Identification, molecular characterization, and pathological features of orf virus in sheep and goats in Punjab province, Pakistan

Abstract

Orf virus (ORFV) causes an acute, contagious, skin disease of sheep and goats which is economically important. The objectives of this study were to identify ORFV and to explore its pathological and phylogenetic profiles in 350 goats and 91 sheep of 14 districts of Punjab, Pakistan, from July 2020 to July 2021. Skin scrapings (total no. of samples = 441) of suspected animals were subjected to polymerase chain reactions, phylogenetic analysis, and pathological observations. The partial length of GIF/IL-2 gene (408bp) was successfully amplified in 58/441 samples. Phylogenetic analysis of GIF/IL2 gene showed that the study isolates belonged to ORFV-cluster I, together with the viruses reported in India and China. Pakistan ORFV isolates were shared 97.6-98.7% nucleotide and 97.6-100% amino acid identities with the reference strain (NC_005336). Moreover, Chinese ORFV-isolates were detected unique multiple amino acid substitutions (F11L, Q21H, D27N, I46V, N49S, N82D, D103N, S129G) with study isolates. Naturally infected animals were anorexic, emaciated, dull, and depressed. The macroscopic lesions included multifocal to coalescing, ulceration followed by proliferative papules, pustules, and crust formation on the epidermis of gums, lips, mouth commissure, muzzles, nose, and udder. Histopathological examination revealed hyperplasia, anastomosing rete ridges formation and degenerative changes, including spongiosis and vacuolation of epidermal cells. Keratinocytes exhibited eosinophilic intracytoplasmic inclusion bodies with pyknotic and karyorrhexis nuclei. This is the first report on molecular characterization of ORFV from Pakistan, with insight into its pathogenesis and comparative analysis of pathological alterations and genetic diversity between ORFV strains reported in different geographical areas.