Cattle health during the dog days of summer: Pinkeye

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Click here for Part 1: Footrot, of the Cattle health during the dog days of summer articles.

Pinkeye in cattle is most commonly caused by the Moraxella bovis (M. bovis) bacteria, but there are other species like M. bovis’ younger sister, Moraxella bovoculi, that can come into play – and they’re not all covered by the same treatments.

“Things like dust, ultraviolet light, tall grasses with seeds that irritate the eyes and flies transporting infectious organisms from one animal to another make pinkeye a multi-factor infection,” says John Maas, former veterinarian with the University of California at Davis Cooperative Extension, and chairman of the Beef Quality Assurance Advisory Board.

Photo by Laura Mushrush Regardless of bacteria perpetrator, the initial infection starts with an ulcer in the center of the eye so small it generally can’t be detected by human sight.

“If it’s a seed or scratch, a lesion will typically occur on the side of the eye,” he explains, adding that this can lead to pinkeye. “So the ulcer in the central part of the eye is the clinical sign of pinkeye.”

More often than not, flies moving from one animal to another are the biggest spreaders of the infectious organisms.

“Face flies make a living by using their raspy tongue to irritate the tissue around the eyes and nose to feed on secretions,” says Maas. “That’s how the bacteria is so easily spread from one eye to another.”

Bacteria is so highly transmittable, ranchers can spread it if they come into contact with an infected animal and then come into contact with a clean animal. Because of this, when treatment is given, doctoring equipment must be disinfected, disposable gloves should be worn and contaminated clothing should be washed.

While there are vaccines available to help prevent pinkeye, most take 4 to 6 weeks to become effective.

“The immune system takes time to get revved up, so vaccinating during an outbreak will only help with prevention in the future, not the present time,” explains Maas.

In the case of an outbreak, producers should instead go straight to an antibiotic treatment, which will in turn slow down the spread of the bacteria.

For pinkeye treatment, eye patches can be very beneficial to speedy recovery since they prevent dust and sunlight from further irritating the eye. However, if used, Maas stresses the importance of making sure the eye is not completely sealed off so the healing process can be monitored.

“When it starts to heal, the secretions will start to dry up. If they do not, you may have to follow up with more treatment,” he says. “It’s important to monitor the process, because serious damage can be done if it’s not.”

A supplementation program focusing on the same trace minerals used in preventing footrot (copper and selenium) will also help eliminate susceptibility to pinkeye by boosting the immune system.

See the full article and more in the digital edition of the June-July issue of Drovers/CattleNetwork.



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Walter Hylton    
vA  |  July, 19, 2014 at 06:54 AM

As an experienced veterinarian in VA, I beg to differ in regard to the cause of central corneal ulcers. They can indeed result from mechanical damage by fescue or orchardgrass seeds or chaff and result in pinkeye that is indistinguishable from other central corneal pinkeye. My feeling is that in an outbreak, if any of the observed ulcers are not central (most non-central ones will be ventromedial- lower down on the eye surface and towards the middle of the face), then the outbreak is likely caused by mechanical abrasion of the cornea by seeds or chaff. In other words, all non-central ulcers are mechanically induced, but central ulcers may or may not be centrally induced. In this part of the country, outbreaks invariably occur most often when fescue and orchardgrass seeds start to mature and shed chaff, continue until all the seeds have fallen off, and then come to an screeching halt. Often outbreaks during the feeding seasons can be traced to how the hay or other forage is fed, i.e., if the cattle are exposed to forage above eye level.


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