Objective: To analyze the changes of leptospirosis epidemic characteristics before and after the Phase 2 'reservoir store water project' in Chongqing section of the Three Gorges dam area and to provide prevention, control and intervention measures to prevent the spread of leptospirosis from infectious focus to the Three Gorges dam area and downstream region of Changjiang River.
Methods: Changshou district and Fengdu county were selected as surveillance sites. We monitored the source of infection through examining the serum antibody of patients, healthy groups together with farm cattle measured by micro agglutination test (MAT).
Result: Sporadic cases were reported before and after the storage of water in the reservoir. There was no significant difference found between mouse density before and after the Phase 2 reservoir project (chi2 = 1.00, P > 0.05). The main species of rat were Sewer rat before and Insectivorea after the storage of water. The germ-carrying rate of rats was 1.72% (10/583) and positive carrying rate of rats was 16.51% (18/109) when using PCR. Results showed a significant difference when comparing it to culture method (chi2 = 51.80, P < 0.01). Positive rate of leoptopirosis appeared in the serum of patients was 73.33% (33/45) with the major serum group as the Australia group. The rate of infection among the healthy group was 26.84% (233/868). There was significant difference seen between the serum antibody positive rate of epidemic prophase (23.85%) and epidemic anaphase (29.86%) of the healthy group (chi2 = 3.99, P < 0.05). The GMRT of ox serum antibody of leoptopirosis was 29.97 with Bailen group as the predominant microbial population.
Conclusion: There was no epidemics of leptopirosis occurred in the Three Gorges dam area. There was no significant difference between mouse density before and after the storage of water in the reservoir. However, the major species of rats had a change. The natural infection level of people living in the dam area was low, but there existed potential of leoptopirosis outbreak.