蒙古马胃蝇蛆病的组织损伤研究与虫体鉴定

Pathological observation and pathogen identification of Mongolian horses infection with horse stomach fly maggots

为了明确蒙古马马胃蝇蛆感染组织的病理变化及感染虫体种类,2021年12月份在内蒙古和林和呼伦贝尔屠宰场各收集到9例感染马胃蝇蛆的蒙古马病料,对感染马的咽部、胃部、十二指肠进行病理学观察,并且利用光学显微镜和扫描电镜对胃蝇第三龄幼虫进行形态学观察,同时选取胃蝇第三龄幼虫,通过PCR方法扩增线粒体细胞色素氧化酶亚基Ⅱ(COXⅡ)基因。利用MEGA6.0软件对胃蝇COXⅡ基因和GenBank数据库中胃蝇科的其他种类同源序列进行Clustal W比较,构建系统发育树。结果表明:感染马的病理变化主要为咽部、胃部、十二指肠黏膜出现不同程度的损伤和增生性炎变化,黏膜层水肿,炎性细胞浸润,上皮细胞空泡化。咽部出现虫体肉芽肿,胃部出现蝇蛆损伤的炎性寄生灶。和林蒙古马马胃蝇的第三龄幼虫口脊骨的页部、伪头小刺特征与黑腹胃蝇幼虫的形态一致。呼伦贝尔蒙古马马胃蝇的第三龄幼虫口脊骨、棘刺特征和肠胃蝇相似。系统发育树表明,和林蒙古马马胃蝇与GenBank数据库中黑腹胃蝇聚在一起,而呼伦贝尔蒙古马马胃蝇单独成为1个分支,与其他胃蝇的遗传距离很大。所以和林蒙古马马胃蝇鉴定为黑腹胃蝇,呼伦贝尔蒙古马马胃蝇是基因变异较大的胃蝇变种。

In order to clarify the pathological changes of tissues infected with horse stomach fly maggots and the species of horse stomach flies infected,nine Mongolian horses infected horse stomach fly maggots were collected from each of the slaughterhouses in Helin and Hulunbeier,Inner Mongolia,in December 2021.Pathological observations were made on pharynx,stomach,and duodenum of the infected horses,and morphological observations were made on the third instar larvae of the stomach fly using light microscope and scanning electron microscope.And the larvae of third instar of the horse stomach fly were selected at the same time.The mitochondrial cytochrome oxidase subunitⅡ(COXⅡ)gene was amplified by PCR.The phylogenetic tree was constructed by comparing the homologous sequences of the COXⅡgene with those of other species of the Gasterophilidae in the GenBank database using MEGA 6.0,Clustal W software.The results showed that the pathological changes in the affected horses mainly con sisted of different degrees of damage and proliferative inflammation in the pharyngeal,gastric,and duodenal mucosa,with edema of the mucosal layer,infiltration of inflammatory cells,and vacuolization of epithelial cells.There were granulomas formed in the pharynx,and inflammatory focis of parasitic lesions of maggots in the stomach.The characteristics of oral cristae and papillary sensilla of the third instar larvae of the Helin Mongolian horse stomach fly were consistent with the morphology of the third instar larvae of Gasterophilus pecorum.The third instar larvae of Hulunbeier Mongolian horse stomach fly had similar oral spine and spine characteristics to those of Gasterophilus intestinalis.The phylogenetic tree indicated that Helin Mongolian horse stomach fly clustered with G.pecorum from the GenBank database,whereas Hulunbeier Mongolian horse stomach fly was alone in a single branch,with a large genetic distance from the other stomach fly genus.Therefore,Helin Mongolian horse stomach fly was identified as G.pecorum,and Hulunbeier Mongolian horse stomach fly was a genetically more variable stomach fly variant.