Sensing & Seeing - Ocular Infections 2023 PDF

SENSING & SEEING Ocular Infections I & II Tessa LeCuyer [email protected] Infections of: Extraocular Tissues Eyelids = blepharitis Conjunctiva = conjunctivitis Cornea = keratitis Nasolacrimal system = dacryocystitis Intraocular Tissues Uvea = uveitis Iris & ciliary body = anterior uveitis Choroid = po...

SENSING & SEEING Ocular Infections I & II Tessa LeCuyer [email protected] Infections of: Extraocular Tissues Eyelids = blepharitis Conjunctiva = conjunctivitis Cornea = keratitis Nasolacrimal system = dacryocystitis Intraocular Tissues Uvea = uveitis Iris & ciliary body = anterior uveitis Choroid = posterior uveitis Retina = retinitis Optic nerve = optic neuritis Lecture Structure 1. Background Information ØWhat normally prevents eye infections? ØWhat factors might predispose to eye infection? ØHow do the pathogens get there? ØHow do the pathogens cause damage ØWhat causes the damage? ØWhat is your approach to diagnosis? 2. Specific ocular pathogens What Prevents Eye Infections? Are microorganisms normally found in the eye? Conjunctiva has low numbers of bacteria Normal flora & transient Mostly Gram + Fungi are transitory Cornea has VERY few bacteria Intraocular tissues are sterile What Prevents Infections? Which organisms can be found in the Eye? Conjunctival Sac Ø Predominantly Gram + Staphylococci Streptococci Corynebacterium Ø Occasional Gram – Neisseria Moraxella Ø Fungi Rare & transitory What stops them from spreading into the eye? Defense Mechanisms of the Eye 1. Normal Flora of the Conjunctiva ØPresent in low numbers üPrimarily gram positive bacteria e.g., Staphylococci, Streptococci, Cornynebacterium üFungi only there transitorily ØPlay an important role in colonization resistance (limit the ability of pathogens to attach & cause disease) Normal Flora play a major role in defense of the eye. Indiscriminate use of antibiotics may disrupt this defense mechanism. Defense Mechanisms 2. Tears and Blinking Ø“Rinse” the ocular surface ØContain antibacterial substances Øe.g., IgA, lysozyme, and lactoferrin So why do we get eye infections? Predisposing (Risk) Factors 1. Extraocular Infections: Ø Most extraocular infections are secondary Ø They need some breach in ocular defenses to allow disease to occur: ü Trauma Breaks in epithelial barrier of cornea, conjunctiva, ultraviolet radiation Ears, lip folds, mouth Keratoconjunctivitis sicca Local or systemic Viruses and bacteria; local or systemic infections ü ü ü ü Infections in adjacent structures Drying of the cornea Immunosuppression Co-infection with other agents Predisposing (Risk) Factors 2. Intraocular Infections Ø Most intraocular infections are secondary Ø Often ocular manifestations of systemic infections or disease ü Variable predisposing factors ü Depends on the infectious agents ü Immunosuppression (systemic) Ø Some intraocular infections result from direct inoculation ü Often secondary to trauma (can be hard to detect) Routes of Pathogen Entry 1. Extraocular Infections Ø Most common route of entry is direct inoculation ü Infection/overgrowth with existing normal flora in nearby sites e.g., S. pseudintermedius from the conjunctiva ü Inoculation of exogenous bacteria e.g., saprophytes such as P. aeruginosa ü Inoculation of viruses or recrudescence of existing infections e.g., Feline Herpes Virus-1 Routes of Pathogen Entry 2. Intraocular Infections ØA. Most common route is through systemic infections ü Eyes often target organs for systemic infections ü Access via uveal or vascular tracts ü Typically, infectious agents or immune complexes become established in the uvea v Typically chorioretinitis