Human Orf Virus Infection from Household Exposures — United States, 2009–2011

Orf, also known as contagious ecthyma, is a zoonotic infection caused by a dermatotropic parapoxvirus that commonly infects sheep and goats; it is transmitted to humans through contact with an infected animal or fomites. In humans, orf manifests as an ulcerative skin lesion sometimes resembling bacterial infection or neoplasm. Human infection typically is associated with occupational animal contact and has been reported in children after visiting petting zoos and livestock fairs (1). Cases lacking these exposure histories might be misdiagnosed, leading to unnecessary treatment of orf lesions, which do not usually require any specific treatment (2). This report describes four cases of human orf associated with household meat processing or animal slaughter, highlighting the importance of nontraditional risk factors. Orf should be included in the differential diagnosis of patients with clinically compatible skin lesions and a history of household meat processing or animal slaughter. Persons and communities with these exposure risks also should receive counseling regarding the use of nonpermeable gloves and hand hygiene to prevent infection.

Case Reports

Patient A. In April 2009, a woman aged 63 years punctured her right hand on a bone of a recently slaughtered goat near her home in Greece. She subsequently noted a small, pink and white papule at the site of injury that enlarged over the following week. The papule became tender and developed an erythematous border.

Two weeks later, the woman traveled to Pennsylvania to visit her son. By that time, a large bulla had developed at the wound site. On May 14, she went to an emergency department (ED) where a 3 cm bulla with a necrotic core was noted on her right palm (Figure 1). She had no fever, lymphedema, pain, or tenderness. Cultures were negative for bacteria and fungae. Histopathologic examination of the bulla roof revealed areas of necrosis and reticular degeneration of the epidermis with eosinophilic cytosolic inclusions typical of poxvirus infection. Bulla fluid and roof samples sent to CDC were positive by quantitative polymerase chain reaction (qPCR) for orf virus DNA. The outcome of patient A's infection is unknown.

Patient B. In October 2010, a man in Massachusetts aged 42 years assisted with a lamb sacrifice for the Muslim holiday Eid al-Adha, during which he held the lamb's head with his left hand. Approximately 5 days later, a small papular lesion developed on his left fifth finger, which gradually became swollen and painful.

Two weeks later, the man went to an ED at which the lesion was incised and drained; no pus was noted. He was prescribed cephalexin for presumed bacterial infection and discharged. After 1 week of treatment without improvement, a dermatologist was consulted. At that time, the lesion had become a 1.5 cm nodule with a violaceous border and a central crust; the back of the man's left hand and forearm were faintly erythematous with diffuse, nonpitting, tender edema (Figure 2). He had no lymphadenopathy or systemic symptoms.

On December 10, a biopsy of the lesion showed marked expansion and necrosis of the epidermis, focal reticular degeneration, diffuse lymphocytic infiltrate, papillary dermal edema, and telangiectasias. Bacterial culture showed rare, coagulase-negative staphylococci; fungal and mycobacterial cultures were negative. To prevent secondary infection, patient B was treated with mupirocin ointment and instructed to soak the hand in an astringent solution (aluminum acetate). Tissue sent to CDC for parapoxvirus testing was positive for orf virus DNA by qPCR. His lesion completely resolved within 4 weeks after the biopsy.

Patient C. In April 2011, a man of Ethiopian descent aged 35 years, residing in Massachusetts, cut his left thumb with a knife while slaughtering a lamb as part of Easter festivities. He washed the wound with water and applied lemon juice and alcohol. He did not seek medical attention.

One week later, the injury site had become swollen and tender without discoloration, drainage, or bleeding. A fluctuant lesion developed at the site, and the man sought care at a walk-in clinic 2 weeks after his injury. He was prescribed cephalexin for a presumed bacterial infection and advised to go to an ED for evaluation. At the ED, his thumb lesion was incised and drained. Cultures from the site grew Staphylococcus aureus, and antibiotics were continued. Incision and drainage were repeated 2 days later, but the lesion did not improve, and the patient was referred to hand surgery and infectious disease specialists.

At the infectious diseases clinic, the lesion was examined and noted to be 2 × 2 × 2 cm and firm, without discoloration, purulent discharge, fluctuance, or bleeding (Figure 3). The man had no systemic symptoms. Parapoxvirus infection was suspected, and the lesion was removed surgically. Histopathology showed hyperkeratosis, epidermal necrosis, and dermal infiltrate of mixed inflammatory cells consistent with orf infection; qPCR testing at CDC was positive for orf virus DNA. At follow-up 2 weeks after surgery, the man's thumb was healing and had no signs of infection.

Patient D. In June 2011, a pregnant woman from Sudan, aged 28 years, cut her right hand on a bone while preparing a lamb's head at her at home in Virginia. The woman's family purchases a lamb's head from a local butcher or market twice yearly for a traditional Sudanese dish. Two weeks after the injury, she noted a lesion, but did not seek medical care because the lesion caused minimal discomfort.

