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Pinkeye of cattle is also known as infectious bovine keratoconjunctivitis (IBK). The primary cause of contagious pinkeye is thought to be the bacteria, Moraxella bovis. Most studies on how to treat and control pinkeye have been directed against this particular bacterium. Better management of pinkeye may be possible if producers understand that term ‘pinkeye’ may describe many different eye lesions of cattle and not all ‘pinkeye’ is IBK, nor contagious.
The cow’s eye is normally resistant to invasion by microbes and not all cattle exposed to Moraxella get pinkeye. This indicates pinkeye is not simply an infectious bacterial disease but is multifactorial. To control outbreaks of pinkeye producers should try to identify and mitigate any predisposing factors. The most important are.
Whilst it may not be possible to avoid many of these risk factors, producers should ask.
Other eye lesions that look like IBK can be caused by trauma e.g. thistles, grass seeds, silage, hay bales; other infectious agents, e.g. mycoplasma, herpes virus; and eye cancer. Producers should inspect cattle with eye lesions closely and consider seeking veterinary advice. True Moraxella-IBK usually starts in the middle of the eye (Figure 1). IBK outbreaks are more common in calves and weaners, in the warmer months when feed is drying off.
Figure 1. Acute pinkeye. Image courtesy of Mac Kneipp
Early identification, treatment and segregation of affected cattle may help control a pinkeye outbreak. Treatments directed against the eye lesions include antibiotics and anti-inflammatories as eye ointments, powders, sprays and oral and injectable drugs (Figure 2). Pinkeye ointments are long acting, one treatment lasts 48 hours. They are superior to pinkeye powders and sprays which require many repeat treatments and may cause irritation on application. Under no circumstances should treatments like kerosene be used. Producers should be careful not to cause further eye trauma or spread contagious infection when treating.
Eye patching may protect the affected eye and prevent further spread. Fly control may be indicated. Veterinarians can prescribe treatment for pinkeye and provide additional treatments such as subconjunctival (under the upper eyelid) injections, temporary tarsorrhaphy (suturing eyelids together), injectable antibiotics and pain relief.
There is a vaccine against Moraxella but limited data on its efficacy. Vitamin ADE injection has been used for cattle in drought conditions with no green feed.
Figure 2. Using a subconjunctival injection to treat an animal with pinkeye. Image courtesy of Mac Kneipp