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Infectious bovine
keratoconjunctivitis (IBK or pink-eye) is a disease
that can affect the eyes of beef or dairy cattle at
any age, although range calves and feedlot cattle are
the most frequent victims of the disease. The
infection rarely results in death, but production
losses in an affected herd may be significant.
Severely infected cattle, suffering pain, will lose
both appetite and body condition and in the worst
cases can starve to death. Herd outbreaks can involve
up to 80% of the animals and last from three to four
weeks.
Contributing
factors
Herd
outbreaks of pinkeye may occur at any time of the
year, but the incidence is higher during the warm
summer months. A number of contributing factors have
been identified.
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Sunlight
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Lack
of pigmentation of the eyelid
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Prominence
of the Fly population
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Resistance
related to
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Other
corneal
Characteristic
signs of pinkeye
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Reddening of the eyeball and swelling of
the eyelid lining
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Watery discharge from the eye
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Excessive blinking in bright sunlight
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The center of the cornea becomes whitish
in color after several days and may become elevated
and ulcerated.
Spontaneous healing often
occurs at this stage. If healing fails to happen, the
area of whiteness progresses to cover the entire
eyeball. The discharge from the eye gradually lessens
but becomes thicker and more whitish in color.
Complete recovery at this stage requires three to five
weeks. Severely infected eyes may go on to develop
penetrating ulcers. Such eyes occasionally rupture and
complete blindness results. Pinkeye is often confused
with the presence of foreign material in the eye,
physical injury or other diseases. Early cases of
cancer eye can look like pinkeye. Infectious bovine
rhinotracheitis (IBR) can also resemble the early
stages of pinkeye.
Veterinarians
are best able to recognize and differentiate the
various disease conditions that affect the eyes of
cattle. They will also provide professional advice
regarding the treatment of pinkeye and the elimination
of predisposing factors in the environment.
Effective
treatment of pinkeye
There
are few good scientific reports of effective
treatments for pinkeye. Since spontaneous recovery is
not uncommon, some treatment prescriptions have been
unjustly credited with being more effective.
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Most strains of M. bovis appear
to be sensitive to tetracyclines, penicillin,
erythromycin and neomycin. The bacterium is usually
resistant to cloxacillin (commonly found in dry cow
mastitis ointments).
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The use of aerosol sprays and powders
generally cause additional irritation to infected
eyes. These products cause increased tear secretion
that in turn washes away the antibiotic. Eye drops or
ointments are better alternatives for mild or early
cases of pinkeye. They are non-irritating and do not
result in excessive tear secretion. They do, however,
have to be given in repeated doses to sustain adequate
drug levels. The injection of a mixture of antibiotics
such as penicillin, streptomycin or gentamycin, under
the lining of the affected eyelids is recommended in
herd outbreaks where repeated treatments are
impractical. Often one injection is sufficient, but
the treatment will need to be repeated in three or
four days for severe or advanced cases of pinkeye. An
intramuscular treatment is generally not recommended
because very high dosages of an antibiotic are
required to ensure adequate levels of the drug reach
the eyes and tear glands.
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Other methods of treatment include
performing eye surgery to protect the affected eyeball
from further injury and promote healing or the gluing
of protective plastic covers onto the skin around the
eyes to avoid further eye irritation. In addition to
medical treatment, good management and nursing care is
required to bring about full recovery. General
recommendations include: housing in shaded areas (to
avoid direct sunlight); provision of adequate feed and
water; reduction of dust, flies and other physical
causes of eye irritation.
Pinkeye
prevention
The
prevention of pinkeye is difficult because the causes
and predisposing factors are so varied. Insecticide
impregnated eartags are effective for controlling face
and horn flies. Tall grasses can be kept short through
pasture management, to prevent eye irritation while
the cattle are grazing.
The fact that animals are
immune to pinkeye for up to twelve months after
infection suggests vaccination should be a reasonable
means of control. Up to now it has been impossible to
make an effective preparation that guarantees immunity
against any of the many strains of pinkeye prevalent
in the cattle population. It appears the immunity
stimulating components are variable from one strain of
M. bovis to the next. Researchers have not agreed
what kind of immunity is required and are still unsure
how complete resistance to pinkeye can be achieved
through vaccination. |
