Ultrasound and histopathological investigations of experimentally induced Staphylococcus aureus mastitis in goats

- We investigate the ultrasound findings in experimental S. aureus mastitis in goats.
- Our results showed specific ultrasonographic and histopathological udder alterations.
- Histopathological examinations showed udder changes specific for acute inflammation.
- Ultrasound imaging could be useful in evaluation of the extent of udder lesions.

The purpose of the present study was to investigate the ultrasound and histopathological findings in experimentally induced Staphylococcus aureus mastitis in goats. The experiment was conducted using six clinically healthy goats, 2-4 years of age, weighing 48-54 kg. The experimental infection was done with stationary-phase culture of a field S. aureus strain isolated from the milk of a cow with clinical mastitis. Ultrasound measurement of udder structures established statistically significant changes in teat canal length, teat wall thickness and diameter of lactiferous ducts. A clear sign of inflammation was the ultrasound visualization of hyperechoic structures in the teat cistern, which were identified as milk coagula after milking. The ultrasonography of udder parenchyma on post infection hour 72 showed large hyperechoic zones, statistically significant (P < 0.05) narrowing of lactiferous ducts and inability for visualization of anechoic blood vessels. On post infection hour 168 that corresponded to the 3rd day of treatment of goats, teat cistern content was normal and anechoic. Histopathological results showed vacuolar degeneration of epithelial cells, serous exudate in glandular duct lumens consisting of multiple neutrophils, as well as interstitial changes-haemorrhages, oedema and mononuclear proliferations of lymphocytes and histiocytes. The analysis of results indicates that ultrasonography combined with histopathological examinations could be successfully used for detection and monitoring of the time course of goat udder alterations caused by experimental S. aureus mastitis.