Bovine Ophthalmology Flashcards
OCULAR ANATOMY
NORMAL RUMINANT ANATOMY
• Complete bony orbit
• Upper & lower lacrimal puncta
• Horizontal pupil
• Corpora nigra
• Tapetum lucidum with “stars of Winslow”
• Holangiotic fundus
CONGENITAL ABNORMALITIES
- Bovine viral diarrhea virus (BVDV)
- Bluetongue virus
- Dermoid
BOVINE VIRAL DIARRHEA VIRUS
- Pestivirus
-
Most common maternal infection causing multiple ophthalmic defects
- Usually between 76 – 150 days of gestation
- Skeletal and CNS abnormalities
- Range of ocular defects in calves
- Cataracts, microphthalmia, PPMs
- Retinal dysplasia
- Chorioretinitis: retinal degeneration, ONH atrophy, chorioretinal scarring
BLUE TONGUE VIRUS
BLUE TONGUE VIRUS
BLUE TONGUE VIRUS
- Orbivirus
- Culicoides gnat vector
- “Dummy” calves
- Hydrancephaly
-
Blindness with normal PLRs
- Cortical blindness
- Profound corneal edema
DERMOID
- Plaque of differentiated skin in an abnormal location
- Temporal limbus most common site
- Also third eyelid, medial/lateral canthus, eyelid, conjunctiva
- Inherited in Herefords
- Breeding recommendations
- Treatment
- Small and hairless → benign neglect
- Painful or impairing vision → superficial keratectomy
ESOTROPIA
- Bilateral Convergent Strabismus and Exophthalmia (BCSE)
- Inherited
- Affects many breeds
- Brown Swiss
- Jersey
- Progressive
- Abducent nerve motor nucleus defect (histopathologic finding)
ACQUIRED ABNORMALITIES
- Acquired strabismus
- Orbital disease
- Blepharitis
- Keratitis
- Conjunctivitis
- Neoplasia
ACQUIRED STRABISMUS
ORBITAL DISEASE
• Space occupying lesions
• Most common clinical sign is exophthalmos
• Prognosis depends on etiology
• Neoplastic
• Inflammatory/infectious
ORBITAL NEOPLASIA
- name some
• Lymphosarcoma
• Caused by BLV
• Diagnosis via biopsy
• Palliative treatment for orbital lymphosarcoma (<6 months)
• Metastatic SCC
• Metastatic adenocarcinoma
• Meningioma
• Lymphangiosarcoma
ORBITAL NEOPLASIA
- clinical signs
- Physical exam may reveal systemic abnormalities
- Lymphadenopathy
- Melena
- Cardiac arrhythmia
- Uterine and renal masses
ORBITAL INFLAMMATION
- Cellulitis/abscess
- Other associated signs of disease
- Causes:
- Trauma to ocular tissues
- Plant foreign material (oral)
- Dehorning
- Actinomyces pyogenes
- Frontal or maxillary sinusitis
- Pasteurella multocida
- Actinomyces pyogenes
- Treatment:
- Address underlying disease
- Systemic antibiotics
- Trephine/drain/lavage
- Enucleation
BLEPHARITIS: BACTERIAL
- Dermatophilosis
- Dermatophilus congolensis
- Filamentous, gram + aerobe
- Infective motile stage in wet scabs
- Distal extremities, muzzle, & dorsum
- Treatment:
- Dry environment (iodine or chlorhexidine shampoo)
- Penicillin (20,000 IU/kg) +/- streptomycin (10 mg/kg) IM for 3-5 days OR one long-acting oxytetracycline (20 mg/kg) injection
BLEPHARITIS: FUNGAL
- Dermatophytosis
- Trichophyton spp.
