Infestation with , a large worm (15-35 cm long) that occurs throughout the world, and infests about 650 million people. The worms live in the small intestine and feed on its contents; their lifespan is about a year. The female worms can produce large numbers of eggs (up to 200,000 per day) which are excreted in faeces. The larvae develop in the soil. Faeces containing eggs can reach vegetables and fruit as a result of manuring, and man can be infested by eating unwashed produce. The larvae hatch in the small intestine and grow into adult worms, which can cause discomfort if they crawl through passages such as the junction of the liver and the pancreas. They can also block the intestine, causing abdominal pain, loss of appetite and diarrhoea. Usually infestation causes no discomfort, in which case no treatment is necessary. Prevention is the most important matter: human excrement should not be used as fertilizer for fruit or vegetables, and all such produce should be washed.