Pox diseases are viral diseases that affect many animals, including people and birds. Some poxviruses also cause zoonoses. Typically, lesions of the skin and mucosae are widespread and progress from macules to papules, vesicles, and pustules before encrusting and healing. Most lesions contain multiple intracytoplasmic inclusions, which represent sites of virus replication in infected cells. In some poxvirus infections, vesiculation is not clinically evident, but microvesicles can be seen on histologic examination and, in some, proliferative lesions are characteristic.
Infection is acquired either by inhalation or through the skin (eg, sheeppox Sheeppox and Goatpox Sheeppox virus (electron microscopy). Sheeppox and goatpox are serious, often fatal, diseases characterized by widespread skin eruption. Both diseases are confined to parts of southeastern Europe... read more ). In certain instances (eg, fowlpox Fowlpox in Chickens and Turkeys Fowlpox is a worldwide viral infection of chickens and turkeys. Nodular lesions on unfeathered skin are common in the cutaneous form. In the diphtheritic form, which affects the upper GI and... read more , swinepox Swinepox Swinepox is an acute, often mild, infectious disease characterized by skin eruptions that affects only pigs. It is present in the USA, particularly in the Midwest, and has been reported from... read more ), the virus is transmitted mechanically by biting arthropods. Infection may be followed by generalized lesions (eg, sheeppox) or remain localized (eg, pseudocowpox Pseudocowpox in Cattle The parapox virus of pseudocowpox (electron microscopy, low magnification of 20,000x) in a skin scraping from a clinically affected cow, visualized by mixing a heavy metal stain (phosphotungstic... read more ). Strains of poxvirus with reduced virulence are used to immunize against some infections, the classic example being the global eradication of smallpox in people by immunization with strains of live vaccinia virus.
Poxviruses can be classified according to their physicochemical and biologic properties. Immunologically, the viruses of smallpox, cowpox, and monkeypox are, among others, closely related to vaccinia virus and are classified within the genus Orthopox. The avian poxviruses, the myxoma viruses, and some of the other poxviruses (eg, swinepox) are species-specific. The viruses of orf Contagious Ecthyma in Sheep and Goats Contagious ecthyma is an infectious dermatitis of sheep and goats that primarily affects the lips of young animals. The lesions are characteristic, and diagnosis is confirmed by PCR assay. The... read more , pseudocowpox Pseudocowpox in Cattle The parapox virus of pseudocowpox (electron microscopy, low magnification of 20,000x) in a skin scraping from a clinically affected cow, visualized by mixing a heavy metal stain (phosphotungstic... read more , and bovine papular stomatitis Papular Stomatitis in Large Animals Photograph of a cow with bovine papular stomatitis, manifested by reddish, raised, ulcerated lesions on the lower lip. Viral papillomas are found around the lips and mouths of young animals... read more are parapoxviruses and are also closely related. It has been recognized that several orthopoxvirus infections of domestic animals and people, notably cowpox Cowpox in Cattle In cowpox, a mild, eruptive disease of dairy cows, lesions are seen on the udder and teats. Although once common, cowpox is now extremely rare and reported only in western Europe. The virus... read more and monkeypox, are acquired from rodent reservoir hosts. Many of these rodent hosts have not been unequivocally identified. Thus, although the use of adjectives such as "cowpox" and "monkeypox" to describe these viruses may be epidemiologically inaccurate and misnomers, their retained use reflects both historical association and, until a better nomenclature evolves, pragmatism ( See also Cowpox Virus Infections in Cats and Other Species Cowpox Virus Infections in Cats and Other Species In addition to cattle, cowpox virus may infect cats, people, and other species. Infection in cattle is now rare, with domestic cats in Europe now the most commonly diagnosed species. Skin ulcers... read more ).
Poxvirus infections can be confirmed in the laboratory using several diagnostic techniques. The orthopoxviruses can usually be isolated in cell culture and by inoculation of embryonated eggs. Examination of clinical samples by negative-staining electron microscopy is frequently used to visualize virus particles. PCR and gene sequencing are widely used to further characterize virus isolates.