Introduction

Ringworm, also called dermatophytosis, is caused by exposure to one of several forms of environmental fungi. Once the fungi become established on a dog’s hair, nails or outer layers of skin, characteristic ringworm signs begin to appear.

Symptoms of Ringworm

This superficial fungal infection causes few if any troublesome symptoms in affected animals. However, ringworm must be managed carefully, because it is highly contagious. When they do appear, signs of ringworm infection in dogs include:

• Circular regions of unexplained hair loss (alopecia), with varying degrees of crusting and scaling but usually without itchiness or scratching
• Small patchy areas of hair loss
• Hair breakage
• Crusty skin patches
• Scaly skin patches
• Cutaneous bumps (on the skin)
• Irritated, inflamed hair follicles
• Poor haircoat
• Pustules on the skin
• Skin abscesses (uncommon)

The most characteristic signs of ringworm are areas of elevated skin, caused by inflamed hair follicles, which take a circular or oval shape. Ringworm can occur anywhere on a dog’s body, including the face and legs. The infection typically stays in one main area. The patches may grow, but they do not routinely spread to other locations on the body. However, if a dog has an impaired immune system or another underlying medical condition, ringworm is more likely to spread across its skin. Ringworm does not normally cause itchiness or scratching, but it can.

Dogs at Increased Risk

Young puppies have an increased chance of contracting ringworm due to their underdeveloped immune systems. Dogs whose immune status is compromised, such as those in high-density housing facilities and those with cancer, poor nutritional status, parasites or other systemic diseases and those undergoing chemotherapy, are also predisposed to ringworm infection. Ringworm is highly contagious between dogs and can infect people as well.