Giardia lamblia, Giardia intestinalis – a parasitic protozoan belonging to the group of flagellata, causing a disease called giardiasis (lambliosis) in humans and animals. Its characteristic feature is having two cell nuclei and four pairs of flagella arranged symmetrically around the body axis. The abdominal surface of the parasite is flattened and equipped with a cling disc, thanks to which it adheres to the epithelial cells of the small intestine, where it begins to multiply intensively. Then some of the parasites are transformed into cysts that are excreted with faeces.
Giardiasis is often called the disease of dirty hands – there is the risk of getting infected with parasites directly from another human (e.g. through contact with an ill person who has not washed their hands after using the toilet). The infection with Giardia lamblia also occurs when cysts in contaminated water or food are ingested. Cysts of this parasite show high resistance to chlorine and can survive in chlorinated water for up to three months. The most common symptoms of the disease are anorexia, painful abdominal cramps, watery diarrhoea or allergic reactions with various types of rash. The infection is often asymptomatic. In the chronic phase of the disease, the diagnosis is difficult because cysts are excreted from the body irregularly and in variable amounts.