Patient description: A 17 year old boy complains of vomiting, non-bloody diarrhea, abdominal pain, fever, chills and loss of appetite for the past 3 days. He ate a salad at a restaurant prior to his diarrhea onset. Physical exam was remarkable for pallor, jaundice, and diffuse abdominal tenderness. Lab results were as follows: Hemoglobin: 9.7 g/dL Platelet: 110,000 /cu.mm Creatinine: 3.6 mg/dL blood urea nitrogen (BUN): 73 mg/dL direct bilirubin: 2.4 mg/dL lactate dehydrogenase (LDH): 881 IU/L (normal: 110-265 IU/L) Peripheral blood smear showed a moderate number of schistocytes and helmet cells. Shiga-like toxin-producing E. coli (STEC) stx1/stx2 were found in stools. He has no other underlying disease and he is not on any medications.

Clinical trial eligibility criteria: eligible ages (years): 14.0-80.0,  Schistosomiasis (SCREENING): 1. Male or non-pregnant female subjects 2. Age 14-80 years (per participant self-report) 3. Resident of Tienegubougou, Bougoudiana or surrounding villages 5. Consent to a blood draw to screen for filarial infection and a urine exam to screen for schistosomiasis 6. Must be willing to have blood samples stored  (SCREENING): 1. Known to be pregnant (by history) 2. Chronic medical conditions, including but not limited to diabetes, renal or hepatic insufficiency, immunodeficiency, psychiatric disorder, seizure, that in the investigators judgments are deemed to be clinically significant 3. History of hypersensitivity reaction to PZQ. 4. Weight less than 20 kg (INTERVENTIONAL STUDY): 1. S. haematobium infection documented at screening and within 14 days prior to the baseline visit 2. The subject agrees to storage of samples for study (INTERVENTIONAL STUDY): 1. Pregnancy (by urine beta-HCG) 2. Chronic kidney or liver disease 3. Hgb <10 mg/dL 4. PZQ treatment since the screening visit 5. Concomitant Schistosoma mansoni, Wuchereria bancrofti (Wb) or Onchocerca volvulus infection 6. Use of immunosuppressive therapies, including steroids, within the past month 7. Any condition that in the investigator s opinion places the subject at undue risk by participating in the study. OF AND WOMEN: Pregnant women will be excluded from this study since it involves administration of medications contraindicated in pregnancy. Children less than 14 years old will be excluded because of the amount of blood required for the immunologic studies. The age of consent in Mali is 18 years of age, so children aged 14 to 17 years will sign an assent form in addition to the consent form to be signed by a parent or tutor. However, married women between the ages of 14 and 17 will sign consent as adults in view of the laws governing emancipation of women in Mali. Subjects who do not participate in this study will receive PZQ as part of the national schistosomiasis control program. Participation of Women: -Pregnancy: The effects of praziquantel on the developing human fetus are unknown (pregnancy category B). For this reason, females of childbearing-age must have a negative pregnancy test result prior to receiving praziquantel. Since the half-life of praziquantel is short (3-4 hours), contraceptive measures will not be required post-treatment. -Breast feeding: Praziquantel is known to be present in breast milk for up to 3 days following a single dose and is not approved for use in children under the age of 4 years. Consequently, women will be asked to suspend breastfeeding after treatment with PZQ for 3 days. Formula will be provided for breastfed children affected by their mother s participation during this time to ensure adequate nutrition. Depending on the age of the child, formula may be given. A pediatric nurse will be present during this time to provide assistance and counsel to the mothers