“Pinkeye refers to an inflammation of the eye and surrounding tissues,” said Dr. John Middleton, associate professor and section head, for Food Animal Medicine and Surgery with the College of Veterinary Medicine at the University of Missouri. “Classically, the term ‘pinkeye’ in cattle has been synonymous with the condition termed infectious bovine keratoconjunctivitis (IBK) caused by the bacterium Moraxella bovis.”
Inflammation of the eye and surrounding tissues can be caused by a number of agents including viruses and bacteria. “The term ‘pinkeye’ usually refers to an infection of the eye with bacteria of the Moraxella genus, namely Moraxella bovis, Moraxella Bovis or Moraxella bovoculi,” Middleton said. “While the bacteria appear to be the primary cause of the disease, a number of risk factors predispose to infection. These risk factors include age, breed, season, ultraviolet light exposure, face flies, dust, pasture condition, lack of skin pigment around the eyes and host immune status.”
“Face flies can serve as an important vector for transmission of bacteria from one animal to the next. Irritation of the eye increases the risk of infection,” Middleton added.
According to Whitney Whitworth, associate professor of animal science at the University of Arkansas at Monticello, symptoms of pinkeye include Conjunctivitis, which is swelling of the eyelid. “Affected animals will also show profuse tearing and weeping of the eye. They may also be quite sensitive to bright light and may seek shade. The cornea may appear white; there are also corneal ulcers later in infection.”
Middleton added that as the inflammatory response develops, a cloudy spot usually occurs in the center of the surface of the eye and may ultimately develop into an ulcer. “This process usually takes about 24-48 hours. After another 24-48 hours the surface of the eye surrounding the ulcer will redden as new blood vessels develop in the tissues. Some animals will spontaneously cure (7-10 days) with little to no scarring, while other animals will develop chronic disease that can take 1-2 months to resolve and a permanent opacity may be seen in the center of the eye. In the most severe cases, the eye may perforate resulting in permanent blindness.”
Treatments include Oxytetracycline for the early stage of infection; eye patches are also helpful in some instances. “Other types of antibiotics (penicillin) may be given in the conjunctiva, but those types of injections should only be given by someone trained to give shots in the eye,” Whitworth said.
“Animals who are white-faced are the most prone to have problems,” Whitworth said. “Cattle who have pigmentation on their face, even a ring-eye on an otherwise white-faced animal will have much fewer problems.”
Whitworth concluded, “Animals in dry, dusty environments or those who have been stressed as well as those who have allergic reactions to certain plants or pollens tend to have pinkeye problems which are exacerbated. Fly control is of critical importance. Flies can carry the bacteria for three days after feeding on ocular (eye) discharge of an infected animal.”
