Equine conjunctivitis

EQUINE EQUINE CONJUNCTIVITISCONJUNCTIVITIS

OPTOM FASLU MUHAMMEDOPTOM FASLU MUHAMMED

OutlineOutline

Anatomy/Physiology Anatomy/Physiology Clinical signsClinical signs Clinical and Clinical and

diagnostic diagnostic examinationexamination

OutlineOutline

EtiologiesEtiologies Diagnosis/treatment Diagnosis/treatment

of selected of selected etiologiesetiologies

Conjunctival Conjunctival Anatomy/PhysiologyAnatomy/Physiology

Composed of Composed of nonkeratinized, stratified nonkeratinized, stratified squamous epithelium and squamous epithelium and underlying substantia underlying substantia propriapropria

Capable of rapid and Capable of rapid and dramatic response to dramatic response to insultsinsults Richly supplied by blood Richly supplied by blood

vesselsvessels Loose arrangement of Loose arrangement of

conjunctival stromaconjunctival stroma Resident lymphoid tissueResident lymphoid tissue Specialized antigen-Specialized antigen-

presenting cells (M-cells)presenting cells (M-cells)

Conjunctival Conjunctival Anatomy/PhysiologyAnatomy/Physiology

Often secondarily involved Often secondarily involved in other intraocular, in other intraocular, extraocular, and systemic extraocular, and systemic diseasesdiseases Anatomical proximity and Anatomical proximity and

shared blood supply with shared blood supply with other ocular structuresother ocular structures

Extensive Extensive vascular/lymphoid tissuevascular/lymphoid tissue

Relatively accessible and Relatively accessible and observableobservable

Conjunctivitis Clinical Conjunctivitis Clinical SignsSigns

Conjunctivitis associated Conjunctivitis associated with some combination of with some combination of the following clinical the following clinical signs:signs: Ocular discharge:Ocular discharge:

epiphora, mucoid, or epiphora, mucoid, or mucopurulentmucopurulent

Chemosis:Chemosis: edema edema resulting from increased resulting from increased permeability of permeability of conjunctival vessels with conjunctival vessels with fluid extravasationfluid extravasation

Hyperemia:Hyperemia: red red discoloration from discoloration from conjunctival vessel conjunctival vessel vasodilatationvasodilatation

Ocular discomfort:Ocular discomfort: blepharospasm, rubbingblepharospasm, rubbing

Conjunctivitis Clinical Conjunctivitis Clinical SignsSigns

Conjunctivitis Conjunctivitis associated with some associated with some combination of the combination of the following clinical signs:following clinical signs: Tissue proliferation:Tissue proliferation:

lymphatic, epithelial lymphatic, epithelial hyperplasia, or hyperplasia, or keratinizationkeratinization

Ulceration:Ulceration: any severe any severe conjunctivitis or those conjunctivitis or those associated with associated with particular etiologies particular etiologies (viral, chemical, (viral, chemical, trauma)trauma)

Pigmentation Pigmentation or or depigmentationdepigmentation

Conjunctivitis Conjunctivitis ExaminationExamination

Physical Physical examination examination To rule-out primary To rule-out primary

or concurrent or concurrent systemic diseasessystemic diseases


Complete ophthalmic Complete ophthalmic examination:examination: Focal light source and Focal light source and

magnificationmagnification Adnexa, extraocular, Adnexa, extraocular,

and intraocular and intraocular structuresstructures

Including Schirmer Including Schirmer tear tests, fluorescein tear tests, fluorescein stain, tonometrystain, tonometry

Examine behind Examine behind nictitans membranenictitans membrane


Conjunctivitis diagnostics:Conjunctivitis diagnostics: Conjunctival cytologyConjunctival cytology

Scrapings, swabs, aspirates Scrapings, swabs, aspirates often helpful in diagnosisoften helpful in diagnosis

Microbiologic diagnosticsMicrobiologic diagnostics Cultures, PCR, IFA, etc… as Cultures, PCR, IFA, etc… as

indicated for select cases indicated for select cases where infectious etiology where infectious etiology suspectedsuspected

Biopsy/histopathologyBiopsy/histopathology For conjunctivitis that is For conjunctivitis that is

severe, chronic, severe, chronic, unresponsive to treatment, unresponsive to treatment, or associated with mass or associated with mass formationformation

