Histopathological study and F1L gene sequence analysis of contagious ecthyma in small ruminants of Shiraz suburb, Iran.

Contagious ecthyma, also known as Orf, is a common viral skin disease of sheep and goats caused by a Parapoxvirus. This research was conducted with the aims of histopathological study and genetic analysis of Orf virus with PCR technique based on F1L gene in 50 sheep and goats suspicious of contagious ecthyma in affected areas of Shiraz suburb. All 50 contagious ecthyma-like tissue samples were maintained in 10% buffered formalin, embedded in paraffin, sectioned into 5μm slices and dyed with hematoxylin-eosine. The histopathological examination showed 100% positivity. Epidermal hyperplasia with prominent rete ridges, hydropic degeneration of the necrotic keratinocytes, eosinophilic intracytoplasmic inclusion bodies in vacuolated cells and subcorneal pustules were the main hallmarks of this disease. For molecular analysis, after DNA extraction, all samples were amplified by PCR method and the outcome demonstrated positivity in 25 specimens (50%). Of these, 10 definitely positive specimens were analyzed for nucleotide sequencing. Thus, a strain named Orf-059-Shiraz was recorded in the GeneBank and subsequently underwent phylogenetic analysis. The outcome of the molecular study approved half of the positive ecthyma specimens in histopathological method. Furthermore, phylogenetic analysis based on 059 gene showed that this gene is highly conserved. Utilization of histopathology and clinical signs can assist with rapid and low-cost diagnosis of infectious ecthyma whereas PCR is able to dissociate from similar diseases among clinical samples of endemic regions.