Mastitis is characterized by physical, chemical and bacteriological changes in the milk and pathological changes in the
glandular tissue of the udder and affects the quality and quantity of milk. The bacterial contamination of milk from the affected cows
render it unfit for human consumption and provides a mechanism of spread of diseases like tuberculosis, sore-throat, Q-fever,
brucellosis, leptospirosis etc. and has zoonotic importance. Somatic cell count (SCC) is a useful predictor of intramammary infection
(IMI) that includes leucocytes (75%) i.e. neutrophils, macrophages, lymphocytes, erythrocytes and epithelial cells (25%). Leucocytes
increase in response to bacterial infection, tissue injury and stress. Somatic cells are protective for the animal body and fight infectious
organisms. An elevated SCC in milk has a negative influence on the quality of raw milk. Subclinical mastitis is always related to low
milk production, changes to milk consistency (density), reduced possibility of adequate milk processing, low protein and high risk for
milk hygiene since it may even contain pathogenic organisms. This review collects and collates relevant publications on the subject.