and then penetrates through the wall of the duodenum and enters the circulatory system. It then reaches the blood, reaches the liver through the portal vein, and ends up reaching the lungs. All of this happens in the first week of ingestion of the eggs.
As soon as the larva reaches the lungs, it damages the alveolar membrane and also matures there. From there, it is again coughed up and goes inside the gastrointestinal system. When the larva re-enters the small intestine it matures into an adult worm in about a month. In the presence of both females and males, they mate and produce hundreds and thousands of eggs per day. The eggs then are eliminated from the body through the feces into the soil. As the eggs get a favorable environment to mature, they again enter their infective stage beginning the cycle again.