Parapoxviruses Clinical Presentation

Updated: Oct 07, 2015
  • Author: Luke Bloomquist, MD; Chief Editor: Mark R Wallace, MD, FACP, FIDSA  more...
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Presentation

History

Most patients report direct contact when feeding or treating animals or when visiting or working on farms, although indirect contact with contaminated fomites also causes infection. Parapoxvirus species are quite resistant to heat, cold, and drying and may persist on fences, feeding troughs, and barn beams for days to months. Patients often have a history of trauma, frequently minor; lesions occur at the site of trauma. Human-to-human transmission is exceedingly rare.

According to some sources, human infections occur with higher frequency in the spring and autumn, corresponding with the lambing and calving seasons. Young animals are more susceptible to infection and infected animals are more likely to require assistance with feeding, which necessitates close contact with the infected animal by the human caretaker.

Other reports suggest a higher incidence during the winter, presumably from the use of gorse, a prickly animal feed that may cause trauma and facilitate infection in an animal. [11]

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Physical

Parapoxvirus lesions progress through 6 stages, each lasting approximately 6 days, as follows:

  1. The maculopapular stage, characterized by a discrete erythematous macule(s) or papule(s), follows an incubation period of 3-7 days. These lesions are usually located on the fingers, hands, or forearms; however, several reports show involvement of the face, neck, ear, and periocular area.
  2. The target stage is next; lesions have a red center, a white middle ring, and a red halo.
  3. The acute stage occurs by weeks 2-3. The lesion appears nodular and weeping.
  4. The regenerative stage occurs by weeks 3-4. The lesion becomes ulcerated and thin-crusted.
  5. The papillomatous stage develops by weeks 4-5.
  6. The regressive stage with thick dry crusting and reduction in elevation occurs by week 6, and then the lesion resolves without scarring. [17]

Unusual presentations include giant orf, widespread papulovesicular or bullous lesions, or hemorrhagic pustular nodules. These can occur in immunosuppressed or, rarely, otherwise healthy individuals. [18]

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Causes

Direct contact with infected animals, either alive or dead, is most typical but is not required for infection; transmission also occurs from contaminated fomites such as shears, feeding troughs, barn doors, and fences. [19] Skin trauma, even trivial, is a risk factor for infection.

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