Ferrari Flavia A G, Goddard Jerome, Caprio Michael, Paddock Christopher D, Mixson-Hayden Tonya, Varela-Stokes Andrea S
Department of Basic Sciences, College of Veterinary Medicine, Mississippi State University, Mississippi State, MS 39762, USA.
Ticks Tick Borne Dis. 2013 Sep;4(5):439-44. doi: 10.1016/j.ttbdis.2013.04.010. Epub 2013 Jul 12.
Gulf Coast ticks, Amblyomma maculatum, and the zoonotic agents they transmit, Rickettsia parkeri, are expanding into areas in the United States where they were not previously reported, and are emerging threats for public and veterinary health. The dynamics of this tick-pathogen system and implications for disease transmission are still unclear. To assess genetic variation of tick and rickettsial populations, we collected adult A. maculatum from 10 sites in Mississippi, 4 in the northern, one in the central, and 5 in the southern part of the state. PCR amplicons from tick mitochondrial 16S rRNA and rickettsial ompA genes as well as 5 intergenic spacer regions were evaluated for genetic variation using single-strand conformation polymorphism analysis. Frequencies of the 4 tick 16S haplotypes were not significantly different among regions of Mississippi, but within sites there were differences in distribution that can be explained by high migration rates. Phylogenetically, one lineage of tick haplotypes was a species-poor sister group to remaining haplotypes in the species-rich sister group. No genetic variation was identified in any of the 6 selected gene targets of R. parkeri examined in the infected ticks, suggesting high levels of intermixing.
墨西哥湾沿岸蜱虫（斑点钝眼蜱）及其传播的人畜共患病原体帕克立克次体正在向美国此前未报告过的地区扩张，对公共卫生和兽医健康构成新出现的威胁。这种蜱虫-病原体系统的动态变化及其对疾病传播的影响仍不清楚。为了评估蜱虫和立克次体种群的遗传变异，我们从密西西比州的10个地点采集了成年斑点钝眼蜱，其中该州北部4个、中部1个、南部5个。利用单链构象多态性分析评估蜱虫线粒体16S rRNA、立克次体ompA基因以及5个基因间隔区的PCR扩增子的遗传变异。密西西比州各地区间4种蜱虫16S单倍型的频率没有显著差异，但在各个地点内分布存在差异，这可以用高迁移率来解释。从系统发育角度来看，蜱虫单倍型的一个谱系是物种较少的姐妹群，与物种丰富的姐妹群中的其余单倍型相对。在受感染蜱虫中检测的帕克立克次体的6个选定基因靶点中均未发现遗传变异，这表明存在高度混合。
