Molecular characterisation of contagious ecthyma (ORF) virus from small ruminants

Contagious ecthyma (CE) or contagious pustular dermatitis (CPD) is an acute, contagious, debilitating and economically important zoonotic viral skin disease that affects domesticated as well as wild ruminants. In the present study, three different polymerase chain reaction (PCR) assays and nucleotide sequence analysis were employed successfully for the identification and characterisation of CE/CPD virus from nine [scabs (n = 8) and cell-culture adapted (n = 1)] field samples. PCR assays based on B2L gene encoding major envelope glycoprotein (based on the full length and partial length amplification) and GIF/IL-2 gene (GM-CSF and interleukin-2 inhibitory factors) were standardised. The B2L specific assays yielded amplicons of 1, 137 and 235 bp, whereas the IL-2 PCR yielded 408 bp products. The PCR amplicons were gel purified and sequenced using BigDye terminator chemistry to confirm specific amplification and to study the genetic variability among field isolates of ORF viruses. Sequencing studies demonstrated that both B2L and GIF/IL-2 genes were highly conserved with > 96 and 98% nt sequence identity, respectively. The ORF virus isolates in the present study demonstrated high relatedness with other Indian strains. Further, these studies have also shown that sequencing studies can be reliably used to identify the ORF virus isolates in clinical samples along with their genetic relatedness.