武汉沉湖湿地候鸟、留鸟和家禽间禽流感病毒的传播

The purpose of this study is to uncover the circulation and diversity of avian influenza viruses (AIVs) in the wintering migratory birds, the transmission potential of AIVs from migratory birds to resident birds or domestic poultry, and the dynamic transmission of AIVs among multiple hosts in wintering wetland. The following research will be performed in the core area in Chenhu wetland, Wuhan City. First, the species, quality and density of resident birds and domestic poultry will be investigated before wintering birds arrive in wintering area; The prevalence of AIVs in these hosts will also be determined. Second, after wintering birds arrive in wintering area, the fresh droppings and water in habitats of migratory birds, the fresh droppings around the nesting area of resident birds, and the swabs and fresh droppings of domestic poultry will be collected; Viruses will be isolated and the subtypes, genome sequences will be determined; The hosts of the AIV-positive samples will be identified with a mitochondrial analysis; The spatial and temporary pattern of AIVs in the wintering area will be demonstrated through analyzing the genetic characteristics of virus strains; The results will shed light to the dynamic distribution of AIVs in wintering area. Third, the prevalence of AIVs in resident birds and domestic poultry will be determined after the migratory birds’ departure. Fourth, evaluate of the potential risk of infection will be performed via determine the characteristics of some isolates: the viruses will be tested for receptor binding activities, resistance in different pH and temperature, growth curve in vitro, pathogenicity in animal model. The results will reveal the ecological transmission chains of AIVs in wintering area. The results will also provide the key basis for controlling the source of infection, cutting the way of transmission, and preventing the epidemic and circulation of AIVs.

本课题的目的是研究越冬地候鸟禽流感病毒的多样性，病毒从候鸟传给留鸟或者家禽的可能性以及病毒在越冬地不同宿主间的动态传播。本课题拟在武汉沉湖湿地核心区开展以下研究内容：（1）在候鸟抵达前秋季，调查散养家禽、留鸟的种类、数量、密度及禽流感病毒流行情况的本底数据；（2）在候鸟抵达后的冬春季，采集候鸟聚集区新鲜粪便及水体、留鸟筑巢点新鲜粪便、家禽拭子或新鲜粪便；分离鉴定不同宿主流行毒株，确定采集样品所属宿主种类，分析不同时间和空间、不同宿主流行毒株的遗传信息，以此阐明冬春季越冬地禽流感病毒的动态分布；（3）在候鸟飞离后，监测湿地核心区散养家禽、留鸟是否继续存在禽流感病毒流行；（4）对部分毒株的生物学特性如：受体结合，耐酸碱、耐热，体外生长及致病性进行分析，评估病毒风险。通过本研究，掌握禽流感病毒生态传播链，为有效控制传染源、切断传播途径和防止禽流感的发生与流行提供重要依据。

禽流感病毒亚型多，重配复杂，携带禽流感病毒的禽类是人感染的主要风险源之一。只有掌握病原的流行特征与遗传变异规律，才能有效控制传染源、切断传播途径，控制疫病的发生与流行。湖北地区水网密布，地处东亚-澳大利亚迁徙路线上，每年冬春季节大量候鸟在此越冬，而且活禽保有量高、活禽交易频繁，这些为禽流感病毒的传播提供了绝佳的机会。申请人自2013以来，每年冬春季节在武汉市沉湖湿地及湖北省其它湖泊、散养家禽及活禽市场采集样本，先后24次共采集野鸟样本8, 600多份，分离禽流感毒株122株，其中H1亚型51株，H3亚型1株，H4亚型1株，H5亚型25株，H6亚型26株，H7亚型4株，H9亚型10株，H11亚型6株。我们完成其中108株病毒全基因组测序并深入分析遗传进化关系。我们的结果表明位于长江流域的越冬湿地是多种禽流感病毒流行的混合地，一些基因片段能在越冬地候鸟中持续流行数年，越冬地大量候鸟聚集为病毒的重配及病毒进化提供了“温床”。我们观察到来自北美的病毒基因片段持续发生跨洲传播，输入我国越冬地候鸟中，提示跨洲传播的风险。我们发现我国家禽中流行的禽流感病毒（H5, H9）持续输入越冬地候鸟，虽然未引发疫情，但候鸟携带病毒实现大范围扩散成为可能。我们的研究揭示湿地及越冬候鸟在禽流感生态中扮演重要角色，我们的研究提供了越冬候鸟中禽流感病毒流行的第一手资料，为我国禽流感的防控提供了科学数据。