and anterior uveitis Routes of Pathogen Entry 2. Intraocular Infections Ø B. Direct inoculation (Local Injury) ü Less common ü Usually unilateral Cat claw injury How do eye pathogens cause damage? Mechanisms of Damage: 1. Adhere 2. Invade Tissues 3. Evade Host Defense Mechanisms 4. Cause Host Cell Damage Which Organisms Cause Eye Infections? Bacteria Bacteria All Species Dogs and Horses ü Staphylococcus & Streptococcus spp* ü Borrelia burgdorferi* ü Trueperella & Corynebacterium spp ü Leptospira* ü Pseudomonas aeruginosa** Cattle (sheep/goats) ü Coliforms (E. coli, Klebsiella, Proteus) ü Moraxella bovis** ü Chlamydia spp* ü Listeria monocytogenes Dogs ü Histophilus somni* ü Brucella canis ü Moraxella ovis ü Ehrlichia canis* ü Mycoplasma conjunctivae* ü Rickettsia rickettsia* ü Mycoplasma bovoculi Cats Rabbits ü Chlamydia felis* ü Pasteurella multocida* ü Mycoplasma felis* Birds ü Mycoplasma gallisepticum* Which Organisms Cause Eye Infections? Viruses Fungi Cats All Species ü Feline Herpesvirus-1** ü Feline Coronavirus/FIP* ü Feline Leukemia Virus ü Feline Immunodeficiency Virus ü Feline Panleukopenia Virus Dogs ü Canine Distemper Virus** ü Canine Adenovirus** ü Canine Herpesvirus-1 Horses ü Equine Herpesvirus-1 and -2 ü Equine Viral Arteritis Virus Cattle ü Bovine Herpesvirus-1 ü Bovine Viral Diarrhea Virus ü Malignant Catarrhal Fever* ü Aspergillus spp. ü Penicillium spp ü Fusarium spp ü Dermatophytes (e.g., Microsporum spp, Trichophyton spp ) Dogs ü Blastomyces dermatitidis* ü Histoplasma capsulatum* ü Prototheca spp Dogs and Cats ü Coccidioides immitis Cats ü Cryptococcus neoformans* Which Organisms Cause Eye Infections? Parasites Parasites All Species Horses ü Onchocerca spp ü Habronema spp ü Toxocara canis ü Thelazia spp. ü Demodex spp Rabbits Dogs ü Encephalitozoon cuniculi ü Neospora caninum ü Leishmania spp ü Angiostrongylus vasoroum Cats and Dogs ü Toxoplasma gondii* ü Dirofilaria immitis ü Cuterebra spp Diagnosis of Ocular Infections Ø Can be difficult! üOften a presumptive diagnosis is made based on history, signalment and clinical signs! üDefinitive diagnosis is made in heifer Crowded conditions Moraxella bovis - Transmission How do animals ACQUIRE Moraxella bovis? ØPrimarily via: ü Infected or carrier animals ü Flying Insects (mechanical transmission) not vectors How does M. bovis cause Disease? Two Factors are ESSENTIAL for M. bovis virulence 1. Fimbriae (Pili) ü Mediate attachment of bacteria but still need some eye damage to attach ü Basis for vaccine (“Piliguard +7”) 2. Hemolysin ü Toxic for corneal epithelial cells ü Damaged epithelial cells induce inflammatory cell infiltration Initiates damage to corneal epithelial cells What Disease does M. bovis Cause? Bovine Keratoconjunctivitis =“Pink Eye” ØRange of ocular signs: üConjunctivitis üEpiphora üHyperemia üProfuse lacrimation üPhotophobia üBlepharospasm üKeratitis üCorneal Ulcers What Disease does M. bovis Cause? Pink Eye in Cattle – Moraxella bovis Corneal Ulcer Ulcer with neovascularization What Disease does M. bovis Cause? Potential Sequelae: 1) Globe rupture 2) Secondarily infection à hypopyon Endophthalmitis with pus in anterior chamber (hypopyon) Severe corneal ulceration with possible rupture How do we Treat M. bovis? ØMay be self-limiting ØDark stall free of dust, etc üIs this really practical??? ØSubconjunctival (bulbar) antibiotics üPenicillin G üCeftiofur ØSystemic antibiotics üTetracyclines & Tulathromycin ØMedicated Eye patches Subconjunctival antibiotics How do we control M. bovis? ØAvoid predisposing factors ØIsolate affected animals ØDecrease stocking rates ØAdd shade, fly control etc ØVaccination Fungal