犬源型黑热病高发区隐性感染犬传播作用与患病影响因素的研究

Kala Azar is a major parasitic disease that is widely distributed in the world and seriously jeopardizes people's health. The number of people being threatened by Kala Azar reaches up to 350 million, and the number of patients is about 500,000. Gansu is a province with the most serious prevalence of canine Kala Azar in China, ranked the first in the number of new cases occurring each year. Dogs with visceral leishmaniasis are the primary source of infection; patients are mostly infants and young children; the transmission medium is peri-wild Phlebotomus chinensis. Following the Wenchuan earthquake in 2008, natural factors and the ecological environment have changed, and the large number of stray dogs have become the source of infection of Kala Azar; as a result, the epidemic situation has recovered and showed a tendency to spread to non-prevalent regions. A previous survey shows that a lot of dogs with latent infection exist in Kala Azar epidemic areas in Gansu Province. This project is intended to locate dogs using GPS so as to track quantity changes and antibody outcomes of newly infected dogs and analyze their transmission potential and spatial aggregation. The correlation between dogs with latent infection and incidence of Kala Azar in people will be analyzed to investigate the role of latently infected dogs in transmission of Kala Azar. No related reports are currently available at home and abroad. This project will investigate transmission media, susceptible populations, natural factors and social factors and reveal prevalence characteristics and incidence rules of canine Kala Azar as well as factors influencing transmission of Kala Azar so as to provide a scientific basis for controlling canine Kala Azar in our country.

黑热病在世界上分布广泛，是严重危害人民健康的重大寄生虫病。全球受黑热病威胁人口达3.5亿，患者约50万。甘肃省是我国犬源型黑热病流行最严重的省份，每年发病人数居全国第一位，患者以婴幼儿为主。传染源为内脏利什曼病病犬，传播媒介为近野栖型中华白蛉。2008 年汶川地震灾害后, 自然因素和生态环境有所改变，当地大量无主犬的存在形成黑热病传染源，出现疫情回升潜势,且有向非流行区扩散趋势。调查显示，甘肃省黑热病疫区存在大量隐性感染犬。本项目拟利用GPS对犬进行定位，跟踪调查隐性感染犬的数量变化和抗体转归，明确其具备的传播潜能和空间聚集性。分析隐性感染犬与人群黑热病发病的关系，探讨隐性感染犬在黑热病传播中的作用。迄今国内外尚无此类报道，尚属空白。研究将调查传播媒介、易感人群、自然因素和社会因素，揭示犬源型黑热病的流行特点、发病规律和黑热病传播中的影响因素，为控制我国犬源型黑热病提供科学依据。

甘肃省是我国犬源型内脏利什曼病（黑热病）的主要流行区，利什曼病犬是主要传染源。在甘肃省陇南甘南地区存在大量无症状的隐性感染犬，及时发现传染源并有效阻断其可能造成的继发传播是实现控制黑热病的关键。项目依托甘肃省疾病预防控制中心寄生虫病预防控制所在陇南市文县和甘南藏族自治州迭部县研究现场，针对黑热病高发区隐性感染犬多的问题，开展了犬感染危险因素、聚集性等研究，并对隐性感染犬的数量变化、抗体转归进行分析，评估隐性感染犬在传播过程中的作用。首先，2018-2020年课题组在研究区域内采集家犬血液，分别利用PCR方法和三种胶体金免疫层析检测试条对家犬检测，鉴别出抗体阳性的隐性感染犬。综合研判调查地点的犬感染利什曼原虫的流行特征，持续观察犬血中生化指标变化与临床症状的关系，探索犬利什曼病发展的迁延过程。其次，课题组收集2017-2019年研究区域内地理、气温、海拔、社会和经济等数据资料，采用流行病学统计分析的方法对自然和社会多种危险因素进行分析评估，阐明隐性感染犬患病的影响因素及传播风险。最后，根据隐性感染犬的地理坐标，利用空间聚集性模型模拟隐性感染犬的空间分布，评估隐性感染犬的空间聚集性和在黑热病流行中的传播作用。本项目为犬源型黑热病防控策略精准制定提供了理论和实践依据。