The Innate Immunity in Bovine Mastitis: The Role of Pattern-Recognition Receptors

Mastitis is the most costly disease for dairy farmers and industry, which are mainly caused by the entry of bacteria to the teat canal. Shortly after the entry of the invading bacteria, the innate immunity recognizes the invading pathogen through pattern recognition receptors and initiates the inflammatory response necessary to eliminate the invading bacteria. This initial inflammatory response releases cytokines and chemoattractants for the rapid and massive influx of neutrophils from the blood to the site of infection which form the first line of cellular defense against bacteria This article reviewed the role of the most recent knowledge regarding the innate immunity in bovine mastitis focusing in the two major mastitis pathogens: Escherichia coli and Staphylococcus aureus the S. aureus appears to mostly circumvent the host immune response, as the Toll-Like Receptors (TLRs) signaling pathways. The Intramammary Infections (IMIs) by this bacteria result in a very moderate host response with minimal observable innate immune response, which are related to well-known ability to this pathogen to establish chronic IMI. Otherwise, E. coli elicits a strong and earlier response, mainly through TLR4, that is associated with the severity of the mastitis and the clinical manifestation commonly observed in dairy cows infected with this pathogen. Suboptimal and dysfunctional mammary defenses may contribute to the development of severe acute inflammation or chronic mastitis that adversely affects the milk production and quality. Thus, a better understanding of mastitis pathogen interaction to the host may be useful for future control of mastitis.