Immunopathology of Mastitis

Mastitis is derived from Greek words ‘Mastos’ means breast and ‘itis’ means inflammation. It is an inflammatory condition of the mammary gland caused by bacterial, viral and fungal infections. Mastitis occurs most oftenly in lactating mammals. Mastitis is characterized by physical, chemical, and bacteriological changes in the milk. It is a common disease of high milking cows like exotic and cross breeds. Mastitis incidence is higher in cows from third lactation onwards, when optimum milk production occurs. It is the most costly disease for dairy farmers and industry, as a consequence of decreased milk production and quality, treatment costs, animal replacement costs, and difficulties in marketing of poor quality dairy products. Mastitis arises as a result of complex interplay between infectious agents, managemental practices and environmental factors. It is a response to injury or infection, which serve to neutralize and destroy the infectious agents and promote healing and then return to normal function. The most important changes in milk include discolouration of milk and presence of flakes. Innumerable genera and species of bacteria cause mastitis. Predominant organisms are Staphylococcus aureus followed by Streptococcus agalactia. The other organisms include E. coli, Streptococcus uberis, Streptococcus dysagalactia, Streptococcus pyogenes, Corynebacterium pyogens, Corynebacterium bovis, Mycobacterium bovis, Nocardia asteroids, Leptospira interrogans serovar Pomona, Leptospira interrogans hardjo, etc. Fungal agents such as Trichophyton spp., Aspergillus fumigatus, and yeast such as Candida spp., Cryptococcus neoformans, etc can cause mastitis. Viruses causing mastitis are infectious bovine rhinotracheitis, bovine viral diarrhea, foot-and-mouth disease, pseudo cowpox, etc, and predispose cows to bacterial mastitis.