Mastitis is defined as the inflammation of one or more mammary glands. Mastitis is predominantly caused by bacterial pathogens and occasionally mycotic or algal microbes. The spectrum of disease can range from subclinical to life-threatening, and treatment is directed accordingly. The prognosis is good for resolution of the infection and preservation of the gland in most cases; however, in some cases of mastitis in dairy cows, chronic infection may require culling the animal from production.
Mastitis has been reported in almost all domestic mammals and has a worldwide geographic distribution. Climatic conditions, seasonal variation, bedding, housing density of animal populations, and husbandry practices, such as milking protocols for dairy animals, affect the incidence and etiology. However, mastitis is of greatest frequency and economic importance in species that primarily function as producers of milk for dairy products, particularly dairy cattle and goats.
Pathological changes to milk-secreting epithelial cells from inflammation decreases function, ie, milk production. Depending on the pathogen, decreased milk production may continue into further lactations, which decreases productivity and, for beef and other meat-producing animals, potential weight gain for suckling offspring. Although most infections result in subclinical local inflammation or mild clinical cases, more severe cases can lead to agalactia or even profound systemic involvement, including death.
Mastitis in sows is discussed elsewhere.
