Ringworm (Dermatophytosis)

Ringworm (Dermatophytosis)

Species: Dog

Breeds Affected: All Breeds (puppies <1 year, or dogs that are malnourished or immunocompromised, are more susceptible)

Ringworm is not actually a worm, but a fungal infection of the skin, hair, or nails caused by dermatophyte fungi (commonly Microsporum canis, M. gypseum, or Trichophyton). It is highly contagious to other animals and humans via direct contact or shared items. The fungus invades hair shafts and skin surface, leading to characteristic lesions. Environments like shelters or kennels facilitate its spread.

• Classic signs are patchy
• circular areas of hair loss with crusty or scaly red skin
• often on the head
• ears
• paws
• and forelimbs. The lesions may expand in a ring shape (hence “ringworm”) and can be mildly itchy. In mild cases
• you may just see brittle or broken hairs and slight redness. Some dogs
• especially healthy adults
• carry the fungus without showing symptoms
• but they can still infect others. The nails can also be affected (becoming rough or brittle) in certain cases.

Treatment depends on severity and typically involves antifungal medications for several weeks. For localized/mild cases, a veterinarian may prescribe a topical antifungal cream or shampoo (e.g. miconazole or ketoconazole shampoo, lime sulfur dip) to apply to lesions and the coat. More widespread infections often require oral antifungal drugs (such as itraconazole, terbinafine, or griseofulvin) to completely eliminate the fungus. It’s important to continue treatment for the full recommended duration (often 6-8 weeks) even if lesions improve, to prevent recurrence. Environmental decontamination (washing bedding, vacuuming hair) is also crucial to remove shed fungal spores.

Topical antifungals are commonly used: medicated shampoos or rinses containing agents like chlorhexidine and miconazole, or lime sulfur dips, to kill fungus on the skin surface. Oral antifungal medications may be prescribed for systemic treatment – itraconazole and terbinafine are used frequently in dogs (griseofulvin is an older option). These drugs help eradicate the infection from the hair follicles. Treatment is lengthy, and lab tests (fungal cultures) are often done to confirm the dog is clear of ringworm before stopping medication. During treatment, disinfectant cleaning of the home (bleach solution for surfaces, laundering pet bedding) is recommended to prevent re-infection.