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Characteristics of orf in a farming community in mid-Wales

^a The Surgery, Caeherbert Lane, Rhayader, Powys LD6 5ED

Orf, a parapox viral infection of sheep and goats, has been recognised for over 200 years. Human cases were first recorded in the 1930s.¹ Transmission occurs by direct inoculation, commonly from the infected muzzles of hand reared lambs. The true incidence and prevalence of human orf is unknown, and workers familiar with the disease may not report infection. The typical target-like lesions most often affect the hands and heal spontaneously in six to seven weeks. Complications include secondary infection, erythema multiforme, and a generalised papulovesicular eruption.²

I recorded the morbidity from and the prevalence, seasonal variation, and complication rate of human orf in a farming community in mid-Wales, a population at risk of the disease.

Patients, methods, and results

Questionnaires were sent to 292 patients at this practice who worked with sheep and were aged between 16 and 65 on 1 January 1995. The results from 251 questionnaires were analysed (effective response rate 86%). Table 1 shows the high exposure to and recognition of orf in sheep. Nearly all respondents claimed to be able to recognise human orf. Almost a third (73) reported having had it, with over a third reporting previous infection in a household member. Of the 73 reported cases, 34 (47%) were in women and 39 (53%) in men. Over a fifth reported two or more attacks, the second attack mostly occurring within two years. Most respondents had had their first attack in their teenage or early adult life, which is in keeping with starting work on the family farm. Most cases (60/73 (82%)) occurred in spring or summer. In addition, I identified 58 separate episodes of orf infection from general practice records. Thirty four (59%) occurred in April, May, and June--19 (33%) in May alone (table 1).

Table 1--Exposure to, recognition of, and infection with
orf in mid-Wales farming community
-----------------------------------------------------------------
                                                   No (%) of
                                               respondents giving
                                                 positive replies
-----------------------------------------------------------------
All respondents (n = 251)
Would you recognise orf in a sheep?                  237 (94)
Have you ever handled sheep with orf?                224 (89)
Would you recognise orf if you caught it
 yourself?                                           196 (78)
Have you ever had orf?                                73 (29)
Have any other members of your household
 had orf?                                             86 (34)
Would you be prepared to take part in further
 research on the treatment of orf?                   205 (82)
Patients who had had orf (n = 73)
How often have you had orf?
 Once                                                 58 (80)
 Twice                                                10 (14)
 More than twice                                       5 (7)
What was the length of time between attacks?
  1 Year                                               3 (20)
  2 Years                                              6 (40)
  3 Years                                              2 (13)
 >3 Years                                              4 (27)
How old were you when you had orf?
 Teenager                                             21 (29)
 In 20s                                               18 (25)
 In 30s                                               14 (19)
 In 40s                                               15 (21)
 In 50s                                                4 (5)
 In 60s                                                1 (1)
What time of year did you have orf?
 Spring                                               38 (52)
 Summer                                               22 (30)
 Autumn                                               10 (14)
 Winter                                                3 (4)
Did you consult a doctor?                             56 (77)

Sixteen respondents (22%) reported an accompanying red blotchy rash; erythema multiforme, toxic erythema, or allergic reaction was recorded in the general practice notes in nine cases (12%). Eight respondents (11%) indicated that they had blisters on their arms, body, face, or mouth when they had had orf. Widespread vesicular eruption was confirmed from the records in only three cases (4%). All of these had preceding erythema multiforme. Of the 24 people (33%) whose work was affected, four reported problems for less than a week, 11 for one to two weeks, and nine for more than two weeks. Eleven patients (15%) had time off work: three for less than one week, three for one to two weeks, and five for more than two weeks.

There were no reports of human to human spread.

Comment

Orf is common in flocks in mid-Wales. Most people who work with sheep can recognise both animal and human infection, but self diagnosis and lack of effective treatment could explain why almost a quarter of patients with orf chose not to consult a doctor. One episode of orf may³ or may not⁴ confer life long immunity. Although a fifth of my respondents reported two or more attacks, infection declined with increasing age. The seasonal variation correlated with the end of the lambing season.

The mechanism of the papulovesicular eruption is not understood, but such a dramatic rash is unlikely to be ignored by both patient and doctor. The hands are most commonly infected (occasionally the face), which explains why patients' jobs are affected and they lose time at work. Most attacks occur at the busiest time of the farming year, and illness is clinically significant. As there is no effective treatment, further evaluation of simple preventive measures such as wearing gloves and isolation of infected sheep needs to be carried out, although costs and practical considerations may prove difficult to overcome.

I thank Jane Jones of Rhayader Surgery for her help in completing this study, Trish Buchan for her help with the questionnaire and interpretation of results, and Dr Hywel C Williams for critical comments on the manuscript.

Funding: Montgomeryshire Medical Society and Powys NHS Trust.

Conflict of interest: None.

1. Peterkin GAG. The occurrence in humans of contagious pustular dermatitis of sheep ("orf"). Br J Dermatol 1937;49:492-7.
2. Wilkinson JD. Orf: a family with unusual complications. Br J Dermatol 1977;97:447-50. [Medline]
3. Highet AS, Kurtz J. Viral infections. In: Champion RH, Burton JL, Ebling FJG. Texbook of Dermatology. 5th ed. Oxford: Blackwell Scientific, 1992: 873-5.

[Medline]

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