Conjunctivitis EtiologiesConjunctivitis Etiologies Inflammation of Inflammation of

the conjunctiva is a the conjunctiva is a common condition common condition and may be a:and may be a: Primary or Primary or

secondary disease secondary disease processprocess

Result of ocular or Result of ocular or systemic diseasesystemic disease

Conjunctivitis EtiologiesConjunctivitis Etiologies The conjunctiva The conjunctiva

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

Conjunctivitis EtiologiesConjunctivitis Etiologies Secondary conjunctivitis Secondary conjunctivitis

more common than more common than primary in the horseprimary in the horse

Secondary conjunctivitis Secondary conjunctivitis typically occurs as a typically occurs as a result of adjacent ocular result of adjacent ocular inflammation or systemic inflammation or systemic disease: disease: Intraocular disease: Intraocular disease:

uveitis, glaucomauveitis, glaucoma Extraocular disease: Extraocular disease:

corneal ulcers or corneal ulcers or abscesses, blepharitisabscesses, blepharitis

Systemic disease: Systemic disease: infectious, neoplastic, infectious, neoplastic, immune-mediatedimmune-mediated

Conjunctivitis EtiologiesConjunctivitis Etiologies The diagnosis and The diagnosis and

treatment of treatment of secondary secondary conjunctivitis should conjunctivitis should be directed toward be directed toward the underlying ocular the underlying ocular or systemic conditionor systemic condition

Secondary ConjunctivitisSecondary Conjunctivitis

Conjunctivits secondary to Conjunctivits secondary to a corneal ulcera corneal ulcer

Conjunctivits secondary to Conjunctivits secondary to anterior uveitisanterior uveitis

Primary Conjunctivitis Primary Conjunctivitis EtiologiesEtiologies

Idiopathic, immune-mediated: Idiopathic, immune-mediated: eosinophilic, lymphocyticeosinophilic, lymphocytic

AllergicAllergic InfectiousInfectious

Bacterial: Bacterial: Streptococcus equiStreptococcus equi, , Moraxella equiMoraxella equi, , ChlamydiaChlamydia, , etc…etc…

Fungal: Fungal: AspergillusAspergillus, , RhinosporidiumRhinosporidium, , Histoplasmosis, Histoplasmosis, Blastomycosis, Cryptococcus, Blastomycosis, Cryptococcus, etc…etc…

Viral: Equine herpesvirus 2 Viral: Equine herpesvirus 2 and 5and 5

Parasitic: Onchocerciasis, Parasitic: Onchocerciasis, Habronemiasis, Habronemiasis, Thelazia Thelazia lacrimalislacrimalis, Trypanosomiasis, Trypanosomiasis

Toxic/Chemical: Toxic/Chemical: Stachybotryotoxicosis, alkali/acid Stachybotryotoxicosis, alkali/acid burnburn

Primary Conjunctivitis Primary Conjunctivitis EtiologiesEtiologies

Trauma: blunt or Trauma: blunt or penetratingpenetrating

Frictional irritants: Frictional irritants: entropion, ectopic cilia, entropion, ectopic cilia, distichia, foreign bodiesdistichia, foreign bodies

Keratoconjunctivitis siccaKeratoconjunctivitis sicca Exposure: facial nerve Exposure: facial nerve

dysfunction, dysfunction, lagophthalmoslagophthalmos

ActinicActinic NeoplasticNeoplastic

Eosinophilic Eosinophilic ConjunctivitisConjunctivitis

Idiopathic infiltration of Idiopathic infiltration of conjunctiva with eosinophilsconjunctiva with eosinophils

May be present with or May be present with or without corneal lesionswithout corneal lesions

Diagnosis: eosinophils on Diagnosis: eosinophils on cytology or histopathology cytology or histopathology without parasites presentwithout parasites present


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


Conjunctival biopsy from a horse with Conjunctival biopsy from a horse with eosinophilic keratoconjunctivitis displaying eosinophilic keratoconjunctivitis displaying

numerous eosinophilsnumerous eosinophils

Lymphocytic Lymphocytic ConjuctivitisConjuctivitis

Lobulated or smooth, Lobulated or smooth, pink conjunctival massespink conjunctival masses Composed of Composed of

lymphocytes and lymphocytes and macrophagesmacrophages

Most common Most common locations: dorsal bulbar locations: dorsal bulbar conjunctiva and third conjunctiva and third eyelideyelid


Diagnosis: lymphocytic Diagnosis: lymphocytic aggregates on aggregates on cytology/histopathologycytology/histopathology

