The purpose of this study is to evaluate, treat and follow patients with parasitic infections. People with a known or suspected parasitic infection who are at least 1 year old may be enrolled. This study does not involve any experimental treatments. Participants will have a physical examination and laboratory tests on blood, stool, or urine. Blood samples may be collected at regular intervals, but no more than 450 ml (15 ounces) of blood will be drawn from adults, and no more than 7 ml (1-1/2 teaspoons) per kg (2.2 pounds) of body weight from children, in any 6-week period. Other tests may include x-rays, electrocardiogram (EKG), or tissue biopsy (surgical removal of a small tissue sample), depending on the individual s condition. Patients may be offered treatment or may be referred to another study that is more appropriate for the problem. Any treatment provided in this study will be according to standard medical practice for the patient s specific medical problem. Patients responses to treatment will be evaluated at regularly scheduled clinic visits. The length of time between visits and the total duration of the study for a given individual will be determined by the study doctor, based on that person s medical condition. ...