Equis ISSN 2398-2977

Foot: white line disease

Synonym(s): Candida, onchomycosis, hoof rot, dew poisoning, yeast infection

Contributor(s): Steve Adair, Graham Munroe

Introduction

  • Cause: unknown, but possible factors include environment, nutrition, mechanics, infection.
  • Signs: progressive hoof wall separation, lameness.
  • Diagnosis: clinical signs, radiography.
  • Treatment: debridement of all affected tissue, stabilize remaining hoof wall, prevent further infection.
  • Prognosis: guarded to good.

Pathogenesis

Etiology

  • Unknown but certainly multifactorial.
  • Excessive mechanical stresses on weakened stratum medium/lamellar junction leading to separation and defects in the hoof wall.
  • Bacterial, fungal or yeast infection secondary to other predisposing factors that lead to the hoof separation or a defect initially.
  • Protease-producing fungi such asPseudoallsheria,ScopulariopsisandScedosporiumin combination with bacteria have been implicated, but cultures are often mixed and non-specific.

Predisposing factors

General
  • Unhygienic environmental conditions.
  • Hot and wet environments can lead to softening of the horn and easier entry of material into cavities.
  • Hot, dry conditions may encourage cracks and separations.
  • Improper trimming and shoeing   Farriery: incorrect shoeing  ; excessive toe length, long toe-low heel, club feet and sheared heels   Foot: heel - sheared   increase mechanical stresses placed on the hoof wall leading to separation.
  • Nutritional deficiencies   Hoof: biotin deficiency 02    Foot: vitamin A deficiency  .
  • Vascular damage to dermal lamellae associated with chronic laminitis   Foot: laminitis  may lead to increased separation at the sole/wall junction   Hoof: separation - laminitis  .

Pathophysiology

  • Keratinolytic process that originates on the solar surface.
  • Progressive separation in non-pigmented horn at the junction between the stratum medium and internum which may involve variable amounts of the toe, quarters and/or heel    →   lameness and rotation of pedal bone in severe cases.
  • Etiology not fully understood; genetic, environmental, nutritional, mechanical and infectious cases implicated.
  • Environmental:
    • Excessive moisture.
    • High heat and humidity.
    • Environmental contamination with soil and/or urine/feces.
  • Nutritional deficiencies or imbalances:
    • Vitamins, especially biotin   Hoof: biotin deficiency 02    Foot: vitamin A deficiency  .
    • Proteins; lysine and methionine.
    • Trace elements; copper, zinc and selenium.
  • Mechanical:
    • Damage to stratum medium/lamellar junction weakens the integrity of hoof wall. Preexisting conditions such as laminitis   Foot: laminitis  result in hypertrophy of epidermal tissues and mild fissure formation in hoof wall and white line.
    • Excessive length of toe due to foot conformation   Musculoskeletal: conformation  and/or foot trimming problems.
  • Infection:
    • Invasion of the horse by opportunistic bacteria, fungi or yeasts leading to digestion of horn and separation extending proximally.

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 PubMed and VetMedResource.
  • O'Grady S E (2011) A fresh look at white line disease. Equine Vet Educ 23 (10), 517-522 VetMedResource.
  • Kempson S A & Robb R (2004) Use of topical disinfectant as part of a hoof care programme for horses with diseases of the hoof capsule. Vet Rec 154 (21), 647-652 PubMed.
  • O'Grady S E (2002) White line disease - an update. Equine Vet Educ 14 (1), 51-55 VetMedResource
  • Keller M et al (2000) Keratinopathogenic mould fungi and dermatophytes in healthy and diseased hooves of horses. Vet Rec 147, 619-622 PubMed.
  • Higami A (1999) Occurrence of white line disease in performance horses fed on low-zinc and low-copper diets. J Equine Sci 10 (1), 1-5 VetMedResource.
  • Kuwano A et al (1999) A survey of white line disease in Japanese racehorses. Equine Vet J 31 (6), 515-518 PubMed.
  • Kuwano A et al (1998) Ochomycosis in white line disease in horses - pathology, mycology and clinical features. Equine Vet J Suppl 26, 27-35 PubMed.
  • O'Grady S E (1997) White Line Disease. J Equine Vet Sci 17(5), 236-37 VetMedResource.
  • Turner T A (1997) White Line Disease. Equine Vet Educ (6), 313-16 VetMedResource.
  • Redden R F (1990) White Line Disease. Equine Pract 12 (6), 14-18 VetMedResource.

Other sources of information

  • Turner T A & Anderson B H (1996) Use of antibiotic-impregnated hoof repair material for the treatment of hoof wall separation. A promising new treatment. In: Proc AAEP Congress 42. pp 205-207.


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