Zoonotic Mastitis Pathogens in Dairy Cows: Prevalence and Risk Factors of <em>E. coli</em> and <em>S. aureus</em> in the West Arsi Zone, Ethiopia

Mastitis is a leading disease in dairy cows, significantly affecting milk quality and yield, and posing notable public health risks due to milk contamination with zoonotic pathogens. This study aimed to isolate and determine the prevalence of Staphylococcus aureus and Escherichia coli, and assess their associated risk factors in mastitic milk samples from selected dairy farms in Shashamane and Arsi Negelle districts, West Arsi Zone, Ethiopia. A total of 83 mastitis-positive milk samples were examined bacteriologically. The results revealed that 50.6% of the samples tested positive for S. aureus and 24.1% for E. coli, confirming their prominent role in bovine mastitis. Risk factor analysis showed that only the stage of lactation was significantly associated with S. aureus prevalence (p &lt; 0.05), with early lactation cows being most affected. Additionally, significant associations (p &lt; 0.05) were identified between both pathogens and hygiene-related variables, including the cleanliness of milking processes, milking equipment, handlers’ hands, and cow housing conditions. In contrast, variables such as breed, age, parity, production system, and settlement type did not show statistically significant associations. These findings emphasize the need for enhanced hygiene management, regular mastitis screening, and farmer education to reduce the burden of mastitis and improve milk safety. The study provides critical evidence for designing context-specific intervention strategies and highlights the necessity for further research into antimicrobial resistance profiles of mastitis pathogens in the region.