Abstract:

Objective To understand the water infectivity of schistosomes in key water areas of Hanchuan City, and explore the use of sentinel mice in surveillance and forecast of schistosomiasis. Methods Surveillance and forecast sites were set up in North Han River, Diaocha Lake, and Miaowu Ditch in 2014. Sentinel mice （male Kunming mice, n=20 in each site） were placed there within the first ten-day period of June and September, respectively. Field detections lasted 4 h each, for a total of 2 days. The loss and death rates of mice were recorded. Humans and livestocks with activities in these sites were also examined for schistosome infection. The sentinel mice recovered were raised in laboratory for 35 days, dissected, and examined for liver granulomas and adult worm counting. The distribution of sites with positive detections and their infection status were analyzed. Emergency measures were taken in the positive sites. Results A total of 13（5 sites in North Han River, 5 in Diaocha Lake, and 3 in Miaowu Ditch） surveillance and forecast sites were set up. No infected snail was detected in any of these sites in spring 2014. The detection rate of living snails in North Han River （18.7%, 224/1 201) was significantly higher than that in Diaocha Lake（12.8%, 852/6 644） and in Miaowu Ditch （6.4%, 202/3 147）（P<0.01）. Of the 520 mice placed, 6 were lost, and 514 were recovered, among which 4 mice died during laboratory raising. The remaining 510 sentinel mice were then dissected, revealing infection in 4 mice, with a positive rate of 0.8%. Twenty-seven Schistosoma japonicum worms were collected, and the mean worm burden of positive mice was 6.8 worms per mouse. Three sites （Sansi village, Kangjia village and Doubu village） were found to be positive sites of infection in September, with the detailed number of 2, 1 and 0 in North Han River, Diaocha Lake, and Miaowu Ditch respectively, with a positive rate of 1.5% （3/197）, 0.5% （1/195） and 0 （0/118） in sentinel mice （P>0.05）. In addition, among the 22 cattle found in the 13 sites, 2 were infected with schistosomes; and among the 62 fishermen and boatmen, 2 were infected. Emergency measures were taken in the three positive sites, and no high endemicity occurred. Conclusion The monitoring of sentinel mice infections can improve the sensitivity of the surveillance and forecast system of schistosomiasis. The infected fishermen and cattle remain the major source of schistosomiasis transmission in Hanchuan City.

Key words: Schistosomiasis japonica, Sentinel mouse, Water infectivity, Surveillance and forecast, Hanchuan City