Strep ag Mastitis Can Be Eliminated From Your Herd

Streptococcus agalactiae, or Strep ag, is a common causes of mastitis. It is not unusual to find over half of a herd infected, however clinical cases seldom exceed 2-4% at any single point in time. Strep ag mastitis is generally non-clinical, but produces high somatic cell count (SCC) and reduces milk production.

Strep ag is highly adapted to the mammary gland and is regarded as a contagious mastitis pathogen. It has been found in bedding, on teat skin, and on the hands of milkers, but it must be present in the mammary gland to grow and multiply. The most common source of infections is other infected cows. Strep ag is spread by the milking unit, milkers' hands, or common udder prep cloths. In herds where Strep ag has been eliminated, reinfection can occur by purchasing infected cows or heifers, or by the careless use of equipment at fairs and livestock shows. New animals should be sampled and cultured before adding to the milking herd.

Detecting Strep ag infections requires milk sampling and bacterial cultures. Infections should be suspected when bulk tank SCC begins to rise and remains high. Bulk tank sampling can serve as an excellent method for identifying and monitoring infected herds even when a low number of cows are infected. However, a single sampling should not be relied on when infection numbers are low.

Strep ag can be controlled and eradicated from a herd by good milking practices including proper udder preparation using single use towels, post-milking teat dip, and treating infected animals. This is one of the few organisms which responds to most commercial intramammary antibiotic products in both the lactating and dry period. However, some chronic infections do not respond to therapy. If repeated lactating or dry cow treatment does not eliminate the infection, the cow should be culled to prevent infecting other cows.

Strep ag eradication is relatively easy and cost-effective. Once this organism has been eliminated from the herd, careful control as previously mentioned should be used to prevent reinfection. Other types of mastitis may also be present in the same herd and a complete mastitis control program should be instituted to reduce all infections.


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