Stages of Ascaris Lumbricoides

The giant roundworm Ascaris lumbricoides currently infects roughly one-fourth to one-third of the human population with most cases occurring in tropical and subtropical climates. In the United States, it is estimated that four million people are infected with Ascaris lumbricoides. Giant roundworms grow up to 35 cm (13.77 inches) and can cause serious health problems. Ascaris lumbricoides follows a complicated life cycle when inside a human host.

Ingestion

• Ascaris lumbricoides infestations start when a human ingests large roundworm eggs in soil containing human feces or when crops grown with human manure are not cleaned properly. This is particularly common in tropical third-world countries that do not have adequate food sanitation policies or clean water supplies. Eggs do not become infectious until 18 days to a few weeks after they are laid. Giant roundworm eggs in the soil can remain infectious for up to 10 years or more.

Small Intestine

• After being swallowed, large roundworm eggs enter the second stage, where they enter the small intestine. The eggs hatch into larvae and burrow into the wall, known as the lumen, of the small intestine. As the larvae grow, they eventually enter the bloodstream through the lumen in order to reach the next stage of development.

Lungs

• Ascaris lumbricoides larvae migrate through the bloodstream into the lungs. The larvae grow for an additional two weeks in the alveolar walls, the air-containing compartments of the lungs. After this growth period, they migrate up the bronchial tree, reaching the top of the lungs. An infected human will then cough and usually swallow some of the larvae, unknowingly.

Diegestive System

• The larvae are carried through the digestive system after being swallowed, where they once again reside in the small intestine. With time, they will grow into adult worms. The entire process from being swallowed to maturing into adult worms lasts between two and three months. Adult worms mate and the female roundworms begin to produce roughly 240,000 eggs a day. These eggs are then disposed off in human feces in order to repeat the process all over again. Adult Ascaris lumbricoides can live in the small intestine for between one and two years before dying.

Symptoms

• Ascaris lumbricoides symptoms are usually minor. The migration of the larvae from the lumen to the lungs can cause fever, cough or wheezing. In severe cases, Loffler's pneumonia may occur, which can cause a fatal bacterial infection. Digestive effects can include passing worms through the mouth or anus, nausea or vomiting. Severe infestations of the giant roundworm can result in malnutrition and bowel obstruction.