Canine ocular manifestations of systemic disease: when the primary problem isn't the eye (Proceedings)

• Complete medical history

     o Weight loss, anorexia, vomiting, diarrhea, animals environment (exposure to other animals, mycotic organisms), travel history

• Complete physical examination

• Bloods: CBC/ Chem /T4 /Serology

• Radiographs – Thoracic for mycotic, neoplastic conditions

Etiologies

• Infectious

     o Bacterial, Viral, Fungal, Rickettsial, Protozoal, Parasitic, Algal

• Metabolic/Circulatory

     o Diabetes, Thyroid diseases, Hypertension

• Neoplastic

     o Lymphoma, metastatic tumors

• Toxic

     o Drugs, nutritional disorders

• Immune-Mediated

• Uveodermatologic syndrome

Uveitis- differential diagnosis

Infectious

• Fungal

     o Blastomycosis

     o Histoplasmosis

     o Cryptococcus

     o Coccidiomycosis

     o Candidiasis

• Viral

     o FeLV/ FIV

     o FIP

     o Canine Distemper

     o Adenovirus

• Algal (prototheca)

• Bacterial

     o Brucellosis

     o Bartonella

     o Babesia

• Protozoal

     o Toxoplasmosis

     o Leishmaniasis

• Rickettsial

     o Ehrlichia

     o RMSF

• Parasitic

     o Dirofilaria

     o Toxocara

Uveitis- differential diagnosis

• Immune Mediated

     o Uveodermatologic syndrome

     o ERU

     o Lens –induced (phacolytic)

• Traumatic

     o Lens capsule rupture

     o Blunt trauma

     o Penetrating trauma

• Toxic

• Neoplastic

     o Lymphoma

     o Melanoma

• Metabolic

     o Systemic hypertension

     o Hyperlipidemia

• Idiopathic

Blastomycosis

• Blastomyces dermatitidis

     o dimorphic fungi

• In soil a saprophytic mycelial form

     o producing infective spores (conidia)

• In tissues is a budding yeast 5-20 um

     o thick double contoured wall

• Endemic to various river valleys

     o North America-"Blasto Belt".

Blastomycosis

• Establishes in lungs (inhalation)

     o disseminates via lymph nodes or blood to skin, eyes, bones, lymph nodes, brain & testicles.

• Lymphadenopathy, fever, harsh lung sounds, draining skin lesions, cough, & emaciation

• Blastomycosis - Treatment

• Itraconazole

• Fluconazole

• Ketoconazole

• Amphotercin B

• Topical / Systemic Corticosteriods

Coccidiomycosis

Cryptococcus

• Diagnosis

     o Cytologic – India ink, Gram's stain, Wright's stain

          • cerebral spinal fluid, vitreous humor

          • CSF: neutrophilic pleocytosis, increased protein, organisms seen in 60% of positive samples.

     o Cryptococcal capsular antigen test

          • using latex agglutination from serum or CSF

     o Fungal culture

     o Usually poor prognosis for dogs

Histoplasmosis

• Dimorpic fungus Histoplasma capsulatum

     o soil saprophyte.

• Life cycle similar to blasto and coccidiomycosis

• Ocular lesions not as severe as other fungi

• Most infections are subclinical respiratory infections

• If disseminated

     o digestive tract & reticuloendothelial system

• Anterior uveitis

     o pyogranulomatous multi-focal to coalescing lesions

• Optic neuritis

• Retinal detachment

Toxoplasmosis

• Obligate intracellular protozoal parasite

• Felines are the only known definitive hosts

• Three infective stages of T gondii recognized:

          • 1) tachyzoites (the rapidly multiplying form)

          • 2) bradyzoites (tissue cyst form)

          • 3) sporozoites (within oocysts).

• Anterior uveitis, retinitis, & choroiditis

• Less common lesions

          • extraocular myositis & optic neuritis

Erlichiosis

• Ehrlichia canis

• Tick vector

• Three disease stages:

          • 1) acute (1-3 wks),

          • 2) subclinical (average of 11 wks)

          • 3) chronic

• Platelet deficiency, vasculitis (or both)

• Ocular hemorrhages and mucosal petechial hemorrhages

• Natural infection :10-15% have ocular lesions

• Ocular signs may be present in all stages

• Anterior uveitis

• Optic nerve may be inflammed and retinal vessels may seem engorged with perivascular infiltrates and papillary hemorrhages

• Retinal hemorrhages common and retinal detachments occur with exudates

RMSF

• Rickettsia rickettsii – similar ocular lesions to Ehrlichia canis, but milder.

• Tick born

• Conjunctivitis, chemosis, retinal vasculitis, mild anterior uveitis, petechiation

• Systemic thrombocytopenia, anemia, vasculitis, arthritis

Lyme disease

• Borrelia burgorferi

• Clinical cause of uveitis in dogs

• Tick born

• Treatment:

     o Doxycycline

• Prevention

     o Tick repellants

     o Vaccination?

Canine lymphosarcoma

• Most common metastatic neoplasia to the canine eye & cause for neoplastic uveitis in dogs.

