Malassezia Pachydermatis

Research testing completed determining hyupersensitivity response in Westies
Robert E. McCaskill, DVM
Health Committee
Winter 2002

Research completed on Studies of the host (canine) immune response to the opportunistic pathogen Malassezia pachydermatis. Researchers identify that reactivity to Malassezia pachydermatis in dogs in IgE-mediated.

Goals and Results - The goals of the study were to:

1. To confirm that atopic dogs mount a Type-1 hypersensitivity response to the yeast Malassezia pachydermatis.
   
   Results - our researchers found little anti-Malassezia 1gE detected in the serum of dogs regardless of the severity of their infection. They have yet to perform statistical analysis of these results; however, it is their conclusion that the levels detected would generally be considered clinically irrelevant. They felt that these results were contrary to the significant in-vitro- (skin test) reactions seen in atopic dogs with Malassezia infections. This disparity led our researchers to question the role of anti-Malassezia IgE in the pathogenesis of canine Malassezia dermatitis. They therefore utilized a technique know as the test of passive coetaneous anaphylaxis (Prausnitz-Kustner testing) to determine if dogs with strong positive skin test responses to intradermal injection of the extract possessed anti-Malassezia in the serum. They utilized 3 techniques and were successful in demonstrating the passive transfer of in-vivo reactivity from the serum of skin test-positive dogs to the skin of normal dogs. This is the first definitive proof that reactivity to Malassezia pachydermatis in dogs is IgE-mediated, and suggests that the failure to detect anti-Malassezia pachydermatis by ELISA was due to flawed technique or reagents.
   
   
2. To test the hypothesis that atopic dogs also produce Malassezia reactive T-lymphocytes that express a type-2 cytokine profile.
   
   Results - Serum from all dogs was banked and our researchers are still attempting to perfect the Western Blotting technique to better characterize the specific allergenic components of the yeast organism to which allergic dogs are reacting.
   
   
3. To provide guidelines for the proper culture and freezing intervals of the organism prior to extraction for use as a skin-testing agent.
   
   Results - With the perfecting of their Western Blotting technique, our researcher indicated it would be possible that a recombinant allergen could be commercially produced that would increase availability of Malassezia allergen for routine clinical uses. Currently, there is no commercial extract available for skin testing of domestic animals. Additional microbiological studies have not yet been completed due to the late starting date of the studies. While the results cannot be predicted yet, positive or negative results will be equally interesting and publishable. They expect completion by the end of 2001.

Our support of this research has allowed for definitive proof that Malassezia pachydermatis can produce allergic skin disease in the dog. Veterinary dermatologists have for the last several years provided information on Malassezia infections to veterinary clinicians. They will now be able to explain that these infections are mediated by an IgE response. With the development of a commercially available test, veterinarians will also have at their disposal a diagnostics test that will be definitive to skin disease suspicious to be caused by Malassezia. With a definitive diagnosis, veterinarians will be able to use treatment protocols that either eliminate or control a pets skin disease.

Our Board would like to thank all those who donated money, time or a case for this research. Your support has allowed the Foundation to improve the life of Westies through research and knowledge.