What color does ringworm glow under a Wood's lamp in cats? - briefly
Ringworm in cats, caused by dermatophytes, does not consistently fluoresce under a Wood's lamp. However, certain species of Microsporum canis, a common feline dermatophyte, may exhibit a dull greenish glow when exposed to the Wood's lamp light.
What color does ringworm glow under a Wood's lamp in cats? - in detail
Ringworm, a fungal infection caused by dermatophytes, is a common dermatological issue in cats. One of the diagnostic tools used to identify ringworm is the Wood's lamp, a type of ultraviolet (UV) light. This lamp emits long-wave UV light, specifically in the range of 320-400 nanometers, which can cause certain substances to fluoresce. In the case of ringworm, the fungus responsible for the infection, particularly Microsporum canis, can produce a compound called pteridine, which fluoresces under this specific wavelength of light.
When a cat suspected of having ringworm is examined under a Wood's lamp, the affected areas of the skin or fur may glow. The characteristic color of this fluorescence is typically a bluish-green or apple-green hue. This glow is a result of the pteridine compound reacting to the UV light emitted by the Wood's lamp. It is important to note that not all strains of ringworm will fluoresce under the Wood's lamp, and the presence of fluorescence does not confirm the diagnosis of ringworm. However, the absence of fluorescence can help rule out certain types of ringworm, specifically those caused by Microsporum canis.
The use of the Wood's lamp is a non-invasive and quick diagnostic tool, but it should be used in conjunction with other diagnostic methods, such as fungal cultures or polymerase chain reaction (PCR) tests, to confirm the presence of ringworm. This is because the Wood's lamp can sometimes produce false positives or false negatives. For instance, certain medications, dyes, or other substances can cause fluorescence, leading to a false positive result. Conversely, some strains of ringworm may not produce the fluorescent compound, resulting in a false negative.
In summary, the characteristic glow observed under a Wood's lamp in cats with ringworm is a bluish-green or apple-green color. This fluorescence is due to the presence of pteridine, a compound produced by certain strains of the ringworm fungus, particularly Microsporum canis. While the Wood's lamp can be a useful diagnostic tool, it should be used in combination with other diagnostic methods to accurately confirm the presence of ringworm in cats.