Antimicrobial Usage for the Management of Mastitis in the USA: Impacts on Antimicrobial Resistance and Potential Alternative Approaches

Mastitis is the most frequently diagnosed disease of dairy cattle responsible for the reduction in milk quantity and quality and major economic losses. Dairy farmers use antibiotics for the prevention and treatment of mastitis. Frequent antimicrobial usage (AMU) undeniably increased antimicrobial resistance (AMR) in bacteria from dairy farms. Antimicrobial-resistant bacteria (ARB) from dairy farms can spread to humans directly through contact with carrier animals or indirectly through the consumption of raw milk or undercooked meat from culled dairy cows. Indirect spread from dairy farms to humans can also be through dairy manure fertilized vegetables or run-off waters from dairy farms to the environment. The most frequently used antibiotics in dairy farms are medically important and high-priority classes of antibiotics. As a result, dairy farms are considered one of the potential reservoirs of ARB and antimicrobial resistance genes (ARGs). To mitigate the rise of ARB in dairy farms, reducing AMU by adopting one or more of alternative disease control methods such as good herd health management, selective dry-cow therapy, probiotics, and others is critically important. This chapter is a concise review of the effects of antimicrobials usage to control mastitis in dairy cattle farms and its potential impact on human health.