• Usually bilateral anterior uveitis

• Also common

     o Posterior uveitis, retinal infiltrates &detachment

• Thickened third eyelids

• Diagnosis

     o Lymph Node biopsy

     o Splenic/liver aspirate

Diabetes mellitus

• Young dogs-most susceptible to developing cataracts

• Rare in cats

• Increased blood sugar overwhelms hexokinase

     o Polyols are formed & accumulate in the lens

     o Resulting in an osmotic gradient

          • Rapidly developing cataracts (within 72 hrs)

     o often have deep clefts.

Diabetes mellitus

• Evaluate blood glucose and blood fructosamine

• Prior to surgery –

     o control accompanying uveitis

     o perform an electroretinogram and ocular ultrasonography

• Post-op inflammation control is necessary

     o oral and topical nonsteroidals.

     o May need treatment for 2 or more months.

Uveo-dermatologic syndrome

• An immune-mediated condition

     o poliosis, vitiligo, & severe bilateral uveitis.

     o Akitas, Siberian Huskies, & Samoyeds.

• Severe uveitis, blindness, retinal detachment & glaucoma

• Depigmentation of eyelids, lips and nose.

• No specific diagnostic test

     o Classic clinical signs and breed.

• Systemic oral corticosteroids & azathioprine

     o azathioprine takes up to 4 weeks to become effective

     o Monitor WBC count and liver enzymes carefully

• Topical prednisolone

Sudden acquired retinal degeneration

• A syndrome of acute blindness of unknown etiology.

• Acute vision loss

     o Initially ± retinal degenerative changes

     o Over time the retina will exhibit gross degenerative changes.

• Absent pupillary light responses

• Diagnostics

     o Electroretinogram (ERG) wave form is extinguished

     o Rule out Cushings Disease

• Therapy

     o No therapy to date to reverse blindness.

     o Treat for Cushing's if indicated.

• Unfortunately, vision loss is almost always permanent.

Hypertensive retinopathy

• Occurs in both dogs and cats much more commonly in cats

• Ocular-most common findings are hyphema and retinal detachment

     o Fundus exam often reveals tortuous vessels, retinal hemorrhages & focal degeneration

• Systolic readings greater than 160-180 mmHg

• Treatment

     o Amlodipine 0.625mg orally daily

     o Topical antiinflammatories (steroidal and nonsteroidal) oral antihypertensive medication,

     o oral dichlorphenamide (Daranide® 1-2 mg/lb PO BID for up to 30 days) for its effect on improving the chance for retinal reattachment.

• Prognosis – dependent upon time of detachment

Feline infectious diseases

• Feline Leukemia Virus

• Feline Immunodeficiency Virus

• Feline Infectious Peritonitis

• Feline Herpesvirus

• Systemic Fungal Diseases

• Toxoplasmosis

Feline immunodeficiency virus

• Systemic

     o Lymphoma

     o Immunosuppression

          • leukopenia, lymphopenia, anemia, weight loss, persistent diarrhea, opportunistic & secondary infections

     o Coinfection

          • Chlamydia psittaci prolonged infection

          • Toxoplasma gondii increased severity

• Ocular

     o Usually due to lymphosarcoma

     o Pars planitis, retinopathy, conjunctivitis, orbital disease

Feline infectious peritonitis

• Clinical Signs-Systemic

     o Anorexia, weight loss, lethargy, mild fever, mild URI or intestinal signs

     o EFFUSIVE

          • Ascites, thoracic effusion, pericardial effusion, abdominal masses (adhesions or mesenteric lymphadenopathy)

     o NON-EFFUSIVE

          • Granulomatous lesions in spleen, liver, kidney, omentum, lungs and/or LNs

          • Typically develop ocular signs

          • May develop CNS signs

Feline infectious peritonitis

• Clinical Signs-Ocular

     o Anterior and posterior uveitis

     o Bilateral granulomatous anterior uveitis with chorioretinitis

     o "Mutton-fat" keratic precipitates

     o Secondary glaucoma, cataract formation, lens luxation

Feline herpesvirus

• Acute and Chronic FHV-1

     o Initially colonizes the oral and naso-pharyngeal mucosa and conjunctiva

     o Corneal ulceration occurs with viral replication in corneal epithelium

     o Stromal keratitis with deep neovascularization occurs with immune response to viral antigen

• Latent FHV-1

     o Virus localizes in trigeminal ganglion, can migrate down trigeminal nerves to cornea and conjunctiva

Feline herpes virus clinical signs

• Systemic

     o Upper respiratory infection with fever, lethargy, inappetence

• Ocular

     o Conjunctivitis with serous to purulent discharge

     o Corneal ulceration (dendritic, Rose Bengal +)

     o Symblepharon

     o Stromal keratitis

     o Sequestra

     o Possible anterior uveitis

Feline herpesvirus therapy

     o Topical antivirals:

          • Idoxuridine

          • Vidarabine (Vira-A®)

          • Trifluridine (Viroptic®)

     o Topical antibiotics for secondary ocular infections

     o L-lysine 250-500mg PO BID