PROGRESSIVE REPORT:
RESEARCH PROJECTS
New Project - Studies of
the Host (Canine) Immune Response to the Opportunistic Pathogen Malassezia
pachydermatis
Principle Investigator -
Daniel Morris, DVM, Dipl., ACVD
School of Veterinary
Medicine University of Pennsylvania
Philadelphia, PA 19104
This study will supplement
our knowledge of the multi-factorial cause of atopic dermatitis. One
contributing factor that is especially difficult to manage is
infection by the yeast Malassezia pachydermatis. This organism
increases the itching and self-trauma of many affected dogs by as much
as 75% over their baseline atopic disease (referred to as Malassezia
dermatitis or MD).
Skin and ear canal
infections caused by M. pachydermatis are very common clinical
problems in veterinary medicine. Dogs appear to express a more
extensive type of disease process than humans, likely due the more
oily nature of their skin and ear canal secretions.
Currently, antifungal
chemotherapy is the treatment of choice in dogs, but the recurrent
nature of the problem and the concerns regarding drug toxicity and
cost make it an imperfect therapy. More complete knowledge of the
skin’s immune regulation of yeast infection may allow safer
treatment protocols to be developed.
About our principal
investigator: Dr. Daniel
Morris, is an Assistant Professor of Dermatology at the University of
Pennsylvania. He received his Doctor of Veterinary Medicine degree
from Kansas State University in 1992. In 1995, he completed a
Residency in Dermatology from Michigan State University. He became a
Diplomate in the American College of Veterinary Dermatology in 1996.
He has published numerous peer-reviewed publications with particular
emphasis directed to Malassezia dermatitis.
What is Malassezia
pachydermatis? M.
pachydermatis, is a lipophilic budding yeast. It is part of the
commensal microflora of canine skin. I has been shown to contribute to
the atopic dermatitis phenotype of dogs by producing a Type-1
hypersensitivity response similar to aeroallergens, whereby it
produces a severely pruritic inflammatory disease.
Signalment: MD
is seen mainly in dogs with seborrheic skin disorders. Older dogs with
chronic skin disease may be predisposed.
Signs: The
pruritis responds poorly to cortisone. The pet presents a history of
mild chronic skin disease. The client indicates that there is a
strong, rancid odor. The Westie maybe relegated to the garage because
of the smell.
Physical findings: Itch,
red skin, skin with scale, sebaceous crust, malodor, and
lichenification of the skin. Face, ventral neck, axillae, groin,
perineum, and paws are the common areas affected.
Causes and risk factors:
primary seborrhea (hereditary
keratinzation disorders). Secondary seborrhea due to an underlying
hypersensitivity dermatoses (flea allergy dermatitis, atopy, food
hypersensitivity, contact hypersensitivity), endocrine disorders, and
ectoparasitism.
Diagnosis: Skin
cytology that reveals increased budding yeast organisms. Skin testing
may yield allergic factors or that the animal is immunocompromised.
Treatment: Specifically
treat underlying skin disorders. Keratolytic shampoos containing
sulfur, salicylic acid, tar, or benzoyl peroxide are often used in
conjunction with an antifungal shampoo containing miconazole,
ketoconzole, or chlorhexidine (4%). Bathing every 2 - 3 days is often
helpful.
Medications:
Drugs and fluids: Antifungal
creams or lotions (miconazole, ketoconazole, or clotrimazoe) applied
once to twice daily may assist localized cases. Ketoconzole is
indicated in widespread or locally severe cases.
Contraindications: Imidazole
antifungal drugs have been associated with life-threatening cardiac
arrhythmias in man when administered concomitantly with certain
antihistamine. Ketaconazole is contraindicated during pregnancy.
Reference:
Scott DW, Miller WH,
Griffin CE. Muller and Kirk’s small animal dermatology. 5th ed.
Philadelphia: WB Saunders, 1995:351. Author: Jon D. Plant.
Tilley LP, Smith, FWK Jr.
5 Minute Veterinary Consult canine and feline. Baltimore: Lippincott
Williams & Wilkins, 1999
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