Giving Pink Eye the Stink Eye
With summer in full swing comes the usual veterinary problems in a large animal clinic: lacerations on horse legs, over-heated alpacas, warts on show calves, hoof rot in sheep, and a lot of pink eye in beef cattle. Let’s take a closer look at this common ophthalmologic issue in cows.
Pink eye in cattle, medically known as infectious bovine keratoconjunctivitis, is a contagious bacterial infection of the eye. Cattle pink eye is different from human pink eye, which, although usually infectious, is not highly contagious. Pink eye in cattle also looks clinically different and is usually much more severe than the disease in humans.
Pink eye in cattle is most commonly caused by a bacterium called Moraxella bovis. This crafty microbe uses tiny hair like structures called pili to attach to the white part, or the conjunctiva, of the eye and cause damage. M. bovis is spread by flies, which feed on eye secretions and are a constant source of irritation to cattle in the summer months, providing the perfect recipe for eyeball infection.
Once introduced to the eye, M. bovis causes irritation and tearing. The first clinical sign of pink eye infection in cattle is an animal squinting. Very soon after initial infection, the cornea begins to cloud up and soon becomes completely white. An ulcer will form on the cornea and if not treated, can result in permanent blindness. Sometimes the damage to the eye is so severe, the eye itself will protrude from the socket.
Pink eye most commonly affects beef calves and in some herds can greatly affect productivity. The eye pain and subsequent stress that pink eye causes can result in profound weight loss, or lack of weigh gain, in beef calves, which is obviously a cause for concern for the farmer. For the health and well-being of the animal and the farmer’s bottom line, pink eye should be treated as quickly as possible.
One of the best ways to treat pink eye in cattle is a subconjunctival injection of antibiotics to kill the infection and steroids to help with the inflammation. This is where a steady hand, proper head restraint, and a non-queasy stomach really come in handy because subconjunctival means an injection directly into the white part (conjunctiva) of the eye. With the animal’s head held completely still in a chute, a needle is inserted just under the conjunctiva. The mix of antibiotics and steroid is then slowly and carefully injected so that a small bleb of medicine appears. Yes, this hurts the animal initially, but it works wonders. Many pink eye cases respond within a day or so.
Sometimes an intramuscular injection of antibiotics (often oxytetracycline) can also be used. I do this if the farm lacks proper facilities to restrain the animal for an eyeball poke (that’s a medical term, by the way).
If treated promptly, the cornea will clear up and sight will return. If corneal ulceration was severe, sometimes a small scar will remain on the eyeball. Cattle usually get pink eye only in one eye. If both eyes are infected, sometimes a calf will have to be penned to allow healing and sight to return.
Prevention is always better than the cure itself, and proper fly control is really the best way to go to keep pink eye from ravaging through a herd. Sometimes this is difficult, however, and other times it just seems like a farm has a really hot strain of M. bovis. Younger calves can be vaccinated against multiple strains of M. bovis and we recommend this if a particular farm has had issues in the past. Between vaccinations, fly control, and a good ol’ eyeball jab, we give the stink eye to pink eye in the summertime.
Dr. Anna O'Brien