First identification of orf virus from an outbreak of contagious ecthyma in Polish sheep

Contagious ecthyma (CE) is a skin disease of goats, sheep and some other domesticated and wild ruminants worldwide, including Poland. The infection is caused by the orf virus (ORFV) of the Parapoxvirus genus. It is characterised by the appearance of skin lesions in the form of papules and pustules, most often in the area of the mouth and nostrils, hooves and genitals. The disease causes economic losses, especially in countries with high sheep and goat production. In Europe, the threat posed by this disease is rather underestimated, but following the re-emergence of foot-and-mouth disease (FMD) in the region in 2025, there is increased vigilance and a need to have differential diagnostic methods proven and ready.

DNA was extracted from lesions on mouth and hooves of sheep. The animals were on a farm located in southwestern Poland on which FMD was ruled out. A PCR was performed using two pairs of specific primers for detecting vIL10 and GIF gene fragments which were then sequenced.

Sequencing confirmed ORFV infection in all tested sheep samples. The sequences obtained for Polish viruses were also highly homologous to other parapoxviruses, indicating that the method used may be applicable for broad diagnosis of parapoxvirus infections not only in ruminants.

This is the first molecular characterisation of ORFV in sheep in Poland. It signals a potential herd biosecurity problem in view of the neglected but re-emerging nature of CE. The marked genetic divergence between Polish field ORFV isolates and currently available vaccine strains may influence CE vaccine efficacy in Poland.