Before determining the effects that Yersiniosis had on the expression levels of cDNA encoding rainbow trout PACAP splicing variants (PACAP and PRP/PACAP) and VIP/PACAP receptor subtype 2 (VPAC2) in the spleen, head, kidney, and skin of rainbow trout, the presence of the disease was determined by visual examination, microbiological testing, and conventional PCR. Here, VIPR2 is linked to Yersinia infectious disease.