The past two years we’ve seen a huge resurgence of pinkeye and other eye problems in our practice. While I may have some of the answers, the reasons behind these outbreaks do vary with the conditions. One year was unique because of the lush growth of grass and a very high face fly population. In dry years producers graze alfalfa and the coarse stems regularly cause eye abrasions. This article offers a quick review of pinkeye and the more common preventative measures.
Pinkeye technically is known as Infectious Bovine Keratoconjunctivitis (IBK) caused by a bacteria, Moraxella Bovis, that is quite contagious. Young children are sent home from school if they contract the human form as it can spread very easily. Pinkeye is by far the most common eye problem in cattle.
Producers initially will notice the eye tearing and the conjunctiva (pink area surrounding the eye) swollen and red. Pinkeye most commonly affects just one eye. The theory is immunity develops, making the second eye less susceptible but I have also seen severe cases where both eyes are involved. As the infection progresses the cornea (eyeball) becomes cloudy and blue. The pinkeye organism attaches to the surface of the eye and causes an ulcer. This creates pain and the subsequent tearing and blepharospasm (eyelids clamped shut). The tears concentrate the organism with blinking towards the centre of the eye. For this reason, pinkeye always causes the worst damage near the middle of the eyeball. Occasionally the ulcer will perforate through the globe, releasing the liquid behind the eye. The eye then has a popped-out appearance and all sight is lost. These cases will not recover. In severe cases the eye will protrude so much it will need to be removed. Other cases of perforation have the eyeball collapsing and shrivelling up into the eye socket.
Any condition that changes the healthy integrity of the eye can predispose cattle to pinkeye. Generally younger animals are most susceptible because exposure implies inherent immunity has built up in the older stock. Sunlight causes squinting and stress on the eye and that also predisposes it to pinkeye.
Cattle with dark pigment around the eye such as Black Angus or the goggle-faced Simmentals are much less susceptible. Much like football players who darken the area below their eyes to prevent glare from the sun, pinkeye eye patches or strips of bluejean can be glued over the eye of treated cattle to avoid further irritation from sunlight. A dark spray can be applied around the eye on white-faced cattle which gives them a raccoon-like look, but it works.
Flies, especially face flies, are real culprits at spreading the pinkeye organism as they feed on eye secretions. Fly prevention, whether it be insecticide ear tags, oilers, pour-ons such as CyLence or systemic endectocides substantially cut down fly numbers. They have varying treament durations so must be applied during the peak fly season June to August in our area.
We have several producers and one community pasture who apply CyLence right as the cattle leave the truck for the pasture. This has the added benefit of helping prevent the spread of pinkeye and increasing weight gains because of the decreased fly irritation. Pinkeye, although not life threatening, will cause decreased weight gains.
For breeding bulls to be fully functional its best if they have binocular vision for greater depth perception so they see cycling cows. So you definitely want both of their eyes healthy.
Calves with large scars on their eyes also bring lower prices at sales because of this blemish. Aside from the appearance there is the danger of working with cattle that are blind in one eye. They are often difficult to sort and a bit spookier as a result of impaired vision. These are all reasons we want to keep pinkeye to a minimum in our herds.
Two fairly effective vaccines are available for Moraxella bovis and producers that have continual problems
with pinkeye will use these. Breeding bulls is another group where it may pay to vaccinate. Vaccinating in the face of an outbreak has proven beneficial. When you need to run a group through treat the clinical cases and vaccinate them as well as the healthy herd mates.
Treatment of clinical cases involves antibiotics such as long-acting tetracyclines (which provide good levels of active ingredient in the tears) or penicillin at low volumes, 2-3 cc, injected into the conjunctiva of the eye. A good rule of thumb is that once the tearing stops the infection is under control. Only time will gradually diminish the white scar caused by the infection. Treating when there is only a white scar does nothing. Depending on the size of the initial scar it may eventually disappear or leave a white area in the middle of the eye. This diminishes sight but vision around the scar will allow cattle to function quite normally.
Two years ago we saw a tremendous amount of damage to the eyes of cattle that were grazing tall alfalfa and grass stands. When pastures get lush and ripen off cattle graze through these stands to access the finer new growth. The cornea can be lacerated in these situations, leading to the same condition as a bad pinkeye. In these cases the injury will not be in the middle of the eye as with true pinkeye but regardless, the treatment is the same. Likewise foreign objects such as grass awns and barley beards will sometimes become lodged in the eye. So when treating for pinkeye always have a close look for foreign objects especially when there has been a lot of wind while the cattle were on pasture. These objects need to be removed before healing can occur.
Many conditions mimic true pinkeye so always examine the eyes closely when tearing is first noticed, as earlier treatment will minimize the chance of permanent damage.