What is Ringworm?
Ringworm is a highly contagious fungal infection that affects the surface of the skin. These fungi are known as dermatophytes. Common genera include Microsporum and Trichophyton. They live in the outer layer of the skin called the stratum corneum which is mainly composed of rough dead skin cells known as keratinized cells.
How is Ringworm Transmitted?
Ringworm is transmitted through direct contact with an infected individual or an object that has previously been exposed to pathogen, such as clothing and bedding (fomites). Ringworm is a zoonotic disease meaning it can be transmitted between animals and humans.
Clinical Symptoms Include...
- Slightly raised red lesions
- Circular patches of hair loss (alopecia)
- Scaly, crusty or ulcerated skin
- Brittle hair
- May or may not be itchy (pruritus)
How is Ringworm Diagnosed?
Ringworm is diagnosed with a Wood’s lamp combined with hair microscopy and fungal culture. A Wood’s lamp is a portable black light that causes certain types of fungi to glow (fluoresce) in a dark room. A positive result is indicative of ringworm, however a negative result does not rule it out as only some species of Microsporum fluoresce. Hair microscopy involves examining a hair sample under a microscope to look for the presence of dermatophytes. This technique is used to confirm the results of Wood’s lamp test.
A fungal culture is the most reliable diagnostic test for ringworm. It is performed by taking a hair sample containing dead skin cells from the outer edges of the lesion with tweezers or a toothbrush. The sample is placed in a bottle of dermatophyte test medium and stored in a dark place at room temperature for 10-14 days. If dermatophytes are present in the sample, the agar (a component of the test medium) will change from orange to red.
What are the Treatment Options for Ringworm?
Treatment of ringworm may consist of a topical ointment or solution that is applied to the infected area and/or oral antifungal medication.
- Lime sulfur dip is a topical solution that is commonly used to treat ringworm.
- Antifungal shampoos containing an antifungal medication, such as miconazole are also available.
- Prescribed antifungal medications including ketoconazole, terbinafine, and fluconazole
When Handling a Pet with Ringworm, Remember to:
- wear disposable gloves and dispose of them immediately after use
- cover exposed skin
- thoroughly decontaminate all surfaces with a 1:10 bleach solution
- minimize contact with infected animals until the infection has resolved