JPC SYSTEMIC PATHOLOGY
Signalment (JPC # 1757055): Flying squirrel (Glaucomys sabrinus)
HISTORY: Cutaneous mass located beneath the ear
HISTOPATHOLOGIC DESCRIPTION: Haired skin: Diffusely hair follicles are markedly expanded and occasionally disrupted by numerous arthropods that are 80 to 100 um in diameter, have a smooth chitinous exoskeleton, jointed appendages, bands of striated muscle, and a reproductive tract which often contains abundant 4um basophilic bodies. Admixed with arthropods are abundant neutrophils and fewer eosinophils and macrophages, keratin, and cellular debris. The follicular epithelium is hyperplastic with cells piled up to 15 cells thick, with hyperkeratosis, or occasionally is attenuated. Multifocally there is intracellular and intercellular edema within the follicular epithelium. Diffusely expanding the dermis are many lymphocytes, plasma cells, macrophages, and plump fibroblasts. In areas of ruptured follicles (furunculosis), there are similar infiltrates admixed with neutrophils, eosinophils, hemorrhage, and. Multifocally within follicles there are mite eggs measuring 40 um x 60 um.
MORPHOLOGIC DIAGNOSIS: Haired skin: Folliculitis and furunculosis, eosinophilic and neutrophilic, chronic, diffuse, moderate, with marked follicular ectasia, hyperkeratosis, and intrafollicular arthropods, flying squirrel (Glaucomys sabrinus), rodent.
ETIOLOGIC DIAGNOSIS: Epidermal acariasis
CAUSE: Psorergates simplex
- Family Psorergatidae
- Follicular mite of the mouse
- Rare in laboratory mice; common in wild/pet mice
- The life cycle is unknown but believed to be completed on the host as all life stages can be present in a single hair follicle
- Transmission is by direct contact
- Infection results in dermal pouches
- Self-mutilation with secondary infection can occur
TYPICAL GROSS FINDINGS:
- Mange-like condition; yellow crusting
- Head, shoulders, lumbar area
- Comedone formation
- White nodules or pockets on the visceral side of the dermis
TYPICAL LIGHT MICROSCOPIC FINDINGS:
- Mites present in the hair follicle
- Cystic follicles with keratosis
- Variable degrees of inflammation
- Mite is round, 90-150um in length; adults have 4 legs with 5 segments; larvae have 3; medial spine on each femur; ventral anus with tubercle on each side
- Demodex musculi: Very uncommon, located in the superficial dermis at hair follicle openings
- Myobia musculi: Most common fur mite; epidermal hyperplasia; asymptomatic to severe inflammation (hypersensitivity)
- Psorergatidae family
- Psorobia ovis: Sheep itch mite; pruritus and alopecia; fleece damage
- Psorobia bos: Nonpathogenic mite of cattle; nonpruritic, scaling, and alopecia
- Psorobia (formerly Psorergates) sp.: Case in a Siamang that caused dry flaky skin
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