Orf and Milker's Nodule

Orf and Milker's Nodule - Pox on the Farm

• Zoonotic viral infections caused by the Parapoxvirus genus.
• Acquired via direct contact with infected farm animals; lesions typically on hands/fingers, self-limiting.
• Orf (Contagious Ecthyma / Contagious Pustular Dermatitis)
  • Definition: Viral skin disease primarily from infected sheep and goats.
  • Agent: Orf virus.
  • Reservoir: Sheep, goats. 📌 Orf has an Ovine (sheep) origin.
• Milker's Nodule (Pseudocowpox)
  • Definition: Viral skin infection primarily from infected cattle (udders/teats).
  • Agent: Pseudocowpox virus.
  • Reservoir: Cattle.

⭐ Orf virus infection is the most common human parapoxvirus infection globally.

Orf and Milker's Nodule - Farm Alarm Pox

• Mode of Transmission: Primarily through direct contact with infected animals (sheep/goats for Orf, cattle for Milker's Nodule) or their lesions; also via fomites.
• High-Risk Groups: Individuals with occupational exposure like farmers, veterinarians, sheep shearers, and butchers.
• Incubation Period:
  • Orf: 3-7 days.
  • Milker's Nodule: 5-14 days.
• Seasonality: Orf incidence often ↑ after lambing season.

⭐ Occupational exposure is the primary risk factor for both Orf and Milker's Nodule.

Orf and Milker's Nodule - Pox Eruption Parade

Orf (Contagious Ecthyma)

• Parapoxvirus from sheep/goats.
• Six stages over 4-6 weeks:
  1. Maculopapular
  2. Targetoid (bull's-eye)

     ⭐ The 'target lesion' appearance (Stage 2) is highly characteristic of Orf.

  3. Acute/Nodular (weeping)
  4. Regenerative (dry nodule)
  5. Papillomatous
  6. Regressive (crusted, resolves) 📌 Mnemonic: My Tall Naughty Rabbit Poops Regularly.
• Lesions: Solitary/multiple, firm, reddish-blue, 1-3 cm; fingers, hands, forearms. Painful, exudative.

Milker's Nodule (Pseudocowpox)

• Parapoxvirus from cattle.
• Lesions: 1-5 lesions, smaller (0.5-1 cm), firm, cherry-red/bluish papules/nodules; hands.
• Less exudative/painful vs Orf. Central depression/crust.

Systemic Symptoms

• Mild fever, malaise, lymphadenopathy (more in Orf).

Orf vs. Milker's Nodule

Orf and Milker's Nodule - Pox Patrol Protocol

• Etiology: Parapoxvirus; zoonotic. Orf from sheep/goats, Milker's Nodule from cattle.
• Diagnosis: Clinical. Animal exposure history; characteristic lesions (papule → targetoid nodule/vesicle, often hands).
  • DDx: Pyogenic granuloma, herpetic whitlow, cowpox, anthrax, tularemia, SCC.
• Investigations (Usually not required):
  • EM: Ovoid parapoxvirus particles (scrapings/biopsy).
  • Biopsy: Acanthosis, ballooning degeneration, eosinophilic intracytoplasmic inclusions.
• Management:
  • Self-limiting; resolves in 4-8 weeks (immunocompetent).
  • Supportive: Clean, dry lesions; analgesics.
  • Topical antiseptics/antibiotics for secondary infection.
  • Severe/immunocompromised: Cidofovir (topical/intralesional), imiquimod.
• Prevention: Gloves with animals, hygiene. Animal vaccination (Orf).

⭐ Reinfection with Orf is possible as immunity is not lifelong or complete.

High‑Yield Points - ⚡ Biggest Takeaways

• Orf (from sheep/goats) and Milker's Nodule (from cattle) are zoonotic Parapoxvirus infections.
• Present as solitary or few painless, firm, reddish-purple nodules, typically on hands/fingers.
• Orf lesions may show a characteristic targetoid pattern or central umbilication.
• Both conditions are self-limiting, resolving spontaneously, usually within 6-8 weeks.
• Diagnosis is mainly clinical, based on exposure history and lesion morphology.
• Complications include secondary bacterial infection, lymphadenopathy, and erythema multiforme.