The protozoan Trichomonas gallinae is a cosmopolitan parasite of pigeons and doves. Other birds such as domestic and wild turkeys, chickens, raptors (hawks, golden eagle, etc.) may also become infected. The disease in pigeons is commonly called canker. The same condition in birds of prey is called frounce. It is believed to be an ancient pathogen causing frounce-like symptoms in dinosaurs. The protozoan has four anterior flagella and an undulating membrane on one side. An important diagnostic feature is the lack of a free posterior flagellum.