The Eyes Have It - Part 1
I was taught at school, and later reinforced by my boss, that any eye issue should be considered an emergency, even if it sounds minor. Forgive me a little literary quotation, but I think Charlotte Brontë summed it up quite nicely: "The soul, fortunately, has an interpreter – often an unconscious but still a faithful interpreter — in the eye."
Let’s explore some of the most common eye issues seen in large animal practice.
Eye Disorders of Small Ruminants — Sheep and Goats
Sheep and goats, while so different in some ways, are quite similar in other physiologic aspects, and eye issues are a good example. Several times a year, I see sheep and goats with one or both eyes swollen and tearing, with discharge, and with a cloudy cornea. Occasionally, the cornea will be so opaque that the animal has trouble seeing. Most commonly, this is an infection from one of two troublesome bacteria: Chlamydia or Mycoplasma.
This condition is usually referred to as "pinkeye," though I try not to use this confusing and vague name, since cattle get another form of pinkeye caused by a different bacteria; keratoconjunctivitis, which is just plain harder to say.
Chlamydia and Mycoplasma are, unfortunately, sometimes ambitious microbes. They can cause other illnesses besides the relatively benign eye troubles. Both can cause reproductive problems and birth defects, and Mycoplasma can also cause nasty respiratory disease. They are also contagious, meaning in a herd housed in close quarters, I usually will see multiple cases.
Treatment for pinkeye in small ruminants is usually in the form of topical antibiotic eye ointments from the tetracycline family. Eyes that are swollen and inflamed are also quite painful, so much so that goats especially (who tend to be more sensitive to pain and other nasty things like swearing and rainy days) will sometimes go off of their feed and distance themselves from the others. Pain medication, both topical and systemic, can help with this.
Usually I tell owners the eye will look worse before it starts to get better. Barring further complications, the eyes usually heal well.
Eye Disorders of Large Ruminants — Cattle
Cattle get pinkeye as well, but as I alluded to before, the bovine version is caused by a different bacterium, this time Moraxella bovis. Pinkeye in cattle is also called IBK (infectious bovine keratoconjunctivitis) and is the most common infectious cause of eye problems in this species (if only horses were this simple!).
IBK looks ugly, hurts, and can go through a herd quickly. Usually starting with a watery, squinty, eye, this infection quickly escalates to corneal edema (a cloudy eye), then a nasty corneal ulcer.
Many experienced cattle farmers know pinkeye very well and some are comfortable treating it on their own. Systemic oxytetracycline helps, but if the eye is bad enough, I’ll gross everyone out and administer a scleral injection of antibiotic and steroid. That’s right, an injection right into the white part of the eye.
This was terrifying the first time I did it, but a cow’s eyeball is a tough eyeball and as long as the head is firmly restrained and kept still with the help of a chute with a head gate and halter, we’re good to go. Usually, with these direct eyeball sticks (a technical term), the eye looks much better within 24 hours.
There are vaccines against IBK and in some herds we do recommend it. The trouble is that there are a few different serotypes of Moraxella bovis and the vaccine may not prevent against them all at the same rate. Other recommendations include proper manure management to decrease fly populations, since these insects spread the disease, and proper quarantine of new stock before admittance into the herd.
Next week: equine ophthalmology. Horse eye drama deserves an entire blog all to itself, and then some.
Dr. Anna O’Brien