I) Quarantine is the detention or isolation of persons or animals suspected of having been exposed to a communicable disease. II) The aim of this is to stop the disease from having a chance to spread. Ill) Therefore, a period of quarantine is usually necessary for animals arriving from abroad. IV) The detention period is determined by the longest usual incubation period of the disease in question. V) The quarantine is lifted if symptoms of the disease do not appear during that time.