by: Heather Smith Thomas

Eye problems in cattle and horses can be caused by burdock slivers. This plant has seeds that stick to fur or clothing. When ripe, the burrs release hundreds of microscopic barbed slivers. If a sliver gets into the eye, it can cause inflammation and infection that may puzzle your veterinarian, since the microscopic sliver is not easily seen. The cornea of the eye may become inflamed and ulcerated; the eye may turn cloudy and have a white spot or bulge on it.

In cattle the problem may be mistaken for pinkeye, but pinkeye is generally a summer problem when face flies spread infection from animal to animal. By contrast, burdock slivers usually get into the eye in fall or winter after burrs are ripe. A sliver may become embedded in the eyelid, where it scratches the eye every time the animal blinks, creating an ulcer on the eyeball. The sliver is so small that the usual tools used by a veterinarian to examine an eye (a focal light and magnifying lens) may not be powerful enough to locate and identify the foreign object.

Gerald Stokka DVM, MS (Associate Professor of Animal Sciences, North Dakota State University) has seen many eye problems in livestock. “The diagnosis of an eye problem is important. True pinkeye, if it's a bacterial infection, causes weeping (the first thing you'll notice), and then if you are able to look very closely you will see redness of the conjunctiva, the covering of the white part of the eye. It is trying to get more blood to that area. You'll see a little ulcer start to form, and it's usually right in the middle of the cornea rather than off to one edge. This can be a clue,” says Stokka.

“If the ulcer occurs some other place than in the center, you may be dealing with a sticker, plant awn or some other foreign body that has gotten stuck under the eyelid and scraped the cornea. In order to make the diagnosis, you have to confine that animal and look into the eye,” he says.

“You need a good light to see something as small as a plant awn or a hair scratching on the cornea every time the eye blinks. The eye is very sensitive to scratches. Even if the foreign matter is no longer there, and the scratch is significant, there are always bacteria present that could cause an eye infection. This may take a while to clear up,” he says.

The burdock slivers are more difficult to find than most plant material because they are almost microscopic. “You have to be diligent in your search, and the animals don't like you doing that. It helps to have the animal restrained in a headcatch, with a halter to pull the head to one side or the other. Then you use your fingers to peel back the eyelids and take a look both top and bottom, and in the front part where the third eyelid is located, to see if you can find anything foreign there,” says Stokka.

The animal has to hold very still for this kind of examination. “I use a tissue paper or lens paper to wipe that area, to see if that will wipe it out. Even if I can't see anything, I'll still wipe it. Sometimes I've been successful, even when I can't identify anything there, just by wiping the area. This might pull it loose and get it out of there, if it's a tiny particle like a burdock sliver. If I feel like there's an infection going on in that eye, I'll prescribe an antibiotic.

In years past, many veterinarians injected a small amount of antibiotic (such as penicillin) under the surface of the conjunctiva or inner surface of the eyelid, for longer-lasting effects than topical eye medications. “Today I prefer to use a systemic antibiotic labeled for pinkeye (such as oxytetracycline) that can flood the eye via the tears. This is easier to administer.”

“This has been my approach, in distinguishing the infectious pinkeye outbreaks from the eye problems that have a foreign body stuck under there and irritating the eye. There is a lot of pain involved, and it will give the animal relief if you can remove the foreign body or wipe it out of the eyelid tissues,” Stokka says.

Carl Dahlen, Beef Specialist, North Dakota State University Animal Science Department, says it's hard to know how many cases of “pinkeye” are actually pinkeye. “All we see is the signs of an irritated eye and an ulceration. Most of our winter pinkeye is due to some kind of irritation that allows micro-organisms to proliferate. The eye problem is preceded by some type of insult to the surface of the eye. It might be windy conditions blowing dust into the eyes in a dusty feedlot, or chaff blowing into the eye, or something like burdock getting caught under an eyelid,” he says. The scratch on the cornea allows access by pathogens that may cause an eye infection.

“What we call ‘winter pinkeye' has become more prevalent and it's usually due to some kind of irritation to the eye,” he says.

“Getting rid of the burdock patches in a field or pasture can help prevent irritation from burrs. Spraying these plants at the right time of year, or chopping them down before the burrs are ripe can help. We've used a little tractor with a brush hog to get where we could—to drive every pasture and chop down those patches. In places you can't drive to, you end up chopping them by hand or whatever works,” he says.

“Ranchers may not be as concerned about the eye issues as just the fact that the burdock tends to take over certain areas of the pasture. It competes and crowds out other plants and nothing else grows there,” says Dahlen.

There's also the factor that the plants are readily spread to new areas by animals that get covered with burrs. Livestock and wildlife will spread these tenacious plants to other fields and pastures. In many instance cattle buyers will refuse to purchase a group of animals that are covered with burrs. There are multiple reasons to try to eliminate these noxious plants in your pastures.

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