How is a ringworm infection diagnosed?
Diagnosis is made in one or more of the following three ways: • Identification of the typical “ringworm” lesions on the skin. This method is not very accurate and may lead to misdiagnosis. • Fluorescence of infected hairs under a special ultraviolet light known as a Wood’s lamp. Most cases of canine ringworm caused by M. canis will glow with a yellow-green flourescence when the skin and coat are examined in a dark room with a Wood’s lamp. However, not all cases of M. canis will fluoresce, and neither T. mentagrophytes and M. gypseum fluoresce under a Wood’s lamp. Some skin ointments and other materials will fluoresce and may give a false positive result. While this technique is acceptable in certain situations as a rapid screening tool in multi-animal facilities, diagnosis made on Wood’s lamp evaluation is not always reliable. The preferred method for diagnosing ringworm in dogs is by fungal culture of a sample of hair or skin cells. This method is the most accurate. A positive culture
