Abstract
BackgroundRhipicephalus (Boophilus) microplus is an economically important tick of cattle involved in the transmission of Babesia bovis, the etiological agent of bovine babesiosis. Commercial anti-tick vaccines based on the R. microplus 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 Bm86 gene product in tick biology is critical to identifying additional methods to utilize Bm86 to reduce R. microplus infestation and babesia transmission. Additionally, the role played by Bm86 in R. microplus fitness during B. bovis infection is unknown.ResultsHere we describe in two independent experiments that RNA interference-mediated silencing of Bm86 decreased the fitness of R. microplus females fed on cattle during acute B. bovis infection. Notably, Bm86 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 B. bovis from surviving female ticks to their larval offspring. The results also show that Bm86 is expressed, in addition to gut cells, in larvae, nymphs, adult males and ovaries of partially engorged adult R. microplus females, and its expression was significantly down-regulated in ovaries of ticks fed on B. bovis-infected cattle.ConclusionThe R. microplus Bm86 gene plays a critical role during tick feeding and after repletion during blood digestion in ticks fed on cattle during acute B. bovis infection. Therefore, the data indirectly support the rationale for using Bm86-based vaccines, perhaps in combination with acaricides, to control tick infestation particularly in B. bovis endemic areas.
Highlights
Rhipicephalus (Boophilus) microplus is an economically important tick of cattle involved in the transmission of Babesia bovis, the etiological agent of bovine babesiosis
In a previous study we showed that the R. microplus actin, tubulin, G6PDH, and PHGPx, reference genes commonly used in tick studies, are not stably expressed among tick stages and tick tissues, and they are inadequate for RT-qPCR
Effect of Bm86 silencing on tick fitness The effect of Bm86 silencing on the fitness of R. microplus females fed on cattle during acute B. bovis infection was examined in two independent experiments
Summary
Rhipicephalus (Boophilus) microplus is an economically important tick of cattle involved in the transmission of Babesia bovis, the etiological agent of bovine babesiosis. The one-host tick Rhipicephalus (Boophilus) microplus is an economically important ectoparasite of cattle involved in the transmission of the apicomplexan protozoan Babesia bovis, the etiological agent of bovine babesiosis [1]. Bm86-based vaccines have shown some effect on controlling R. microplus and other ticks species, and they can reduce the use of acaricides [7,8,9]. Their efficacy as a stand-alone solution for tick control has been a matter of debate [6]
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