Canis ISSN: 2398-2942

Skin: dermatophytosis

Synonym(s): Ringworm

Contributor(s): Susan Dawson, Rosanna Marsella, David Scarff, David Godfrey

Introduction

  • Cause: infection with Microsporum spp Microsporum canis and Trichophyton spp Trichophyton spp most common.
  • Direct and indirect transmission.
  • Common zoonosis.
  • Signs: clinical signs depend on degree of host adaptation and immunocompetence.
  • Diagnosis: clinical signs, Wood's lamp examination, fungal culture, PCR, microscopy.
  • Treatment: responds to treatment with antifungal agents.
  • Prognosis: often self-limiting.
    Print off the owner factsheet on Ringworm Ringworm to give to your client.

Pathogenesis

Predisposing factors

General

  • Immunosuppression.
  • Genetic factor in small terriers.
  • Certain behaviors, eg interactions with wildlife increase the risk of infection with Trichophyton spp dermatophytes.

Pathophysiology

  • Transmitted by contact with infected hair and scale, fungal elements in environment or on fomites.
    • M. canis: source is usually infected cat.
    • T. mentagrophytes: source is rodents or their environment.
    • T. erinacei: source is hedgehog.
    • M. persicolor: source is vole.
    • M. gypseum: inhabits rich soil; exposure occurs during digging and rooting in contaminated areas.
  • Mechanical disruption of stratum corneum facilitates infection.
  • Fungal hyphae invade hair shaft and migrate downwards, and require actively growing hair to survive.
  • Host immune response determines clinical signs; often self-limiting in healthy dogs.
  • In M. persicolor infection stratum corneum only is infected.
  • Fungal growth in hair → keratinolytic enzymes → penetration of cuticle and hair shaft.
  • At keratogenous zone, fungus either reaches equilibrium with keratin production or is expelled.
  • When hair enters telogen phase or inflammatory response mounted → spontaneous resolution.
  • Toxins produced in stratum corneum → cutaneous inflammation.
  • Deeper penetration of keratin suface of epidermis → furunculosis → scarring.

Diagnosis

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Treatment

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Prevention

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Outcomes

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Further Reading

Publications

Refereed papers

  • Recent references from VetMed Resource and PubMed.
  • Moriello K A, Coyner K, Paterson S, Mignon B (2017) Diagnosis and treatment of dermatophytosis in dogs and cats: Clinical Consensus Guidelines of the World Association for Veterinary Dermatology. Vet Dermatol 28 266-e68 PubMed.
  • Garg J, Tilak R, Garg A, Prakash P, Gulati A K, Nath G (2009) Rapid detection of dermatophytes from skin and hair. BMC Res Notes 2, 60 PubMed.
  • Jackson H (1999) Common cutaneous diseases of the canine foot. In Practice 21, 54-61.
  • DeBoer D J et al (1995) Inability of two topical treatments to influence the course of experimentally induced dermatophytosis in cats. JAVMA 207 (1), 52-57.
  • Sparkes A H, Gruffydd-Jones T J, Shaw S W, Wright A I & Stokes C R (1993) Epidemiological and diagnostic features of canine and feline dermatophytosis in the UK (1956-1991). Vet Rec 133, 57-61.
  • Medleau L & Chalmers S A (1992) Resolution of generalized dermatophytosis without treatment in dogs. JAVMA 201,1891-1892.

Other sources of information

  • Leutenegger C (2017) Validation of a qPCR Panel to aid in the diagnosis of dermatophytosis. Abstract presented at: European College of Veterinary Internal Medicine; September 14–16, 2017; St. Julian, Malta.
  • Foil C S (1990) Dermatophytosis. In: Infectious disease of the dog and cat. Ed C E Greene. W B Saunders, Philadelphia. pp 659-668.
  • Foil C S (1986) Antifungal agents in dermatology. In: Current Veterinary Therapy IX. Ed R W Kirk. W B Saunders, Philadelphia. pp 560-565.


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