Alopecia

Etiology

• Hereditary causes are uncommon.
• Acquired causes include interference with growth of the hair or because of discomfort, the guinea pig causes destruction of the hair through self-trauma (scratching, licking). Determine behavioral vs. infectious/inflammatory although behavioral problems can lead to infectious/inflammatory skin conditions:
  • This can include 'barbering' from other guinea pigs.
  • Some stressed, anxious, fearful, or even bored guinea pigs overgroom.
• There are many causes of alopecia which can be divided into inflammatory and non-inflammatory conditions.
• Inflammatory diseases of the dermis: pruritus, deep pyoderma.
• Ectoparasites: demodicosis, Chirodiscoides, Trixacarus caviae, Gyropus ovalis, Gliricola porcelli, Ctenocephalides felis.
  • Trixacarus caviae Trixacarus caviae Acariasis: alopecia generally on dorsum, shoulders, and flanks. May be generalized. May be associated with crusting, hyperpigmentation, lichenification. Intensely pruritic. Guinea pig may be anorexic, painful, losing weight, etc. Most common ectoparasite found in guinea pigs.
  • Chirodiscoides caviae Chirodiscoides caviae: alopecia generally in groin and axilla. Mites are on the surface of the hairs and easily seen on collected hairs. Asymptomatic infection is common.
  • Cheyletiella parasitivorax: alopecia on dorsum.
  • Demodex caviae: alopecia usually on face, head and forelegs. Most animals are healthy carriers and clinical disease is not common.
  • Lice Pediculosis: alopecia, lesions around ears, dorsum. Heavy infestations: lice may be found anywhere on the body.
  • Asymptomatic infections are common with most ectoparasites in guinea pigs.
• Dermatophytosis Dermatophytosis :
  • May be pruritic.
  • Most cases are caused by Trichophyton mentagrophytes Trichophyton mentagrophytes: alopecia generally on face, eyes, nasal bridge initially. The disease can become generalized if not treated.
  • One study showed similar dermatophytosis infection rate in both animals with skin lesions and healthy animals.
• Pyoderma:
  • Location depends on initial cause.
  • Exfoliative dermatitis found most commonly on the ventrum.
  • Self-mutilation and pyoderma can complicate severe cases of ectoparasitic infections.
  • Staphylococcus spp Staphylococcus spp most commonly found.
• Miscellaneous conditions:
  • Burns: these can be thermal or chemical. Mainly show up on feet, but can include ventrum, face. Chemical burns from topical agents may be on dorsum. (as in boiling water).
  • Listed in the literature is allergic alopecia such as food allergy, atopy, contact, insect hypersensitivity, but proving these may be difficult clinically in guinea pigs.
  • Neoplasia Neoplasia overview, eg epitheliotropic lymphoma Cutaneous neoplasia.
  • Hormonal disorders such as hyperthyroidism Hyperthyroidism, hyperadrenocorticism and ovarian cysts may produce alopecia.
  • Areas of alopecia can also be the consequence of barbering and fight wounds.

Predisposing factors

General

• Stress.
• Poor husbandry: soiled bedding, crowding, too high humidity and environmental temperature.
• Hypovitaminosis C.
• Immune suppression has been suggested as a cause for infections with Trixacarus caviae Trixacarus caviae and dermatophytosis Dermatophytosis.
• Ectoparasitic infection may predispose to pyoderma.

Specific

• Adult female developing ovarian cyst(s) Cystic ovarian disease. 

Pathophysiology

• Depends on the etiology.
• Any disease that affects hair follicles results in hair loss.
• Hereditary causes are uncommon.
• Acquired causes include interference with growth of the hair or because of discomfort, the guinea pig causes destruction of the hair through self-trauma (scratching, licking). Determine behavioral vs. infectious/inflammatory although behavioral problems can lead to infectious/inflammatory skin conditions:
  • This can include 'barbering' from other guinea pigs.
  • Some stressed, anxious, fearful, or even bored guinea pigs overgroom.
• Processes can be either inflammatory or non-inflammatory.

Timecourse

• Dependent on etiology.
• Ectoparasites generally start slowly, but over the course of a few weeks begin to have an effect.
• Lice may build up large populations before there is hair loss.

Epidemiology

• In social or colony situations, ectoparasites will spread to all, mainly by direct contact. Asymptomatic animals are likely to occur.
• Dermatophytosis is also contagious.
• Pyodermas generally are an individual animal problem.
• Social causes including barbering, stress may appear in multiple individuals in group housing.