Moraxella bovis is the most frequently identified bacterial agent causing IBK. Moraxella
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. Moraxella
Mycoplasma spp., Acholeplasma, Chlamydia, bovine herpesvirus I (IBR) and bovine adenovirus are among the agents suspected to predispose cattle to Moraxella colonization or to add to the severity of IBK.Moraxella
Mycoplasma bovis can cause eye infections resembling those seen with Moraxella bovis as well.
Physical factors and eye irritants, such as flies, dust, wind and sunlight also predispose to IBK. Flies are considered common vectors in transmission of IBK-related microbial agents among cattle, and outbreaks are common during peak fly season.
Although IBK is not fatal, it exacts an economic toll through decreased weight gain, lower milk production, additional labour and treatment costs, and devaluation of disfigured animals or carcasses.
There is general agreement that affected animals fail to put on weight as quickly as uninfected animals. Hereford x Shorthorn crosses affected by IBK were on average 22.8 kg lighter than unaffected animals at 15 months old¹.