Bovine mastitis: Risk factors and isolation of Gram-negative bacteria in Western Algeria

Across-sectional study was conducted inwestern Algeria between February and October 2024, aimed atdetermining the prevalence ofbovine mastitis, Gram-negative bacilli, and their associated risk factors. Atotal of524cows were sampled using clinical examination and the California mastitis test. Milk samples from the affected quarter were subjected tobacteriological assays. Three generalised linear mixed models were used toidentify the risk factors for clinical mastitis (CM) and subclinical mastitis (SCM), aswell asGram-negative bacilli isolates associated with bovine mastitis. Model selection was performed using the Akaike information criterion. The prevalence ofmastitis was 59.7% atthe cow level, ofwhich 12.6% was CM and 47.14% SCM. Overall, 65.5% ofthe mastitis cows showed apositive culture for Gram-negative bacilli. The most commonly isolated bacteria wereEscherichiaspp. (44%), Klebsiellaspp. (23.1%), and Pseudomonas spp. (11.6%). The parity, contact with visitors, and daily milk yield (l/day) were identified asrisk factors for SCM indairy cows. However, foremilk discarding reduced the risk ofdeveloping SCM. Ahistory ofmastitis, udder injuries, udder and leg hygiene scores, and parity were identified asrisk factors for CM. Nevertheless, none ofthe variables examined were risk factors for anudder infection bythe Gram-negative bacilli isolates.