Parapoxvirus

Parapoxvirus is a genus of large, enveloped, brick-shaped DNA viruses in the family Poxviridae, subfamily Chordopoxvirinae. The genus comprises several species that infect domestic and wild ruminants and cause localized skin and mucosal lesions. The genome is a linear double-stranded DNA molecule, and the viruses replicate in the cytoplasm of host cells.

Key members include Orf virus, Pseudocowpoxvirus, and Bovine papular stomatitis virus. Orf virus predominantly infects sheep and goats and causes contagious ecthyma. Pseudocowpoxvirus and Bovine papular stomatitis virus infect cattle, producing characteristic teat and muzzle lesions in the former and papular dermatitis in the latter.

Clinical features vary by host but typically involve crusted or proliferative lesions at contact sites including lips, udders, teats, and mucosa. In calves and lambs, nodular to proliferative lesions may occur; systemic illness is rare. Humans can be infected from contact with infected animals, with Orf being the best known parapoxvirus zoonosis, causing nodular, sometimes ulcerative lesions on hands or fingers that usually heal over several weeks.

Transmission occurs via direct contact with lesions, contaminated equipment, or fomites. The viruses are relatively stable in the environment and can be spread by milking equipment and shearing tools. No specific antiviral therapy exists; management is supportive and involves isolating infected animals and maintaining hygiene. Vaccines are used in some settings to prevent Orf in sheep and goats; vaccination strategies vary.

Diagnosis relies on clinical signs supported by laboratory tests such as PCR, virus isolation, or electron microscopy. Serology is less useful for acute diagnosis. Parapoxvirus infections are generally self-limiting in animals and humans.