In turn, even though R. rickettsii induces an increase in the expression of most genes of the immune signaling pathways Toll, IMD, and Jak-Stat after 24 h of infection [17] and possibly creates a more pro-oxidant environment compared with A. marginale (RmDUOX-A and RmDUOX-B were induced at 24 h post-infection), we observed high rates of R. rickettsii growth and mortality of BME26 cells. This evidence concerns the gene TLR4 and infection.