Tuesday, June 4, 2013

1447. Dermaphytosis --- Diagnosis of ringworm using ultraviolet light

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Date:   09 June, 2013  
Focus: Small animals - dogs, cats, hamsters, guinea pigs, turtles & rabbits
Dermatophytosis: Diagnosis using UV light
Dr Sing Kong Yuen, BVMS (Glasgow), MRCVS
Date:   09 June, 2013  
Be Kind To Pets
Veterinary Education
Project 2010-0129

1447. Dermatophytosis --- Diagnosis of ringworm using ultraviolet light

Hairs, nails and superficial skin surface of the dog are areas affected
The cause is usually Microsporium canis, M. gypseum or Trichophyton mentagrophytes,  

1. Fungal culture with macroconidia identification
Microscopic exam of the macroconidia is necessary to confirm the genus and species

2. UV light - Hairs that show a positive apple-green fluorescence under ultra-violet light (Wood's lamp) examination.
M.canis on hair shaft will show apple-green fluorescence.
But keratin with epidermal scales and sebum may also produce a false-positive fluorescence.

3. Microscopic examination of hair
This often produce false negative results and so the vet may mis-diagnose as the absence of ringworm. Wood's lamp may be used on positive cases to show fluorescence on the fungal hyphae in the hair shaft 
In a case of a white Pomeranian with itchiness and hair loss, I diagnosed ringworm visually, using the microscope and the UV light as shown in the image above.
In a case of an old poodle with multiple warts, the owner complained about generalised itchiness and skin dandruff. The dog had circular areas of skin loss and patches which fluoresces in light green.

Anti-fungal cream and washes and steroids had been used earlier. I switched off the room light and asked Ms Toh, my intern to film the fluorescence but the skin fluorescence results are not satisfactory.  Most likely I have used the incorrect lens which can't focus well. The lens is not able to focus. However, I will put up this video to serve as a learning experience.

Yesterday, on Saturday, Jun 8, 2013, I consulted the camera vendors. I was told that my lens were not appropriate for video. I needed a lens suitable for video production and this lens came with the Canon 700D model available just 2 weeks ago. I have this lens now and hope that future videos will be better quality.
Video 1 - ringworm - ultraviolet light is at:

Video 2 - ringworm - microscopy is at:
Update will be on this webpage:

More info at:
Dogs or Cats
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e-mail judy@toapayohvets.com
tel: +65 9668-6469, 6254-3326
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