JPC SYSTEMIC PATHOLOGY
Signalment (JPC 1856170): 2.5-year-old female grey kangaroo (Macropus fuliginosus)
HISTORY: Two cutaneous masses, one on the right distal tibia and one on the left forelimb digit, were excised.
HISTOPATHOLOGIC DESCRIPTION: Haired skin: Arising from the epidermis and compressing the subjacent dermis is a focally extensive, exophytic, papillary, epidermal proliferation with multiple closely associated elongated folds with central cores of lamellated keratin and necrotic debris. The stratum spinosum is expanded by keratinocytes that frequently exhibit ballooning degeneration with pale swollen cytoplasm and often contain a single 15 - 20 µm amphophilic to basophilic irregularly shaped intracytoplasmic viral inclusion body (molluscum body) surrounded by a clear halo that peripherally displaces the nucleus. There is moderate parakeratotic hyperkeratosis and a serocellular crust composed of viable and degenerate neutrophils, fibrin, erythrocytes, and high numbers of expelled molluscum bodies. Diffusely there is marked epidermal and follicular hyperplasia with acanthosis and hypergranulosis. The subjacent dermis is infiltrated by nodular aggregates of moderate numbers of lymphocytes, plasma cells, macrophages and fewer viable and degenerate neutrophils.
MORPHOLOGIC DIAGNOSIS: Haired skin: Hyperplasia, epidermal and follicular, papillary, marked, with parakeratotic hyperkeratosis, lymphoplasmacytic and histiocytic dermatitis, and numerous intracytoplasmic viral inclusion bodies (molluscum bodies), grey kangaroo (Macropus fuliginosus), marsupial
ETIOLOGY: Molluscum contagiosum virus
ETIOLOGIC DIAGNOSIS: Molluscipoxviral dermatitis
CONDITION: Molluscum contagiosum
- Mildly contagious, self‑limiting, cutaneous infection primarily of humans caused by a molluscipoxvirus (linear double stranded DNA)
- Transmission via direct skin-to-skin contact and through infected fomites
- May be anthropozoonosis (infectious disease in which the etiologic agent is carried by humans and transferred to other animals)
- Immunocompromised animals are more susceptible
- Clinical, histological, and ultrastructural similarity of lesions have been reported in birds, (chickens, sparrows, and pigeons) chimpanzees, horses, South American sea lions, macropod marsupials
- World-wide distribution
- Presence of a DNA sequence encoding a conserved domain of epidermal growth factor may explain the proliferative nature of the lesions; a similar sequence has been described in some orthopoxviruses
- Molluscum contagiosum viral protein binds to FADD using a death effector domain-mediated interaction that results in interference with apoptotic signaling pathways and protects cells from Fas- and TNFR-induced apoptosis
TYPICAL GROSS FINDINGS:
- Multiple, 1 ‑ 8 mm, circular, smooth or roughened surface, gray to white papules
- Umbilicated with a central pore; often a caseous plug or waxy exudate
TYPICAL LIGHT MICROSCOPIC FINDINGS:
- Well-demarcated foci of epidermal hyperplasia and hypertrophy pear or flask shaped lobules in the superficial dermis
- Markedly hypertrophic or swollen, brightly eosinophilic, dyskeratotic individual centrally enlarged keratinocytes
- Containing pathognomonic large intracytoplasmic viral inclusion bodies ‘molluscum bodies’ that periphery displace the nuclei
- Electron dense, intranuclear particles that spare the nucleolus in keratinocytes of the stratum spinosum immediately superficial to the basal cells
- Intracytoplasmic, large clusters of oval to brick-shaped pox virions within keratinocytes
- Individual mature virions measure 300 x 200 x 100 nm and contain a biconcave nucleoid and two lateral bodies
- As keratinocytes move toward the surface, molluscum body enlarges
- In the dermis subjacent to epithelial lesions, fibroblasts have bizarre nuclei, and virus or inflammatory cells are absent
- Papillomaviral dermatitis: Differentiation is based on identification of the characteristic molluscum bodies with molluscipoxvirus
- Chimpanzees: Multifocal to coalescing , circular, smooth or roughened surface, gray to white papules on the palms and soles of feet
- Horses and donkeys: Numerous multifocal to coalescing cauliflower like nodules or plaques; commonly affecting glabrous skin; usually non pruritic and non painful
- Clinically similar to two other orthopoxviral infections that bear resemblance to molluscum contagiosum, but differ in having generalized and larger lesions:
- Uasin Gishu (UGDV); can be grown in culture unlike molluscum contagiosum
- Equine viral papular dermatitis
Animal poxviruses in subfamily Chordopoxvirinae5
· Cowpox virus
· Vaccinia virus (buffalopox virus, rabbitpox virus)
· Horsepox virus
· Camelpox virus
· Ectromelia virus (mousepox virus)
· Monkeypox virus
Unassigned member of the genus:
· Uasin Gishu disease virus
· Orf virus (contagious pustular dermatitis virus, contagious ecthyma virus)
· Pseudocowpox virus (milker's nodule virus)
· Bovine papular stomatitis virus
· Parapox virus of red deer
Unassigned members in the genus:
· Auzduk disease virus (camel contagious ecthyma virus)\
· chamois contagious ecthyma virus
· sealpox virus
· Fowlpox virus
· Pigeonpox virus
· Sheeppox virus
· Goatpox virus
· Lumpy skin disease virus
· Myxoma virus
· Rabbit fibroma virus (Shope fibroma virus)
· Swinepox virus
· Molluscum contagiosum virus
· Tanapox virus
· Yaba monkey tumor virus
- Abee CR, Mansfiled K, Tardif S, Morris T. Nonhuman primates in biomedical research. Volume 2: Diseases. 2nd San Diego, CA: Elsevier; 2012:7.
- Fox R, Thiemann A, Everest D, Steinbach F, Dastjerdi A, Finnegan C. Molluscum contagiosum in two donkeys.Vet Rec. 2012;170:649-651.
- Hargis AM, Myers S. The integument. In: Zachary JF, ed. Pathologic Basis of Veterinary Disease. 6th St. Louis, MO: Mosby Elsevier; 2016:1119.
- MacLachlan NJ, Dubovi EJ. Fenner’s Veterinary Virology, 4th ed. London, UK: Elsevier; 2011: 161.
- Maudlin EA, Peters-Kennedy J. Integumentary system. In: Maxie MG, ed. Jubb, Kennedy, and Palmer’s Pathology of Domestic Animals. Vol 1. 6th Philadelphia, PA: Elsevier Saunders; 2016: 616, 621.
- Scott DW, Miller WH. Equine Dermatology. 2nd ed. St Louis: Elsevier Saunders; 2011: 253-255.
- Vermi W, et al. Spontaneous regression of highly immunogenic molluscum contagiosum virus (MCV)-induced skin lesions is associated with plasmacytoid dendritic cells and IFN-DC infiltration. J Invest Dermatol. 2011:131(2); 426-434.