Ringworm (Dermatophytosis) in Guinea Pigs
A fungal skin infection, most commonly caused by Trichophyton mentagrophytes. Highly contagious between guinea pigs AND transmissible to humans (zoonotic). Causes patchy hair loss and crusty skin.
Last updated: 2026-05-08
Severity
mild
When to Act
See Vet Soon
Symptoms & Signs
Patchy hair loss
Circular or irregular patches of hair loss, typically starting on the face, ears, and feet.
Crusty, scaly skin
Dry, flaky, crusty lesions in the bald patches — may be itchy.
Lesions spreading slowly
Patches enlarge and new lesions appear over weeks.
Behavioral Changes to Watch For
Pets can't tell us what's wrong. These behavioral changes are often the first clues that something is wrong.
🐾 Mild itching
May scratch more than usual — but less intensely pruritic than mange mites.
What You May Notice:
Your guinea pig scratches at their face or ears more often than usual.
Causes & Risk Factors
Causes
- •Fungal infection — Trichophyton mentagrophiae (most common), Microsporum canis, Microsporum gypseum
- •Transmitted by direct contact with infected guinea pigs or contaminated environment (bedding, toys, brushes)
- •Spores can survive in the environment for months
- •Zoonotic — can be transmitted to humans (especially children and immunocompromised individuals)
Risk Factors
- ⚠Young guinea pigs (immature immune system)
- ⚠Overcrowding and poor ventilation
- ⚠High humidity
- ⚠Concurrent illness or stress
- ⚠Vitamin C deficiency (weakened immune defenses)
How It's Diagnosed
- 1Wood's lamp examination — some species fluoresce (but Trichophyton mentagrophiae, the most common in guinea pigs, does NOT)
- 2Fungal culture (DTM) — gold standard; takes 1-3 weeks for results
- 3Microscopic examination of hair plucks — look for fungal hyphae and arthroconidia
- 4Clinical signs + history — crusty, patchy alopecia on face/ears is classic
Treatment Options
Topical Antifungal Therapy
Mild, localized cases may respond to topical treatment alone.
Steps
- 1.Miconazole or clotrimazole cream applied to lesions twice daily
- 2.Enilconazole (Imaverol) dips — diluted per instructions, applied twice weekly
- 3.Lime sulfur dips — effective but strong-smelling
- 4.Continue treatment for 2-4 weeks beyond clinical resolution
Expected Outcome
Lesions stop spreading and begin healing within 1-2 weeks.
Precautions
- !Wear gloves when handling an infected guinea pig
- !Lime sulfur can stain fur and skin temporarily yellow
Oral Antifungal Therapy
For severe, widespread, or refractory cases.
Steps
- 1.Itraconazole or terbinafine — oral, prescribed by a vet
- 2.Typically 2-4 weeks of treatment
- 3.Often combined with topical therapy for best results
Expected Outcome
Systemic elimination of the fungus.
Precautions
- !Oral antifungals can be hepatotoxic — monitor for decreased appetite
- !Must be precisely dosed — use a compounding pharmacy
Environmental Decontamination
Essential to prevent reinfection and human transmission.
Steps
- 1.Thoroughly clean and disinfect the cage and all accessories
- 2.Discard porous items (wood, cardboard) that cannot be disinfected
- 3.Vacuum carpets and upholstery thoroughly
- 4.Wash bedding in hot water with bleach if possible
- 5.Wash hands thoroughly after every handling
Expected Outcome
Elimination of fungal spores from the environment.
Precautions
- !Fungal spores are very hardy — thorough cleaning is essential
- !Infected guinea pigs should be isolated from other pets
Common Medications Used
| Medication | Usage | Important Notes |
|---|---|---|
| Miconazole Cream | Topical antifungal cream | OTC. Apply to visible lesions twice daily. Wear gloves. |
| Itraconazole | Oral antifungal for severe/refractory cases | Prescription only. Monitor appetite during treatment. |
Prevention
- ✓Quarantine new guinea pigs for 2-3 weeks before introducing to existing pets
- ✓Good hygiene — regular cage cleaning and hand-washing
- ✓Maintain proper vitamin C levels — supports immune function
- ✓Avoid overcrowding
- ✓Good ventilation to reduce humidity
When to See a Veterinarian
- ⚠️Patchy hair loss with crusty skin
- ⚠️Lesions that don't resolve with OTC antifungals
- ⚠️If your family members develop circular, itchy skin lesions — see a doctor AND vet
Frequently Asked Questions
Can I catch ringworm from my guinea pig?
Prognosis
Excellent with appropriate treatment. Lesions resolve within 2-4 weeks. Reinfection is common if environmental decontamination is inadequate.
References
- [1] BSAVA — Manual of Rodents
- [2] Guinea Lynx — Fungal Infections
Related Conditions
Canine Atopic Dermatitis (Environmental Allergies)
The most common allergic skin disease in dogs, affecting 10-15% of the canine population. Genetically predisposed dogs develop hypersensitivities to environmental allergens like pollen, dust mites, and molds. Causes intense itching and recurrent skin/ear infections.
mildFood Allergy (Cutaneous Adverse Food Reaction) in Dogs
An immune-mediated reaction to dietary proteins, causing skin disease and/or gastrointestinal signs. Often looks identical to environmental allergies. Diagnosis requires a strict elimination diet trial — there is no reliable blood or saliva test.
mildHypothyroidism in Dogs
The most common endocrine disease in dogs, caused by insufficient thyroid hormone production. Leads to a slowed metabolism affecting nearly every body system. Easily diagnosed and treated with daily medication.
mildVitamin C Deficiency (Scurvy) in Guinea Pigs
Guinea pigs, like humans, cannot synthesize their own vitamin C. Deficiency leads to scurvy — a painful, potentially fatal multisystem disease. Easily preventable with proper diet and supplementation.
moderate