Infectious bovine keratoconjunctivitis in dairy herds: Presence of haemolytic Moraxella bovis and Moraxella bovoculi.

Infectious bovine keratoconjunctivitis (IBK) is a multifactorial disease with a significant economic impact on dairy production. This study aimed to investigate the epidemiology of IBK in dairy herds in Argentina. Haemolytic Moraxella spp. presence, environmental and management practices associated with milk production, and the presence of virulence genes were evaluated. An observational study was conducted over one year on nine dairy farms. Ocular swabs (n = 2142) were collected and analyzed by culture and PCR for identification and virulence gene profiling. Epidemiological data and environmental variables were also recorded. Haemolytic Moraxella spp. were isolated from 57.6% of eyes, with M. bovoculi being more prevalent than M. bovis. However, no association was found between the presence of haemolytic Moraxella spp. and IBK clinical signs. In addition, no relationship was observed between the climatic season and the presence of haemolytic Moraxella spp. in the eyes. However, the occurrence of IBK lesions showed a clear seasonal pattern. Increased ultraviolet radiation and high temperatures were associated with a higher incidence of IBK, and fly control significantly reduced disease risk. Although commercial vaccines only targeted M. bovis, vaccinated herds showed lower IBK prevalence and reduced haemolytic M. bovis isolation rates. In this study, MbxA, fur, plb, tfpI/Q and pilA genes were not associated with IBK signs. These findings suggest that the mere presence of haemolytic Moraxella spp. is insufficient to trigger IBK and support the hypothesis that environmental stressors play a key role in disease onset. Further studies are needed to identify the specific mechanisms that initiate corneal lesions and optimize preventive strategies.