Induction of mastitis in Awassi lactating ewes with a slime producing Staphylococcus aureus

Abstract EN

The aim of this study was to investigate the clinico-pathological changes in the mammary gland of Awassi ewes inoculated with a slime producing Staphylococcus aureus.

Five ewes were examined clinically by visual inspection and palpation of the teats and udder halves for local and generalized reaction and milk samples were collected in sterile test tubes aseptically for bacterial examination and California mastitis test (CMT) to confirm that these ewes were free from intramammary infection prior to inoculation.

The ewes were inoculated with one mL PBS containing 7x102 CFU of slime producing Staph.

aureus through the teat canal.

Post inoculation, all the ewes were examined clinically and bacteriologically daily for appearances of clinical signs, then the ewes were slaughtered 6 days later, one centimeter cubes from different parts of the mammary gland were obtained and fixed in 10% buffered formalin, processed, embedded in paraffin, sectioned, and stained with Haematoxylin and Eosin (H&E) and examined for presence of pathological lesions.

The ewes showed systemic disturbances and developed mastitis within 24 h post inoculation, the body temperature, pulse and respiratory rates were elevated accompanied with depression and loss of appetite.

The main lesions in the udder characterized by fibrosis of interstitial tissues with polymorphonuclear neutrophils (PMNs) and mononuclear leukocyte infiltration as well as suppuration in the wall of necrotic milk ducts in addition to abscess surrounded by fibrous connective tissue.

This study clearly showed that the slime producing Staph.

aureus induced severe mastitis in lactating Awassi ewes, and is the first description of some clinico-pathological features of the ewes mastitis experimentally induced by this organism in Iraq.