Serological evaluation of ultrasound examination for chronic schistosomiasis japonica in a previously endemic area—the Chikugo River Basin, Japan

Abstract

Ultrasound diagnosis of chronic schistosomiasis japonica was assessed by comparison with the results of serological tests using enzyme-linked immunosorbent assay (ELISA) with egg and adult worm antigen, and the circumoval precipitation test. The subjects were persons resident in the Chikugo River Basin in Kyushu, southwest japan, where schistosomiasis used to be highly prevalent. Of 93 individuals with a past history of infection, 37 (39·8%) presented the characteristic echo pattern of the disease (network, sieve, mottled or mixed pattern). In the serological tests, the ultrasound (US)-positive subjects showed a significantly higher IgG antibody-positive rate in ELISA (81·1% for egg-ELISA), than the US-negative subjects (37·5% for egg-ELISA). Individuals bearing dead Schistosoma japonicum eggs proven by tissue biopsy showed a similar antibody-positive rate (76·5% for egg-ELISA) to that of the US-positive subjects. Sera of a group which had no schistosomiasis characteristic echo pattern, but had liver fibrosis, hepatomegaly or liver cirrhosis as shown by US, were also highly positive (71·4% for egg-ELISA). The present serological studies thus confirmed the usefulness of ultrasound diagnosis for chronic schistosomiasis japonica. Furthermore, we were able to determine certain indications of liver abnormality currently undefined in the normally utilized US classifications.