Micro organism causing mastitis

MICROORGANISMS CAUSING MASTITIS

There are a great number of microorganisms on and in cow udders. Watts⁵² identified 137 species and subspecies of microbes that can be associated with the mammary gland of the cow. Several of them are part of the normal flora and, with few exceptions, do not cause mastitis (footnote B). On the contrary, they may protect udders from infection caused by pathogenic bacteria.
Several other microorganisms may, however, cause infection in the mammary glands. The most common, those that cause about 90% of mastitis infections, are given in Table 2. There are contagious microorganisms and environmental microorganisms. Infected cows are the main source of contagious microorganisms, which survive and proliferate on the skin and on teat wounds. They consist of Streptococcus agalactiae, Staphylococcus aureus and Streptococcus dysgalactiae. Environmental microorganisms (Escherischia coli and other coliforms, Streptococcus uberis) do not remain on the teat. Rather, their presence indicates a high degree of contamination of soil, bedding, and water caused, particularly, by manure.
To infect a quarter, a microorganism must first enter the quarter and the cow must be unable to get rid of it before it multiplies (footnote C). The following is a typical scenario that leads to mastitis infection.

1. Contact with the microbe: The number of microorganisms multiplies near the orifice (or sphincter) of one or several teats. This is where hygiene and milking habits play an important role in preventing microbes from entering the quarter.
2. Entry of microbe into the teats: Entry may be forced by the milking machine, particularly at the end of milking. Injured teats (injuries, keratin injured inside teat) or teats whose openings are too large may be easily invaded. This is where adjusting milking machines and preventing injuries is critical.
3. Immune response of the cow: the cow's first line of defense is to send white blood cells (leucocytes) to eliminate the microbes that have penetrated the teat. If the response is insufficient, the microbes multiply and the cow shows other immune responses such as fever. The effectiveness of the cow's immune system depends on many factors. This is also an area where farmers can do a great deal to ensure good immune response.

B For example, Staphylococcus hyicus, Staphylococcus epidermis and Corynebacterium bovis.
C It is possible that some microorganisms enter the udder from other parts of the body, but this theory is still under debate. It therefore must be assumed that the main entry of microbes is the teat.
Table 2 - Main microorganisms involved in mammary infections, their characteristics and prevention

Species	Main Source	Living Conditions	Propagation Factors	Symptoms	Preventive Treatment
Streptococcus agalactiae	Infected cows	Infected quarter and udder only	Using same rag for cleaning udders	Mild fever for about 24 hours	Wash udders after milking, reduces problem by 50% Cull infected cows
Staphylococcus aureus	Infected cows	On abnormal udder and teat, milkers, vagina, tonsils	Transmitted by hands or rags, enters during milking	Often quite acute for a few days after calving. May be fatal. Quarter swells and turns purple. Quickly affects entire system. In chronic state, udder hardens, aqueous secretion, eventual atrophy of the quarter. Intermediate form produces granular secretion. Milk hotter than normal.	Wash udders after milking, reduces problem by 50% Cull infected cows
Streptococcus dysgalactiae	Infected cows	Infected quarter, injuries		Pronounced swelling of one or more quarters. Milk highly abnormal. High fever in serious cases.	Wash udders after milking, reduces problem by 50% Cull infected cows
Streptococcus uberis	Contaminated environment	On cow's skin, mouth, ground	Neglected udder washing, insufficient drying, lack of bedding, muddy yards	Pronounced swelling of one or more quarters. Milk highly abnormal. High fever in serious cases. Affects mostly dry cows and heifers.	Wash teats only, dry well with disposable paper towels for each cow Supply generous bedding
Escherischia cold	Contaminated environment	Ground, bedding (sawdust and shavings), manure, water	Dirty calving stall, lack of bedding, inadequate udder washing	Often very serious. May lead to loss of quarter or even death. Thin yellow secretions, with granular texture resembling bran. Often high fever.	Wash teats only, dry well with disposable paper towels for each cow Supply generous bedding
Corynebacterium pyrogenes	Certain insects	Humid valleys, wooded areas		Pronounced systematic reaction due to toxins caused by bacteria. Often more than one quarter affected. They become hard, produce thick smelly secretion like cheese and difficult to eliminate. Followed by abscess that bursts, releasing creamy pus, and tissue loss.