IMMUNITY AND MORBIDITY IN SCHISTOSOMIASIS-JAPONICUM INFECTION

Schistosomiasis japonica differs significantly from Schistosoma manson i infection in several epidemiologic, immunologic, and operational cha racteristics for control. Because of numerous nonhuman hosts, transmis sion remains high despite aggressive case finding and treatment of hum an cases. Diagnosis of infection using the Kato-Katz stool technique i s less sensitive and specific in this than in other species of human s chistosomes, making case finding and treatment a less effective approa ch to control. Clinically, morbidity induced by S. japonicum appears u nrelated to intensity of infection, and is more severe than that of S. mansoni in terms of liver pathology and stunting of child growth and development. Both hepatic enlargement and fibrosis appear to be revers ible and preventable with aggressive treatment but several operational characteristics for control of infection due to S. japonicum make the community impact of case-finding and treatment with praziquantel less pronounced than would have been predicted by the analysis of individu al cases. In the Philippines, rebound morbidity following reinfection mandates short treatment intervals between screening and treatment to have a significant impact on morbidity, while in China inapparent infe ction (infection not diagnosed by a single stool examination) appears to be a common cause for persistent hepatic pathology. The authors con clude that for S. japonicum, mass treatment or targeted mass treatment is a more cost-effective approach than case-finding and treatment for control.