Signalment:  

Adult, 55 lb. male pygmy goat, Capra hircusThe pygmy goat presented with ulcerated oozing pustular lesions on the face and muzzle prior to euthanasia

Gross Description:  

Numerous confluent ulcerative, scabby, verrucous and proliferative oozing lesions are present on the muzzle, commissures of the lips, surrounding the eyes, left lateral tongue and the dental pad. A circular ulcer is also present on the left cheek below the left eye. Creamy white exudate drains from some of the larger lesions.  The thorax contains creamy tan pus and the pleural surfaces are lined with thick exudate forming adhesions to the thoracic wall and diaphragm. The lungs are consolidated ventrally with multifocal variably sized abscesses containing thick tan pus. 

Histopathologic Description:

The lesions consist of locally extensive papillary projections of acanthotic, hyperkeratotic epidermis and extensive dermal (or submucosal) inflammatory infiltrate of neutrophils, histiocytes, and lymphocytes with occasional epidermal or dermal pustules and microabscesses. Numerous small capillaries course throughout the dermis. Occasional ballooning vacuolation of keratinocytes with rare eosinophilic intracytoplasmic inclusions are seen. The epidermis is covered with thick serocellular crusts containing degenerating cells and small clusters of bacteria. Deep anastomosing rete pegs extend into the dermis (or submucosa). 

Morphologic Diagnosis:  

1. Muzzle: Lymphocytic, neutrophilic, histiocytic, pustular and proliferative dermatitis and stomatitis with papillomatous epidermal hyperplasia, acanthosis, hyperkeratosis and occasional eosinophilic intracytoplasmic inclusions in keratinocytes
2. Lungs: Severe fibrinosuppurative bacterial bronchopneumonia (not included)

Lab Results:  

Aerobic bacterial cultures of the muzzle yielded heavy growths of Arcanobacterium pyogenes and moderate growths of Pseudomonas aeruginosa and Staphylococcus intermedius.
Aerobic bacterial cultures of the lungs yielded heavy growths of Pasteurella trehalosi and Arcanobacterium pyogenes.
Electron microscopy: Tissues from muzzle and lips yielded Parapoxvirus (179 X 300nm)

Condition:  

Parapoxvirus

Contributor Comment:  

Contagious pustular dermatitis (contagious ecthyma, sore mouth, orf) is an infectious dermatitis of sheep and goats with worldwide distribution, caused by Parapoxvirus. The genus Parapoxvirus is a member of the Poxviridae family, and includes orf virus, bovine papular stomatitis virus, and pseudocowpox virus. It is an ovoid, enveloped, double stranded, DNA virus. Transmission is into skin abrasions through aerosols, direct contact, or through mechanical transmission via arthropods.⁶ Lesions typically develop on commissures of lips and buccal cavity, but also develop on feet, teats (from nursing an affected kid), and genitals. Lambs and kids are at greatest risk because they are immunologically na_ve, and the colostrum from a previously infected animal does not provide protection. Due to its tropism for epithelial cells, Parapoxvirus will cause epidermal hyperplasia, producing papular lesions usually within 7 days. Papular lesions progress to vesicles, pustules, and then crusty scabs. In a 2002 study of 16 persistently infected goat kids, lymph node enlargement, premature thymic involution, and a number of secondary bacterial infections were present. It is suggested in this study that individual susceptibility factors of the host, such as breed, genetic susceptibility and immune defects, are contributing factors in orf virus persistence and progression.¹ Infections typically last 3-4 weeks, depending on the severity of systemic disease. Cell mediated immunity is of high importance in recovery from infection. Antibiotics are recommended to prevent secondary complications such as cellulitis, mastitis, aspiration pneumonia, and necrotizing stomatitis. Animals that do recover have transient to solid immunity. Mortality rates in lambs is reported to be 15%.² Transmission between sheep and goats can occur, but is uncommon. Parapoxvirus may also be transmitted to humans causing similar pustular lesions, commonly on the forearm, hands and face.³

Diagnosis of Parapoxvirus is based on the recognition of characteristic lesions and lesion distribution. Microscopically, eosinophilic intracytoplasmic inclusion bodies are visible, along with vacuolation and swelling of keratinocytes. The virus particles can also be photographed with an electron microscope. The virus can survive in the environment for months in the scab material shed from affected animals. Virulent, live virus vaccines do exist but are only recommended for use in persistently infected herds.⁴ Contagious pustular dermatitis is of economic significance because lambs and kids become reluctant to eat or suckle, causing weight loss and reduced growth rates. Differential diagnosis for contagious pustular dermatitis should include Foot and Mouth disease, Rinderpest, and Bluetongue.

JPC Diagnosis:  

1. Mucocutaneous junction, lip: Cheilitis, proliferative and necrotizing, focally extensive, severe, with intracytoplasmic eosinophilic inclusion bodies, pygmy goat (Capra hircus), caprine.
2. Haired skin, lip: Abscess, focal, with foreign material and fungal hyphae.

Conference Comment:  

Members of the parapoxvirus genus include orf virus, papular stomatitis virus, peseudocowpoxvirus, parapoxvirus of red deer in New Zealand, and squirrel parapoxvirus.⁵ Other species that have been tentatively included include auzduk disease virus, chamois contagious ecthyma virus and seal parapoxvirus. ⁵ Seal parapoxvirus is the preferred term used rather than 'sealpox virus' to distinguish it from the orthopoxviruses that cause similar clinical diseases.⁷

Characteristic ultrastructural features of parapoxvirus include 250nm X150nm particles, with an oval- to dumbbell- shaped core surrounded by a membrane, lateral bodies, and a surface membrane.⁵

Histopathologic lesions of contagious ecthyma are typical of other poxviral lesions except they usually have a very brief vesicle stage, a prominent ulcer and crust stage, and inclusion bodies present for only a brief period of time during the vesicular stage.²

There is variation in sections. Some sections have a focal ulcer with bacterial colonies and neutrophilic mural folliculitis with fungal arthrospores, both likely secondary to the ulcerative lesions induced by the orf virus.

References:

1. de la Concha-Bermejillo A, Guo J, Zhang Z, Waldron D: Severe persistent orf in young goats. J Vet Diagn Invest 15:423-431, 2003
2. Hargis AM, Ginn PE. The integument. In: Pathologic Basis of Veterinary Disease, eds. McGavin MD, Zachary JF, 4th ed., pp. 1174-1175. Elsevier, St. Louis, MO, 2007
3. Jones T, Hunt R: Diseases caused by viruses. In: Veterinary Pathology, 5th ed., p. 303. Lea & Febige, Philadelphia, Pa, 1983
4. Michelsen PG: Diseases of the alimentary tract, contagious ecthyma. In: Large Animal Internal Medicine, ed. Smith BP, 2nd ed., p. 805. Mosby Inc., St. Louis, Missouri, 1996
5. M+�-+ller G, Gr+�-�ters S, Siebert U, Rosenberger T, Driver J, K+�-�nig M, Becher P, Hetzel U, Baumg+�-�rtner W: Parapoxvirus infection in Harbor seals (Phoca vitulina) from the German North Sea, Vet Pathol 40:445-454, 2003
6. Quinn PJ, Markey BK, Carter ME, Donnelly WJ, Leonard FC: Poxviridae. In: Veterinary Microbiology and Microbial Disease, p. 335. Blackwell Science Ltd, Oxford, UK, 2002
7. Tryland M, Klein J, Nord+�-+y ES, Blix AS: Isolation and partial characterization of a parapoxvirus isolated form a skin lesion of a Weddell seal, Virus Res 108:83- 87, 2005

A virtual slide is not available for this case.

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