Lapis ISSN 2398-2969

Trichophyton spp

Contributor(s): Vetstream Ltd, Will Easson, Anna Meredith, Sarah Pellett

Introduction

Classification

Taxonomy

  • Phylum: Ascomycota.
  • Class: Eurotiomycetes.
  • Family: Arthrodermataceae.
  • Genus: Trichophyton.
  • The Arthrodermataceae are a family of fungi compromising three genera of dermatophytes; Epidermophyton, Microsporum and Trichphyton.

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Clinical Effects

Epidemiology

Habitat

  • Main reservoir hosts of Trichophyton species include dogs, horses, cattle, cats, pigs, monkeys and poultry.

Lifecycle

  • Reproduces both sexually (via ascospores, found only in the non-parasitic phase) and asexually.
  • Asexual reproduction occurs in the non-parasitic phase via microconidia and occasionally macroconidia.
  • Asexual reproduction occurs during the parasitic phase via arthroconidia.

Transmission

  • Most commonly direct contact; also, fomites.
  • Poor management such as overcrowding, unhygienic conditions, suboptimal nutrition and poor ventilation.
  • Source of rabbit infection from exposure to other infected animals, such as cats, dogs and other rabbits.
  • In other species immunocompromising conditions or diseases may predispose to infection and this may also occur in the rabbit.
  • Rabbits can be asymptomatic carriers.

Pathological effects

  • Dermatophytes are able to hydrolyze keratin and cause some damage to the epidermis and hair follicle.
  • A hypersensitivity reaction is then mounted, and the fungus moves away from the site of inflammation to normal skin.
  • This causes the classic circular ringworm lesion with healing at the center and inflammation at the edge.
  • Site of lesions generally around the face, head and feet but can occur anywhere on the body.
  • Lesions often begin as dry scaly skin and alopecia.
  • Pruritis is variable.
  • In more severe cases scaling, crusts and erythema may be observed.

Other Host Effects

  • Some species have become adapted for survival in the skin of specific host species, ie they are zoophilic, eg T. erinacei (European hedgehogs), T. mentagrophytes (rodents), T. verrucosum (cattle).
  • Zoonotic potential.

Control

Control via animal

  • Isolate affected and all in-contact animals due to the infective and zoonotic nature of dermatophytosis.

Control via chemotherapies

  • Topical: clotrimazole Clotrimazole, and miconazole Miconazole have been reported as a topical application for localized dermatophytosis.
  • Topical: enilconazole Enilconazole has been reported to be applied topically, diluted 1:50 water and applied to lesions every 1-3 days for 3-4 applications.
  • Oral: itraconazole at 5 mg/kg administered orally for 6-8 weeks or until there has been two negative cultures, Adverse effects include hepatotoxicity. Blood work to monitor hepatic enzymes is advised during treatment.
  • Oral: griseofulvin Griseofulvin has been reported at 25 mg/kg to be administered orally every 24 h for 4-6 weeks or until there are two negative cultures. Adverse effects include possible bone marrow suppression as reported in dogs and cats, potential neurological side effects as reported in dogs and cats, and this is contraindicated in pregnant animals as it is teratogenic.
  • Oral: terbinafine at 10 mg/kg has been administered every 24 h via the oral route and has been used successfully in other species.
  • Treatment should continue until there are two negative cultures, four weeks apart.

Control via environment

  • In infected colonies, in-contact animals should also be treated.
  • Environmental treatment essential:
    • Bleach diluted 1:10 has been reported.
    • Wear gloves when cleaning the environment.
  • Discard wooden cages, hides and toys as they cannot be disinfected thoroughly.

Other countermeasures

  • Clip hair from affected site (wear gloves and thoroughly disinfect the clipper blades).

Diagnosis

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Further Reading

Publications

Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Donnelly T M, Rush E M & Lackner P A (2000) Ringworm in small exotic pets. J Exotic Pet Med (2), 82-93.
  • Parker W M & Yager J A (1997) Trichophyton dermatophytosis - a disease easily confused with pemphigus erythematosus. Can Vet J 38 (8), 502-505 PubMed.

Other sources of information

  • Hess L & Tater K (2012) Rabbits: dermatological diseases. In: Ferrets, Rabbits and Rodents: Clinical Medicine and Surgery. 3rd edn. Eds: Quesenberry K E & Carpenter J W. Saunders/Elsevier, USA. pp 232-244.
  • Oglesbee B (2011) Ed. Dermatophytosis. In: Blackwell’s five-minute veterinary consult: small mammal. Wiley Blackwell. pp 386-387.

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