- Usually self-limiting; immune to reinfection
- Goal of treatment = limit spread to unaffected animals and humans
- ZOONOTIC
- Treatment:
- Topical and systemic antifungals, iodine shampoos, dry environment, and good nutrition
- Vaccination available
BLEPHARITIS: PARASITIC
BLEPHARITIS: PHOTOSENSITIVITY
- Photodynamic agents → UV sensitivity
- Do not confuse with solar irritation (sunburn)
- Acute periocular changes +/- corneal edema
- Identify underlying cause
- Primary: Ingestion of photodynamic agents
- Secondary: Hepatitis and/or bile duct obstruction leading to phylloerythrin accumulation systemically
- Inherited: Defects in porphyrin metabolism
- Treatment
- removal from sunlight
- prevention of ingestion of toxins +/- laxatives
CORNEA & CONJUNCTIVA
• Major sites for ophthalmic disease in food animals
• Profound economic impact
KERATITIS/CONJUNCTIVITIS
- Infectious bovine keratoconjunctivitis (IBK)
- Malignant Catarrhal Fever (MCF)
- IBR
- Listeria
- Thelazia spp.
- Environmental factors (e.g. dust/pollen/fumes)
INFECTIOUS BOVINE KERATITIS (IBK)
- agent
- properties
- transmission
- “Pink eye”
-
Moraxella bovis
- Other possible agents(?): IBR, M. ovis, M. bovoculi, Mycoplasma spp
- Gram-negative bacillus
- Pathogenic enzymatic properties
- Multiple organism serotypes
- Some nonpathogenic
- Transmission
- New animal, fomites, contact, and handlers
- Vectors: face fly (Musca autumnalis), house fly (Musca domestica), and stable fly (Stomoxys calcitrans)
IBK
- environmental factors
- predisposing factors
-
Environmental factors
- Sunlight (UV radiation)
- Dry environment (dust, pollens, grasses)
- Shipping stress
- Face flies → number correlates with infection rate!
-
Predisposing factors
- Bos taurus > Bos indicus breeds
- Herefords & Hereford crosses most common
- Increased incidence/severity in young cattle
- < 2 years of age
IBK
- pathogenesis
- Pathogenic strains are piliated
- Q pili – attachment to corneal epithelium
- I pili – maintenance of infection
- Bacteria release enzymes (β- hemolysin)
- Damage corneal epithelium & allow access to stroma
- Proteases
- Released by neutrophils & corneal cells
- Lead to progression of ulcer
IBK
- timing of disease
- source
- prevalence
- Acute disease, spreads rapidly
- Source is new animal or carrier in herd
-
Increased prevalence in summer
- UV radiation induced damage to corneal epithelium
- UV radiation induces M. bovis to more aggressive form
- Face flies more numerous
IBK
- signs
- Unilateral or bilateral
- Photophobia, blepharospasm, epiphora
- Conjunctivitis +/- mucopurulent exudate
- Central corneal lesion (opacity → ulcer)
- Corneal vascularization +/- granulation tissue
- Corneal rupture
- Secondary uveitis +/- glaucoma
-
Anorexia results in ECONOMIC LOSS
- Painful and potentially blind
- ↓ milk production
- ↓ weight gain
IBK
- treatment
IBK MEDICAL THERAPY
IBK PREVENTION
• Fly control
• Dust bags, insecticide tags, or topical drenches
• Temporary isolation of new animals
• Provide shaded areas
• Personnel disinfection
• Vaccination protocol
• M. bovis bacterins
• Efficacy questioned
• Administer BEFORE fly season
INFECTIOUS BOVINE RHINOTRACHEITIS (IBR)
• Etiology: bovine herpes virus (BHV-1)
• Ocular signs (+/- respiratory disease)
• Conjunctivitis: red/white raised plaques (lymphocytic follicles)
• NON-ulcerative keratitis
• Edema and vessels
• Blinding when severe
• Discharge: serous à mucopurulent
• +/- Anterior uveitis
• May be concurrent with IBK
• Disease course 2-4 weeks (vaccines available)
MALIGNANT CATARRHAL FEVER (MCF) KERATOCONJUNCTIVITIS
- etiology
- types → signs
- Etiology: herpes virus
- ovine HV-2 or alcelaphine HV-1
- Variations in clinical signs
- “Head-and-eye” is classic manifestation
- Other forms affect skin, mucosal surfaces, gastrointestinal and nervous system
- Pyrexia, profuse nasal/ocular discharge, mucosal erosions, dyspnea, diarrhea, & death
MCF
