Contagious ecthyma, also known
as orf or sore mouth, is a zoonotic disease, which means that
it is easily transmitted from animals to humans. It induces
acute pustular lesions in the skin of goats, sheep, and wild
ruminants worldwide. Young animals are the most susceptible
to contracting the disease. Kids and lambs can contract sore
mouth after a few weeks of birth. However, sore mouth outbreaks
in young animals are most frequent during postweaning.
Sore mouth is caused by a poxivirus related to the pseudocowpox
and bovine papular stomatitis virus family. The virus is epitheliotropic,
which means that it has an affinity for the skin; infection
occurs by direct contact. The period of incubation is relatively
short. Susceptible animals usually develop the first signs
of the disease 4 to 7 days after exposure that persists for
1 to 2 weeks or for longer periods. The disease affects sheep
and goats; it is marked by an increase in incidence and severity
if not controlled among small ruminant herds.
Sore mouth outbreaks occur more frequently during periods
of extreme temperatures such as late summer and winter. The
disease initially presents itself as papules (elevation of
the skin) that progresses to blisters (fluid-filled pouches)
or pustules before encrusting. These lesions are found in
the skin of the lips. They can spread around the outside and
inside of the mouth, face, lips, ears, vulva, lets, scrotum,
teats, and feet, usually in the interdigital region. Extensive
lesions on the feet can lead to lameness in adults and young
animals. The infection is spread by direct and indirect contact
from infected animals or by contact with infected tissue or
saliva containing the virus.
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During the course of the
disease, blisters eventually break down to release more of
the virus and later develop into wet pus-like (suppurative)
scabs. These lesions can persist for 3 weeks and can become
a site for the development of secondary bacterial infections.
Scab tissues are extremely painful, to the point of preventing
sick animals from eating. Because infected kids present lesions
on their gums and lips, does and ewes can acquire lesions
on their udder. The lesions on the udder are due to direct
contamination during nursing that causes mastitis (inflammation
of the mammary gland) in does and ewes. Severe to moderate
enlargement of the lymph nodes, arthritis, and pneumonia resulting
from sore mouth has been reported. Most animals acquire immunity
after contracting the disease; however, subsequent outbreaks
in herds are common with a less severe form of the disease.
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| Merck Veterinary Manual. (2006).
Contagious ecthyma (orf, contagious pustular dermatitis, sore
mouth). Whitehouse Station, NJ: Merck & Co., Inc.
de la Concha-Bermejillo, A., Guo, J., Zhang,
Z., and Waldron D. (September 2003). Severe persistent orf
in young goats. Journal of Veterinary Diagnostic Investigation,
15(5), 423-31.
Haig, D. M., and Mercer, A. A. (1998). Ovine
diseases. Orf. Veterinary Research, 29(3-4), 311-326.
Haig, D. M., McInnes, C. J. (2002). Immunity
and counter-immunity during infection with the parapoxvirus
orf virus. Virus Research, 88(1-2), 3-16.
Key, S. J., et al. (2007). Unusual presentation
of human giant orf (Ecthyma Contagiosum). The Journal of Craniofacial
Surgery, 18(5), 1076-1078.
Zamri-Saad, M., Roshidah, I., al-Ajeeli,
K. S., Ismail, M. S., and Kamarzaman, A. (1993). A severe
complications induced by experimental bacterial superinfection
of orf lesions. Tropical Animal Health and Production, 25(2),
85-88.
UNP-0063, April 2008, Maria Lenira Leite-Browning,
DVM, Extension Animal Scientist, Alabama A&M University
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