The specimens of the group of flagellated protozoans live in the sexual organs and excretory system of their hosts. They are characterized by a specific number of free flagella and often possess an additional recurrent flagellum, which is attached at some places of the single limiting membrane of these parasites. The stability of the cell body is often reached by the formation of a so-called axostyle (see Trichomonas vaginalis), which consists of one to several rows of microtubules, which make the specimens appear with a pointed terminal pole. The species of birds, cattle, horses, donkeys, camels, etc. are of veterinary importance, since they may introduce severe diseases (see examples in Table 1).