• Ocular Signs
- Photophobia
- Excessive lacrimation
- Exophthalmos
- Nystagmus
- Conjunctivitis (severe)
- Keratitis
- Perilimbal corneal edema progressing to complete opacification
- Bullous keratopathy and corneal erosions are common
- More severe than IBR
MCF
- diagnosis
- prevention
• Diagnosis
• PCR testing available
• Grave prognosis
• Prevention
• No vaccine or treatment
• Keep cattle away from sheep in endemic regions
BOVINE OCULAR SQUAMOUS CELL CARCINOMA (OSCC)
- who
- why important
• Cattle most affected of production animal species
• BPV may play a role
• Most economically important neoplasm of large animals
• Accounts for 9.15% of slaughterhouse condemnations
OSCC
- risk factors
• Periocular depigmentation
• Hereford, Ayrshires, Simmental
• UV radiation
• Age
• Older cattle ↑ risk (average age 8.1 yrs)
• Genetic predilection
• Bos taurus > Box indicus
• Herefords overrepresented
CLINICAL FINDINGS (OSCC)
- Any ocular or periocular location
- 75%: bulbar conjunctiva and cornea
- 90% on limbus and 10% on cornea
- 25% affect palpebral conjunctiva, nictitating membrane, eyelids
- Multiple or single lesions
- Unilateral or bilateral
OSCC PATHOPHYSIOLOGY
- Progressive disease with malignant transformation
- Hyperplastic epithelial plaque (may regress) → papilloma (may regress) → noninvasive carcinoma (in situ) → invasive carcinoma
-
Local invasion may be aggressive
- Palpate orbital rim
- Bony involvement had poor prognosis
- Palpate orbital rim
-
Metastasis is rare and occurs late in disease
- 5% of animals at slaughter (higher if invasive SCC)
- Systemic metastasis more common with eyelid and nictitating membrane tumors
- Local lymph nodes and lungs
OSCC DIAGNOSIS & TREATMENT
- Diagnosis
- Appearance
- Histopathology (biopsy)
- Treatment:
- *consider practicality*
- Surgical excision (most common)
- Cryotherapy/laser therapy (CO2)
-
Enucleation or exenteration
- +/- block resection: retropharyngeal ln, mandibular salivary gland, parotid salivary gland and subparotid ln
- Euthanasia/slaughter
- Hyperthermia
- Immunotherapy
- Radiation
- Photodynamic therapy
- Recurrence rate 30-40%
OSCC PREVENTION
- Selective breeding
- Pigment around the eyes
- Lines without high incidence of disease
- Difficult to manage environmental factors
UVEITIS
- Neonatal infections
- Umbilical infection, pneumonia, scours, etc.
- Bacterial septicemia in adults
- Mastitis, metritis, traumatic reticuloperitonitis, MCF, IBK, TEME, listeriosis, tuberculosis, neoplasia, trauma
- Clinical signs
- Pain, photophobia, flare, hypopyon, miosis, swollen iris, peripheral corneal edema and vessels
- Secondary changes: glaucoma, cataract, phthisis bulbi
- Treatment
- Topical steroids, topical atropine, flunixin meglumine
- Address underlying cause if known
OCULAR SURGERY
NERVE BLOCKS
• Auriculopalpebral nerve block
• For ocular examination or surgery
• Causes eyelid akinesia
• Inject lidocaine SQ where nerve crosses zygomatic arch
• 5-7 cm caudal to supraorbital process
• Local lidocaine block
• For eyelid anesthesia during surgery
• Inject lidocaine SQ at planned incision site
• “Ring block” for enucleation or exenteration
PETERSON NERVE BLOCK
- Retrobulbar block for CATTLE
- Blocks cranial nerves II, III, IV, V (ophthalmic and maxillary branches only), and VI
- Insert 10 cm, 18g needle at caudal angle between supraorbital process and zygomatic arch → direct posterior and walk off coronoid process anteriorly → advance to pterygopalatine fossa → inject 15-20 mL of lidocaine
- Mydriasis indicates successful block
- Complications: apnea, death 8-9 minutes later if inject into vessel or nerve sheath
FOUR POINT BLOCK
• Retrobulbar nerve block for surgery
• Insert 6 cm needle transconjunctivally adjacent to the globe
• Dorsal, medial, ventral and lateral
• Inject 5-10 mL of lidocaine at each site
• Mydriasis indicates successful block
“EN BLOC” TRANSPALPEBRAL ENUCLEATION
