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Read-Only Case Details Reviewed: Oct 2010



November 2019



Signalment (JPC# 2070431): Chicken, breed and age unspecified


HISTORY: This bird had multiple raised proliferative lesions over its body.


HISTOPATHOLOGIC DESCRIPTION: Feathered skin: Multifocally, the epidermal and follicular epithelium is hyperplastic up to ten times normal thickness, characterized by a markedly thickened stratum spinosum (acanthosis) with long rete ridges, and multifocally overlain by a thick serocellular crust. Within the stratum spinosum, the majority of keratinocytes are markedly swollen (ballooning degeneration) and contain a 15-30 um eosinophilic intracytoplasmic viral inclusion body (Bollinger body) that often peripheralizes the nucleus. Multifocally there are large areas of coagulative necrosis within the epidermis that extend into the dermis and are characterized by loss of differential staining with retention of tissue architecture, admixed with foci of lytic necrosis characterized by partial to full thickness epithelial loss (erosion and ulceration) with replacement by karyorrhectic and cellular debris and many degenerate heterophils and bacterial colonies. Within the areas of necrosis and infiltrating into the dermis and subcutis are numerous viable and degenerate heterophils with macrophages, lymphocytes, and plasma cells admixed with abundant fibrin, hemorrhage, and edema. Similar inflammatory cells infiltrate into and surround portions of the panniculus carnosus where the muscle fibers are multifocally necrotic with brightly eosinophilic shrunken cytoplasm and pyknotic nuclei. Small caliber blood vessels within the superficial dermis are lined by markedly hypertrophied endothelium.


MORPHOLOGIC DIAGNOSIS: Feathered skin and subcutis: Dermatitis, necrotizing and proliferative, subacute, multifocal, marked, with ballooning degeneration and eosinophilic intracytoplasmic viral inclusion bodies, breed unspecified, chicken.


ETIOLOGICAL DIAGNOSIS: Avipoxviral dermatitis


CAUSE: Avian poxvirus





·      Poxviruses: Largest animal virus (300-400 nm); double stranded brick-shaped DNA virus; cytoplasmic DNA synthesis and packaging within infectious virus particle are characteristic of pox virus

·      Avian poxvirus: Genus Avipoxvirus; family Poxviridae

·      Common, slow spreading viral disease of domestic, pet and wild birds; reported in 232 speciesTransmission via inoculation from direct contact with injured skin, through mechanical transfer (including cannibalism and artificial insemination), mosquitoes, blood-sucking arthropods, and inhalation of aerosolized feathers and scabs containing virus

·      Two forms (can manifest as one or both):

·      Cutaneous form (dry pox): Most common form

·      Diphtheritic form (wet pox): Lesions in respiratory, GI, nasal cavity and conjunctiva



·      Virus enters host cells by fusion with plasma membrane and endosomal uptake

·      Poxviruses encode several proteins that affect host cell: e.g. vaccinia virus growth factor (VGF) uses cell receptors for epidermal growth factor (EGF) to stimulate proliferation of keratinocytes

·      Increasing metabolism of keratinocytes surrounding infection causes greater susceptibility of those cells

·      Other proteins inhibit complement-mediated cell lysis and inhibit inflammatory response to retard immune clearance and analogues of tumor necrosis factor and superoxide dismutase



·      Gradual onset that may go undetected until cutaneous lesions are numerous

·      Turkey infection is generally more chronic than chickens

·      Canaries can have systemic infection with high mortality

Cutaneous form:

·      Mild reduction in weight gain

·      Decreased egg production

·      Lack of flock vigor

·      Mortality is low

Diphtheritic form:

·      Lesions in upper respiratory tract or GI tract may lead to dyspnea or inappetence

·      Lesions in nasal cavity or conjunctiva lead to nasal or ocular discharge

·      Mortality due to suffocation, starvation, and dehydration



Cutaneous form:

·      Papular lesions on unfeathered skin of the head, neck, vent, legs, and feet

·      Papules, vesicles, pustules, crusts which progress to terminal reddish-brown to black scabs; may appear as horny growths

·      Pigmented skin will usually be discolored after infection due to epidermal damage

Diphtheritic form:

·      Raised, buff to yellow plaques on mucous membranes; predominate in mouth but also in sinuses, nasal cavity, conjunctiva, pharynx, larynx, trachea, esophagus



·      Eosinophilic intracytoplasmic inclusion bodies (Bollinger bodies) located within epithelial cells - pathognomonic

·      Epithelial hyperplasia with ballooning (hydropic) degeneration



·      Elementary bodies (Borrel bodies) measure 250 x 354nm and are located within the inclusion bodies (Bollinger bodies)

·      Virus is brick shaped and consists of an electron-dense biconcave core with two lateral bodies within each concavity



·      Skin scraping can demonstrate squamous epithelium with ballooning degeneration and Bollinger body

·      ELISA

·      Virus Isolation

·      EM



Cutaneous pox:

