Around 1850, many millions of leeches were used annually in Europe for medicinal purposes. It was believed that bleeding had a positive effect on sick people, by draining off the "contaminated" blood. The old practice of using leeches in this way continued in this country right up until the 1920s. Leeches are still used at some Norwegian hospitals - the Norwegian drug depot imports about a hundred leeches annually. In addition to other uses, they can suck out blood clots that arise from impact injuries.
Leeches are on the list of endangered species in Norway, but they are still found many places in Hordaland. Around Flakkavågen there are many small tarns where leeches still can be found. There are also reports of leech-tarns at Bømlo, Stord and Osterøy. On Stord, it is said that many leech localities known from earlier times have disappeared, possibly because there are fewer grazing animals in the outlying areas. Blood leeches must have access to blood in order to survive, and they tend to find it on grazing animals.