Equine Conjunctivitis

1. 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

2. Outline • Anatomy/Physiology • Clinical signs • Clinical and diagnostic examination

3. Outline • Etiologies • Diagnosis/treatment of selected etiologies

4. 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) Conjunctival Anatomy/Physiology

5. 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 Conjunctival Anatomy/Physiology

6. 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 Conjunctivitis Clinical Signs

7. 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 Conjunctivitis Clinical Signs

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

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

10. 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 Conjunctivitis Examination

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

12. 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

13. 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 Conjunctivitis Etiologies

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

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

16. 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 Primary Conjunctivitis Etiologies

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

18. 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

19. 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

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

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

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

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

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

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

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

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

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

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

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

31. 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) Parasitic Conjunctivitis

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

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

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

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

36. 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 Traumatic Conjunctivitis

37. 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 Traumatic Conjunctivitis

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

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

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

41. 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 Conjunctival Neoplasia

42. 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 Conjunctival Neoplasia

43. Conjunctival Neoplasia Conjunctival squamous cell carcinoma Conjunctival lymphoma

44. Questions????