Alopecia in guinea pigs is partial or complete absence of hair where it is normally present.

Pathophysiology

Alopecia is hereditary (genetic) or acquired.

Acquired alopecia is inflammatory or non-inflammatory.

Skin and exocrine glands are vulnerable.

Signs

History: duration and progression, pruritus, infection or dermatological signs.

Examination:

  1. Distribution — focal, multifocal, symmetric, generalised. Assess whether hair loss is from follicle or shaft damage;
  2. Secondary lesions — infection / ectoparasites. Distinguish non-inflammatory (hair loss without inflammation) from inflammatory (hyperpigmentation, lichenification, erythema, excessive shedding, pruritus, secondary skin disease).

Causes of alopecia in guinea pigs

Non-inflammatory conditions that inhibit or slow follicle growth:

  • Neurological / behavioural — stress-related shedding, self-barbering, often sacrum and perineum;
  • Nutritional — protein deficiency, vitamin C deficiency;
  • Hyperestrogenism — ovarian cysts (common cause of dorsal/lateral/flank alopecia); pregnancy-associated symmetric flank alopecia;
  • Diabetes
  • Hypothyroidism

Inflammatory alopecia — direct follicle damage; severe dermal inflammation (pruritus, deep pyoderma); ectoparasites — demodicosis; Chirodiscoides; Trixacarus caviae (shoulders, back, flanks — may generalise, crusted, hyperpigmented); Gyropus ovalis, Gliricola porcelli, Ctenocephalides felis, Chirodiscoides caviae (groin/axilla — mites visible on hairs microscopically); Cheyletiella parasitivorax (back); Demodex caviae (head and thoracic limbs);

  • Dermatophytosis — often pruritic; Trichophyton mentagrophytes often affects face, limbs, sometimes back;
  • Bacterial pyoderma — location depends on cause; exfoliative dermatitis often ventral;
  • Thermal burns
  • Allergic skin disease — atopy, food allergy, flea allergy dermatitis
  • Neoplasia

Risk factors

Comorbidity, vitamin C deficiency, overcrowding, poor husbandry.

Differential diagnosis

Distribution, localisation, and severity guide differentials. Testing depends on underlying disease — useful for endocrinopathies such as diabetes. CBC often normal except pyoderma or parasites. Abdominal ultrasound may diagnose polycystic ovaries.

Diagnostic methods

  • Skin scrapes — deep scrapes for Trixacarus and Demodex; clip hair before scraping; use mineral oil for glide;
  • Comb-through for lice and fleas;
  • Impression smears for bacterial or yeast infection;
  • Tape test for superficial ectoparasites;
  • Culture and sensitivity — infected sites often contaminated;
  • Dermatophytes: Wood’s lamp (limited — Trichophyton often non-fluorescent); fungal culture on Sabouraud/Dermakit (slow, up to ~1 month); direct microscopy of hairs at lesion edge;
  • Skin biopsy — include normal and abnormal skin; assess follicular cycle (anagen/telogen); bacteria, fungi, neoplasia, parasites.

Treatment

Multiple causes may coexist. Empirical therapy may start from most likely differentials when cause remains unclear. Clip hair around lesions with fungal or bacterial dermatitis. Treat all in-contact animals for ectoparasites; clean environment thoroughly.

Prevention: isolate sick animals, reduce stress, early weaning, diet correction, unlimited hay.

Vitamin C deficiency — corrective diet and supplementary vitamin C until signs resolve (50–100 mg/kg SC q24h); maintenance 30–50 mg/kg PO q24h after resolution.

Ovarian cyst alopecia

  • ovariohysterectomy;
  • hCG 1000 IU/ guinea pig IM, repeat 7–10 days; or GnRH 25 µg IM every 2 weeks for two injections.

Ectoparasites

  • ivermectin 0.2–0.8 mg/kg SC every 7–10 days for 3 doses — often effective for mites;
  • selamectin 6–12 mg/kg topically q10d × 2; imidacloprid/moxidectin may be safe; pyrethrin flea powder — avoid overdose.

Bacterial skin infections: clip hair, cleanse with dilute iodine or chlorhexidine; antimicrobial shampoos as adjunct for pyoderma or dermatophytosis (chlorhexidine + ethyl lactate).

Systemic antibiotics safe in guinea pigs when indicated: enrofloxacin 5–15 mg/kg PO q12–24h (poor anaerobe cover; may cover some streptococci); trimethoprim-sulpha 15–30 mg/kg PO q12h; chloramphenicol 30–50 mg/kg PO q8–12h; azithromycin 30 mg/kg PO q12–24h.

Base therapy on culture when possible; treat ≥2 weeks past clinical resolution. Avoid oral gram-positive–selective antibiotics (penicillins, macrolides, lincosamides, cephalosporins) — risk fatal dysbiosis and enterotoxaemia.

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