Infestation with a Fasciola flatworm 2-3 cm long, which lives as a parasite in sheep and cattle. Liver flukes occur throughout the world, but human beings are affected only from time to time. The worm lives in the bile ducts of the liver, where eggs are produced and passed out of the body via the faeces. The larvae emerge from the eggs in water, and develop before attaching themselves to plants which grow on river banks. If the plants are eaten, the liver fluke passes through the intestinal wall to the liver, where it develops into a fully-grown worm. Infestation in man can be caused by eating watercress. The worms cause inflammation of the bile duct, followed by constipation, resulting in pain, fever and jaundice, but infestation can also occur without symptoms. Treatment with drugs, lasting 10 days, is usually effective. It is low blood pressure (hypotension) Blood pressure in which the upper value is lower than 90 mm of mercury, often accompanying shock. A special form of low blood pressure is so-called orthostatic hypotension. If someone quickly stands up from a sitting or lying position, extra blood flows into the legs and lowers blood pressure in the brain for a few seconds, causing slight giddiness. The condition does not require treatment, but sufferers should take it into account when standing up. Sheep and cows, but not usually man, are affected by liver fluke in the Western world.