Farm animal ophthalmology

Question 1

Besnoitiosis

Answer 1

This is a protozoal parasite which has a severe affect on the skin. This is a transmissible disease.

Characteristic cystic-like changes, bubbles on the sclera.

Question 2

Infectious bovine rhinotracheitis (IBR)

Answer 2

Cause:

• Infectious Bovine Rhinotracheitis (BHV-1)
• Affects URT and eye

Signs:

• Conjunctivitis: Hyperaemia and chemosis (oedema)
• bilateral serous ocular discharge
• diffuse corneal oedema

Question 3

Malignant Catarrhal Fever

Answer 3

Cause:

• OHV-1 (Rhadinovirus genus, Gammaherpesvirinae subfamily)
• cow is the dead-end host so- high mortality.
• Nasal and ocular discharge
• Enlarged lymph nodes
• Uveitis: red eyes, corneal oedema and hypopyon
• Occasionally CNS signs

Question 4

New Forest Disease (IBK) - Infectious Bovine Keratoconjunctivitis

Answer 4

Cause:

• Moraxella bovis - New Forest Eye
• gram -ve, aerobic bacterium which attacks cornea
• found in many recovered and normal cattle.

Clinical signs:

• young stock
• associated with being at pasture - flies, more common in summer
• New Forest - flies and trees outside.
• cornea opaque, superficial ulcers or perforated eye/ iris (quite common).
• The iris can sometimes prolapse (bottom right picture)

Treatment:

• Topical Cloxacillin ointment
• Tetracycline (advisible as often secondary mycoplasma)
• Bulbar conjunctival injection
• NSAIDs
• NO TOPICAL STEROIDS - ulceration risk
• suture eyelids (pain control and reduce risk of perforation)

Prevention:

• Fly control and pasture control
• No extended immunity
• cattle eyes have an amazing ability to repair.

Question 5

Silage eye/ Bovine iritis

Answer 5

• Association with listeria - is it an immune reaction?
• Might be physical trauma (burying head in silage feeders)
• winter housed cattle in particular, cattle fed silage.
• they will eventually go blink.
• Opaque eye - accumulation of fibrin and white cells within the chamber and cornea itself.

Signs:

• Anterior inflammation of the iris
• Intraocular inflammation
• No other systemic signs

Treatment:

• Using steroids rather than antibiotics - injection into bulbar and then farmer gives topical eye drops.
• Over a few weeks, the eye commonly returns to normal

Prevention:

• Feeding management

Question 6

Cancer eye

Answer 6

• Squamous cell carcinoma
• Disease of ocular surface, not intra-ocular
• Looks like a papilloma
• Can also affect iris and third eyelid
• Particularly common in animals with light coat colour and Hereford cattle, possible association with sunlight.

Peterson and infiltrating nerve blocks needed for enucleation in cattle.

Question 7

Cataracts

Answer 7

An association between cataracts and BVDV.

Question 8

Pink eye (sheep)

Answer 8

• Infectious corneal disease of sheep - like New Forest disease.
• Occurs in housed sheep - direct contact, rather than via flies.
• surface infection caused by mycoplasma or chlamydia.