<p>Abstract</p> <p>Background</p> <p><it>Rhipicephalus </it>(<it>Boophilus</it>) <it>microplus </it>is an economically important tick of cattle involved in the transmission of <it>Babesia bovis</it>, the etiological agent of bovine babesiosis. Commercial anti-tick vaccines based on the <it>R. microplus </it>Bm86 glycoprotein have shown some effect in controlling tick infestation; however their efficacy as a stand-alone solution for tick control has been questioned. Understanding the role of the <it>Bm86 </it>gene product in tick biology is critical to identifying additional methods to utilize Bm86 to reduce <it>R. microplus </it>infestation and babesia transmission. Additionally, the role played by <it>Bm86 </it>in <it>R. microplus </it>fitness during <it>B. bovis </it>infection is unknown.</p> <p>Results</p> <p>Here we describe in two independent experiments that RNA interference-mediated silencing of <it>Bm86 </it>decreased the fitness of <it>R. microplus </it>females fed on cattle during acute <it>B. bovis </it>infection. Notably, <it>Bm86 </it>silencing decreased the number and survival of engorged females, and decreased the weight of egg masses. However, gene silencing had no significant effect on the efficiency of transovarial transmission of <it>B. bovis </it>from surviving female ticks to their larval offspring. The results also show that <it>Bm86 </it>is expressed, in addition to gut cells, in larvae, nymphs, adult males and ovaries of partially engorged adult <it>R. microplus </it>females, and its expression was significantly down-regulated in ovaries of ticks fed on <it>B. bovis</it>-infected cattle.</p> <p>Conclusion</p> <p>The <it>R. microplus </it><it>Bm86 </it>gene plays a critical role during tick feeding and after repletion during blood digestion in ticks fed on cattle during acute <it>B. bovis </it>infection. Therefore, the data indirectly support the rationale for using Bm86-based vaccines, perhaps in combination with acaricides, to control tick infestation particularly in <it>B. bovis </it>endemic areas.</p
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