Blink of an Eye
HEATHER SMITH THOMAS
inkeye causes tremendous
loss each year for cattle producers,
due to poor weight
gains, prices docked because
of eye damage or blindness, or calves
cut back at sale time. Dr. Annette M.
O’Connor, Professor of Epidemiology,
Department of Large Animal Clinical
Sciences, Michigan State University
says Moraxella Bovis is considered to
be the bacteria most commonly associated
“However, there are other organisms
that might be involved. For many
years there’s been speculation that M.
bovoculi might also be a cause,” says
Just having M. Bovis in the eye isn’t
enough to cause pinkeye. Researchers
suspect that trauma to the eye may
enable bacteria to establish an infection.
“M. Bovis is usually just in the
conjunctiva (the delicate membrane
that lines the eyelids and exposed surface
of the white of the eye), in the
lubricating fl uid. We think trauma
enables the bacteria to bind to the
cornea and cause the disease,” she
suggests. Trauma may include intense
Cattle is a
BY HEATHER SMITH THOMAS
ultraviolet light, tall grasses that
scrape or cut the eye while the animal
grazes, dusty or windy conditions that
irritate the eye, and face fl ies.
Pinkeye incidence usually peaks in
summer — probably because there are
a lot of fl ies, the grass is long, it’s usually
dry and dusty, and there’s a lot of
ultraviolet light. “There is also speculation
that infection with other agents
such as mycoplasmas and infectious
bovine rhinotracheitis (IBR) can affect
the eye and cattle are more likely to
get pinkeye,” says O’Connor.
“This is a multifactorial disease with
several components, but we’re not
sure we know what all those components
are. There are probably multiple
combinations; there’s not just
one set of factors that cause pinkeye,”
SEE THE SIGNS
The affected eye is very sensitive
to bright light and pain. The animal
holds the eye closed. The fi rst signs
are squinting, blinking due to pain,
and excessive tears. The hair on the
face below the eye is wet. If you catch
it at that stage, treatment is very
effective. The infection clears quickly,
without damage to the eye that might
occur if the disease is neglected.
Next signs (after the eye has been
sensitive/watering for a day or more)
include haziness or cloudiness of the
eye, and there may be a hole/ulcer on
the surface of the eyeball. Sometimes
the eye will heal on its own with
just a scar in that area, but in many
instances, if left untreated, the ulcer
may become larger and deeper, and
tissue may protrude from that hole.
The bulging area may be red.
The end-stage is a serious case
when the eyeball ruptures. It may
rupture if the ulcer goes completely
through the tissue — but most often
ruptures due to trauma. The animals
can’t see and may run into something,
or another animal hits them.
The eyeball is weak at that spot and
may rupture when bumped.
EDITOR: As always, we recommend a
good visit with your consulting veterinarian
to help you get a preventative handle
on the situation specifi c to your operation.
44 I WORKING RANCH I JUNE / JULY 2020