·      Trichophyton megninii and T. simii (I-F11): Dermatophytic fungus

·      Knemidokoptes gallinae: Mite in basal shafts of feathers

·      Knemidokoptes mutans (I-P12): Mite that lives within unfeathered skin

·      Bumblefoot

Diphtheritic pox:

·      Vitamin A deficiency (D-M09): Pustules on the mucosa of the mouth, pharynx, esophagus and crop in young birds, inflamed eyelids; squamous metaplasia of the nasal mucosa; keratinization of intestinal enterocytes, decreased goblet cells and blunting of villi (severe deficiency)

·      Infectious laryngotracheitis (P-V11): Alphaherpesvirinae (Gallid herpesvirus 1); mucohemorrhagic or caseous exudates of the trachea; intranuclear inclusion bodies in epithelial cells

·      Trichomonas gallinae: Raised, caseous lesions in the mouth, pharynx, esophagus, and crop

·      Capillaria annulata or contorta: Thickened, inflamed to sloughed mucosa

·      Candida albicans (D-F05): White-grey pseudomembranous patches on the mouth, pharynx, esophagus and crop; pseudohyphae and budding yeast

·      Aspergillosis (P-F06): Yellow-grey nodules in trachea, lungs and airsacs


Avian poxviruses:

·      Avipoxvirus is recognized in several domestic and wildlife avian species with similar lesions (e.g. turkeypox virus, falconpox virus, psittacinepox virus)

·      Some avipoxviruses may have oncogenic properties; Passeriformes and Columbiformes may be predisposed to tumor formation after surviving infection

·      Canarypox usually has a desquamative pneumonia

·      Wildlife and Zoo: North Island brown kiwi, penguins, pelicans, psittacines, ducks, raptors, galliformes, passerines.



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2.    Campbell TW. Infectious agents. In: Exotic Animal Hematology and Cytology. 4th ed. Ames, IA; John Wiley & Sons, Inc.;2015:323-324.

3.    Cheville NF, Lehmkuhl H. Cytopathology of viral diseases. In: Cheville NF, ed. Ultrastructural Pathology, 2nd ed. Ames, IA: Wiley-Blackwell; 2009: 319-327.

4.    Crespo R, Franca MS, Fenton H, Shivaprasad HL. Galliformes and Columbiformes. In: Terio Ka, McAloose D, St. Leger J, eds. Pathology of Wildlife and Zoo Animals. San Diego, CA: Elsevier; 2018: 741-767.

5.    Fenton H, McManamon R, Howerth EW. Anseriformes, Ciconiiformes, Charadriiformes, and Gruiformes. In: Terio Ka, McAloose D, St. Leger J, eds. Pathology of Wildlife and Zoo Animals. San Diego, CA: Elsevier; 2018: 693-716.

6.    Jarmin S, Manvell R, Gough RE, Laidlaw SM, Skinner MA. Avipoxvirus phylogenetics: Identification of a PCR length polymorphism that discriminates between the two major clades. J Gen Virol. 2006; 87: 2191-2201.

7.    Krone O, Essbauer S, Wibbelt G, Rudolph M, Cough RE. Avipoxvirus infection in peregrine falcons (Falco peregrinus) from a reintroduction programme in Germany. Vet Rec. 2004; 154: 110-113.

8.    Murer L, Westenhofen M, Kommers GD, Furian TQ, et al. Identification and phylogenetic analysis of clade C Avipoxvirus in a fowlpox outbreak in exotic psittacines in southern Brazil. J Vet Diagn Invest. 2018; 30(6): 946-950.

9.    Schmidt RE, Reavill DR, Phalen DN. Special sense organs. In: Pathology of Pet and Aviary Birds. 1st ed. Ames, IA: Iowa State Press; 2003:197-201.

10. Smith DA. Palaeognathae: Apterygiformes, Casuariiformes, Rheiformes, Struthioniforme; Tinamiformes. In: Terio Ka, McAloose D, St. Leger J, eds. Pathology of Wildlife and Zoo Animals. San Diego, CA: Elsevier; 2018: 633-648.

11. Stidworthy MF, Denk D. Sphenisciformes, Gaviiformes, Podicipediformes, Procellariiformes, and Pelecaniformes. In: Terio Ka, McAloose D, St. Leger J, eds. Pathology of Wildlife and Zoo Animals. San Diego, CA: Elsevier; 2018: 649-681.

12. Tripathy DN, Reed WM. Pox. In: Swayne DE, ed. Diseases of Poultry. 13th ed. Ames, IA: Wiley-Blackwell; 2013: 333-349.

13. Trupkiewicz J, Garner MM, Juan-Salles C. Passeriformes, Caprimulgiformes, Coraciiformes, Piciformes, Bucerotiformes, and Apodiformes. In: Terio Ka, McAloose D, St. Leger J, eds. Pathology of Wildlife and Zoo Animals. San Diego, CA: Elsevier; 2018: 793-817.

14. Wunschmann A, Armien AG, Hofle U, et al. Birds of Prey. In: Terio Ka, McAloose D, St. Leger J, eds. Pathology of Wildlife and Zoo Animals. San Diego, CA: Elsevier; 2018: 717-739.

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