Derm Path 2

• Infectious dermatitis


  • Viral diseases
  • Bacterial diseases
  • Fungal diseases
  • Myiasis/nematode larval migration
• Infectious dermatitis - Viral


  • Poxviridae family
  • Herpesviruses
  • Papillomaviruses
  • Morbillivirus
  • Porcine circovirus 2
  • Vesicular skin diseases
• Poxviridae family


  Intracytoplasmic eosinophilic inclusion bodies (ICIBs)
• Parapoxvirus


  • Often zoonotic
  • Orf
  • Pseudocowpox
  • Bovine papular stomatitis virus
• Capripoxvirus


  • Fairly species-specific
  • Sheep pox
  • Goat pox
  • Lumpy skin disease virus
• Orthopoxvirus


  • Cowpox - zoonotic with broad host range
• Suipoxvirus


  • Species-specific
  • Swinepox
• Avipoxvirus


  • Fowl pox
• Orf (Parapoxvirus)


  • Contagious ecthyma, sore mouth, scabby mouth, contagious pustular dermatitis
  • Hosts: sheep, goats, humans
  • High morbidity/low mortality
  • NOT the same as sheep pox or goat pox
• Pseudocowpox (Parapoxvirus)


  • Hosts: Cattle and humans (zoonotic - "milker's nodules")
  • Transmission: direct contact, abraded skin
  • Lesions: teat (most common), udder, inguinal region, mouth of suckling calves
  • Incubation ~7 days; ~6 weeks to heal
• Bovine papular stomatitis virus (Parapoxvirus)


  • Cattle and humans (zoonotic)
  • Cattle <1 year of age most common
  • Human lesions: identical to milker's nodules
  • Transmission: direct contact, abraded skin
  • Gross lesions: Muzzle, nostrils, lips, mouth; Teat and udder
  • Similar to pseudocowpox but more papillomatous, centrally ulcerated, and crusty
  • May develop more generalized, fatal form
• Sheep pox & goat pox (Capripoxvirus)


  • Different, but very closely related viruses
  • Species preference but not completely species-specific
  • Viremia → systemic disease
  • Sheep pox - more severe (Mortality: 30-50%; ~100% in young; Often have proliferative lung lesions and pneumonia)
  • Goat pox - milder (Mortality: typically around 5%)
  • Distribution (FAD to U.S.): Northern Africa, Southeastern Europe, Parts of Asia
• Lumpy skin disease virus (Capripoxvirus)

  • Hosts: cattle, buffalo, wild hoofstock
  • Systemic signs: Fever and generalized lymphadenopathy; Skin lesions: Nodules extending into subcutis with central necrosis
  • Histology: Vasculitis with cutaneous infarction; Intracytoplasmic eosinophilic inclusions in endothelial cells and pericytes
  • Mortality varies (1% to >50%); high morbidity
  • Transmission: blood-feeding arthropods
  • Distribution (FAD to U.S.): Africa, Middle East, Turkey
  • Primary differential diagnosis (gross/clinical): Pseudo-lumpy skin disease (herpesviral disease) - milder
• Cowpox (Orthopoxvirus)


  • Wide host range - zoonotic
  • Reservoir: wild rodents
  • Gross lesions: similar appearance to pseudocowpox
  • Distribution: Europe, Asia (FAD to U.S.)
• Swinepox (Suipoxvirus)


  • Host specific (swine only); mild disease with low mortality
  • Transmission: Direct contact with infected pigs, Sucking louse (Haematopinus suis) - mechanical vector, Transplacental: congenital swinepox
  • Gross: papules → umbilicated pustules
  • Histology: intracytoplasmic inclusions in keratinocytes (early)
• Avian pox (Avipoxvirus)


  • Many avian species affected
  • Transmission: direct contact, biting insects
• Herpesviruses

  • Intranuclear inclusion bodies
  • Bovine herpesvirus 2
  • Equid herpesvirus 3
  • Felid herpesvirus 1
• Bovine herpesvirus 2


  • Bovine herpes mammillitis = localized form
  • Differentials: Cowpox, pseudocowpox, bovine papular stomatitis virus
  • "Pseudo-lumpy skin disease" = generalized form
  • Differential diagnosis (gross/clinical): Lumpy skin disease (FAD and more severe disease)
  • Infection is much more common than associated disease
  • Transmission: Mechanical vectors via abraded skin, Biting flies
  • Histology: intranuclear inclusions
• Remember: lumpy skin disease is a poxvirus → cytoplasmic inclusions
• Equid herpesvirus 3 (equine coital exanthema)

