Dematophytosis – Clinical Aspects

Presenter: David Grant BVetMed CertSAD FRCVS, Independent Veterinary Surgeon

After watching last week’s webinar titled “Dermatophytosis – Clinical Aspects”, I came to the conclusion that there are some changes I could make to improve my usual approach to diagnosing and managing cases of dermatophytosis.

David Grant led this webinar and delivered practical advice on how to avoid underdiagnosing and overdiagnosing this disease which is so effective at presenting itself in a variety of ways. For example, affected patients can have focal alopecia, diffuse alopecia, scale and crusts, inflammatory lesions, nodules or lesions which look remarkably similar to military dermatitis in cats. The lesson here, David advises, is to never diagnose dermatophytosis based on clinical signs alone, as there are a number of conditions which can so easily look like this disease. And on the flip side, there are a number of conditions which dermatophytosis can so easily mimic.

I’m glad to say that diagnosing this condition without performing further tests is not a trap I’ve ever fallen into, but after listening to this webinar I have made errors on my route to a diagnosis. For example, I frequently use the Wood’s lamp, religiously waiting a good length of time for it to warm up (something I have done correctly). However, I had never realised it could take several minutes for infected hairs to actually fluoresce. Of course, hovering a Wood’s lamp over a fractious animal for several minutes may not always be practical, so David suggests to take a coat brushing onto some paper and using the Wood’s lamp on these brushings away from the uncooperative patient.

Trichoscopy can also be a powerful diagnostic tool and the more we look at infected hairs under the microscope the better we get at diagnosing dermatophytosis. Infected hair shafts look fuzzy due to disrupted keratin, and under a high magnification these hair shafts have grape like spores attached to them. Hair plucks can also be sent away for dermatophyte culture which helps to identify the species although David does discuss ways of doing this in practice. Growth without identification of the species can also be achieved in practice by using dermatophyte culture medium which turns red within ten days if positive. However he advises that plates should be checked daily because if an excess of growth is present and the plates have not been checked regularly it can be difficult to ascertain if the plate has become contaminated, making interpretation impossible.

If you succeed in the challenge of diagnosing dermatophytosis, a treatment plan will need to be implemented and David discusses three steps which need to be taken to achieve a cure. These steps are:

  1. Confining the pet to a room which can be easily cleaned and disinfected
  2. Administering topical and systemic treatment
  3. Thorough cleaning and disinfecting of all contaminated areas

David discusses each of these areas in detail, including the use of his preferred topical treatment, Malaseb shampoo, and systemic treatment, itraconazole. In respect of treatment, I was reassured by David’s advice that I was managing these cases appropriately but I now understand I have not been treating these cases for long enough. David advised treatment is often necessary for anywhere between six to ten weeks and should only end after attaining two negative dermatophyte cultures two weeks apart.

This webinar was an excellent guide to diagnosing and managing cases of dermatophytosis in practice and its value, as well as the respect given to David Grant as a speaker, was reinforced by the attendance of several other dermatologists.

At the beginning of this webinar David cited a paper (Sparkes et al) which stated that out of 8349 submitted samples from dogs suspected of having dermatophytosis only 16% yielded positive results on dermatophyte culture. This would indicate that vets could be over diagnosing a condition which is in fact relatively rare.

However missing its diagnosis can also have real consequences, not only for the animals but also for the owners due to its zoonotic potential. For these reasons and for the very fact that this was an engaging and practical discussion about dermatophytosis, this webinar really should not be missed.

The Stethoscope (MRCVS)

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