Canis ISSN: 2398-2942

Microsporum canis

Synonym(s): M. canis

Contributor(s): Rosanna Marsella, David Scarff

Introduction

Classification

Taxonomy

  • Genus: Microsporum.
  • Perfect state: Ascomycetes.

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Clinical Effects

Epidemiology

Habitat

  • Dermatophytes may be geophilic (soil reservoir), zoophilic (animal reservoir) or anthropophilic (human reservoir).
  • M. canis is zoophilic.

Lifecycle

  • Non-parasitic state (including culture).
  • Septate branching hyphae (the mycelium) are produced.
  • Asexual reproductive units (macro- and micro-conidia) are found in the aerial mycelium.
  • Sexual spores (ascospores) are produced.

Parasitic state

  • Hyphae and arthroconidia (also asexual reproductive units) seen.

Transmission

  • Most commonly direct contact; also fomites.
  • Source most commonly an infected cat.

Pathological effects

  • Dermatophytes are able to hydrolyse keratin and cause some damage to the epidermis and hair follicle. A cell-mediated hypersensitivity reaction is then mounted and the fungus moves away from the site of inflammation to normal skin. This causes the classic ringworm circular lesion with healing at the center and inflammation at the edge.
  • Lesions may occur anywhere on the body.
  • In the cat: often subclinical in adults, generally non-inflammatory except in young kittens. May become generalized in debilitated kittens.
  • In the dog: typically non-inflammatory scaly patches with alopecia. May be kerion when hair follicles rupture.

Other Host Effects

  • Can cause subclinical or inapparent infection in the host animal; it may cause persistent sub-clinical infection in long-haired cats.

Control

Control via chemotherapies

  • Topical: enilconazole Enilconazole , clotrimazole Clotrimazole , tolnaftate, natamycin Natamycin , ketoconazole Ketoconazole although these are not licensed for this use in the dog. Lime sulfur (Lym dip) is a very effective topical.
  • Oral: griseofulvin Griseofulvin + ketonazole (Nizoral tablets), itraconazole (Spornox capsules) or fluconazole (Diflucan tablets).

Control via environment

  • In infected cat colonies, in-contact cats should also be treated.

Vaccination

  • It does prevent development of lesions after challenge.

Other countermeasures

  • Hair should be clipped from affected areas.

Diagnosis

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Further Reading

Publications

Refereed papers

  • Recent references from VetMedResource and PubMed.
  • Morielio K A & DeBoer D J (1995) Feline dermatophytosis - recent advances and recommendations for therapy. Vet Clin North Am Small Anim Pract 25(4), 901-921.
  • Pinter L, Ellis H J, Ciclitira P J & Noble W C (1995) Production and use of monoclonal antibodies to Microsporum canis. Vet Microbiol 46(4), 435-44.
  • White-Weithers N & Medleau L (1995) Evaluation of topical therapies for the treatment of dermatophyte-infected hairs from dogs and cats. JAAHA 31(3), 250-3.
  • Sparkes A H et al (1993) Epidemiological and diagnostic features of canine and feline dermatophytosis in the United Kingdom from 1956 to 1991. Vet Rec 133(3), 57-61.

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