Streptococcus uberis is a major environmental mastitis-causing pathogen. The infections
are predominantly subclinical and are frequently undetected and untreated for extended
periods of time. More information about the pathogenesis of S. uberis mastitis would be
useful. To our knowledge, no experimental studies into the mastitis pathogenesis caused
by S. uberis have been described in lactating goats. The aim of this study was to reproduce
an experimentally induced S. uberis subclinical mastitis in lactating goats aimed to
evaluate the inflammatory response, dynamics of infection and the pathological findings
within the first hours of intramammary inoculation with S. uberis. Six Saanen goats in midlactation
were inoculated with 1.7 108 cfu of S. uberis. Bacterial growth peaked in milk
from challenged right mammary halves (RMH) at 4 h PI. Shedding of viable bacteria
showed a marked decrease at 20 h PI. Mean somatic cell counts in milk from the RMH
peaked at 20 h PI. Inoculation with S. uberis was followed by a decrease in the mean total
number of leukocytes. Signs and systemic symptoms were not evoked by intramammary
inoculation. S. uberis could be isolated in tissue from all RMH. Histological examination of
specimens of the RMH and lymph nodes of the goats showed an increased inflammatory
response throughout the experiment. The histological findings correlated with the
immunohistochemical detection of S. uberis in RMH. In conclusion, the experimental
inoculation of S. uberis in lactating goats is capable of eliciting an inflammatory response
and causing pathological changes, resulting in a subclinical mastitis. This investigation
shows that goat might to represent a valuable model for the study of the mastitis
pathogenesis caused by S. uberis.