Subolesin expression in tick vector species experimentally infected with A. marginale. Subolesin expression was characterized in D. variabilis (D.v.), D. andersoni (D.a.), D. reticulatus (D.r.), R. sanguineus (R.s.), R. annulatus (R.a.) and R. microplus (R.m.) whole ticks after transmission feeding (5 pools of 10 ticks each). Subolesin mRNA levels were analyzed by real-time RT-PCR and normalized against tick 16S rRNA using the comparative Ct method [9, 32]. The graph depicts the infected to uninfected subolesin mRNA ratio (± SD) calculated by dividing normalized subolesin mRNA levels in infected ticks by the average of the normalized subolesin mRNA level in uninfected control ticks (N = 20). Normalized subolesin mRNA levels were compared between infected and uninfected ticks by Student's t-Test (*P < 0.05).