Equis ISSN 2398-2977

Dermatophilus spp

Contributor(s): Susan Dawson, Richard Walker, Beatrice Funiciello

Introduction

Classification

Taxonomy

  • Family: Actinomycetalaes.
  • Genus: Dermatophilus.
  • Species: congolensis.

Etymology

  • Gk: derma - skin; philein - to love.

Active Forms

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Clinical Effects

Epidemiology

Habitat

  • Infected animals, especially cattle, sheep, goats and horses.

Lifecycle

  • Filaments → motile zoospores → germination → septate hyphae → divides to release zoospores.

Transmission

  • Direct and indirect contact.
  • Some arthropod vectors.
  • Injury or wetting of skin creates portal of infection.

Pathological effects

  • Antibodies are produced but protection is not long-lasting and recurrences occur.
  • Cellular and humoral response thought to play a role in healing.
  • Mainly neutrophils, but also mononuclear cells and plasma cells are involved in local defense.
  • Predilection site of Dermatophilus is the living epidermis.
  • Infection depends on disruption of haircoat, sebaceous secretions and stratum corneum by soaking or trauma.
  • Zoospores move to deeper layers → germinate → hyphae and filaments spread through epidermis → colonize hair follicles.
  • Neutrophilic exudate forms under infected epidermis that becomes separated from the dermis.
  • Infected epidermis keratinizes → new epidermis forms under neutrophil layer → scab consisting of layers of neutrophilic exudate and infected keratinized epidermis.
  • Scabs easily lifted. Primary lesions painless or mildly painful and show no or mild pruritus.
  • In horses, wetting favors development of rain scald along the dorsum, and mud fever on the lower limbs Dermatophilosis.

Other Host Effects

  • Most infections result in clinical signs.
  • May live as a commensal on healthy animals.

Control

Control via animal

  • Avoid exposure to wet, or muddy fields.
  • Dry off thoroughly after exposure to heavy rain.
  • Protect areas of skin trauma.
  • Topical treatments with povidone-iodine Povidone-iodine shampoo or chlorhexidine Chlorhexidine solution.

Control via chemotherapies

Control via environment

  • In tropical areas, provide protection from arthropod vectors.

Vaccination

  • None available.

Diagnosis

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Further Reading

Publications

Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Frank L A, Kania S A & Weyant E (2016) RT-qPCR for the diagnosis of dermatophilosis in horses. Vet Derm 27 (5), 431-e112 PubMed.
  • Hiraizumi M & Tagawa Y (2014) Isolation and characterization of flagellar filament from zoospores of Dermatophilus congolensis. Vet Microbiol 173 (1-2), 141-146 PubMed.
  • Ambrose N C, Lloyd D & Maillard J-C (1999) Immune Responses to Dermatophilus congolensis Infections. Parasitol Today 15 (7), 295-300 PubMed.
  • Ambrose N C, Mijinyawa M S & Hermoso de Mendoza J (1998) Preliminary characterisation of extracellular serine proteases of Dermatophilus congolensis isolates from cattle, sheep and horses. Vet Microbiol 62 (4), 321-335 PubMed.
  • Ambrose N C, El Jack M A, McOrist S & Boid R (1997) Electrophoretic and antigenic characterisation of Dermatophilus congolensis extracellular products. Vet Microbiol 59 (1), 37-51 PubMed.
  • Masters A M, Ellis T M & Grein S B (1997) Dermatophilus congolensis: Strain differences in expression of phospholipase activities. Vet Microbiol 57 (2-3), 199-213 PubMed.
  • Ambrose N C (1996) The pathogenesis of dermatophilosis. Trop Anim Hlth Prod 28 (2), 29S-37S PubMed.
  • Ellis T M, Masters A M, Sutherland S S, Carson J M & Gregory A R (1993) Variation in cultural, morphological, biochemical properties and infectivity of Australian isolates of Dermatophilus congolensis. Vet Microbiol 38 (1-2), 81-102 PubMed.
  • Zaria L T (1993) Dermatophilus congolensis infection (dermatophilosis) in animals and man! An update. Comp Immun Microbiol Infect Dis 16 (3), 179-222 PubMed.
  • Evans A G (1992) Dermatophilosis - diagnostic approach to nonpruritic, crusting dermatitis in horses. Comp Cont Educ Pract Vet 14 (12), 1618 VetMedResource.
  • Gogolewski R P, Mackintosh J A, Wilson S C & Chin J C (1992) Immunodominant antigens of zoospores from ovine isolates of Dermatophilus congolensis. Vet Microbiol 32 (3-4), 305-318 PubMed.
  • Hänel H, Kalisch J, Keil M, Marsch W C & Buslau M (1991) Quantification of keratinolytic activity from Dermatophilus congolensis. Med Microbiol Immunol 180 (1), 45-51 PubMed.
  • Martinez D & Prior P (1991) Survival of Dermatophilus congolensis in tropical clay soil submitted to different water potentials. Vet Microbiol 19 (2), 135-145 PubMed.

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