Etiology of Bovine Mastitis

Mastitis in dairy animals is the primary concern of dairy farmers, which is the most common disease that causes huge economic losses in the dairy industry. The economic losses due to mastitis are from a reduction in milk yield, condemnation of milk with antibiotic residues, veterinary treatment costs, and death. In addition, some mastitis pathogens also cause serious human diseases associated with the contamination of milk or milk products with bacteria or their toxins. Bovine mastitis is mainly caused by a wide range of environmental and contagious bacterial mastitis pathogens. Contagious pathogens are those whose main reservoir is the infected udder. Contagious pathogens mainly spread among animals during milking process whereas environmental pathogens spread from environment to udder at any time. The source of the environmental pathogens is the surrounding environment of an animal. The major contagious pathogens include Staphylococcus aureus, Streptococcus agalactiae, and Mycoplasma spp. and the minor contagious pathogens include Corynebacterium bovis and others. Major environmental pathogens include coliform bacteria (Escherichia coli, Klebsiella spp., Enterobacter spp. and Citrobacter spp.), environmental streptococci (Strep. dysgalactiae, Strep. uberis). This chapter covers detailed review of published data on contagious and environmental pathogens responsible for bovine mastitis.