Ascariasis is caused by a round worm Ascaris Lumbricoides. This worm is one of a group of roundworms (known as nematodes) that may infest the human gut. Infestations are common in Indonesia, Southeast Asia and other less developed countries.
Adult roundworms are between 20 and 40cm long, and live in the small intestine. After fertilisation, the females release a large number of microscopic eggs that pass out in the faeces and can survive for many years in the soil. In areas where human faeces is used as a fertiliser, it is easy for them to be swallowed again on food; or if sewerage contaminates the water supply, they may be swallowed in a drink. Once swallowed, the eggs hatch into larvae that burrow through the gut wall into the bloodstream and move through the heart into the lungs. There they penetrate into the small air tubes (bronchioles) of the lung, wiggle their way up through larger airways to the back of the throat from where they are swallowed again to enter the small intestine and grow into mature adults that may live for up to a year.
At all stages the larvae and worms can cause symptoms including a cough, shortness of breath, fever, wheezing, chest pain, abdominal pains and discomfort, nausea and gut obstruction. If severe infestations are left uncontrolled, the worms may move into the gall bladder and pancreas, rupture the bowel, and cause other severe complications that may result in death. The diagnosis is confirmed by finding eggs in the faeces.
A number of drugs are available to treat the disease, but they often have side effects. If patients are given the correct treatment at a relatively early stage of the disease, full recovery is normal.