Epidemiology of Staphylococcus aureus Mastitis in Dairy Heifers

Abstract

The objectives of this study were to: (1) determine the significance of Staphylococcus aureus in heifers, (2) determine the sources of S. aureus on dairies, and (3) determine the most likely sources of S. aureus mastitis in heifers. Heifers from 23 herds were studied during objective 1 and 700 heifers from 7 herds were studied for objectives 2 and 3. The body sites sampled from prepartum heifers were: teat skin, muzzles, vaginas, rectums, and lacteal secretions. Milk samples were obtained from all females at parturition (milk samples were obtained from pastpartum heifers prior to first milking). The environmental sites sampled were: air, bedding, nonbovine animals, dairy personnel, tools, housing, flies, water, feedstuffs, and equipment. A typing procedure was used to determine if the S. aureus isolate from a source was the same strain as the S. aureus isolate from a heifer's intramammary infection at parturition. The overall conclusions were: (1) S. aureus mastitis in heifers can be an important disease in most dairy herds regardless of the lactating herd prevalence of S. aureus, (2) measures to eradicate this disease in heifers are likely to fail because S. aureus appears to be ubiquitous even in herds with low prevalence of S. aureus mastitis, and (3) intramammary antibiotic therapy in prepartum heifers may be a justifiable control measure.