[Analysis on morbidity and chemotherapy effects of Schistosoma japonicum infection in fishermen on Dongting Lake].

OBJECTIVE

To clarify and evaluate the morbidity of schistosome infection and the effectiveness of chemotherapy among fishermen on East Dongting Lake.

METHODS

Information on water-contact, history of infection and of praziquantel (PZQ) treatment among fishermen was collected. Kato-Katz method and miracidium hatching test were applied to detect the pathogens in stool specimen. Serum antibodies against soluble egg antigen (SEA) were detected with ELISA and IHA. B-ultrasonic examination was used to determine the pathological changes of liver and spleen. Chemotherapy [PZQ 40 mg/(kg x d)] was given to the fishermen followed by a re-examination after a transmission season.

RESULTS

The first investigation (six months before chemotherapy) showed that among 268 people inquired, 90.7% were frequently or intermittently contacting water, 24.0% were treated with PZQ each year, 39.4% had never been treated in the recent five years. Stool positive rate was 68.1% (111/163) and the geometric mean eggs per gram feces (EPG) were 48.77. Males had a higher infection rate (76.0%) and intensity (62.97 EPG) compared with that of females (58.7% infection rate and 30.42 EPG). The highest positive rate (83.3%) was in the age group of 11 to 20 years old. The prevalence of those who frequently or intermittently contacted water and were never treated before was 76.3% (106/139) and 79.7% (51/64), respectively. Serological positive rate was 88.0% (IHA) or 78.7% (ELISA). B-ultrasound revealed 77.4% (82/106) of the fishermen showing pathological changes in liver and/or spleen due to schistosomiasis. 37.7% of the patients showed II-III stage liver fibrosis (male: 53.0%, female: 15%), 58.5% hepatomegaly and 19.8% splenomegaly. The second investigation (six months after chemotherapy with PZQ) showed a stool positive rate of 35.4% and an average EPG 36.13 in the treatment group which were considerably lower than 56.5% infection rate and 68.47 EPG in the group without treatment. In 39 patients treated, the reversion rate from egg positive to negative was 48.7%, pathological change in liver and spleen declined by 40.6%.

CONCLUSION

The prevalence and morbidity of schistosomiasis in fishermen on Dongting Lake were high due to frequent exposure to the affected water, and chemotherapy can effectively reduce the prevalence, the intensity of infection and morbidity of the fishermen.