Farm animal ophthalmology Flashcards
When do you get transplacental infection of bovine foetus?
125-175d gestation (numerous congenital defects possible)
Possible in utero effects - IBR
- retinal atrophy
- optic neuritis
- cataract
- micropthalmia with retinal dysplasia
- these often –> blindness
Other than ocular lesions, how does IBR affect bovine feoetus?
- URT –> red nose and eyes
- eye lesions: conjunctivitis (hyperaemia + oedema), diffuse corneal oedema possible t
- usually presents with bilateral serous ocular discharge
Tx - IBR
symptomatic
Prevention - IBR
- vaccination
- biosecurity
What is OVH2? Transmission?
Ovine herpesvirus 2
- transmitted sheep to cattle
CS - OBH2 in cattle
- GI signs: anorexia and diarrhoea
- agalactia
- pyrexia (41-41.5)
- RT signs: mucopurulent ND, severe dyspnoea with stertor d/t obstruction of nasal cavities with exudates
- enlarged LNs
- ocular signs (common, corneal opacity, unilateral then bilateral, hypopyon may develop (often die first)
Define hypopyon
= leukocytic exudate in AC, usually accompanied by red conjunctiva and underlying episclera. a form of anterior uveitis
Dx - OVH2
viral DNA by PCR
Tx - OVH2
frequently PTS
Colloquial names - Moraxella bovis
= New Forrest eye, Pink eye
What type of bacteria is Moraxella bovis?
- gram negative
- aerobic
Where is Moraxella bovis found?
in eyes of many recovered and apparently normal cattle
Outline disease - Moraxella bovis
- mutifactorial
- cattle are carriers
- Fomites: flies, dust, long grass (thus common in summer/ early autumn)
- tends to be unilateral
CS - Moraxella bovis in cattle
- tearing and photophobia
- conjunctival hyperaemia and chemosis
- corneal changes may follow (oedema, ulcer, abscess, hypopyon)
- vision loss may develop within 3 d
Tx - Moraxella bovis
- early (to resolve problem and prevent spread)
- cloxacillin
- TC
- bulbar conjunctival injection
- no topical steroid (corneal ulcer risk)
- OTHER: isolate infected animals, fly control
What type of bacteria is Listeria monocytogenes and where is it found?
- gram positive
- microaerophilic
- in poorly fermented alkaline silage
CS - Listeria monocytogenes
- Encephalitis and abortion
- CN deficits
- OCULAR: strabismus and nystagmus
- ‘silage eye/ red eye’ (originates directly from silage, innoculation when animal eats and head goes into silage)
Dx - Listeria monocytogenes
- CS
- Time of year
Tx - Listeria monocytogenes
- Antibiosis : chlortetracycline or penicillin, in early stages (IM, subconjunctivally)
- NSAIDs to reduce inflammation
What neoplasia can affect bovine eye?
SCC (malignant)
Outline SCC in bovine eyes
- animals > 5 yo usually
- low pigment is a predisposing factor (common with white heads = Hereford, associated with actinic radiation = sun)
Lesions stages - SCC
- plaque (hyperplastic epithelium)
- papilloma (non-malignant, high regression rate)
- SCC in situ (non-invasive)
- invasive SCC (past the epithelium’s lamina propria)
Name 3 possible ocular locations for bovine SCC
- sclera
- nictitating membrane (TE)
- eyelid
Outline SCC metastases
- it is an invasive tumour
- draining lymphatics can take it to cervical LNs
Tx - SCC
- excision usually with enucleation
- bone invasion complicates tx as doesn’t allow removal
- act early d/t welfare and financial implications
- cannot travel to market/ slaughter with ulcerative skin lesion
Name 3 nutritional problems in cows that affect eyes
- hypovitaminosis A
- lead poisoning
- cerebro-cortical necrosis (CCN)
How does hypovitaminosis affect the eye?
–> complete blindness
How does lead poisoning affect the eye?
- no menace and mydriasis
- can be followed by blindness
How does CCN affect bovine eye?
blindness
What is another name for infectious keratoconjunctivitis in sheep?
pink eye (caused by Mycoplasma spp)
Outline infectious keratoconjunctivitis in sheep
- often seen in winter when in close proximity indoors
- spread via fomites such as feed troughs
- can be complicated by secondary infection with Chlamydia
Tx - infectious keratoconjunctivitis in sheep
- OTC IM
- NSAID
Can Listeria monocytogenes affect sheep?
Yes just like cattle causes ‘silage eye’
- originates from silage
- inoculation when animal eats and head goes into silage
Outline nutritional ocular disease in sheep
- SAME AS CATTLE:*
- hypovitaminosis A - complete blindness
- lead poisoning - no menace, mydriasis, can be followed by blindness
- cerebro-cortical necrosis (CCN) - blindness
Can ‘twin lamb disease’ of pregnant ewes affect the eyes?
Yes - can lead to blindness in terminal stages
