塔里木盆地荒漠型黑热病宿主动物调查研究

目的调查并查找新疆塔里木盆地荒漠型黑热病自然疫源地的宿主动物。方法参考世界卫生组织(WHO)黑热病宿主动物的5个标准,采用流行病学方法查明荒漠型黑热病患者被感染的主要生境;采集疫区不同生境优势动物,以特异性抗体检测方法筛查抗体阳性动物;调查疫区不同生境白蛉密度和传播媒介吴氏白蛉自然感染利什曼原虫的感染率;采用特殊培养基和敏感动物从患者、阳性动物和吴氏白蛉中分离利什曼原虫,开展分子遗传学相似性鉴定;以吴氏白蛉开展优势动物吸血实验,查找吴氏白蛉的供血宿主;对照黑热病宿主动物的5个标准,根据上述实验调查结果,采用排除法确认天然宿主动物,同时确认荒漠型黑热病疫区的核心区;黑热病暴发时在核心区及其周边以杀虫剂灭蛉,与对照区比较,根据两个区的实际控制效果和时间,最后确定宿主动物。结果荒漠型黑热病患者被感染的生境是胡杨柽柳生境及其相邻农田;胡杨柽柳生境的优势动物为塔里木兔(Lepus yarkandensis)、子午沙鼠(M.meridianas)、毛脚三趾跳鼠(D.sagitta)和科氏三趾矮跳鼠(S.crassicada);共获得16种动物1374份样品(野生动物1137份、家畜237份),只有塔里木兔(45/485)检出抗利什曼原虫阳性个体,从塔里木兔分离出4株利什曼原虫(4/485)。在疫区的所有生境中,只有胡杨柽柳生境中的塔里木兔的抗体阳性率和吴氏白蛉的利什曼原虫感染阳性率最高;吴氏白蛉只能吸到塔里木兔和大耳猬的血,吸血率分别为9.5%和3.3%;塔里木兔的利什曼原虫分离株与当地黑热病患者和传播媒介吴氏白蛉分离株的乙酰氨基葡萄糖磷酸转移酶(NAGT)核基因鉴定结果显示相似性100%,属婴儿利什曼病2型;自2008年黑热病暴发以来,实验区飞机喷洒杀虫剂灭蛉一次,连续7年无流行,对照区流行2次,每次流行持续2年。结论所有动物中只有塔里木兔与WHO规定的黑热病宿主动物的5个标准最接近,传播媒介吴氏白蛉的供血宿主实验是验证天然宿主动物的重要方法;荒漠型黑热病患者被感染的生境是查找黑热病宿主动物的关键区域,即胡杨柽柳核心区及其相邻农田;核心区灭蛉是长期有效控制黑热病流行的重要措施,能为证明荒漠型黑热病宿主动物提供重要证据。

Investigation on natural host animals of desert type of kala-azar in Tarim Basin

Objective To investigate and discover the host animals of desert type of kala-azar(DT-ZVL)in the natural foci in Tarim Basin.Methods By referring to the five criteria of WHO for the host animals of kala-azar,the main infected habitats of patients with DT-ZVL were identified with epidemiological method.The dominant animals in different habitats were collected,and screened the positive animals with specific antibody detecting method.The densities of sandflies in different habitats and the infection rate of natural infection with Leishmania in the Phlebotomus wui were investigated.The special culture medium and sensitive animal were taken for isolating Leishmania from the patients,positive animals and P.wui for identifying the similarity of molecular genetics.In order to find out the blood supply hosts of P.wui,the blood sucking test in the dominant animals was carried out with P.wui.Compared with the five criteria of kala-azar hosts,and referred to the results of test and investigation mentioned above,the natural host animals were confirmed with the exclusive method,and the core area in the DT-ZVL epidemic region was confirmed at the same time.Insecticide was taken to kill P.wui in and around the core area during the outbreak of DT-ZVL.Finally,the host animals were confirmed according to the actual control effects and time in the outbreak area and control area by comparing with the contrast area.Results The infected habitats of the patients with DT-ZVL was Euphratica and Tamarix growing area and their adjacent farmland.The dominant animals were Lepus yarkandensis,M.meridianas,D.sagitta and S.crassicada.Totally 1374 samples of 16 animal species were obtained,including 1137 samples of wild animals and 237 samples of domestic animals.The antibody to Leishmania was detected positive only in L.yarkandensis,and four Leishmania strains were isolated.The positive rate of the antibody in L.yarkandensis and infection rate of P.wui were the highest in the Euphratica and Tamarix habitats among all habitats in the epidemic region.P.wui only sucked the bloods of L.yarkandensis and Hemiechinus auritus,with the rate of sucking blood of 9.5%and 3.3%.Genetic identification results showed that the similarities of nuclear gene of N-acetylglucosamine-1-phosphate transferase(NAGT)were 100%among Leishmania strains isolated from L.yarkandensis,kala-azar patients and P.wui,and the gene type belonged to infant leishmaniasis type 2.Since the outbreak of DT-ZVL in 2008,the aircraft sprayed insecticide one time to kill sandflies in the experimental area,and there was no DT-ZVL epidemic in the following 7 years,while two epidemics of DT-ZVL occurred in the contrast area,and each epidemic lasted for 2 years.Conclusions Out of all the animals,only L.yarkandensis is the closest to the five criteria of kala-azar host by WHO.The tests of blood supply hosts of P.wui is an important method for verifying the natural host animals.The infected habitats of the patients with DT-ZVL is the key area of finding the host animals of kala-azar,that is the core area of Euphratica and Tamarix growing area and their adjacent farmland.Killing P.wui in the core area is the effective measure to control the epidemic of kala-azar for a long time,and can provide important evidence for verifying the natural host animals of kala-azar.