Sonographic and histological udder parenchyma changes after intramammary infection of sheep with Mycoplasma agalactiae.

INTRODUCTION: The sonographic findings of the udder parenchyma and udder lymph nodes in 30 lactating sheep after experimental infection with Mycoplasma agalactiae are described. The objective of the study was to describe infection related changes in the udder parenchyma and udder lymph nodes using physical, sonographic, and histological examination and to detect associations between sonographic and histological changes of the tissues. Animals were intramammarily infected with different mutant cocktails and the wild type PG2. One group served as a negative control. A 15 MHz linear transducer (Esaote MyLab 30 CV, Esaote, Florence, Italy) was used for sonographic examinations. Compared with the uninfected control group with homogeneously granular parenchyma, the udder lymph nodes were larger and the udder parenchyma was more inhomogeneous and partially hyperechoic. The corresponding histological findings in infected mammary glands comprised proliferation of interstitial connective tissue, non-purulent interstitial mastitis, and purulent galactophoritis. The infected udder lymph nodes showed reactive hyperplasia. The findings obtained in this study may improve the diagnosis of Mycoplasma mastitis in sheep.