Although plasma TRP concentrations were significantly higher in the clinically normal than the diseased koalas (Fig 2B and S6 Table), the concentration could be dependent on the stage of infection due to the nearly complete TrpR of C. pecorum pathogens, whereby TRP biosynthesis is upregulated by the pathogen when the concentration is low [25, 27, 28]. This evidence concerns the gene WARS1 and infection.