Schistosomiasis: The Disease, Anti-Schistosoma Vaccine Candidates and Baboons as Ideal Models in Schistosomiasis Studies

Schistosomiasis is still a major health hazard in developing countries. Acute form, Katayama's syndrome occurs weeks after the initial infection and manifestations include fever, cough, abdominal pain, diarrhea and hepatosplenomegaly. Chronic infection may cause granulomatous reactions and fibrosis in the affected organs. These reactions may result in: colonic polyposis with bloody diarrhea; portal hypertension with haematemesis and splenomegaly; cystitis and ureteritis with hematuria, which can progress to bladder cancer; pulmonary hypertension; glomerulonephritis; and CNS lesions. Cerebral granulomatous disease may be caused by ectopic S. japonicum eggs in the brain, and granulomatous lesions around ectopic eggs in the spinal cord from S. mansoni and S. haematobium infections may result in a transverse myelitis with flaccid paraplegia. At present the effective control method is chemotherapy with use of praziquantel as the drug of choice. But with the possibility of drug resistance and re-infection, the focus is on development of vaccine[s] that can reduce the incidence of the disease. Different Schistosoma antigens capable of inducing some protection in experimental animals have been identified. The potential of these vaccine candidates need to be validated fully in humans. As a starting point, these antigens need to be tested in an animal model that is biologically and immunologically closely related to humans. Baboons may be the ideal models for this purpose as prelude for human clinical trials. This article reviews the disease schistosomiasis; anti-Schistosoma vaccine candidates; and also looks at baboons as ideal models in schistosomiasis studies.