On July 7, the woman was hospitalized for preeclampsia. While she was hospitalized, a dime-sized, crusted, vesicular lesion was incidentally noted on her right palm near the wrist. The lesion was opened, releasing a slight amount of serous fluid, but no pus. A diagnosis of orf was suggested by an infectious disease consultant, and swabs of the crust were sent to CDC for parapoxvirus testing. Specimens were positive for orf virus DNA by qPCR. Several weeks after the initial evaluation, the woman was examined by a state public health officer who noted that the lesion was healing without signs of infection.

Reported by

Isaac I. Bogoch, MD, Rajesh T. Gandhi, MD, Div of Infectious Diseases, Massachusetts General Hospital, Boston; Yuval Bibi, MD, Dermatology Dept, Harvard Vanguard Medical Associates, Boston; Voraphat Dejsuphong, MD, International Graduate Dermatology Program, Boston Univ School of Medicine; Catherine M. Brown, DVM, Massachusetts Dept of Public Health. David Enis, MD, George Cotsarelis, MD, Dept of Dermatology, Univ of Pennsylvania School of Medicine, Philadelphia; Esther Chernak, MD, Philadelphia Dept of Public Health. Donald Poretz, MD, Inova Fairfax Hospital, Falls Church, Virginia. Whitni Davidson, MPH, Hui Zhao, MD, Yu Li, PhD, Div of High-Consequence Pathogens and Pathology, National Center for Emerging and Zoonotic Infectious Diseases. Jennifer M. Bass, CDC Experience Applied Epidemiology Fellow; Danielle M. Tack, DVM, EIS Officer, CDC. Corresponding contributor: Jennifer M. Bass, jbass@cdc.gov, 404-718-4655.

Editorial Note

Although human orf cases most commonly are reported as a result of occupational exposure to infected sheep and goats, household meat preparation and animal slaughter also pose risks for orf infection. Given the endemic state of orf among sheep, goats, and certain other animals, and the largely decentralized nature of small ruminant markets for custom or home slaughter, feasible mechanisms to prevent infected sheep and goats from reaching consumers are limited.

Clinicians should be knowledgeable about household risks and should be able to recognize signs of orf infection. Human orf lesions generally appear on fingers, hands, or forearms after a 3–7 day incubation period. A typical lesion slowly progresses from a small, erythematous macule or papule (Figure 3) to a large nodule with a red center, white halo, and peripheral erythema (Figure 2). The nodule weeps, ulcerates, and crusts over (Figure 1). Papillomas might form before the lesion regresses. Most infections are self-limited, resolving in 4–8 weeks without scarring. Potential complications include erythema multiforme, deforming scars, and secondary bacterial infections (2–4); severe disease has occurred in immunocompromised hosts (5). Treatment consists of basic wound care, but case reports suggest that topical imiquimod might facilitate healing, especially in immunocompromised patients (5,6). Nonpermeable gloves should be used during direct contact with lesions; however, human-to-human transmission has not been reported. Protective immunity to orf is incomplete; persons can be infected multiple times (4).

Independent markets and local butchers offering live or freshly slaughtered animals are common in metropolitan areas and often cater to immigrants who prepare traditional meat dishes (e.g., patients A and D) or practice animal slaughter in association with religious observances (e.g., patients B and C). Clusters of orf infection have been reported in Turkey (2), Jordan (7), and Belgium (8) after Eid al-Adha because of increased animal slaughter for this event; a similar case previously was reported in the United States (9). Lamb sacrifice also plays a role in Passover and Easter observances, and many Sephardic Jews and Christians consume lamb during these spring holidays. In ethnically diverse communities, health-care providers might be unaware of patients having this type of animal contact and of the seasonal increases in contact associated with religious events. The popularity of hobby farming and home butchering also increases opportunities for household orf exposures.

In nonoccupational settings, where safe practices cannot be enforced, injuries can occur while handling animals, thus providing sites for orf inoculation. Patients A and D incurred puncture wounds from animal bones, and patient C cut his hand with a knife during slaughter; orf subsequently developed from those wounds. Persons who handle sheep or goats at home should be counseled to wear nonpermeable gloves, especially when wounds or rash are present. Injuries that occur during animal slaughter or processing should be cleansed thoroughly with soap and water.

Orf infection is rare in the general community. Persons who contract the virus occupationally likely know of its benign nature and might not seek treatment. Most physicians, therefore, have not encountered patients with orf and might mistake orf lesions for life-threatening conditions such as cutaneous anthrax or neoplasm (2,10). Rapid diagnosis is critical for preventing unwarranted psychological stress, unnecessary surgeries, and inappropriate antibiotic use. Histopathology and microscopy can support a diagnosis of a parapoxvirus infection. PCR can definitively identify orf virus (4) and is available at CDC (telephone: 404-639-4129); clinicians should contact their state health department to request PCR testing. Informational materials for at-risk patients and communities are available at http://www.cdc.gov/ncidod/dvrd/orf_virus.

Acknowledgments

Julia Murphy, DVM, Virginia Dept of Health. Scott K. Smith, MS, Mary G. Reynolds, PhD, Christine M. Hughes, MPH, Andrea M. McCollum, PhD, Div of High Consequence Pathogens and Pathology, National Center for Emerging and Zoonotic Infectious Diseases, CDC.

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