NADIS disease bulletins are written specifically for farmers, to
increase awareness of prevalent conditions and promote disease
prevention and control, in order to benefit animal health and welfare.
Farmers are advised to discuss their individual farm circumstances
with their veterinary surgeon.



Pink Eye in Sheep






PINK EYE IS A COLLOQUIAL TERM WHICH DESCRIBES INFLAMMATORY DISEASES OF
THE EYE, USUALLY DUE TO INFECTIOUS KERATOCONJUNCTIVITIS, LISTERIA OR
TRAUMA.





OVINE INFECTIOUS KERATOCONJUNCTIVITIS (OIKC)

Infectious keratoconjunctivitis is seen in sheep of all ages, but
tends to be more severe in ewes than in lambs. Outbreaks affecting up
to 25% of the flock are commonplace. The disease can become
particularly important when pregnant ewes are involved.



The first sign of OIKC is tear staining extending from the corner of
one or both eyes, associated with conjunctivitis. As the disease
progresses the cornea becomes cloudy and blood vessels are seen
prominently at the periphery of the eye. The ocular discharge becomes
thicker and pus-like as the disease progresses. When both eyes are
severely affected sheep become temporarily blind, resulting in
handling difficulties and losses due to misadventure. In most cases,
healing occurs over a period of several weeks, eventually leaving only
a faint corneal scar. However, in extreme cases the anterior chamber
of the eye may ulcerate, rupture and become secondarily infected,
resulting in permanent blindness. Acquired immunity following
infection is poor and many cases relapse.



The primary causative organisms are believed to be Chlamydia psittaci
and Mycoplasma conjunctiviae, either alone or in combination, but
several other bacteria may also be involved in a secondary role.
Close contact of sheep when trough feeding enables rapid spread of
infection and probably accounts for the high incidence of the disease
during winter months. Outbreaks in recently weaned lambs may be
associated with high stocking rates, dust, long grass and flies which
have been contaminated by tear secretions of infected animals.
Handling of the face and head of lambs when drenching may also provide
a means of spread. Clinically recovered animals may harbour the
causative organisms for several months and may be a source of
re-infection of other animals in subsequent years when their immunity
has waned.






THE DISEASE IS PAINFUL AND PROMPT TREATMENT OF AFFECTED EWES IS
USUALLY RECOMMENDED TO MITIGATE AGAINST THE RISK OF PERMANENT
BLINDNESS.



Treatment is tedious and usually involves the topical application of
aureomycin as a puffer or ointment. There is some evidence to support
the use of intramuscular injections of long acting oxytetracycline,
which may be a practical method for the treatment of OIKC in some
flocks.





LISTERIA IRITIS (silage eye)

Infection of the anterior chamber of the eye is commonly seen in sheep
(and cattle) of all ages associated with the feeding of big bale
silage. The disease is associated with Listeria monocytogenes
infection and up to 25% of the flock can be affected in severe
outbreaks.



The initial presenting signs are excessive tear production, frequent
blinking and avoidance of bright light involving one or both eyes. On
closer examination the iris is swollen and thrown into a series of
radial folds. Within two to three days, more severe inflammatory
changes develop, with blueish white corneal opacity starting at the
border and spreading inwards. Focal aggregations of fibrin in the
anterior chamber of the eye are seen as accumulations of white
material beneath the cornea. In more advanced cases widespread
corneal opacity and vascularisation is often seen. If untreated,
complete healing of this painful condition may take one to three
weeks.



The precise cause of ovine iritis has not been experimentally proven.
Outbreaks are invariably linked to the feeding of big bale silage.
The consistent isolation of L.monocytogenes from conjunctival swabs
taken from affected animals suggests that the organism has an
important role, although in some surveys an equal incidence of L.
monocytogenes has been shown in conjunctival swabs taken from both
normal and affected eyes.



Subconjunctival injection of a combination of oxytetracycline and
dexamethasone usually halts the progression of clinical signs when
administered in the acute stages of the disease and the eyes usually
return to normal within two to three days.



Your vet can advise you about the treatment and management of pink eye
in your flock.

Neil Sargison BA VetMB DSHP FRCVS




"As I was walkin' - I saw a sign there
And that sign said - no tress passin'
But on the other side .... it didn't say nothin!
Now that side was made for you and me!"
Woody Guthrie

A prophet is only despised in his own country....
..........among his own relations...
............and in his own house