Extraocular Infection Ø What are the extra-ocular infections caused by fungi? Periocular Infections (blepharitis) vDermatophytes (ringworm) e.g., Microsporum canis Surface Ocular Infections vPredominantly fungal keratitis vMostly caused by free-living fungi that are transitorily on the conjunctiva e.g., Fusarium, Penicillium, Aspergillus etc. vMore common in horses and production animals Fungal Extraocular Infection Fungal Keratitis: ü Transmission: inoculation of organisms into traumatized corneal epithelium ü Fungal virulence factors may inhibit corneal neovascularization, reduce neutrophil infiltration and cell-mediate phagocytosis and result in impeded healing Fungal hyphae in cytological preparation of corneal swab VIRAL Extraocular Infection Case Presentation: ü 10 week old kitten with an acute onset of disease ü Signs of depression, fever and inappetence ü Serous to mucopurulent ocular and nasal discharge Acute Conjunctivitis & URTI What is your diagnosis? VIRAL Keratitis/Conjunctivitis Feline Herpes Virus-1 ü Important pathogen of cats (kittens); predominantly URT and ocular pathogens ü Route of infection: contact with nasal, oral and conjunctival secretions of infected animals ü Short replication cycle ü Rapid-cell-cell spread ü Tendency to induce cell lysis ü Persistence in sensory ganglia of their host (= latency) Viral Ocular Infection Ø Feline Herpes Virus-1 ü Important pathogen of cats (kittens); predominantly URT and (or linear) ocular pathogens http://www.k2publishing.ca/oldsite_quizzes/cvtcequiz_feline_article.html Sequelae to Feline Herpesvirus-1 Infections Feline Herpes Virus-1 ü Symblepharon = adhesion of the conjunctiva to itself or to the cornea ü May occur in severe cases of FHV-1 infections ü Occurs when area of conjunctiva and corneal epithelial erosion occurs as a result of the cytopathic nature of the virus ü May lead to permanent visual impairment Sequestrum = opaque plaque on cornea VIRAL Keratitis/Conjunctivitis Canine Distemper Virus ü Still significant cause of morbidity & mortality in dogs, despite availability of vaccines! Canine Distemper Virus ü Acute blepharitis and conjunctivitis (often 1st clinical sign) ü Acute keratoconjunctivitis ü Intraocular disease (chorioretinitis, anterior uveitis, optic neuritis) http://www.nexusacademicpublishers.com/table_contents_detail/13/74/html Viral Corneal Edema Canine Adenovirus-1 ü Cause of infectious canine hepatitis, but also have ocular manifestations (~20% of dogs with CAV-1 infections) ü Diffuse corneal edema ü “Blue Eye” v Both natural infections and some vaccinated dogs v Pathology due deposition of immune complexes on endothelial cells of the eye (type III reaction) v Usually self-limiting ü Anterior uveitis Specific Infections - Intraocular II. Intraocular Infections Infections of: Intraocular Tissues Ø Uvea = uveitis Ø Iris & ciliary body = anterior uveitis Ø Choroid = posterior uveitis Ø Retina = retinitis Ø Optic nerve = optic neuritis Intraocular Infections Intraocular Infections Ø May be due to local injury or systemic disease Ø The eye is often a target organ for systemic infectious agents üOcular disease can be the primary complaint üSystemic disease may be unidentified or overlooked üImportant to recognize the systemic involvement to give an accurate prognosis an provide adequate therapy üAnimals with systemic disease should have ocular examinations, which may provide rapid diagnostic clues and prognostic information Intraocular Infections Intraocular Infections Ø Typically, systemic infectious agents or immune complexes access the eye via the uveal or vascular tract and become established in the uvea