Giardiasis is a disease in humans characterized by diarrhea, gas, stomach cramps and dehydration. This can cause severe problems in children and can lead to retardation of growth. It is caused by the protozoan Giardia intestinalis and is the most common intestinal parasitic disease in the world. The protozoan inhabits the intestines of many wild mammals and birds. It is transferred between hosts through the consumption of water contaminated with fecal matter containing G intestinalis. This means that many of the poorer regions of the world, which lack access to water purification services, have higher rates of infection.
Giardiasis is not only found in these regions though, there are still outbreaks in countries with water purification facilities. In October of 2004, in Bergen, Norway (the country’s second most populous city), there were approximately 2500 cases of Giardiasis between late August and early October. The source was found to be sewage lines leaking into the water supply and insufficient water treatment. This outbreak expedited the process of installing water treatment plants that used UV irradiation to purify drinking water in Bergen. Giardiasis is also not a new disease, it has been around for centuries. A pair of latrines from the 13th century were uncovered in the city of Acre in Israel which were linked to the crusaders and were tested for the presence of Giardia and other waterborne pathogens. G intestinalis was found to be present in these latrines, implying that the crusaders suffered from giardiasis.
Giardia intestinalis was first noticed by Antoni van Leeuwenhoek in 1681. The protozoan was studied more extensively in 1859 by Vilem Dusan Lambl and again by Alfred Giard in 1895. They both discovered and catalogued the organism separately and are recognized as the first scientists to describe it. G intestinalis is also known as Giardia lamblia after these two scientists. It was thought to be a harmless protozoan that lived in the intestines of many mammals, such as primates, dogs, beavers, and cats. This opinion changed in the 1970’s when outbreaks of Giardiasis began to occur in communities and people who travelled to areas which relied on unpurified water sources. The disease was studied more after this and the protozoan was found to blame.