This past year has seen a huge resurgence of pinkeye and other eye ailments in our practice. While I may have some of the answers the last year was unique with the lush growth of grass and a very high face fly population. And dry years see producers grazing alfalfa and the coarse stems also cause eye abrasions.
Pinkeye technically is known as infectious bovine keratoconjunctivitis (IBK), caused by the bacteria Moraxella bovis and 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 and worthy of discussion.
Producers initially will notice the eye tearing and the conjunctiva (pink area surrounding the eye) swollen and red. Pinkeye most commonly will affect just one eye. The theory being immunity will develop 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 being clamped shut). The tears concentrate the organism with blinking towards the centre of the eye. Pinkeye therefore always causes the most damage near the very middle of the eyeball. Occasionally the ulcer will perforate through the globe, releasing the liquid behind the eye. The eye will have a popped-out appearance and all sight will be lost. These cases will not recover and 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 getting pinkeye. Generally, younger animals are most susceptible because exposure implies inherent immunity to the older stock. Sunlight, causing squinting and stress on the eyes, predisposes cattle to pinkeye. Cattle with dark pigment around the eye such as Black Angus or the goggle-faced Simmentals are less susceptible. Much like the football players that darken the area below their eyes to prevent glare from the sun, when treating pinkeye eye patches or strips of blue jean can be glued over the eye to totally prevent sunlight from causing further irritation. A dark spray can also be applied around the eye on white-faced cattle, giving them a raccoon-like look.
Flies, especially face flies, are real culprits for spreading the pinkeye organism as they feed on the eye secretions. Fly prevention whether it is insecticidal ear tags, oilers or the pour-ons such as CyLence or the endectocides can be used to substantially cut down fly numbers. They have varying treatment durations so must be applied during the peak fly season June to August in our area.
We have several producers and one community pasture, for instance, applying the pour-on CyLence right as cattle leave the truck to pasture. Decreased fly irritation will give the added benefit of helping prevent the spread of pinkeye and reduce the risk of weight loss. And yes, pinkeye, although not life-threatening, can lead to decreased weight gains.
For fully functional breeding bulls its best if they have binocular vision for depth perception to see cycling cows so you definitely want both eyes healthy. Calves with large scars on their eyes may yield a decreased price because of this blemish. There is also the danger of working with cattle 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 on our herds. A vaccine is available for Moraxella bovis and producers experiencing continual problems will use this vaccine. Breeding bulls are another group it may pay to vaccinate.
TREATING THE INFECTION
Treatment involves antibiotics such as long-acting tetracyclines (which get good levels in the tears) or penicillin at low volumes (two to three cc doses) injected into the conjunctiva of the eye. A good rule of thumb is once the tearing stops the infection is under control and only time will help the white scar to gradually diminish. 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.
Several years ago there was a tremendous amount of damage to eyes from trauma 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 and the same condition as a bad pinkeye is the result. In these situations the injury will not be in the middle of the eye as with true pinkeye, but regardless treatment is the same.
Likewise foreign objects such as grass awns and barley beards will become lodged in the eyes so when treating for pinkeye always have a close look for these foreign objects especially when weather has been very windy. These objects need to be removed before healing can occur.
If possible use fly treatments in the summer and also if possible, select cattle for genetic eye pigment, which helps prevent the disease. †