Diagnosing Ringworm in Dogs

Diagnosing ringworm in dogs can be difficult due to the similarity to other skin disorders. Ringworm is not a worm but a fungus called dermatophytes. Early discoveries called these lesions ringworm because of the circular formation that were thought to be caused by worms. Ringworm lives on the surface of skin and feed on dead skin tissue and hair. There are three types of fungus that cause ringworm, microsporus canis, microsporum gypseum and trichophyton mentagrophytes. Microsporum canis is the most common in dogs.

Transmission of Ringworm

Ringworm is a zoonotic disease which means that it can be transmitted from animal to people and vice versa. Ringworm is very contagious and is spread through direct contact with infected species. Puppies and young dogs are more prone to ringworm because of their immature immune system. Your dog may be more susceptible to ringworm if he has had pre-existing skin diseases or trauma. Ringworm spores can live in the environment for months with the right conditions. They can be found in carpet, bedding and grooming equipment. A mixture of bleach and warm water can kill up to 80 percent of spores.

Symptoms of Ringworm

The incubation period of ringworm is 10 to 12 days. Lesions may appear after this time. Typical ringworm lesions are round and hairless. They grow in size and are irregular in shape. Hair loss is due to the fungi causing hair shafts to break off. These lesions are commonly found on the face, ears, paws and tail. Their appearance is scaly and may or may not itch. The skin is often red and inflamed.

Diagnosing Ringworm

If you suspect that your dog has ringworm, there are test that can be done at your veterinarians office.

  • Wood's Lamp - This is an ultra violet lamp or black light. If your dog is infected with ringworm, 50 percent of the microsporum canis will glow when under the wood's lamp.
  • Fungal Culture - Because ringworm is similar to other skin disorders based on appearance, a fungal culture can be done to confirm a positive identification of the skin infection. Test can take 2 to 3 weeks to show results.
  • Microscopic - This requires a skin scraping of the affected area. A sample is taken and prepared on a slide with potassium hydroxide solution. This solution dissolves the skin cells but not the fungus cells. The slide can then be color stained for easier identification and examined through a microscope.

Treating Ringworm

Griseofulvin is an oral anti-fungal drug that is given to stop fungal reproduction. Side effects of this drug is vomiting, diarrhea and possible birth defects. Lime sulfur dips can be given twice a week either at your veterinarians office or at your home. This is a strong smelling dip that can stain your clothes and jewelry. It will cause temporary yellowing of your dogs coat. It is important that you follow the exact directions for the dip to insure proper effectiveness. If ringworm is left untreated, it will heal itself in 2 to 4 months but infection may return. Treatment is recommended for your dog to relieve him from any suffering and to stop further spreading.