Pathology - Horses

Horses

Ulcerative Keratitis
Figure 1. Superficial punctate ulcerative fungal keratitis in the right eye of a 16-year-old Warmblood mare. Note the small corneal opacities and the miotic pupil.
Source: Andrew S.E. and Willis A.M. (2005) 'Diseases of the cornea and sclera', in Michau T.M. (ed.) Equine ophthalmology. Missouri: Elsevier Inc., pp. 157-251.

Figure 2. Superficial punctate ulcerative fungal keratitis after application of rose bengal stain in a 14-year-old Arabian gelding.
Source: Andrew S.E. and Willis A.M. (2005) 'Diseases of the cornea and sclera', in Michau T.M. (ed.) Equine ophthalmology. Missouri: Elsevier Inc., pp. 157-251.

Figure 3. Keratomalacia or corneal melting in the right eye of a 5-year-old Paso Fino stallion with sterile keratitis.
Source: Andrew S.E. and Willis A.M. (2005) 'Diseases of the cornea and sclera', in Michau T.M. (ed.) Equine ophthalmology. Missouri: Elsevier Inc., pp. 157-251.

  • Vision is a very important factor in horses and hence ulceration needs to be diagnosed accurately and treated aggressively to prevent permanent vision loss or the eye itself
  • Causes
    • Bacteria (e.g. beta haemolytic strep, staph spp)
    • Fungi (e.g. aspergillus, fusarium, curvularia, penicillium)
    • Bacteria and fungi activate endogenous protease in the cornea and this disrupts the balance between protease and antiprotease
  • Clinical signs 
    • Different types of ulcers developed:
      • Melting ulcer
      • Progressive deep stomal ulcer
      • Stomal abscess
      • Desemtocele
      • Corneal laceration
    • Ocular pain
    • Blepharospasm
    • Photophobia
    • Epiphora
    • Miosis
      • Serous to mucoid ocular discharge
      • Focal or diffuse corneal edema
      • Loss of corneal epithelium and stroma
      • Corneal vascularization- aqueous flare and hypopyon,
      • Keratomalacia or corneal melting
  • Treatment
    • Antibacterial reagent
      • Aminoglycosides- gentamycin
      • Fortified solution- cefazolin
      • Chloramphenicol
      • Fluroquinolones
    • Antifungal reagnet
      • Miconazole
      • Voriconazole
      • Silver sulfadiazine
      • Natamycin
    • Surgical options

Sarcoid
Figure 4. A nodular type B sarcoid (also involving the epidermis) on the lower eyelid of a 6-year-old Thoroughbred.
Source: McAuliffe S.B. (2013) Knottenbelt and Pascoe's color atlas of diseases and disorders of the horse, 2nd edn., Liverpool: Elsevier Ltd.

Figure 5. A verrucose sarcoid on the upper eyelid with thickened hyperkeratotic skin.
Source: McAuliffe S.B. (2013) Knottenbelt and Pascoe's color atlas of diseases and disorders of the horse, 2nd edn., Liverpool: Elsevier Ltd.

Figure 6. Focal subcutaneous nodular thickening under the lower eyelid in a yearling, representing a nodular type A sarcoid.
Source: McAuliffe S.B. (2013) Knottenbelt and Pascoe's color atlas of diseases and disorders of the horse, 2nd edn., Liverpool: Elsevier Ltd.

  • Present as solitary or multiple neoplasms of the eyelids and periocular regions of the horses
  • Horses less than 7 years old are most susceptible
  • Types
    • Hyperkeratotic fibropapilloma
    • Fibroblastck fibropapilloma (most aggressive form)
      • Mask the actual size of sarcoid
    • Mixed form
  • Cause
    • Retrovirus
    • Pipilloma virus
    • Flies transfer sarcoid cells to the open wound of another horse
  • Clinical signs
    • Lesions and tumors of the eyelids and periocular regions
      • Occult
      • Nodular
      • Verrucose
      • Fibroblastic
      • Mixed form
    • diagnosed by histologic examination
  • Treatment
    • Eyelid and periocular sarcoids
      • surgical debulking
      • immunotherapy with bacillus Calmette- Guerin (bCG) attenuated mycobacterium bovis cell wass
    • Intralesional chemotherapy with cisplatin or 5- fluorouracil cryotherapy
    • Intralesional radiotherapy
    • Hyperthermia
    • Radiation
    • Carbon dioxide laser excision
    • Homeopathic ointments
    • Caustic chemical lotions

 Reference
  1. Andrew S.E. and Willis A.M. (2005) 'Diseases of the cornea and sclera', in Michau T.M. (ed.) Equine ophthalmology. Missouri: Elsevier Inc., pp. 157-251.
  2. Brooks D.E. (2002) Equine ophthalmology, 1st edn., Verlag: Teton NewMedia.
  3. Brooks D. E., Andrew S. E., Biros D. J., Denis H. M., Cutler T. J., Strubbe D. T. and Gelatt K. N. (2000) 'Veterinary ophthalmology', Ulcerative keratitis caused by beta-hemolytic Streptococcus equi in 11 horses, 3(2-3), pp. 121–125.
  4. Bruce H.G., Cheryl L.C. and Robert L.P. (2004) Veterinary ophthalmology essentials, 1st edn., Philadelphia: Elsevier.
  5. McAuliffe S.B. (2013) Knottenbelt and Pascoe's color atlas of diseases and disorders of the horse, 2nd edn., Liverpool: Elsevier Ltd.
  6. Thomas P.A. (1994) 'Institute of Ophthalmology', Mycotic keratitis — an underestimated mycosis, 32(4), pp. 235-256.
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