Treatment: topical or Treatment: topical or intralesional intralesional corticosteroids, topical corticosteroids, topical cyclosporine, or cyclosporine, or surgical excisionsurgical excision


Conjunctival biopsy from a horse with lymphocytic conjunctivitis Conjunctival biopsy from a horse with lymphocytic conjunctivitis displaying numerous lymphocytes and occasional plasma cellsdisplaying numerous lymphocytes and occasional plasma cells

Bacterial and Fungal Bacterial and Fungal ConjunctivitisConjunctivitis

Bacterial and fungal Bacterial and fungal conjunctivitis conjunctivitis usually secondary usually secondary infections infections

Diagnosis based Diagnosis based upon cytology and upon cytology and culture findingsculture findings Fungal conjunctivitis secondaryFungal conjunctivitis secondary

to keratomycosisto keratomycosis

Bacterial and Fungal Bacterial and Fungal ConjunctivitisConjunctivitis

Treatment: identify Treatment: identify and treat and treat underlying cause underlying cause along with the along with the opportunistic opportunistic infectioninfection

Fungal conjunctivitis secondaryFungal conjunctivitis secondaryto keratomycosisto keratomycosis

Viral ConjunctivitisViral Conjunctivitis Equine herpesvirus Equine herpesvirus

2 and 5 may cause 2 and 5 may cause primary primary conjunctivitis in conjunctivitis in the horsethe horse Diagnosis: virus Diagnosis: virus

isolation, PCR, IFAisolation, PCR, IFA Treatment: topical Treatment: topical

idoxuridine, idoxuridine, trifluridine, or trifluridine, or interferoninterferon

Viral ConjunctivitisViral ConjunctivitisEquine viral arteritis, Equine viral arteritis,

equine adenovirus, equine adenovirus, equine infectious equine infectious anemia, equine anemia, equine influenza, and influenza, and African horse African horse sickness often sickness often cause mild cause mild conjunctivitis conjunctivitis associated with associated with systemic diseasesystemic disease

Parasitic ConjunctivitisParasitic Conjunctivitis Parasitic conjunctivitis Parasitic conjunctivitis

most commonly most commonly occurs with occurs with Onchocerca cervicalisOnchocerca cervicalis:: Insect vectors: Insect vectors:

Culicoides Culicoides spp. spp. Larvae migration Larvae migration

incites inflammationincites inflammation

Lesions: Lesions: temporolimbal temporolimbal conjunctival conjunctival thickening, nodules, thickening, nodules, and depigmentation and depigmentation +/- keratitis+/- keratitis

Parasitic ConjunctivitisParasitic Conjunctivitis Diagnosis: Diagnosis: conjunctival biopsy or conjunctival biopsy or cytology (microfilaria, cytology (microfilaria, eosinophils, eosinophils, lymphocytes)lymphocytes) Treatment: systemic Treatment: systemic

ivermectin and topical ivermectin and topical corticosteroidscorticosteroids

Parasitic ConjunctivitisParasitic Conjunctivitis

OnchocercaOnchocerca limbal conjunctival limbal conjunctival nodulesnodules

in a horsein a horse

Cytology of conjunctival Cytology of conjunctival nodules with nodules with

eosinophils and eosinophils and OnchocercaOnchocerca microfilaramicrofilara

Parasitic ConjunctivitisParasitic Conjunctivitis Habronemiasis may also cause Habronemiasis may also cause

conjunctivitisconjunctivitis HabronemaHabronema and and DraschiaDraschia

spp. (equine gastric worms) spp. (equine gastric worms) Larvae deposited on Larvae deposited on

conjunctiva by flies, conjunctiva by flies, migration incites intense migration incites intense granulomatous or eosinophilc granulomatous or eosinophilc inflammationinflammation

Lesions: proliferative nodules, Lesions: proliferative nodules, granulation tissue appearance, granulation tissue appearance, may be ulcerative, may have may be ulcerative, may have yellow-white exudates (“sulfur yellow-white exudates (“sulfur granules”)granules”) Occur on conjunctiva, Occur on conjunctiva,

nictitans, and periocular nictitans, and periocular skin; most commonly skin; most commonly adjacent to medial canthus adjacent to medial canthus (where flies feed)(where flies feed)


Diagnosis: seasonal, Diagnosis: seasonal, clinical appearance, clinical appearance, cytology/histopathcytology/histopath

