[Survey of endemic situations in schistosomiasis transmission controlled or interrupted regions in Anhui Province].

Objective: To understand the variation rules of schistosomiasis endemic situation before and after schistosomiasis transmission controlled or interrupted, so as to provide the evidence for the consolidation of control achievements.

Methods: In Anhui Province, 3 counties reaching the criteria of schistosomiasis transmission controlled or interrupted were selected and their historical endemic data were collected and analyzed statistically from 10 years before the schistosomiasis transmission controlled to 2008.

Results: In Tianchang City, the Oncomelania hupensis snail area was 3.54 hm2 in a part of the lake marshland in the year reaching the criteria of transmission controlled (1998), and no snails were found in the year of transmission interrupted (2008). No stool-test-positive resident was detected except there were 58 acute schistosomiasis cases in 1993, and the sero-test-positive rate of local residents remained at low levels (0-1.55%). In Taihu County, the snail area was 0.84 hm2 accounting for 0.06% of its historical accumulative snail areas in the year of transmission controlled (1971) , and no snails were found three years before the transmission interrupted (1983). However, the schistosomiasis endemic rebounded 12 years later (1995), there was an outbreak of acute schistosome infections (73 cases), and the snail area increased again to 133.7 hm2 accounting for 2.91% of historical accumulative snail areas. After that, the snail area kept on rising and the infection rates of residents and bovine remained higher than 1%. In Guangde County, the snail area was 32.4 hm2 accounting for 1.90% of its historical accumulative snail areas in the year of transmission controlled (1995). After that, the snail area increased progressively, and the schistosomiasis endemic rebounded and there were acute schistosome infections 5 years later. The Spearman tests showed that the sero-test-positive rate (Tianchang City) and the stool-test-positive rates of residents and bovine (Taihu County) had positive correlations with the snail areas (r = 0.582, 0.401, 0.596, all P < 0.05).

Conclusion: The snail status is a key for the consolidation of schistosomiasis transmission controlled and interrupted. Therefore, a valid surveillance system of snail situation should be established as quickly as possible.