Common Disease Name:
Ringworm, Fungal Infection
Medical Term for Disease:
Dermatophytosis
Species Affected by Disease:
Dogs and cats; transmissible to humans
Age Animal Usually Affected:
More commonly seen in puppies.
Commonly Affected Breeds:
Any
Sex Usually Affected:
Both
Disease Symptoms:
Exposure to or contact with a
fungal spore does not necessarily mean an infection will occur; 
and
infections may not result in symptoms. Dermatophytes grow in the keratinized or
dead skin layers of hair, nail and skin and do not live in living tissue or when
the
skin is inflamed, so use of corticosteroids to calm the skin can
actually prolong the infection. The incubation period is 1-4 weeks. Some
infected animals never show symptoms, but carry the fungal spores, especially
long haired cats. . There may be no symptoms, or patchy hair loss which is
sometimes circular. The classic sign of circular lesions is more common in cats
and often misinterpreted in dogs. Scales, redness, darkened skin and itching
vary. Nail bed infections and lumpy glaucomatous lesions and may also be seen.
Lesions are commonly found on the face,
ears, feet, and tail.
Method(s) of Diagnosis:
A fungal culture with microscopic identification is the best means of confirming the diagnosis of dermatophytosis. If hairs shafts glow positive apple green florescence with a Wood's lamp, these are considered good samples to culture. Some dermatophytes do not fluoresce. Plucking hairs from the edges of a hair loss area are more likely to give a diagnosis. Using a sterile toothbrush to brush the hair coat of an asymptomatic animal yields better results. There is a test media called Dermatophyte Test Media which changes from yellow to a red color when exposed to dermatophytes. Most dermatophytes typically produce this color change during the early and growing phase and should be positive within a few days.
Disease Causes:
The Dermatophyte fungi called Microsporum canis, Trichophyton mentagrophytes, and Microsporum gypseum. These organisms live in the environment and there is a higher incidence of dermatophytosis in regions with a hot and humid climate.
Treatment:
Oral or topical medication
Prognosis:
Many animals will self-clear the infection over a period of a few months. Treatment quickens the cure and helps prevent environmental contamination. Some infections, particularly in long-haired cats or multi-animal household, can be very persistent and frustrating to treat. Animals with poor immunity can be difficult to clear. As well, some immune compromised and sometimes elderly people can have problems with re-infections of the fungi.
Complications:
Very contagious to other dogs, humans, and other animal’s .If there are multiple animals, poor nutrition, poor sanitation & management practices, and no quarantine of newly introduced animals into the household, the problem can be severe and difficult to eradicate.
Prevention:
Quarantining new
arrivals into the household and culturing for dermatophytes is necessary to
prevent re-infection from other animals. Rodents may help spread the disease, so
eliminate. The dermatophyte often lives in soil, so this environment needs to be
avoided or removed. Prophylactic treatment of exposed animals with griseofulvin
for 10-14 days can be used.
Medicines Used for Treatment of Disease:
Griseofulvin is the most widely prescribed systemic drug for the treatment of dermatophytosis. Ketoconozol and iatroconozol are other oral medications. Lufeneron is an 'off-label' medication frequently used at higher doses than for flea control. The most effective topical agents are enilconazole, a topical azole antifungal agent available in Canada, miconazole shampoo and lime sulfur dip (very smelly). Corticosteroids are contraindicated.
Helpful Products:
Miconozole shampoos, environmental cleanliness and treatment with dilute bleach when feasible. If only one lesion, a topical anti-fungal will often stop progression.