  • Gross: Papules, bullae, ulceration
  • Distribution: Penis, prepuce, scrotum; Vulva, perineum; Muzzle - foals
  • Painful lesions, heal ~2-5 weeks
  • Histology: Intranuclear inclusions, Degeneration of keratinocytes
• Felid herpesvirus 1


  • AKA: Feline viral rhinotracheitis virus
  • Very COMMON
  • Persistent or recurrent ulcerative lesions: Face, nose/nasal planum
  • Histology: Intranuclear inclusions, Lots of eosinophils
• Papillomaviruses


  • Many different papillomavirus
  • Often species-specific
  • Commonly affected species: Dogs, Cats, Cattle, Horses
• Papillomavirus-induced lesions


  • Exophytic papilloma
  • Inverted papilloma
  • Canine pigmented viral plaques
  • Feline viral plaques
  • Equine viral papillomatosis
  • Fibropapillomas
  • Equine and feline sarcoids
• Canine viral-induced papillomas


  • Oral viral-induced exophytic papilloma/papillomatosis (CPV 1 and 13)
  • Canine cutaneous exophytic papillomas (CPV 1, 2, and 7)
  • Common sites: Head, eyelids, paws
  • Any age, usually young animals
  • Typically undergo spontaneous regression
  • Some may transform to SCC
• Canine viral-induced papillomas - Inverted papilloma


  • Usually young (<3 yrs of age)
  • Ventral abdomen, groin, limbs
  • Most do NOT regress spontaneously
  • Malignant transformation reported with CPV-2
• Papillated epidermal hyperplasia

  • Hyperkeratosis
  • Hypergranulosis
  • +/- INIB
  • Viral cytopathic effect (koilocytes)
• Papilloma


  Think papilloma
• Canine viral-induced papillomas


  1. Oral viral-induced exophytic papilloma/papillomatosis (CPV 1 and 13)

  2. Canine cutaneous exophytic papillomas (CPV 1, 2, and 7)

  3. Common sites: Head, eyelids, paws

  4. Any age, usually young animals

  5. Typically undergo spontaneous regression

  6. Some may transform to SCC
• Inverted papilloma


  • Usually young (<3 yrs of age)
  • Ventral abdomen, groin, limbs
  • Most do NOT regress spontaneously
  • Malignant transformation reported with CPV-2
• Canine pigmented viral plaques

  • More common in miniature Schnauzers and Pugs
  • May be heritable
  • Other breeds: typically young and immunocompromised
  • Gross: Pigmented macules, papules, and plaques
  • Scaling
  • Histo: Koilocytes and intranuclear inclusions are rare
• Viral plaques


  • Scaly, flat, variably pigmented
  • May resolve or transform to BISC
• Bowenoid in situ carcinoma (BISC)


  • Solitary or multifocal crusting, hyperpigmented, roughly circular plaques
  • Typically middle-aged to older
• Equine viral papillomatosis


  1. Mostly in young horses (<3 yrs)

  2. Exophytic papillomas on muzzle/lips

  3. Typically undergo spontaneous regression
• Aural plaques


  • Any age
  • Do NOT regress or transform
• Equine genital papillomas


  • Typically older horses on penis or vulva
  • Do NOT spontaneously regress
  • Can have malignant transformation → squamous cell carcinoma
• Bovine viral-induced fibropapilloma


  • Papillated epithelial proliferation
  • Dermal fibroblast proliferation
• Teat fibropapilloma


  More of a fibrous component
• Equine sarcoids

  • Etiology: Bovine papillomaviruses (BPV-1, 2, 13)
  • Locally aggressive
  • Excision requires wide margins
  • Many other proposed treatments
  • Recurrence common
• Verrucous & nodular sarcoids

  • Epidermal hyperplasia
• Feline sarcoid


  • Cause: Feline sarcoid-associated papillomavirus (FeSarPV)
  • Considered a novel bovine papillomavirus (similar to BPV-1, -2)
  • Typically young to middle-aged rural/barn cats
  • Clinical lesions: Nose, lips, head, digits
  • Firm, smooth, exophytic masses
  • Histology: identical to equine sarcoid
  • Recurrence is common
  • No metastasis