Orf (Contagious ecthyma)
Orf (Contagious ecthyma) is a Parapox virus infection transmitted from infected ungulates (sheep, goats, reindeer, and musk oxen). It causes a red or violet papule or pustule and later a weeping nodule with central umbilication usually on hand, arm, or face.
CASES/YEAR
6 (US); 120 (Global)
OTHER NAMES
Parapox virus infection;
INCUBATION
3-6 days; [CCDM]
INITIAL SYMPTOMS
Red or violet papule or pustule and later a weeping nodule with central umbilication usually on hand, arm, or face; [CCDM, p. 568]
PRECAUTIONS
"Person-to-person transmission is rare." [CCDM, p. 568]
COMMENTS
Orf is a viral infection transmitted from infected ungulates (sheep, goats, reindeer, and musk oxen). The clinical findings are limited to one or more papules and sometimes regional lymphadenitis. The lesion is described as, "a red to violet vesiculonodule, maculopapule or pustule, that progresses to a weeping nodule with central umbilication." Papules may reach 3 cm in diameter and last 3 to 6 weeks. Patients may have a maculopapular rash on the trunk. A related condition is milker's nodule caused by a different Parapoxvirus. [CCDM, p. 568-9] Parapoxviruses infect sheep and goats; the corresponding human infection is called orf. They also infect dairy cattle; the corresponding human infection is called milker's nodes. [PPID, p. 1818] The orf lesion progresses from a papule to a nodule to a 1-2 cm blister to a weeping ulcer to a crusted ulcer. Patients may have low-grade fever and lymphadenitis. [Guerrant, p. 966]
DIAGNOSTIC
Electron microscopy; Culture; PCR; Serology; [CCDM]
SIGNS & SYMPTOMS
-
>fever
-
H lymphadenopathy
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S entry wound with lymph nodes
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S papules or plaques
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S pustule
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S rash (exanthem)
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S skin blister or vesicles
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S skin or subcutaneous nodule
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S ulcer of skin
ENTRY
Skin or Mucous Membranes (Includes Conjunctiva)
RESERVOIR
Cattle, Goats and Sheep, Deer, Elk and Antelope, Wild Animals
RISK FACTORS
- Handle domestic animals
- Touch infected farm animals
TREATMENT
No specific treatment; [CCDM, p. 569]
REFERENCES FOR CASES/YEAR
1. (US) 1/20 X global cases/yr;
2. (Global) Cases reported in England & Wales: 2 (2007), 3 (2008), 0 (2009), 0 (2011); [Public Health England website] Average = about 1 case/year; Assumption: Incidence worldwide is same as in England & Wales with population of about 50 million and global population of about 6000 million (120 X larger); Calculate: 1 X 120 = 120 and US incidence is 1/20 X 120 = 6;