producing: ü Posterior uveitis or chorioretinitis ü Anterior uveitis ü If overwhelming – endophthalmitis or panophthalmitis Feline anterior uveitis with a clot of inflammatory debris (fibrin) in the anterior chamber (tannish cloudy spot) Bacterial Intraocular Infections Leptospira spp. vAnterior Uveitis including Equine Recurrent Uveitis (ERU) This spirochete will mostly be covered in Eating & Eliminating (causes renal/hepatic disease and abortions) But also an important cause of intraocular disease, especially in horses http://www.thehorse.com/articles/29856/diagnosing-treating-and-managing-equine-recurrent-uveitis Bacterial Intraocular Infection Ø Other Gram negative bacteria can cause ocular disease secondary to systemic infections: üEnterobacterales (e.g., E. coli) vConjunctivitis, keratitis, dacrocystitis, anterior uveitis, etc üHistophilus somni vChorioretinitis, retinal detachment üBorrelia burgdorferi vAnterior and posterior uveitis in dogs and panuveitis in horses üBrucella canis vAnterior and posterior uveitis in dogs Bacterial Intraocular Infection Ø What about tick-borne Rickettsial infections? Ehrlichia canis vOcular lesions frequently occur in dogs vTypical lesions v v v v v v Uni- or bilateral anterior uveitis Conjunctival episcleral hyperemia or hemorrhage Miosis Aqueous flare Hypopyon Keratitic precipitates vPosterior inflammation can also occur vChorioretinitis, retinal haemorrhage, retinal detachment and optic neuritis Rickettsia rickettsii (Rocky Mountain Spotted Fever) vOcular lesions due to vasculitis - mostly ocular hemorrhage Bacterial Intraocular Infection Ehrlichia canis Conjunctival hemorrhage, hyphema Rickettsia rickettsii Viral Intraocular Infection Feline Coronavirus ØCause of feline infectious peritonitis (FIP) which also have ocular manifestations, predominantly in the “dry” form Feline Infectious Peritonitis Keratitic precipitates ü Bilateral granulomatous anterior uveitis and chorioretinits v Frequently see large keratic precipitates and fibrinous exudates in anterior chamber ü May also see pyogranulomatous lesions around retinal vessels (white spots) Viral Intraocular Infection Feline Leukemia Virus (FeLV) ØPredominant ocular manifestation of FeLV infection is ocular lymphosarcoma ØUveal tract is a common site for metastasis Ø Signs: mild uveitis aqueous flare keratitic precipitates Ø With progression: iris thickened glaucoma Viral Intraocular Infection Canine Distemper Virus ØIn addition to conjunctivitis, distemper virus produces a multifocal, non-granulomatous chorioretinitis ØMay also cause optic neuritis (and blindness) Canine Adenovirus-1 (Infectious Canine Hepatitis) Ø Uveitis may also be observed in dogs with CAV-1 infections with miosis and aqueous flare Ø Also, may be associated with vaccination, though less common with the use of CAV-2 in the vaccine Viral Intraocular Infection Malignant Catarrhal Fever ØHighly variable clinical signs, but usually have ocular signs: Ø Edema – eyelids & conjunctive Ø Photophobia Ø Lacrimation Ø Conjunctivitis Ø Progressive corneal opacity - corneal edema Ø Lymphocytic uveitis ØCaused by several gammaherpesviruses that infect an atypical host Ø Sheep-associated MCF in cattle caused by Ovine herpesvirus 2 Fungal Intraocular Infection Systemic Fungal Infections ØSeveral systemic fungal infections have ocular signs ØFrequently associated with posterior uveitis, anterior uveitis and chorioretinitis In many animals, ocular signs are the primary clinical manifestation of systemic mycosis. Fungal Intraocular Infection Histoplasmosis (Histoplasma capsulatum) ØRemember geographical distribution: ü Ø Ohio, Missouri, Mississippi