A cross-sectional study of keratoconjunctivitis among dairy cattle farms subject to Mediterranean climatic conditions.

The epidemiology of bovine keratoconjunctivitis (BK) is complex and involves several conjunctival microbiota as well as host and environmental factors. Data about BK in dairy cattle are scarce, and even scarcer for dairy cattle in Mediterranean climates. We determined the BK prevalence among dairy cattle in Southern Africa's Mediterranean climatic zone by examining 1,675 dairy cattle across 28 herds. Conjunctival swabs were analysed using real-time PCR. Risk factor data were collected by questionnaire and evaluated by multivariable logistic regression. The BK prevalence was 19.4%, (95% CI: 15.0 - 24.8%). Mesomycoplasma bovoculi was demonstrated in 75.7% of the sampled eyes (95% CI: 62.8 - 85.2%) across all farms. Moraxella bovis (18.3%, 95% CI: 11.9 - 27.0%) and Moraxella bovoculi (8.6%, 95% CI: 4.6 - 15.6%) were detected on 89% and 64% of the farms, respectively. Mycoplasmopsis bovis was rarely encountered. Moraxella bovoculi was significantly associated with BK (OR: 2.7, 95% CI: 1.3 - 5.6, Wald P: 0.01). Prevalence varied significantly by age and breed. Shade availability (OR: 2.5, 95% CI: 1.4 - 4.4, Wald P < 0.01), sanitation frequency, (OR: 0.4, 95% CI: 0.2 - 1.0, Wald P: 0.05), fly burden (OR: 2.1, 95% CI: 1.3 - 3.6, Wald P < 0.01) and introduced cattle (OR: 2.0, 95% CI: 1.1 - 3.5, Wald P: 0.02) were significantly associated with the prevalence of BK. Closed herds with proper biosecurity, fly control via sound management practices, and access to shade are recommended for preventing BK in dairy herds farmed in a Mediterranean climate.