Bovine ophthalmology

Question 1

What are the main primary diseases of bovine eyes?

Answer 1

Infectious bovine kerato-conjunctivitis - pink eye, new forest eye
Bovine iritis - silage eye
Squmous cell carcinoma - cancer eye

Question 2

What causes Infectious Bovine Keratoconjunctivitis/New Forest Eye? Clinical signs? Treatment?

Answer 2

Morexella bovis
Poss also Mycoplasma, Pneumonia viruses etc
Lachrymation
Blephorospasm
Ulcers
Treatmnet:
- LA eye ointment (cloxacillin)
- subconjunctival injections (oxytetracycline, ampicillin, amoxycillin), best on bulbar conjunctiva
- suture - third eyelid and eyelids or eyelids only
- eye patches
- photophobia = keep inside

Question 3

Risk factors for IBK? Prevention?

Answer 3

Flies
Woodland
Dust
Chaff
UV light
"Virus pneumonia"

Prevention:

• fly control (ear tags, pour ons, permethrins)
• graze away from fly habitat (woodland)
• ventilation and fly control inside
• vaccine in USA

Question 4

What causes bovine iritis/silage eye? Clinical signs? Treatment?

Answer 4

Associated with big bale silage feeding in winter - uveitis, hypersensitivity reaction?, anecdotal link with Listeria
Clinical signs:
- constricted pupil in early cases
- patchy or multiple areas of corneal opacity
- glaucoma
- white floccules in anterior chamber
- vascularisation later on (inside surface of cornea)
- negative to fluorescein
Treatment:
- antibiotics alone ineffective
- subconjunctival (bulbar) injection of atropine or dexamethasone +/- antibiotic

Question 5

Which cows get ocular squamous cell carcinomas? Significance? Treatment?

Answer 5

Breed disposition in Herefords
>5yo
Related to UV exposure
Locally invasive - can involve cornea, third eyelid, conjunctiva
Remove e.g. from third eyelid but may recur
Enucleation - sedate, auriculopalpebral and peterson blocks (or retrobulbar)

Question 6

When is Malignant Catarrhal fever seen? Clinical signs?

Answer 6

Associated with sheep or wildebeest cograzing - ovine herpes virus 2
"Head and eye form" most common
Persistent pyrexia 41C
Depressed - encephalitis
Nasal and mouth erosions
Lymph nodes enlarged
Respiratory signs
Diarrhoea
Eye lesions - conjunctivitis, eyelid oedema, blepharospasm, corneal opacity (centripetal)

Question 7

Infectious Bovine Rhinotracheitits - Aetiology? Diagnosis? Vaccines? Clinical signs?

Answer 7

BHV1
Latent carriers in trigeminal ganglion
Recrudescence with stress
ELISA serology or swabs for IF
Intra nasal or IM marker vaccine - protection in face of outbreak
Clinical signs:
- pyrexia 41C
- conjunctivitis and serous discharge
- corneal oedema
- nasal lesions and discharge
- severe milk drop

Question 8

Where does Listeriosis infect? Clinical signs? Treatment? Recovery rate?

Answer 8

Infection via V or VII nerve to brain
Encephalitis
Circling disease
Unilateral facial paralysis - droopy ear
Dry eye keratitis
Depressed
Menace test - retraction
Treatment - oxytetracycline or penicllins
65% recovery rate

Question 9

What eye lesions can be caused my BVD, septicaemia and endotoxaemia?

Answer 9

BVD: cataracts - infection between 75-150d of pregnancy but most cataract cases BVDv not found (can be Ag and Ab +ve or -ve), also micropthalmia
Septicaemia: hypopyon
Endotoxaemia: injected conjunctiva

Question 10

Causes of petechiae in the eye?

Answer 10

Septicaemia
Endotoxaemia
Post dystocia

Question 11

Potential cause of blood in the anterior chamber?

Answer 11

Bracken poisoning

Question 12

Causes of blindness?

Answer 12

CCN
Lead poisoning
Vitamin A deficiency
Twin lamb disease in sheep only

Question 13

What causes cerebrocortical necrosis? Diagnosis? Signs?

Answer 13

Thiamine (vitamine B1) deficiency in young growing cattle/sheep
Diagnosis - PME: brain fluoresces under UV light
Signs:
- star gazing in early cases
- -ve menace test: blind
- +ve pupillary response to light
- nystagmus and convulsions
- opisthotonus
Treatment:
- IV thiamine every 3-4 hours
- advise diet change
- monitor rest of group

Question 14

Lead poisoning presentation/clinical signs? Diagnosis? Treatment?

Answer 14

Any age - usually young cattle
Batteries, lead paint etc
-ve menace test
Dilated pupils
Tremors, convulsions
Treatment – Sodium Calcium Edetate (EDTA) IV, sedation, magnesium
Withdrawal periods – inform DVM re: lead in milk and meat
Diagnosis - Pb in kidney, history.
Walk the perimeter of the field to look for sources of lead

Question 15

Vitamin A deficiency - when seen in cattle? Signs?

Answer 15

Growing cattle indoors
Roots and straw diet
Night blindness
-ve menace test
Dilated pupils
Oedema of optic disc

Question 16

What to do to aid bet possible eye examination of a cow?

Answer 16

Restrain in a crush and tie head round to the side with a halter
Consider sedating if restraint is inadequate (usually unnecessary)
Perform an auricopalpebral block - motor
Put an amethocaine in the eye?
Infiltrate local around the eyelids?