JPC SYSTEMIC PATHOLOGY

INTEGUMENTARY SYSTEM

October 2022

I-P09 (NP)

 

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 ruptured by numerous cross and tangential sections of viable and degenerate adult arthropods and eggs. Adults are 80 to 100µm in diameter, have a smooth chitinous exoskeleton, jointed appendages, bands of striated muscle, a reproductive tract that often contains abundant 4µm basophilic bodies, and occasionally an intact digestive tract. Mite eggs are 40µm x 60µm with a thin, eosinophilic shell.  Admixed with arthropods are abundant neutrophils and fewer eosinophils and macrophages, keratin, and cellular debris. The follicular epithelium is either hyperplastic, characterized by acanthosis with cells piling up to 15 cells thick, with multifocal intracellular and intercellular edema and multifocal orthokeratotic hyperkeratosis, or it is occasionally is attenuated. Diffusely expanding the dermis are many lymphocytes, plasma cells, macrophages, and plump fibroblasts (dermatitis); these infiltrates are especially dense and are admixed with neutrophils, eosinophils, hemorrhage, fibrin, and edema in areas of follicular rupture (furunculosis).

 

MORPHOLOGIC DIAGNOSIS: Haired skin: Folliculitis and furunculosis, eosinophilic and neutrophilic, diffuse, moderate, chronic, with marked follicular ectasia, hyperkeratosis, and intrafollicular arthropods, flying squirrel (Glaucomys sabrinus), rodent.

 

ETIOLOGIC DIAGNOSIS:  Epidermal acariasis

 

CAUSE:  Psorergates simplex 

 

GENERAL DISCUSSION: 

• Family Psorergatidae
• Follicular mite of the mouse
• Rare in laboratory mice; common in wild/pet mice

 

PATHOGENESIS:

• The life cycle is unknown but believed to be completed on the host because 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 subcutaneous 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, 90-150µm in length; adults have 4 legs with 5 segments; larvae have 3; medial spine on each femur; ventral anus with tubercle on each side

 

DIFFERENTIAL DIAGNOSIS:

• Demodex musculi:  Very uncommon, located in the superficial dermis and hair follicle openings; reported in transgenic mice with immune compromise; older accounts of mite in tongue and preputial/clitoral glands
• Myobia musculi:  Most common fur mite; epidermal hyperplasia; asymptomatic to severe inflammation (hypersensitivity)

 

COMPARATIVE PATHOLOGY:

• Sheep: Psorergates (Psorobia) ovis. Sheep itch mite; causes pruritus, alopecia, fleece damage; obligate parasite that lives on skin surface and does not penetrate below stratum corneum; does not affect young lambs under 6 months of age; eradicated from the United States
• Cattle: Psorergates (Psorobia) bos. Nonpathogenic mite of cattle; nonpruritic, scaling, and alopecia on head, neck, rump, back, and shoulders.
• NHP: Psororgates mange. Documented in siamangs and gibbons. Flaky skin, multifocal alopecia, and pruritus; mites within or just beneath stratum corneum.

 

REFERENCES:

1. Barthold SW, Griffey SM, Percy DH. Pathology of Laboratory Rabbits and Rodents. 4th ed. Ames, IA: Blackwell Publishing Professional; 2016:87.
2. Bowman DD. In: Georgis' Parasitology for Veterinarians. 10th ed. St Louis, MO: Elsevier Inc; 2014:76.
3. Flynn R. Parasites of Laboratory Animals. Ames, IA: Iowa State University Press; 1973:441-444.
4. Lowensinte LJ, McManamon R, Terio KA. Apes. In: Terio KA, McAloose D, St. Leger J, eds. Pathology of Wildlife and Zoo Animals. Cambridge, MA: Elsevier; 2018: 402.
5. Mauldin EA, Peters-Kennedy J. Integumentary system. In: Maxie MG, ed. Jubb, Kennedy, and Palmer’s Pathology of Domestic Animals.  Vol 1. 6th ed. St. Louis, MO: Elsevier Inc; 2016:678.
6. Strait K, Else JG, Eberhard ML. Parasitic diseases of nonhuman primates. In: Abee CR, Mansfield K, Tardif S, Morris T. Nonhuman Primates in Biomedical Research Volume 2: Diseases. 2nd ed. London, UK: Academic Press; 2012:266, 268.
7. Welle MM, Linder EE. The Integument. In: Zachary JF, ed. Pathologic Basis of Veterinary Disease. 7^th ed. St. Louis, MO: Mosby Elsevier; 2021: 1182.e1.

 

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