Treatment: systemic Treatment: systemic ivermectin, ivermectin, topical/intralesional/systetopical/intralesional/systemic corticosteroids, mic corticosteroids, surgical debulking for surgical debulking for large masseslarge masses


Habronemiasis “sulfur granules” Habronemiasis “sulfur granules” at medial canthus in a horseat medial canthus in a horse

HabronemaHabronema conjunctival nodule conjunctival nodule and blepharitis in a horseand blepharitis in a horse

Parasitic ConjunctivitisParasitic Conjunctivitis Thelazia lacrimalisThelazia lacrimalis

Nematode inhabiting Nematode inhabiting conjunctival fornices and conjunctival fornices and nasolacrimal ductnasolacrimal duct

Diagnosis: identification Diagnosis: identification of parasites during of parasites during clinical examinationclinical examination

Parasitic ConjunctivitisParasitic Conjunctivitis Treatment: Treatment:

Manual removal of Manual removal of parasites with lavage, parasites with lavage, swabs, or forcepsswabs, or forceps

Systemic ivermectin or Systemic ivermectin or topical levamisoletopical levamisole

Traumatic ConjunctivitisTraumatic Conjunctivitis May occur from blunt or May occur from blunt or

penetrating injuriespenetrating injuries

Often dramatic chemosis Often dramatic chemosis initiallyinitially May be associated with May be associated with

subconjunctival subconjunctival hemorrhages or hemorrhages or emphysemaemphysema

Diagnostics: exclude other Diagnostics: exclude other ocular injuries and foreign ocular injuries and foreign bodiesbodies May be difficult on May be difficult on

initial presentationinitial presentation

Traumatic ConjunctivitisTraumatic Conjunctivitis TreatmentTreatment

Most Most lacerations/punctures do lacerations/punctures do not require sutures as not require sutures as the conjunctiva heals the conjunctiva heals spontaneously and spontaneously and rapidlyrapidly

Cold compresses acutely Cold compresses acutely may decrease clinical may decrease clinical signssigns

Topical antibiotics until Topical antibiotics until resolvedresolved

Systemic antibiotics if Systemic antibiotics if penetrating or full-penetrating or full-thickness woundsthickness wounds

Consider systemic Consider systemic nonsteroidal anti-nonsteroidal anti-inflammatoriesinflammatories

Traumatic ConjunctivitisTraumatic Conjunctivitis

Traumatic conjunctivitis with Traumatic conjunctivitis with subconjunctival hemorrahgesubconjunctival hemorrahge

Traumatic conjunctivitis with Traumatic conjunctivitis with conjunctival emphysemaconjunctival emphysema

Actinic ConjunctivitisActinic Conjunctivitis Occurs following Occurs following

chronic UV-light chronic UV-light exoposureexoposure

Diagnosis: ulcerative Diagnosis: ulcerative conjunctivitis adjacent conjunctivitis adjacent to lid margins, to lid margins, develops in areas of develops in areas of conjunctiva that are conjunctiva that are not pigmentednot pigmented

Actinic ConjunctivitisActinic Conjunctivitis Precursor to Precursor to

squamous cell squamous cell carcinomacarcinoma

Treatment: shade Treatment: shade (fly mask, stabling), (fly mask, stabling), monitor for monitor for neoplasia neoplasia developmentdevelopment

Conjunctival NeoplasiaConjunctival Neoplasia Conjunctival neoplasia Conjunctival neoplasia

may masquerade as may masquerade as conjunctivitis initiallyconjunctivitis initially

Most common types: Most common types: squamous cell squamous cell carcinoma, lymphoma, carcinoma, lymphoma, hemangioma, hemangioma, hemangiosarcoma, hemangiosarcoma, papilloma, and papilloma, and melanomamelanoma

Diagnosis based upon Diagnosis based upon excisional/incisional excisional/incisional biopsy, scrapings, or biopsy, scrapings, or aspiratesaspirates

Conjunctival NeoplasiaConjunctival Neoplasia Treatment: Treatment:

Surgical excision Surgical excision (always treatment of (always treatment of choice when complete choice when complete excision possible)excision possible)

Ancillary therapies Ancillary therapies often indicated based often indicated based upon tumor type, upon tumor type, location, extent:location, extent:

Diode laser ablation, Diode laser ablation, cryotherapy, radiation, cryotherapy, radiation, chemotherapychemotherapy

Conjunctival NeoplasiaConjunctival Neoplasia

Conjunctival squamous cell carcinoma Conjunctival lymphoma

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Equine conjunctivitis