Harris Emma K, Verhoeve Victoria I, Banajee Kaikhushroo H, Macaluso Jacqueline A, Azad Abdu F, Macaluso Kevin R
Vector-Borne Disease Laboratories, Department of Pathobiological Sciences, School of Veterinary Medicine, Louisiana State University, Skip Bertman Dr., SVM-3213, Baton Rouge, LA, 70803, USA.
Department of Microbiology and Immunology, School of Medicine, University of Maryland, 685 W. Baltimore St., HSF I Suite 380, Baltimore, MD, 21201, USA.
Ticks Tick Borne Dis. 2017 Jun;8(4):598-604. doi: 10.1016/j.ttbdis.2017.04.003. Epub 2017 Apr 6.
The geographical overlap of multiple Rickettsia and tick species coincides with the molecular detection of a variety of rickettsial agents in what may be novel tick hosts. However, little is known concerning transmissibility of rickettsial species by various tick hosts. To examine the vertical transmission potential between select tick and rickettsial species, two sympatric species of ticks, Dermacentor variabilis and Amblyomma maculatum, were exposed to five different rickettsial species, including Rickettsia rickettsii, Rickettsia parkeri, Rickettsia montanensis, Rickettsia amblyommatis, or flea-borne Rickettsia felis. Fitness-related metrics including engorgement weight, egg production index, nutrient index, and egg hatch percentage were then assessed. Subsamples of egg clutches and unfed larvae, nymphs, and adults for each cohort were assessed for transovarial and transstadial transmission of rickettsiae by qPCR. Rickettsial exposure had a minimal fitness effect in D. variabilis and transovarial transmission was observed for all groups except R. rickettsii. In contrast, rickettsial exposure negatively influenced A. maculatum fitness and transovarial transmission of rickettsiae was demonstrated only for R. amblyommatis- and R. parkeri-exposed ticks. Sustained maintenance of rickettsiae via transstadial transmission was diminished from F larvae to F adults in both tick species. The findings of this study suggest transovarial transmission specificity may not be tick species dependent, and sustained vertical transmission is not common.
多种立克次氏体和蜱虫物种在地理上的重叠，与在可能是新型蜱虫宿主中检测到的多种立克次氏体病原体的分子结果相吻合。然而，关于各种蜱虫宿主传播立克次氏体物种的能力，我们知之甚少。为了研究特定蜱虫和立克次氏体物种之间的垂直传播潜力，将两种同域分布的蜱虫物种，即变异革蜱（Dermacentor variabilis）和斑点钝缘蜱（Amblyomma maculatum），暴露于五种不同的立克次氏体物种中，包括立氏立克次氏体（Rickettsia rickettsii）、帕克立克次氏体（Rickettsia parkeri）、蒙大拿立克次氏体（Rickettsia montanensis）、安氏立克次氏体（Rickettsia amblyommatis）或蚤传猫立克次氏体（flea-borne Rickettsia felis）。然后评估与健康相关的指标，包括饱血重量、产卵指数、营养指数和卵孵化率。通过qPCR评估每个队列的卵块以及未进食的幼虫、若虫和成虫的子样本中的立克次氏体经卵传递和经变态传递情况。立克次氏体暴露对变异革蜱的健康影响最小，除立氏立克次氏体外，所有组均观察到经卵传递。相比之下，立克次氏体暴露对斑点钝缘蜱的健康有负面影响，仅在暴露于安氏立克次氏体和帕克立克次氏体的蜱虫中证明了立克次氏体的经卵传递。在这两种蜱虫物种中，从F代幼虫到F代成虫，立克次氏体通过经变态传递的持续维持能力均有所下降。本研究结果表明，经卵传递的特异性可能不依赖于蜱虫物种，并且持续的垂直传播并不常见。
