Infection with the Asian strains (R103451 and PRVABC59) showed increased expression of the DNA damage inducible transcript 3 (DDIT3)/CHOP and peptidyl-prolyl cis-trans isomerase A (PPIA) genes, while infection with the African strain caused increased expression of fork-head box 06 (FOX06), mitogen activated protein kinase -10 (MAPK10), Insulin inducible gene 1 (INSIG1) and PPIA genes (Fig 3B). Here, PPIA is linked to infection.