Wright Chelsea L, Gaff Holly D, Sonenshine Daniel E, Hynes Wayne L
Biological Sciences Department, Old Dominion University, Norfolk, VA, USA.
Biological Sciences Department, Old Dominion University, Norfolk, VA, USA; University of KwaZulu-Natal, Durban, South Africa.
Ticks Tick Borne Dis. 2015 Jul;6(5):568-73. doi: 10.1016/j.ttbdis.2015.04.011. Epub 2015 Apr 29.
Rickettsia parkeri, an obligate intracellular bacterium, is a member of the spotted fever group of rickettsiae (SFGR), and is transmitted to humans and other animals by invertebrate vectors. In the United States, the primary vector of R. parkeri is the Gulf Coast tick, Amblyomma maculatum Koch. This study investigates the vertical transmission dynamics of R. parkeri within a field-derived, naturally infected colony of A. maculatum. Transovarial and transstadial transmission of the pathogen was observed over three generations, with transovarial transmission efficiency averaging 83.7% and transstadial transmission rates approaching 100%. Fitness costs were determined by comparing reproduction values of the R. parkeri-infected A. maculatum colony to values from a R. parkeri-free colony. No significant reproductive fitness costs to the host ticks were detected in the R. parkeri-infected A. maculatum colony. Significantly fewer engorged F1 nymphs and F2 larvae of the R. parkeri-free colony succeeded in molting, suggesting that there may be some advantage to survival conferred by R. parkeri. The results of this study indicate that R. parkeri is maintained in A. maculatum populations efficiently by transovarial and transstadial transmission without any noticeable effects on tick reproduction or survival.
帕克立克次体是一种专性细胞内细菌，属于立克次体属斑点热群（SFGR），通过无脊椎动物媒介传播给人类和其他动物。在美国，帕克立克次体的主要媒介是海湾沿岸蜱，即黄斑硬蜱（Amblyomma maculatum Koch）。本研究调查了帕克立克次体在野外采集的自然感染黄斑硬蜱群体中的垂直传播动态。在三代蜱虫中观察到了病原体的经卵传播和经变态传播，经卵传播效率平均为83.7%，经变态传播率接近100%。通过比较感染帕克立克次体的黄斑硬蜱群体与未感染帕克立克次体的群体的繁殖值来确定适合度代价。在感染帕克立克次体的黄斑硬蜱群体中，未检测到对宿主蜱虫有显著的繁殖适合度代价。未感染帕克立克次体的群体中，饱血的F1若虫和F2幼虫成功蜕皮的数量明显较少，这表明帕克立克次体可能赋予了一定的生存优势。本研究结果表明，帕克立克次体通过经卵传播和经变态传播在黄斑硬蜱种群中有效维持，且对蜱虫的繁殖或生存没有任何明显影响。
