IBK, commonly known as pinkeye, is a highly contagious ocular disease.
Infectious Bovine Keratoconjunctivitis (IBK) or pinkeye, is a common, highly contagious ocular disease affecting primarily calves. Primarily caused by Moraxella bovis, infection may lead to vision loss in acute cases. The incubation period is typically 2 to 3 days, with a small opaque area appearing on the cornea within two days. Corneal lesions are typically central in location.
Moraxella bovis is probably the most common bacteria causing IBK.
Other gram-negative bacterial cocci related to Moraxella bovis, M. ovis (formerly Branhamella ovis), and M. bovoculi have been isolated from clinical cases of IBK.
Mycoplasma spp., Acholeplasma, Chlamydia, bovine herpesvirus I (IBR) and bovine adenovirus are among the microbial agents suspected to predispose cattle to Moraxella colonization or to add to the severity of IBK.
Mycoplasma bovis can cause eye infections resembling those seen with Moraxella bovis as well.
Physical factors and eye irritants such as flies, dust, wind, sunlight, and chaff also predispose to causing IBK. Flies are considered common vectors in transmission of IBK-related microbial agents among cattle and outbreaks are common during peak fly season.
IBK varies from mild eye irritation with tears and small white ulcers to severe inflammation, resulting in permanent scarring and vision loss. In addition, elevated body temperature and intense pain depress the appetite.
Non-pathogenic strains of Moraxella bovis exist: strains that do not produce pili (bacterial structures that allow attachment to the eye) or cytotoxins are much less capable of producing clinical disease.
Animals with IBK should be treated as early as possible to curb transmission to other animals and minimize the possibility of adverse and possibly permanent damage to the eye. Moraxella bovis are susceptible to several anti-infectives In addition, local treatments (ointments, eye patches, surgical third eyelid flap) may be helpful.
Preventive measures include controlling flies with insect repellent impregnated ear tags, mowing pastures, minimizing dust in hay and feed bunks, providing shade, and, indirectly immunizing against viral diseases, such as IBR. Moraxella bovis bacterins administered prior to fly season may also be helpful.
Although IBK is not fatal, it exacts an economic toll through decreased weight gain, lower milk production, additional labor and treatment costs, and devaluation of disfigured animals or carcasses.
The economic impact of IBK (pinkeye) is difficult to quantify, but industry losses are estimated to exceed $150 million annually, excluding treatment costs. The disease affects 10 million calves each year, with losses due to lower weaning weights and reduced rate of gain.