长江丹徒段沿江重点水域血吸虫感染性监测预警及应急处置

Surveillance of schistosomiasis and responses to the disease in key aquatic regions of the Dantu district along the Yangtze River

目的在易感季节针对已达到血吸虫病传播控制的长江下游镇江市丹徒段沿江重点水域,实施血吸虫感染性监测预警和应急处置技术应用及集成示范,为构建敏感有效的疫情监测预警和处置体系提供参考依据。方法基于流行病学基础数据库和传播危险因素识别,在长江镇江丹徒段68.9km长的滩涂上筛选确定7个高风险区域为监测预警点。于2009-2016年每年的3-5月调查环境螺情与人畜病情;5-9份采用哨鼠法测定水体感染性,并采用现场观察法调查人畜接触江水状况;2009-2011年采用哨螺法测定血吸虫毛蚴对水体的污染性。一旦查见感染性钉螺,或出现急性感染病人,或查见粪检阳性病人,或出现感染性哨鼠,或发现感染性哨螺等疫情,即刻发布预警警示并启动处置程序,针对疫情采取相应应急处置措施。结果 2009-2016年7个监测预警点所在区域均未查见感染性钉螺;在7个监测预警点检查哨鼠3643只,查出阳性哨鼠30只,哨鼠阳性率为0.82%,共发现3个预警点6次哨鼠法测定水体具有感染性。2009-2011年共投放哨螺9 000只,钉螺逸蚴共32 490只次,解剖钉螺5 191只,均未检出毛蚴。针对出现感染性哨鼠的3个监测预警点发布水体感染性预警警示6次;对监测预警阳性点区域重点人群查病2262人,查出DDIA阳性128人,阳性率5.66%;粪检阳性10人,感染率为0.44%;监测男性和女性血清学阳性率分别为6.80%和3.71%,感染率分别为0.56%和0.24%,性别血清学阳性率(χ2=9.42,P<0.01)及感染率(χ2=6.21,P<0.01)差异均有统计学意义。未查出急性血吸虫病病人。检查放养羊228只次,查出阳性12只次,感染率为5.26%。对查出的128例DDIA阳性、10例粪检阳性者及12只次阳性羊均采用吡喹酮进行同步化疗;开展药物灭螺50hm2,应急灭蚴19hm2;并及时采取了健康教育及个人防护、安全用水及粪便管理等集成处置措施,有效控制了疫情发生。结论江滩型血吸虫病传播控制地区实施重点水域感染性监测预警并及时采取有效应急处置措施对扼制疫情的发生发展效果显著。哨鼠法是测定水体感染性客观、敏感和有效方法之一。

Objectives To implement schistosomiasis surveillance and alerts,prompt responses to outbreaks,and integrated interventions in key aquatic regions in the City of Zhenjiang＇s Dantu district（the transmission of schistosomiasis was previously controlled in the Dantu district）along the lower reaches of the Yangtze River during seasons of high prevalence in order to provide scientific evidence for creation of a system for surveillance of schistosomiasis and responses to that disease. Methods Based on a baseline epidemiological database and identification of risk factors for schistosomiasis transmission,a total of 7 surveillance and sentinel sites were selected along 68.9 km of marshlands in the Dantu district along the Yangtze River.A snail survey and a study of schistosomiasis among humans and livestock were performed between March and May from 2009 to 2016.Infectivity of water-borne schistosomes was determined using sentinel mice between May and September.In addition,human and livestock contact with the river was observed,and the contamination of water with miracidia was detected using sentinel snails from 2009 to 2011.If infected snails,acute cases of schistosomiasis,patients with Schistosoma eggs in their feces,infected sentinel mice,or infected sentinel snails were detected,alerts were immediately issued and a prompt response was initiated. Results During the period from 2009 through2016,no infected snails were detected at the 7 surveillance and sentinel sites.A total of 3 643 sentinel mice were tested at the 7 sites,and 30 mice tested positive at a rate of 0.82%.In addition,a bioassay of sentinel mice revealed 6 instances of Schistosoma japonicuminfection in the aquatic regions at 3 surveillance and sentinel sites.A total of 9 000 sentinel snails were released from 2009 to 2011,32,490 snails shed cercariae,and 5 191 snails were dissected,with no miracidia detected.To respond to the detection of S.japonicuminfection in sentinel mice at the 3 surveillance and sentinel sites,alerts regarding the infectivity of water-borne parasites were issued 6 times.A total of 2 262 high-risk patients were examined at surveillance and sentinel sites where S.japonicum was detected,and 128 patients tested positive according to a DDIA at a rate of 5.66%.Ten patients had Schistosoma eggs in their feces,for a rate of infection of 0.44%.The sero-positive rate was 6.8%for men and 3.71%for women,and the rate of infection was 0.56%for men and 0.24%for women.The sero-positive rate（χ^2= 9.42,P〈0.01）and the rate of infection（χ^2=6.21,P〈0.01）differed significantly between men and women.No acute cases of schistosomiasis were detected.A total of 228 sheep were examined,and 12 sheep had Schistosoma eggs in their feces,for a rate of infection of 5.26%.The 128 patients who tested positive according to a DDIA,10 patients with Schistosoma eggs in their feces,and 12 sheep with Schistosoma eggs in their feces were treated with praziquantel.Plots of 10 hm2 were treated chemically and cercariae were promptly controlled in aquatic sections of 19 hm2.Integrated interventions were implemented,including health education,individual protection,water sanitation,and disposal of feces. Conclusion In marshlands where the transmission of schistosomiasis was previously controlled,schistosomiasis surveillance and alerts in key aquatic regions and initiation of effective responses and interventions effectively inhibited the development and spread of schistosomiasis outbreaks.A bioassay of sentinel mice is a sensitive and feasible tool with which to detect the infectivity of water-borne parasites.