Equine Conjunctivitis

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Equine Conjunctivitis

• October 17, 2007
• Eric C. Ledbetter, DVM
• Diplomate American College of Veterinary
  Ophthalmologists
• Cornell University
• College of Veterinary Medicine
• Ithaca, New York, USA

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Outline

• Anatomy/Physiology
• Clinical signs
• Clinical and diagnostic examination

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Outline

• Etiologies
• Diagnosis/treatment of selected etiologies

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Conjunctival Anatomy/Physiology

• Composed of nonkeratinized, stratified squamous
  epithelium and underlying substantia propria
• Capable of rapid and dramatic response to insults
• Richly supplied by blood vessels
• Loose arrangement of conjunctival stroma
• Resident lymphoid tissue
• Specialized antigen-presenting cells (M-cells)

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Conjunctival Anatomy/Physiology

• Often secondarily involved in other intraocular,
  extraocular, and systemic diseases
• Anatomical proximity and shared blood supply with
  other ocular structures
• Extensive vascular/lymphoid tissue
• Relatively accessible and observable

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Conjunctivitis Clinical Signs

• Conjunctivitis associated with some combination
  of the following clinical signs
• Ocular discharge epiphora, mucoid, or
  mucopurulent
• Chemosis edema resulting from increased
  permeability of conjunctival vessels with fluid
  extravasation
• Hyperemia red discoloration from conjunctival
  vessel vasodilatation
• Ocular discomfort blepharospasm, rubbing

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Conjunctivitis Clinical Signs

• Conjunctivitis associated with some combination
  of the following clinical signs
• Tissue proliferation lymphatic, epithelial
  hyperplasia, or keratinization
• Ulceration any severe conjunctivitis or those
  associated with particular etiologies (viral,
  chemical, trauma)
• Pigmentation or depigmentation

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Conjunctivitis Examination

• Physical examination
• To rule-out primary or concurrent systemic
  diseases

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Conjunctivitis Examination

• Complete ophthalmic examination
• Focal light source and magnification
• Adnexa, extraocular, and intraocular structures
• Including Schirmer tear tests, fluorescein stain,
  tonometry
• Examine behind nictitans membrane

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Conjunctivitis Examination

• Conjunctivitis diagnostics
• Conjunctival cytology
• Scrapings, swabs, aspirates often helpful in
  diagnosis
• Microbiologic diagnostics
• Cultures, PCR, IFA, etc as indicated for select
  cases where infectious etiology suspected
• Biopsy/histopathology
• For conjunctivitis that is severe, chronic,
  unresponsive to treatment, or associated with
  mass formation

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Conjunctivitis Etiologies

• Inflammation of the conjunctiva is a common
  condition and may be a
• Primary or secondary disease process
• Result of ocular or systemic disease

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Conjunctivitis Etiologies

• The conjunctiva has limited mechanisms by which
  it can respond to insults, thus the etiology of
  conjunctivitis can usually not be determined from
  clinical signs alone

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Conjunctivitis Etiologies

• Secondary conjunctivitis more common than primary
  in the horse
• Secondary conjunctivitis typically occurs as a
  result of adjacent ocular inflammation or
  systemic disease
• Intraocular disease uveitis, glaucoma
• Extraocular disease corneal ulcers or abscesses,
  blepharitis
• Systemic disease infectious, neoplastic,
  immune-mediated

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Conjunctivitis Etiologies

• The diagnosis and treatment of secondary
  conjunctivitis should be directed toward the
  underlying ocular or systemic condition

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Secondary Conjunctivitis
Conjunctivits secondary to a corneal ulcer
Conjunctivits secondary to anterior uveitis
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Primary Conjunctivitis Etiologies

• Idiopathic, immune-mediated eosinophilic,
  lymphocytic
• Allergic
• Infectious
• Bacterial Streptococcus equi, Moraxella equi,
  Chlamydia, etc
• Fungal Aspergillus, Rhinosporidium,
  Histoplasmosis, Blastomycosis, Cryptococcus, etc
• Viral Equine herpesvirus 2 and 5
• Parasitic Onchocerciasis, Habronemiasis,
  Thelazia lacrimalis, Trypanosomiasis
• Toxic/Chemical Stachybotryotoxicosis,
  alkali/acid burn

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Primary Conjunctivitis Etiologies

• Trauma blunt or penetrating
• Frictional irritants entropion, ectopic cilia,
  distichia, foreign bodies
• Keratoconjunctivitis sicca
• Exposure facial nerve dysfunction, lagophthalmos
• Actinic
• Neoplastic

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Eosinophilic Conjunctivitis

• Idiopathic infiltration of conjunctiva with
  eosinophils
• May be present with or without corneal lesions
• Diagnosis eosinophils on cytology or
  histopathology without parasites present

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Eosinophilic Conjunctivitis

• Treatment
• Topical corticosteroids or cyclosporine tapered
  to least frequent effective dose
• Topical mast cell stabilizers (cromolyn,
  olopatadine, lodoxamide) may also be effective in
  some cases

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Eosinophilic Conjunctivitis
Conjunctival biopsy from a horse with
eosinophilic keratoconjunctivitis displaying
numerous eosinophils
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Lymphocytic Conjuctivitis

