Department of Veterinary Microbiology and Pathology, Washington State University, Pullman, WA, 99164, USA.
Department of Entomology, Faculty of Science, Cairo University, Giza, 12613, Egypt.
Parasit Vectors. 2019 Jan 5;12(1):7. doi: 10.1186/s13071-018-3270-1.
Rhipicephalus microplus is an efficient biological vector of Babesia bovis, a causative agent of bovine babesiosis. Babesia bovis is passed transovarially to the next generation of ticks, which then transmit the parasite to naïve animals. Due to the importance of the R. microplus ovary for tick reproduction and transmission of B. bovis, we investigated the hypothesis that silencing vitellogenin receptor gene expression in the ovary during tick feeding on B. bovis-infected cattle would affect parasite transmission to the next generation of ticks.
Silencing expression of the vitellogenin receptor in the ovary by RNA interference, resulted in reduced tick fertility. We observed reduced egg production (i.e. reduced weight of eggs), a lower rate of embryonic development, and a reduction in hatching. Analysis of individual larvae by PCR confirmed that RNAi mediated downregulation of the R. microplus vitellogenin receptor and also interfered with transovarial transmission of B. bovis. None of the larvae (0/58) from the RmVgR dsRNA-injected group were PCR-positive, whereas 12% (7/58) and 17% (10/58) of larvae from the non-injected and buffer-injected control groups, respectively, were infected with B. bovis.
The combined effects of reduced fecundity and reduced infection in surviving larvae resulting from silencing indicate that vitellogenin receptor is essential for tick reproduction and may play a vital role in B. bovis transmission.
璃眼蜱是牛巴贝斯虫的高效生物传播媒介，后者是引起牛巴贝斯虫病的病原体。牛巴贝斯虫经卵传递给下一代蜱，然后由这些蜱将寄生虫传播给无免疫力的动物。由于璃眼蜱卵巢对蜱的繁殖和传播牛巴贝斯虫至关重要，因此我们假设在蜱吸食感染牛巴贝斯虫的牛时，在卵巢中沉默卵黄蛋白原受体基因的表达，将影响寄生虫向下一代蜱的传播。
通过 RNA 干扰沉默卵巢中的卵黄蛋白原受体表达，导致蜱的生育力降低。我们观察到产卵量减少（即卵的重量减少）、胚胎发育率降低以及孵化减少。通过 PCR 对单个幼虫进行分析证实，RNAi 介导的璃眼蜱卵黄蛋白原受体下调，并且干扰了牛巴贝斯虫的经卵传递。来自 RmVgR dsRNA 注射组的幼虫中没有一个（0/58）PCR 呈阳性，而来自未注射和缓冲液注射对照组的幼虫中分别有 12%（7/58）和 17%（10/58）感染了牛巴贝斯虫。
沉默导致的生育力降低和存活幼虫感染减少的综合影响表明，卵黄蛋白原受体对于蜱的繁殖是必不可少的，并且可能在牛巴贝斯虫传播中发挥重要作用。
