War against mastitis: Current concepts on controlling bovine mastitis pathogens

Mastitis, inflammation of the mammary gland, is one of the most costly and complex diseases of the dairy industry. The economic consequences of bovine mastitis are related to treatment, production losses, culling and changes in milk quality. These factors have a substantial impact on the farm business. The complexity is reflected in the numerous causative pathogens, the variety and magnitude of the physiological responses to these pathogens and the variation in efficacy of control measures for different causative organisms. Whether accompanied by clinical signs or not, an IMI (IMI) is associated with an increase in the somatic cell counts (SCC) in milk. The magnitude of this increase varies according to the bacteria involved in the IMI. The major pathogens (Streptococcus agalactiae, Staphylococcus aureus, Streptococcus spp., coliforms Escherichia coli and Klebsiella spp. and Mycoplasma spp.) are responsible, most of the time, for clinical mastitis. The minor pathogens, staphylococci other than Staphylococcus aureus (mostly Staphylococcus chromogenes, Staphylococcus hyicus, Staphylococcus epidermidis, and Staphylococcus xylosus) or Corynebacterium spp. are associated with a moderate infection and rarely with clinical signs. Based upon their primary reservoir and mode of transmission, mastitis agents are classified as contagious (Staphylococcus aureus and Streptococcus agalactiae), commonly transmitted among cows and environmental pathogens, streptococci other than Streptococcus agalactiae (mostly Streptococcus uberis) and coliform (e.g., Escherichia coli, Klebsiella spp.) witch arise from the cows environment, entering into the udder between milkings, when teats are exposed to mud, manure, and dirty bedding materials. Mastitis is an evolving disease that must be discussed ecologically. As result of that, the causative agents, the milk production environment and the mammary gland as a reservoir, should be understood as a whole. These are the driving forces of the persistence and spread of the disease in the herd. The control of bovine mastitis is mainly based on prevention and the focus has to be on the reduction of new infection risk, the control of mammary gland state and the management of the clinical cases. All control tools are developed to deal with the disease and finally to manipulate the immunity and to reduce the carrier state. Even though some current management practices, such as proper milking hygiene and reduced exposure to environmental pathogens contribute to the decrease in the occurrence of the disease, the treatment for bovine mastitis relies heavily on the use of antibiotics. Antibiotics have been used routinely for the treatment of existing infections and also for preventing new ones mainly at the drying off. But, while dry cow antibiotic therapy has helped to reduce the incidence of mastitis, the emergency of antibiotic-resistant pathogens has provoked considerably damages. The development of preventives measures, like application of vaccines, inmunomodulators, bene ficial microorganisms (probiotics) or their metabolic products (bacteriocins, lactic acid, and hydrogen peroxide), are beginning to be highly considered and applied in many herds. This chapter provides the opportunity to expand our knowledge of bovine mastitis and undoubtedly contributes to the development of novel approaches to mastitis diagnostics and control.