甘肃河西走廊沿线地区蜱携带病原体分子流行病学研究

Molecular epidemiology of tick-borne pathogens along Hexi Corridor of Gansu Province

目的考察、研究甘肃河西走廊沿线地区现存的蜱媒病原体。方法于2020年3、9月分两次采用动物体表捡蜱、农户圈舍捡拾及布旗法采集不同环境下的各类蜱标本,保持存活状态下带回实验室进行形态鉴定,确定蜱标本种类;提取病原体DNA,采用(巢式)PCR法进行病原体扩增;对于莱姆病螺旋体检测阳性的标本采用RFLP方法进行基因型别判定;土拉弗菌检测阳性标本采用亚种判定引物(C6/C8)进行扩增,判定亚种。结果采集到3个蜱种共计2123只蜱标本,其中亚东璃眼蜱814只、草原革蜱567只、波斯锐缘蜱742只,不同蜱种采集地点不同:草原革蜱、亚东璃眼蜱采自野外放养的骆驼体表及其生活的环境中;波斯锐缘蜱采自农户的圈舍内。所有蜱标本中,共计有54只莱姆病螺旋体检测阳性,分型显示病原体属于两种致病基因型:Borrelia garinii及Borrelia afzelii基因型;32份标本土拉弗菌阳性,属于B亚种;122只Q热柯克斯体检测阳性。在调查点内发现的波斯锐缘蜱检测发现携带土拉弗菌及Q热柯克斯体。所有蜱中,共检测到15只来自野外放养骆驼体表的亚东璃眼蜱存在复合感染的现象,10只为土拉弗氏菌与Q热柯克斯体体感染,5只为莱姆病螺旋体与Q热柯克斯体感染。结论甘肃河西调查点内存在至少3个不同的蜱种,蜱携带莱姆病螺旋体、土拉弗菌及Q热柯克斯体;蜱标本中存在复合感染的现象。

Objective To investigate the possible tick-borne pathogens along the Hexi Corridor of Gansu Province.Methods Ticks were collected from animal surfaces,residents'livestock barns and by dragging a cloth over vegetation,and brought back alive to our laboratory for morphological and species identification.Pathogenic DNA was extracted from the tick samples and amplified by nested PCR.Positive specimens of Lyme disease spirochetes were further analyzed using restriction fragment length polymorphism(RFLP)to determine their genotypes;Subspecies determination primers(C6/C8)were adopted to amplify the positive samples of Francisella tularensis for subspecies identification.Results There were 3 species of ticks finally identified and totally 2123 tick samples collected,including 814 Hyalomma asiaticum,567 Dermacentor nuttalli and 742 Argas persicus.Different tick species were collected at different sites:Hyalomma asiaticum and Dermacentor nuttalli were picked up from the surface of wild free-range camels and their living environment,while Argas persicus from residents'barn.Among all the tick specimens,54 samples were tested positive for Lyme disease spirochetes,and RFLP analysis indicated that the pathogen in the samples belonged to 2 genotypes:either Borrelia garinii or Borrelia afzelii.In addition,32 heads were positive for Francisella tularensis,belonging to Francisella tularensis.subsp.holarctica(type B),and 122 heads were positive for Coxiella burnetii.Argas persicus were found to carry both Francisella tularensis and Coxiella burnetii.Coinfection also existed in 15 Hyalomma asiaticum gathered from wild free-range camels,10 of which were infected with Francisella tularensis and Coxiella burnetii,and the other 5 with Lyme disease spirochetes and Coxiella burnetii.Conclusion There are at least 3 different tick species in Hexi Corridor,Gansu Province,and the tick-borne pathogens include Lyme disease spirochetes,Francisella tularensis and Coxiella burnetii.Coinfection exists in the tick specimens.