• Lobulated or smooth, pink conjunctival masses
• Composed of lymphocytes and macrophages
• Most common locations dorsal bulbar conjunctiva
  and third eyelid

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Lymphocytic Conjuctivitis

• Diagnosis lymphocytic aggregates on
  cytology/histopathology
• Treatment topical or intralesional
  corticosteroids, topical cyclosporine, or
  surgical excision

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Lymphocytic Conjuctivitis
Conjunctival biopsy from a horse with lymphocytic
conjunctivitis displaying numerous lymphocytes
and occasional plasma cells
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Bacterial and Fungal Conjunctivitis

• Bacterial and fungal conjunctivitis usually
  secondary infections
• Diagnosis based upon cytology and culture
  findings

Fungal conjunctivitis secondary to keratomycosis
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Bacterial and Fungal Conjunctivitis

• Treatment identify and treat underlying cause
  along with the opportunistic infection

Fungal conjunctivitis secondary to keratomycosis
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Viral Conjunctivitis

• Equine herpesvirus 2 and 5 may cause primary
  conjunctivitis in the horse
• Diagnosis virus isolation, PCR, IFA
• Treatment topical idoxuridine, trifluridine, or
  interferon

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Viral Conjunctivitis

• Equine viral arteritis, equine adenovirus, equine
  infectious anemia, equine influenza, and African
  horse sickness often cause mild conjunctivitis
  associated with systemic disease

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Parasitic Conjunctivitis

• Parasitic conjunctivitis most commonly occurs
  with Onchocerca cervicalis
• Insect vectors Culicoides spp.
• Larvae migration incites inflammation
• Lesions temporolimbal conjunctival thickening,
  nodules, and depigmentation /- keratitis

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Parasitic Conjunctivitis

• Diagnosis conjunctival biopsy or cytology
  (microfilaria, eosinophils, lymphocytes)
• Treatment systemic ivermectin and topical
  corticosteroids

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Parasitic Conjunctivitis
Onchocerca limbal conjunctival nodules in a horse
Cytology of conjunctival nodules with eosinophils
and Onchocerca microfilara
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Parasitic Conjunctivitis

• Habronemiasis may also cause conjunctivitis
• Habronema and Draschia spp. (equine gastric
  worms)
• Larvae deposited on conjunctiva by flies,
  migration incites intense granulomatous or
  eosinophilc inflammation
• Lesions proliferative nodules, granulation
  tissue appearance, may be ulcerative, may have
  yellow-white exudates (sulfur granules)
• Occur on conjunctiva, nictitans, and periocular
  skin most commonly adjacent to medial canthus
  (where flies feed)

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Parasitic Conjunctivitis

• Diagnosis seasonal, clinical appearance,
  cytology/histopath
• Treatment systemic ivermectin,
  topical/intralesional/systemic corticosteroids,
  surgical debulking for large masses

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Parasitic Conjunctivitis
Habronemiasis sulfur granules at medial
canthus in a horse
Habronema conjunctival nodule and blepharitis in
a horse
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Parasitic Conjunctivitis

• Thelazia lacrimalis
• Nematode inhabiting conjunctival fornices and
  nasolacrimal duct
• Diagnosis identification of parasites during
  clinical examination

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Parasitic Conjunctivitis

• Treatment
• Manual removal of parasites with lavage, swabs,
  or forceps
• Systemic ivermectin or topical levamisole

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Traumatic Conjunctivitis

• May occur from blunt or penetrating injuries
• Often dramatic chemosis initially
• May be associated with subconjunctival
  hemorrhages or emphysema
• Diagnostics exclude other ocular injuries and
  foreign bodies
• May be difficult on initial presentation

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Traumatic Conjunctivitis

• Treatment
• Most lacerations/punctures do not require sutures
  as the conjunctiva heals spontaneously and
  rapidly
• Cold compresses acutely may decrease clinical
  signs
• Topical antibiotics until resolved
• Systemic antibiotics if penetrating or
  full-thickness wounds
• Consider systemic nonsteroidal anti-inflammatories

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Traumatic Conjunctivitis
Traumatic conjunctivitis with subconjunctival
hemorrahge
Traumatic conjunctivitis with conjunctival
emphysema
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Actinic Conjunctivitis

• Occurs following chronic UV-light exoposure
• Diagnosis ulcerative conjunctivitis adjacent to
  lid margins, develops in areas of conjunctiva
  that are not pigmented

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Actinic Conjunctivitis

• Precursor to squamous cell carcinoma
• Treatment shade (fly mask, stabling), monitor
  for neoplasia development

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Conjunctival Neoplasia

• Conjunctival neoplasia may masquerade as
  conjunctivitis initially
• Most common types squamous cell carcinoma,
  lymphoma, hemangioma, hemangiosarcoma, papilloma,
  and melanoma
• Diagnosis based upon excisional/incisional
  biopsy, scrapings, or aspirates

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Conjunctival Neoplasia

• Treatment
• Surgical excision (always treatment of choice
  when complete excision possible)
• Ancillary therapies often indicated based upon
  tumor type, location, extent
• Diode laser ablation, cryotherapy, radiation,
  chemotherapy

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Conjunctival Neoplasia
Conjunctival squamous cell carcinoma
Conjunctival lymphoma
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Questions????