After occurrence of Streptococcus agalactiae and Staphylococcus aureus had been reduced on the farms, Streptococcus uberis became the most common cause of mastitis in dairy cows. Inflammation of the mammary gland usually progresses slowly; treatment is often complicated and recurrent infections are common. Streptococcus uberis is able to infect the mammary gland quarters gradually one by one thus we can often see the infection in different phases of development in more quarters at a time. In the past, Streptococcus uberis was considered a so called environmental causal agent which mainly caused subclinical mastitis of a chronic character.
Based on a current view, more strains of these streptococci spread by contact exist. A new species called Streptococcus parauberis was also distinguished in 1990; it is more aggressive, able to destroy the udder tissue and is typical of higher antibiotic resistance.
An increased rate of mastitis caused by Streptococcus uberis is caused by several factors: inadequate hygiene, stress, decrease in immune function. And when screening for pathogens is performed on a farm, the therapy is set “uniformly” based on the most severe pathogen (e. g. Staphylococcus aureus acute mastitis etc.). The treatment plan targeting Staphylococcus is made; this former predominant pathogen recedes, Streptococcus uberis persists, is spread throughout the herd and numbers of recurrent mastitis cases increase.