Valley Ocular manifestations relatively uncommon in dogs, but in cats systemic histoplasmosis can cause: ü ü ü ü ü Granulomatous chorioretinitis Retinal detachment Anterior uveitis Secondary glaucoma Optic neuritis Fungal Intraocular Infection Histoplasmosis (Histoplasma capsulatum) Cat Conjunctival hyperemia Corneoscleral inflammation Corneal edema & vascularization Anterior uveitis Nodular iritis Fungal Intraocular Infection Blastomycosis (Blastomyces dermatitidis) ØRemember geographic distribution üMississippi/Ohio Rivers and central Atlantic states ØOcular lesions in ~50% of dogs Ø Ocular lesions include: ü Chorioretinitis (focal granuloma in the fundus to widespread subretinal infiltrates of the organism with retinal detachment) ü Anterior uveitis ü Endopthalmitis Fungal Intraocular Infection Blastomycosis (Blastomyces dermatitidis) Anterior uveitis, dog Multiple fungal plaques (arrows), cat Fungal Intraocular Infection Cryptococcosis (Crytpococcus neoformans/gattii) ØMost common feline systemic mycotic infection üAlso occurs in dogs üSource: widespread distribution, including in pigeon droppings! ØChorioretinitis with granulomatous inflammation and retinal detachment; optic neuritis Chorioretinitis Multifocal retinal detachment Parasitic Intraocular Infection Ø Parasites can also cause intraocular disease Toxoplasma gondii vDisease may be acute (1° young kittens) or reactivation of latent tissue cysts following immunosuppression Ø Most common lesion is chorioretinitis Ø Multifocal dark gray infiltrates in the tapetal fundus & fluffy white infiltrates in the nontapetal fundus Ø +/- anterior uveitis Summary Intraocular Bacteria Anterior Uveitis – Lepto, B. burgdorferi Fungus Extraocular Blepharitis – Gram + H. somni, B. canis Conjunctivitis – Mycoplasma, Chlamydia, Pasteurella, Moraxella Vasculitis --> uveitis – E. canis, R. rickettsia Keratitis – Gram +, P. aeruginosa, Moraxella Uveitis, chorioretinitis – H. capsulatum, B. Blepharitis - Dermatophytes dermatidis, C. neoformans Keratitis – Opportunistic Parasite Chorioretinitis – T. gondii Blepharitis – Mites, Cuterebra Virus Keratoconjunctivitis – FHV-1, CAV-1, CDV Uveitis – FIP, MCF, CAV-1 Ocular LSA - FeLV Chorioretinitis - CDV Extraocular Infections Blepharitis Keratitis G+ Cocci Dermatophytes Demodex Cuterebra G+ Cocci P. aeruginosa Opportunistic Fungal Keratoconjunctivitis Moraxella bovis FHV-1 Corneal Edema CAV-1 Conjunctivitis Chlamydia Mycoplasma Pasteurella multocida CDV Intraocular Infections – Your Turn Learning Objectives At the end of the lectures you should be able to: 1. Describe the defense mechanisms of the eye against infectious agents 2. Identify the factors that may predispose to infections of the eye as well as the virulence factors that organisms may have to help overcome these defense mechanisms and cause disease. 3. Identify the strategies for diagnosing infections of the eye and the clinical situations where these are appropriate. 4. List the main viral infections of domestic animals that cause ocular disease, and discuss the pathogenesis and ocular manifestations of FHV-1, CDV and CAV-1. 5. List the main bacterial pathogens that cause ocular infections in domestic animals, identify those that most commonly cause disease, and discuss the pathogenesis and ocular manifestations of Pseudomonas aeruginosa and Moraxella bovis infections. 6. Identify the three broad categories of fungal infections of the eye, the agents involved in each category of infection, and the ocular manifestations of these infections. 7. Identify the parasites that may be involved in ocular infections and their primary clinical manifestations.