(A–D) Porcine reproductive and respiratory syndrome virus (PRRSV) RNA detection in serum, saliva, nasal, and rectal swabs from 8-week-old piglets after PRRSV infection using Reverse Transcription-quantitative Polymerase Chain Reaction (RT-qPCR). Different letters indicate significant statistical differences (p < 0.05) between groups: intramuscular (IM) vs intranasal (IN) (a), IM vs Control (C) (b), and IN vs C (c). (E) Titration of PCR and virus isolation-positive serum samples in PAM-KNU cells. (F) PRRSV RNA detection in different tissues from pigs in each experimental group using RT-qPCR. Data are presented as mean ± SD.