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

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

Outline Etiologies Etiologies Diagnosis/treatment of selected etiologies Diagnosis/treatment of selected etiologies

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

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

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

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

Conjunctivitis Examination Physical examination Physical examination To rule-out primary or concurrent systemic diseases To rule-out primary or concurrent systemic diseases

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

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

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

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 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

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

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

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

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

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

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

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

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

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

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

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

Bacterial and Fungal Conjunctivitis Bacterial and fungal conjunctivitis usually secondary infections Bacterial and fungal conjunctivitis usually secondary infections Diagnosis based upon cytology and culture findings Diagnosis based upon cytology and culture findings Fungal conjunctivitis secondary to keratomycosis

Bacterial and Fungal Conjunctivitis Treatment: identify and treat underlying cause along with the opportunistic infection Treatment: identify and treat underlying cause along with the opportunistic infection Fungal conjunctivitis secondary to keratomycosis

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

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

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

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

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

Parasitic Conjunctivitis Habronemiasis may also cause conjunctivitis Habronemiasis may also cause conjunctivitis Habronema and Draschia spp. (equine gastric worms) Habronema and Draschia spp. (equine gastric worms) Larvae deposited on conjunctiva by flies, migration incites intense granulomatous or eosinophilc inflammation 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”) 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) Occur on conjunctiva, nictitans, and periocular skin; most commonly adjacent to medial canthus (where flies feed)

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

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

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

Parasitic Conjunctivitis Treatment: Treatment: Manual removal of parasites with lavage, swabs, or forceps Manual removal of parasites with lavage, swabs, or forceps Systemic ivermectin or topical levamisole Systemic ivermectin or topical levamisole

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

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

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

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

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

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

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

Conjunctival Neoplasia Conjunctival squamous cell carcinoma Conjunctival lymphoma

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