Just as in humans, ringworm is not a worm but a fungal disease that infects skin, hair, and claws by one of the three types of fungus: Epidermophyton, Microsporum, and Trichophyton. These fungi are found worldwide, and all domestic animals are susceptible. Ringworm carried by rodents is picked up by curious dogs digging into rodent burrows. The third form is a soil fungus. Ringworm in dogs generally appears as a red, crusty, rough area of skin with broken hairs and hair loss with hardly any itching. Ringworm can, however, present itself in many ways which are not typical. Due to the susceptibility of young animals, the disease is more common in puppies.
How Does a Dog Get Ringworm?
Dogs can pick up ringworm in several ways:
- Contact with hair, fur and skin from infected animals
- Contact with contaminated bedding, grooming equipment, toys or environment
- Contact with soil containing fungal organisms
Ringworm is spread by contact with animals which already have ringworm, and by touching objects that the infected animal has touched; such as bedding, brushes or grooming equipment, saddles and other tack, furniture, rugs, etc. Not every animal or human who touches infected animals or objects will become infected; the age, immune status, skin condition and grooming habits of the animals influence if the fungus is actually able to grow and infect.
In dogs, the classic Ringworm lesions are patchy areas of hair loss and scaliness, usually with very little inflammation or redness.
Animal/Human Transmission of Ringworm
Some ringworm in dogs can be contagious to people (zoonotic disease), especially children. People with the highest risk for catching ringworm from their pet are young children who have never been exposed, the elderly, or people with a depressed immune system.
Once a person has been exposed to a strain of ringworm, most develop immunity and rarely get the same strain again. If a person develops ringworm, your pets should be examined, although many times the source of infection is actually another person and not a pet.
Diagnosis of Pet Ringworm
Diagnosis of ringworm requires a fungal culture from a sample of hair plucked from the edge of a lesion. This can take several days to a few weeks for growth and a diagnosis.
Although the disease is considered to be self limiting in most healthy people and animals, treatment of infected dogs is usually recommended to speed recovery and prevent passing on the fungus. Most animals will “outgrow” the Ringworm fungus as their body’s immune system fights it off over the course of a few weeks.
Old Animals and Puppies
Due to the susceptibility of young animals, the disease is more common in puppies. Animals that are immunocompromised or very young or old are less likely to rid themselves of the condition without treatment. To some extent, infection may be persistent and widespread in longhaired breeds of dog.
Symptoms of Ringworm in Your Pet:
- Lesions, either single or multiple
- Scaling or crusting
- Patches of hair loss that may be circular
- Minimal to no itching
- Nodules with ulcers or draining tracts are rare, but may occur.
Treatments for Canine Ringworm
Topical treatments involve clipping the hair, bathing with antifungal shampoo and rinses that decrease transmission immediately. Some cases may require systemic antifungal therapy that has been shown to shorten the course of the disease. The anti-fungal drug of choice in dogs is Ketoconazole. Oral medications are generally reserved for severe and/or chronic infections and can be expensive and with side effects.
Treatment must continue until the culture results are negative, even though the animal may look better. Hair re-grows long before the fungus is exterminated. In a single-dog household, treatment can last 3 to 8 weeks and may be needed for longer periods in a multi-pet household.
- Localized infections may be treated with topical therapy alone.
- Systemic antifungal in combination with topical therapy should be used for generalized infections or in dogs with multiple lesions.
- Thoroughly disinfect and vacuum the pet’s environment.
- All in-contact animals should be evaluated for possible infection.
Home Treatment for Ringworm in Pets
Treating your home is also important. Fungal spores can persist in your carpet for up to 2 years, so re-infection is a concern. The more animals in the house, the longer the treatment must go on before the environment is clear. Getting rid of the hair in the house, kennels and pet sleeping areas are the best way to rid the fungus from the environment. This is why veterinarians recommend clipping the pet’s hair (alert the groomer). Fungus likes to grow in dark spaces on hair and debris.
If your pet has ringworm, change the bag each time you vacuum. The parts of a bagless vacuum can be soaked in diluted bleach water between uses. The only reliable killer of the ringworm spores is a 1:10 dilution of bleach in water. Use this with care because it will stain.
Sunlight and Ringworm
Sunlight also kills ringworm. Items that cannot be thrown away can be left in the sun outside to rid them of ringworm contamination.