Pink Eye in Cattle
Pink eye cases are on the rise as the summer progresses, especially with a hot dry summer that allows for fly populations to grow exponentially. Pink eye issues can reduce dry matter intake and can impact growth rates in heifers and other young stock. Prevention and outbreak control is important for managing this disease on your farm.
Cause and Risk Factors
Infectious Bovine Keratoconjunctivitis (IBK) or pink eye, is predominantly caused by a bacteria (Moraxella bovis) that is spread from animal to animal mostly by face flies that feed on infected eye discharge. The bacteria can survive up to 3 days on surfaces and 2 days in the gut of face flies. Flies are by and large, the biggest factor in perpetuating pink eye outbreaks, but other causes of mechanical damage to the eyes can contribute to the severity of cases. This would include sun exposure, heavy dust or plant awn irritation. Any damage to the outer protective layer of the eye can allow invasion of Moraxella bovis.
Usually youngstock are affected more so than older animals. Signs can start with mild ocular discharge and slightly squinted eyelids, which progress to visible white ulcers on the surface of the eye. Ulcers are quite painful and rupture of the eye can be a consequence of severe, deep ulcers. A healing ulcer will have an area of red tissue covering the initial lesion which progresses to pink, then white, and over time, the ulcer will shrink in size and can even fully resolve.
Two products were traditionally used by clients of our clinic for topical treatment of pink eye, both of which have been discontinued within the last year. Wound and Pink eye spray is no longer available or made due to the recall and total discontinuation of the ingredient gentian violet. Special Formula was also commonly used, but it has also been permanently discontinued.
Topical treatments: Topical treatments are ideally applied multiple times a day in order to be effective, which is typically not feasible with cattle. Most mild to moderate cases self-resolve, so it is likely that some traditional treatments were not even that effective, and the cases would have improved without treatment! But if you want to apply a daily topical medication and you have the ability to restrain cattle well and apply treatment to the eye directly, another intramammary antibiotic product would be recommended. Some of our clients have had good success with Spectramast LC applied once a day for a couple of days. Be sure to clean the tip of the ointment tube between animals to prevent spread.
Subconjunctival treatment: Injection of penicillin directly into the conjunctiva (the pink tissue under the lids) requires excellent restraint (locking head gates or a chute) and a veterinarian to perform the procedure. This allows for slow release of therapeutic levels of antibiotic into the eye for about 24 hours.
Injectable Antibiotics: Cattle can be treated with regular antibiotic therapy. For beef animals or young heifers, best options are long-acting tetracycline (Oxyvet 200 LA) or Nuflor spaced apart every 3 days for 2-3 treatments. For lactating cows, Excenel or Ceftiocyl is the best option, as there are no short-acting oxytetracycline products available anymore for lactating cattle.
Other Therapies: For ongoing severe cases, it may be the best option to place a patch over the affected eye to protect from further irritation. This can also be achieved surgically by stitching the eyelids closed. The most severe cases resulting in rupture or prolapse of certain parts of the eye may require that the eye is surgically removed. Obviously these are costly options and so it is best to prevent infection and treat earlier in the course of the disease.
Prognosis and Prevention
Prognosis is good for mild to moderate ulcers as cattle have an enormous capacity to heal their eyes compared to some other species. Healing of superficial and deep ulcers requires weeks to months, but often vision returns fully. Even if the animal has a residual scar on the surface of the eye, vision is not usually dramatically impaired. Again, this takes a good amount of time, and as long as irritation is limited, ongoing therapy is not needed when the eye gets to the healing stage.
There are some commercially available pink eye vaccines, but their overall efficacy is low, and therefore they are not commonly used. There are several different strains of Moraxella bovis as well as some other minor bacteria and viruses that can contribute to cases of pink eye, so there is much variation of the causes of pink eye between farms that makes a one-size-fits-all vaccine not effective in many cases.
In order to prevent pink eye and control the spread of disease, the most important thing you can do is reduce risk factors:
Good fly control, starting early in the season before fly populations begin to expand. Including a variety of fly control methods (premise sprays, pour-ons, strings, or fly tags) is the best strategy, as well as rotating your products from year to year to avoid resistance. Refer to the June MoosNews for more in depth fly control information.
Separating affected animals if your facilities allow for it.
Reduce sun exposure for affected animals.
Evaluate feeding and bedding practices to reduce the amount of dust and debris irritating the face of animals.