Occurrence and Ecologic Features of Streptococcus uberis in the Dairy Cow

SUMMARY In an investigation of the occurrence and ecologic features of Streptococcus uberis in 24 cows for 1 year, examinations were made of 6,836 swabs from 12 anatomic sites of the body and 568 samples of milk. A total of 172 isolates of S. uberis were obtained—154 from the skin swabs and 18 from the milk samples. Udder and teat surfaces seemed to be the most common reservoirs of S. uberis, since 49.64% of the isolates were obtained there. Infection of mammary gland parenchyma appeared to be secondary to infection of udder or teat skin, or both. The occurrence of S. uberis infection was highest in winter, less in fall and spring, and least in summer. The maximal number of isolations was obtained in December and the smallest number in June. Observations recorded on 11 cows having mammary gland infection indicated that S. uberis infection occurred most frequently in older cows. Five of 6 cows in the age group 6 to 12 years were infected, whereas 6 cows of 18 infected in the 3- to 6-year age group were infected. The S. uberis infection occurred most often during the early lactation period, less frequently in the mid- and late-lactation period, and least during the dry period.