3.1.5: Ophthalmology

Question 1

‘New Forest Eye’ and ‘Pink Eye’ are synonyms for which condition?

Answer 1

Infectious bovine keratoconjunctivitis (IBK)

Question 2

Causative agent of Infectious Bovine Keratoconjunctivitis (IBK)?

Answer 2

• Main causative agent: Moraxella bovis
• Often additional pathogens: Mycoplasm spp., Chlamydia spp., herpesvirus

Question 3

Clinical signs of IBK

Answer 3

• Epiphora
• Blepharospasm
• Conjunctivitis
• Keratitis with corneal oedema and cloudiness
• Lesions are more common unilaterally than bilaterally

Question 4

What is pictured here? What might be the cause?

Answer 4

This is a corneal lesion/ulcer.
FB lesions may be located anywhere on the cornea. IBK lesions are generally centrally located.

Question 5

What is pictured here? Which condition might it be associated with?

Answer 5

• This is IBK
• Granulation tissue gives the eye a pink appearnace (hence ‘Pink Eye’)
• Neovascularisation from the periphery into the centre of the cornea, is also visible
• Neovascularisation typically happens 3-4 days after the onset of IBK

Question 6

How is IBK transmitted?

Answer 6

• IBK = contagious
• Transmitted through flies and through close proximity of cattle (e.g. at feed troughs)
• Other vectors: troughs, handler’s hands

Question 7

Treatment of IBK

Answer 7

• Antibiotics and NSAIDs
• Antibiotics can be given systemically (e.g. oxytetracycline, florfenicol) or via topical ointment (Cloxacillin) or via bulbar sub-conjunctival injection (potentiated penicillin)
• NSAIDs e.g. meloxicam
• Stable the patient to reduce light irritation
• Implement fly control measures

Question 8

True/false: cows form immunity to IBK and can probably transfer this through colostrum.

Answer 8

True.
There appears to be life-long immunity to IBK.

Question 9

Prevention and control of IBK

Answer 9

• Fly control: through fly tags, pour-ons, parasitic wasps to reduce fly population, and reducing fly breeding grounds e.g. removing standing water, mouldy feed, avoid grazing in woodlands at risk time periods
• Vaccination: opinions vary. If client decides to use vaccine, the protocol should be initiated at least 4 weeks before the typical IBK season.

Question 10

What is silage eye?

Answer 10

Silage eye: anterior uveitis associated with conjunctival infection with Listeria bacteria (Listeria monocytogenes)

Question 11

Which species are affected by silage eye?

Answer 11

Sheep and cattle of all ages

Question 12

When is silage eye most common? Why is this?

Answer 12

• Late winter into Spring; peaks around March
• Associated with feeding a new batch of silage
• Listeria is ubiquitous, but found in dangerous quantities in silage which has not been fermented sufficiently to kill the bacteria

Question 13

Clinical signs of silage eye

Answer 13

• Excessive tear production, causing tear stains on face
• Aversion to light affecting one or both eyes
• Pain resulting in unwillingness to permit examination of eye
• Forced closyre of the eyelid
• Bluish-white opacity of the eye
• Bulges of the iris

Question 14

What condition is pictured here?

Answer 14

Silage eye

Question 15

True/false: Listeria causes silage eye, but can also cause abortion and neuro signs in cattle and sheep

Answer 15

True

Question 16

Treatment of silage eye

Answer 16

• Bulbar sub-conjunctival administration of a gram +ve antimicrobial OR topical application of ophthalmic antimicrobial preparation
• Bulbar sub-conjunctival administration of anti-inflammatory
• Mydriatic sub-conjunctivally
• ± systemic antimicrobial/anti-inflammatory

Question 17

Prevention of silage eye

Answer 17

• Produce low risk silage: minimise soil contamination of forage (this can be indicated in “silage ash” content)
• Attention to detail when bailing and wrapping, minimise exposure to air through puncturing: ensure appropriate fermentation conditions to limit growth of Listeria
• Make bales/clamp silage with a shorter chop length -> enables cows and sheep to feed without having to bury their heads in the long fibres

Question 18

What lesion is pictured here? How would you detect it?

Answer 18

Corneal ulcer
* Visually observation from multiple angles
* Use fluorescein: allow animal to blink and then observe. Only the corneal stroma takes up the stain so the colour only adheres where the corneal epithelim has been compromised.