Dermatophytosis (Ringworm)

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    What Is Dermatophytosis?

    Dermatophytosis is a superficial fungal infection caused by fungi that require keratin for growth. Superficial fungal infections affect 20% to 25% of the world’s population, and the incidence is increasing.


    Ringworm is a fungal infection of the horny tissue that forms nail, hair and skin. It is caused by Microsporum canis, Microsporum gypseum (from soil), or Trichophyton mentagrophytes (from rodent contact) fungi.

    The disease affects both animals and humans. Young dogs up to one year of age and dogs with a weakened immune system, having other health disorders (for example, diabetes), are most frequently affected. Infected animals usually develop immunity, and the infection will spontaneously disappear after a few weeks to months.

    Studies show that infected cats appear to cause substantial environmental contamination and spread Microsporum canis, contaminating house air and surfaces. Dogs seem to contaminate surfaces, but they never contaminate the air. Since dogs and cats live more and more in contact with humans, and a lot of dogs and cats are carriers of dermatophytes, dermatophytosis is the most important risk of developing a “mange” in humans.

    Clipping away affected hair and burning the clippings should be performed in all cases of generalized dermatophytosis and dermatophytosis in long-haired cats to decrease environmental and human exposure. Confining the animal to easily cleaned areas is helpful.1

    Signs & Symptoms

    The clinical signs of dermatophytosis may include:

    • Alopecia
    • Circular and patchy skin lesions, raised plaques on the skin.
    • Furunculosis on legs and paws (acute abscess of a hair follicle due to infection by Staphylococcus)
    • Facial folliculitis (inflamed hair follicles)
    • Nailbed and nail infection
    • Irritated, scaly skin
    • Persian cats may develop deep furunculosis.1 Because dermatophytes cause facial dermatitis, the infection frequently involves the eyelids and typically produces dry, crusty alopecia around the eyes. The diagnosis is established on the basis of direct microscopic examination of scrapings.4

    Dermatophytosis in dogs reveals in different forms and can often mimic other skin diseases, such as:


    Diagnosis is based on clinical signs. Lesions are examined with a Wood’s lamp (ultraviolet light source) that will expose Microsporum canis fluorescing with a greenish color.

    Skin lesions are more frequent in cats, but in dogs, the lesions are more severe. Most lesions occur on the head and neck. Male dogs are most often affected. Heavily infected animals may develop skin ulcers. The hair becomes thin and broken, while the skin gets scaly and scabby. The Yorkshire Terrier and Jack Russell Terrier may be predisposed to M. canis dermatophytosis.1,3


    Treatment consists of the application of antifungal medications (itraconazole, lufenuron), rinses, and shampoos (lime sulfur, enilconazole rinses, 2% miconazole/chlorhexidine shampoo). The cure may take from 2 to 4 months. The use of disinfectants, such as bleach or enilconazole, has been proven effective to destroy the spores in the environment. A vaccine is used for preventing this fungal infection and is administered at the time of treatment, particularly in cats.

    Video Credits: Dr.Varsha Scooby
    Image Credits: Medmyco, Wikipedia



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