CNS can colonize the teat canal. Some species are also found free-living in the environment. The infection rate is generally higher in primiparous cows. Most CNS infections are transient. Cows and heifers will have a higher prevalence of CNS infection after calving, with a rapid decline over the first week or two of lactation.
Researchers believe cow to cow spread is rare.
CNS are of low pathogenicity. Despite their low pathogenicity, CNS infections can occasionally contribute to clinical cases of mastitis in dairy herds, but CNS are rarely a major cause. A positive culture may show recovery of an organism but this does not mean inflammation of the mammary gland has occurred. Because CNS are commonly found on teat skin and in the streak canal, they are a common cause of contamination of milk samples. Repeated isolation from a particular quarter sampled multiple times builds the case for a persistent and important infection.