The word ‘mastitis’ is derived from the Greek mastos which means breast and itis which is translated inflammation in English. Mastitis therefore, is the inflammation of one or more quarters of the mammary gland. Inflammation is usually a body’s reaction to any injury. It is particularly of concern when associated with microbial infection.
Factors involved in the development of mastitis
Cow as the host
Microorganism as the causative agent
Environment, which can influence both the cow and the microorganism
The cow contract udder infections at different ages and stages of lactation. Infections vary depending on the cow’s ability to overcome infection
Microorganisms of over 100 different types are responsible for mastitis in the dairy cow. Infections by these microorganisms vary depending on the route by which they reach the cow. These also differ in the nature of disease they cause. The infectious agents are contagious and are commonly spread from cow to cow primarily during milking.
The cow’s environment influences the numbers and types of bacteria since different species are found largely in different locations. The levels of hygiene int he cow’s environment influence their presence. The environment is also considered as it influences ability of cow to resist infection.
Development of Mastitis
The quarters of the cow udder are independent and are only interconnected by blood supply. The microorganism enter the udder through the teat sphincter. These cause inflammation of the mammary glands. The affected animals generally show heat, swelling, redness and pain in one or more of the affected quarters, with associated asymmetry of the udder.
The Cow defense mechanism against Mastitis
Teat canal which is initially narrow but dilates and lengthens with age. Its lining consists of stratifies squamous epithelium. It is keratinized and secretes keratin which is sticky and serves to trap bacteria which are the flushed out during milking. Keratin has long chain fatty acids which are in themselves bacteriostatic.
The teat sphincter maintains a tight closure preventing entry of microorganism.
Milk contains lactoferrin which is bacteriostatic in nature. It has also chelates, antibodies and complements, leucocytes and opsonins.
High rates of infection are observed in dry cows compared to lactating ones; this could be due to flashing out of infectious agents during milking.
A number of pathogenic bacteria like Streptococcus spp. and
Staphylococcus spp. occur high in teat skin.
Risk factors for Mastitis
Presence of injurious objects in the cow environment predispose the animal to traumatic wounds which may serve as entry roots for pathogenic microorganisms. Such objects may include barbed wire fences, metal piles, tree stamps etc.
Hygiene levels in the farm- poor practices of hygiene on the cow, milking equipment and the milk-man serves as good growing and multiplication environment for infectious microorganisms. Unclean equipment and milker’s hand do transfer microorganisms from one cow to another increasing the risk of mastitis.
The udder anatomy is a significant factor to consider in the occurrence of mastitis. Such are pendulous udders which are at high risk of being stepped on by the animal as it rises, stepped on by other cows as it lays or being injured by objects as the cow walks. Pendulous udders also picks up bacteria more easily.
Teat anatomy; very long teats are more prone to injury than shorter ones. Teats with loose sphincter allow passage of microorganisms through the teat canal into the glands.
Teat injury creates channels for easy entry of bacteria and provide an environment for bacterial growth.
The prevailing weather conditions; more microorganisms are present in wet seasons.
The milking machine; cleanliness, vacuum pressure may breach the integrity of the teat duct.