Most infections persist and do not respond to treatment during lactation. Dry cow treatment gives better results, but cronic infections can persist into subsequent lactations. Mastitis due to Staph. Infected cows should be considered for culling. However, you should aim to have a herd with no infected cows or a low infection rate.
Every infected cow is a potential source of new infection to additional cows.
Mastitis caused by Strep. Mastitis due to Strep. Treatment against Strep. If high bacteria counts are a problem, treatment of Strep. The CNS group of organisms cannot be classified as strictly contagious - nor can they be categorized as strictly environmental.