Pink Eye in Bison September 2003


Dear Gerald:
I was looking at a small herd of bison (27 animals) that the owner is trying to sell.  He informed me that one or two of his animals have been treated for pink eye.   It appeared that the animal had not been separated from the herd.  The calf with the pink eye appeared to have been treated with some kind of goop in the eye that looked like an antibiotic. What might the probability be that the rest of the bison herd is also infected?  If they are not, what can be done as a precautionary measure to keep the rest of the animals from getting the disease?



Pinkeye in bison is a common condition. Most, if not all bison herds have had some animals get it. Some herds have had a lot of trouble with it while other herds have had only a few animals affected. It is more common in the summer when there is a lot of dust around and the fly population is high. We presume that the cause is the same types of bacteria that are found in beef cattle but we are not sure. Treatments are based on what seems to work in cattle. There is a wide assortments of treatments used but most are based on antibiotic therapy and shielding the eye with patches or flaps.

There is a high probability that the other bison in the herd have been exposed to the pinkeye bacteria. Some animals will likely be carrying the bacteria in the fluids around their eyes. It likely won't cause a problem unless the eye is damaged somehow (dust in the eye, scratch from grass stalks, flicked in the eye with a tail, etc.) or the animal's immune system is weakened (nutritional deficiency, parasitism, chronic disease, etc.). As stated earlier it is likely that every bison herd in the province has the pinkeye bacteria. If they have any number of animals, they likely have some harbouring the bacteria waiting for a chance to cause an infection when the conditions are right. The chance of having a problem with pinkeye in these bison is probably no higher in this group than any other that you would consider buying.

Precautions to take in preventing the disease include:

1. Vaccinate them with a cattle vaccine-even though the effectiveness is unknown it may be worth a try. The problem with the vaccine is that you should boost them with it just before pinkeye season in the summer which is now. Nobody wants to put cows and calves through their handling system at this time of year. You can vaccinate yearlings before turning them out to pasture. They are the most likely group to get infected so it may be worth it.

2. Make sure that the herd is as healthy as possible. Look after parasite problems if they exist. Make sure there are no nutritional deficiencies (copper, selenium, etc.)

3. Control the fly population around your bison to decrease spreading of the bacteria.  Put fly tags in the ear, insecticide oilers on pasture, predator wasps can all work.

4. Control conditions that might scratch the eye and allow the bacteria to cause an infection. Keep pastures short through grazing or mowing and keep dust down (hard thing to do in dry spells).

Gerald Hauer
Bison Centre of Excellence

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