Molecular and virological studies on contagious pustular dermatitis isolates from Egyptian sheep and goats.

Orf virus was clinically diagnosed from different field cases of sheep and goat in Hawamdia, Giza, Egypt during the summer 2006. Skin scabs were collected and used for virus isolation, electron microscopy, PCR and sequencing for confirmation, and differential diagnosis. The aetiological virus was fruitfully isolated on the chorio-allantoic membrane of SPF embryonated chicken eggs indicated by expressing the characteristic pock lesions of Poxviridae family. Electron microscopy examination exposed negatively stained oval-shape virus particles trait for members of the genus Parapoxvirus. A 392 bp fragment of the late transcription factor (VLTF-1) gene of orf virus was amplified by PCR from the DNA extracted from the isolates. Phylogenetic analysis revealed 99% identity with other orf virus strains reported worldwide. Selection and processing of clinical specimens and PCR assay applied in this endeavor, presented a reliable laboratory diagnostic tool for orf infections and first molecular characterization of Egyptian orf isolates.