72 A One-health Perspective on S. aureus Induced Mastitis

Abstract Bovine mastitis, commonly caused by bacteria, is one of the most devastating diseases for the dairy industry worldwide, with high economic, social, and public health impacts. Among the pathogenic bacteria, Staphylococcus aureus is one of the leading pathogens in most countries. Success rate of antibiotic treatment is low such that effective control of S. aureus induced mastitis is currently only possible through prevention of new infections and culling of infected animals. The infection is usually subclinical, causing elevated somatic cell counts but no detectable changes in milk or the udder. S. aureus persists in mammary glands, teat canals, and teat lesions of infected cows and is transmitted to other cows during milking. The direct evidence of cross-species transmission of S. aureus is still scarce. Nevertheless, accumulating indirect evidence supports the zoonotic potential for S. aureus from bovine mastitis to humans. In addition to direct contact, aerosol exposures may also be an important mechanism for the transmission. While animal-adapted livestock-associated methicillin-resistant S. aureus has been known for many years, most S. aureus isolated from mastitic milk in Canada are methicillin-sensitive. S. aureus induced mastitis is a common reason for therapeutic and/or prophylactic use of antibiotics on dairy farms. Occurrence of multidrug resistant, especially methicillin-resistant, S. aureus has been a major public health concern. In this talk, we will address the pathogenesis and strain spectrum of S. aureus induced bovine mastitis, review existing evidence for inter-species transmission, and discuss possible transmission of methicillin-resistance determinants. This talk aims to emphasize the need for the one-health approach for prevention and treatment of S. aureus induced mastitis, in order to provide safe and nutritious milk and milk products to consumers.