What are symptoms of ringworm in dogs?

April 13, 2012

Despite the name, ringworm is not really a worm or a condition caused by a worm. Ringworm is a skin infection caused by dermatophytes or fungus that lives on the skin. This skin infection develops when this type of fungus multiplies on the skin. Dermatophytosis which is commonly known as ringworm is a common skin condition of humans and animals. This highly contagious disease is zoonotic. The infective fungal spores can be spread by an infected pet to humans. Children with poor immune system are most susceptible because they have the inclination to pet the dog. In a household with an infected pet, it is highly probable that a family member will be infected. On the other hand, it is also possible for pets to get the infection from humans. Even without direct contact with an infected human or animal, the dog can be infected by the fungal spores that can exist in the environment for long periods of time. Ringworm is caused by three different types of fungus- Microsporum canis, Microsporum gypseum and Trichophyton mentagrophytes. In dogs, this skin infection is caused by microsporum canis. All dogs are susceptible to this type of skin infection. Due to undeveloped immune system, puppies and young dogs are most vulnerable to the infection. Healthy dogs may carry the microsporum canis fungi as well but because of strong immune systems, the dogs may show no symptoms at all. However, they can still infect other pets and humans.

This type of fungus lives on the surface of the dog’s skin and feed on dead skin tissues resulting to the formation of bald circular lesions. The fungi that live on hair follicles cause the breakage of the hair shafts so that infected skin will be hair-free. These round lesions that commonly appear on the face, on the tips of the ears, on the tail and paws of the dog would have well defined ridges with scaly or crusty centers so that dandruff-like flakes may appear. The raised ridges usually get inflamed, blister and ooze. These circular lesions may or may not itch. As the fungi multiply, the lesions will connect and be irregularly shaped so that the dog’s coat would have a moth-eaten appearance.

The appearance of the dog’s skin would not be enough to correctly diagnose the presence of the fungi. The vet would need to do several tests. Wood’s lamp, commonly known as black light uses ultraviolet light to ascertain the presence of the fungi. About 50% of microsporum canis glow under the ultraviolet lamp. A culture test is the most accurate method of diagnosing ringworm. Scales and crust from the lesion will be collected. In a special medium the fungi will be allowed to grow. Laboratory tests that include complete blood count, urinalysis and biochemical profile will rule out other underlying causes of ringworm.

In a household with more than one pet, ringworm treatment for the affected dog can be quite expensive given the fact that not only the affected pet has to be treated but also the other pets and the environment. Ringworm can be considered as a self limiting skin disease. An infected dog may not need treatment as the condition generally resolves itself after a few months. However, treatment would still be necessary to speed up the cure and to reduce the risk of infecting other pets and also the human family. The hair around the lesion is commonly clipped and antifungal creams are slathered on the lesion. This topical treatment though may not be effective in some dogs. Griseofulvin is a very effective oral medication for ringworm. The medication is administered with the dog’s food. As fungal spores can live in the environment, home cleaning using diluted bleach solution will be extremely necessary to prevent the recurrence of the skin disease.

Discussion

comments