Alopecia

BASICS

DEFINITION

Alopecia is common in chinchillas and is characterized by complete or partial lack of hair in expected areas. It may be multifactorial and can be either a primary or secondary disorder. As many as 60 hairs grow from a single hair follicle in a healthy chinchilla.

PATHOPHYSIOLOGY

• Multifactorial causes
• Disruption in the growth of hair follicles is possible with infection, inflammation, trauma, or blockage of the receptor sites for stimulation of the cycle.

SYSTEMS AFFECTED

• Skin/exocrine
• Behavioral—may cause self‐inflicted chewing, biting
• Gastrointestinal—especially dental disease; may cause anorexia, dysphagia, ptyalism
• Hemic/lymphatic/immune
• Ophthalmic—ophthalmic or dental disease may cause epiphora and conjunctivitis resulting in alopecia surrounding one or both eyes.

GENETICS

• Dental disease—avoid breeding affected animals as inheritance of dental disease is suspected.
• Fur chewing—avoid breeding animals that chew fur.

INCIDENCE/PREVALENCE

Common condition in chinchillas

GEOGRAPHIC DISTRIBUTION

N/A

SIGNALMENT

No specific age or sex predilection

SIGNS

• The pattern and degree of hair loss are important for establishing a differential diagnosis.
• Multifocal patches of alopecia—most frequently associated with folliculitis from mycotic or bacterial infection
• Large, diffuse areas of alopecia—indicate follicular dysplasia or metabolic component; not reported in chinchillas but should be considered
• May be acute or slowly progressive in onset

Historical Findings

• Inappropriate diet—fiber deficiency, other nutritional deficiencies
• Inappropriate frequency or complete lack of dust bath; use of inappropriate dust bath materials
• Inappropriate sanitation, ventilation
• Self‐inflicted or conspecific barbering
• Drooling, dysphagia
• Ocular or nasal discharge
• History of fur slip, fur chewing

Physical Examination Findings

• Alopecia with or without scaling, crusting—distribution may help differentiate the disease process.
• Broken hair shafts—suggestive of barbering (self‐inflicted or conspecific)
• Ptyalism—associated with dental malocclusion; a thorough oral examination is critical for evaluating for premolar/molar malocclusion
• Epiphora—associated with dental malocclusion; a thorough oral examination is critical for evaluating for premolar/molar malocclusion

CAUSES

• Normal shedding pattern—some chinchillas may lose hair in patches when shedding
• Behavioral—barbering; dominant chinchillas may chew or pull out hair of submissive cagemates
• Parasitic—ectoparasites (fleas, lice, and mites)—uncommon in chinchillas because of their dense coat
• Infectious—dermatophytosis, bacterial pyoderma; most often a secondary problem, especially moist dermatitis (e.g., ptyalism, epiphora, and urine scald)
• Trauma—fur slip due to excessive restraint; self‐ or conspecific‐inflicted barbering, bite wounds
• Neoplastic—cutaneous lymphoma, trichofolliculoma, mast cell tumor
• Nutritional—especially protein and fiber deficiencies

RISK FACTORS

Poor husbandry: lack of dust baths, proper ventilation, and sanitation; nutritional deficiencies such as low‐fiber diets leading to fur chewing and other deficiencies allowing for immunosuppression; traumatic handling leading to fur slip.

DIAGNOSIS

DIFFERENTIAL DIAGNOSIS

Differentiating Causes

Pattern and degree are important for differential diagnoses.

Symmetrical Alopecia

• Barbering—broken fur shafts identified on close inspection; most commonly on dorsal flanks, around face and ears; can have a “moth‐eaten” appearance to the coat. Owners may or may not observe barbering between animals.
• Fur chewing—very common in chinchillas; may chew on fur constantly or intermittently and fur may regrow in between episodes. Usually chew dorsal flanks and sides, pregnant females may chew temporarily. Coat may have moth‐eaten appearance.
• Matted fur associated with high environmental temperature (>80°F/26.7°C), humid environment, or if dust baths are inadequate or not provided.

