Abstract
BackgroundThe cattle tick Rhipicephalus (Boophilus) microplus is involved in the transmission of the protozoan Babesia bovis, the etiological agent of bovine babesiosis. Interactions between ticks and protozoa are poorly understood and the investigation of tick genes that affect tick fitness and protozoan infection can set the stage for dissecting the molecular interactions between the two species.ResultsIn this study, RNA interference was used to silence R. microplus genes that had been previously shown to be up-regulated in response to B. bovis infection. The silencing of a putative immunophilin gene (Imnp) in female ticks fed on a calf acutely infected with B. bovis decreased the hatching rate and survival of larval progeny. Interestingly, Imnp was up-regulated significantly in ovaries of R. microplus in response to B. bovis infection and its silencing in female ticks significantly increased the infection rate of the protozoan in larval progeny. The results also showed that the silencing of a putative Kunitz-type serine protease inhibitor (Spi) gene and a putative lipocalin (Lpc) gene decreased the fitness of R. microplus females, but had no significant effect on the infection rate of B. bovis in larval progeny.ConclusionThe silencing of the Imnp, Spi or Lpc genes decreased the fitness of R. microplus females fed on a calf during acute B. bovis infection. The Imnp gene data suggest that this putative immunophilin gene is involved in the defense system of R. microplus against B. bovis and may play a role in controlling the protozoan infection in tick ovaries and larval progeny.
Highlights
The cattle tick Rhipicephalus (Boophilus) microplus is involved in the transmission of the protozoan Babesia bovis, the etiological agent of bovine babesiosis
Transcription level and gene silencing The level of expression and silencing of the Imnp, serine protease inhibitor (Spi) and Lpc genes were investigated by quantitative real-time RTPCR in tick gut and ovary samples collected at day 5 of feeding (Figure 1)
The quantitative real-time RTPCR (qRT-PCR) was normalized to the total amount of RNA used to generate the cDNA and the transcription level was calculated as a relative expression using the formula: Relative expression(sample) = 2[Ct(control)-Ct(sample)], where the control is the lowest Ct value for a given gene of interest (GOI)
Summary
The cattle tick Rhipicephalus (Boophilus) microplus is involved in the transmission of the protozoan Babesia bovis, the etiological agent of bovine babesiosis. The cattle tick Rhipicephalus (Boophilus) microplus is an economically important ectoparasite of bovines implicated in the transmission of the apicomplexan protozoan Babesia bovis, the etiological agent of bovine babesiosis ( (page number not for citation purposes). Adult females R. microplus acquire B. bovis merozoites by ingesting blood from an infected bovine and pass the protozoan transovarially to their larvae progeny that can transmit B. bovis sporozoites to cattle during subsequent feeding [1,2,3]. The control of bovine babesiosis relies on the control of tick populations and the use of live attenuated vaccines in some endemic areas [1,3]. A better understanding of the interactions among ticks, protozoan and cattle is required for the development of epidemiological models and strategies to prevent the reinvasion of R. microplus into zones free of this tick and the introduction of B. bovis into non-endemic areas
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