Multifocal to Focal Alopecia

• Lack of proper dust bath—may cause poor, unkempt coat that becomes matted and sheds abnormally; may cause alopecia and accumulation of scale in matted areas
• Trauma
  • Bite wounds—alopecia, with or without erythema; can abscess; secondary Staphylococcus spp. or Streptococcus spp. infections may occur
  • Fur slip—alopecia, with or without erythema, no scaling
  • Ear trauma, including frost‐bite alopecia with erythema, scaling, necrosis of pinnae
• Fur chewing—may chew on fur constantly or intermittently and fur may regrow in between episodes; usually chew dorsal flanks and sides, pregnant females may chew temporarily
• Dental disease—facial moist dermatitis associated most commonly with ptyalism or epiphora; alopecia, with or without erythema, scale, or ulceration; Staphylococcus spp. or Streptococcus spp. infections can occur secondary to moist dermatitis.
• Dermatophytosis—Trichophyton mentagrophytes are most common, but Microsporum canis and M. gypseum have been identified; partial or complete alopecia with scaling and pruritis; with or without erythema, not always ring‐shaped; may begin as alopecia around eyes, nose, then spread to feet, body, genitals. May be first identified on the “grooming claw” (medial first digit) of hind limbs.
• Cheyletiella spp.—reported in chinchillas, lesions are usually located in the intrascapular or tail‐base region and are associated with large amounts of white scale. Mites are readily identified on skin scrapes or acetate tape preparations on low power.
• Urinary tract infection—perineal moist dermatitis; alopecia, with or without erythema, scale, or ulceration
• Arthritis of hind limbs—perineal moist dermatitis; alopecia, with or without erythema, scale, or ulceration
• Lumbar spinal spondylosis—perineal moist dermatitis; alopecia, with or without erythema, scale, or ulceration
• Pododermatitis of hind limbs—perineal moist dermatitis; alopecia, with or without erythema, scale, or ulceration
• Abscesses—anywhere on body; alopecia, with or without erythema, scale, ulceration
• Ear mites—alopecia around base of ear; may extend to head, neck, abdomen, perineal region, intense pruritis; brown‐beige crusty exudate in ear canal and pinna
• Fleas—patchy alopecia; flea dirt will help differentiate; secondary pyoderma sometimes seen
• Contact dermatitis—alopecia, with or without erythema; scale on ventral abdomen and other contact areas
• Moist dermatitis—alopecia, with or without erythema, scale, or ulceration associated with urinary disease (urine scald), diarrhea, uneaten cecotropes, arthritis, pododermatitis, spinal spondylosis
• Neoplasia—cutaneous lymphoma, cutaneous epitheliotropic lymphoma (mycosis fungoides), trichofolliculoma, mast cell tumors; focal or diffuse alopecia; scaling and erythema; may see crust formation—not reported in chinchillas but should be considered.

CBC/BIOCHEMISTRY/URINALYSIS

To identify evidence of infection, inflammation, and organ function for underlying disease, especially with urine scald, perineal dermatitis, infectious organisms

OTHER LABORATORY TESTS

Fungal cultures—especially DTM for dermatophytes; two negative cultures should be obtained following treatment to ensure clearance of infection.

IMAGING

• Skull radiographs—to identify underlying dental disease in chinchillas with ptyalism, epiphora
• Whole body radiographs—to identify orthopedic, spinal, gastrointestinal, renal, reproductive diseases associated with perineal dermatitis or urine scald
• Abdominal ultrasound—to identify gastrointestinal, renal, reproductive diseases associated with perineal dermatitis or urine scald

DIAGNOSTIC PROCEDURES

• Skin scraping—micro‐spatula with flat‐ended blade (preferable) or dull edge of scalpel blade
• Acetate tape preparation—evaluate on low‐power microscopy for ectoparasites
• Trichogram—cytology of epilated hairs to examine for lice, other ectoparasites, or eggs
• Skin biopsy—especially with suspicion of neoplasia, infectious organisms
• Woods lamp ultraviolet evaluation of Microsporum canis lesions; not very useful as a screening tool—many pathogenic dermatophytes, including T. mentagrophytes, do not fluoresce; false fluorescence is also common.
• Fungal culture—if dermatophytes are...