title: Experimental Staphylococcus aureus intramammary challenge in late lactation dairy cows: quarter and cow effects determining the probability of infection.
abstract: The purpose of this study was to identify factors at the quarter and cow level that determine whether a quarter remains infected after an intramammary challenge with Staphylococcus aureus Newbould 305. A total of 135 cows were studied. Information on animal characteristics, cow-conformation, cow somatic cell count (SCC), and bacteriology, blood vitamin E levels, serology for retro-viral infections, bovine leukocyte adhesion deficiency-carrier status, and the presence of bovine lymphocyte antigens class I alleles was collected on each animal. All quarters of all cows were then challenged with Staphylococcus aureus Newbould 305. The challenge with S. aureus Newbould 305 resulted in 28 cows (20.7%) that did not establish infection in any of the quarters, 21 (15.6%) cows had 1 quarter infected, 35 (25.9%) had 2 quarters infected, 24 (17.8%) had 3 quarters infected, and 27 (20.0%) had all quarters infected. A higher prechallenge SCC decreased the risk of infection. An infection with Corynebacterium bovis prior to challenge decreased the risk of S.aureus infection. Of the bovine lymphocyte antigen alleles, the presence of the W20A allele proved to be significantly associated with a decreased risk of infection. No other factors proved to be significant.
authors.affiliation: Department of Population Medicine and Diagnostic Sciences, College of Veterinary Medicine, Cornell University, Ithaca, NY 14850, USA.
authors.forename: Y H
authors.initials: YH
authors.lastname: Schukken
authors.forename: K E
authors.initials: KE
authors.lastname: Leslie
authors.forename: D A
authors.initials: DA
authors.lastname: Barnum
authors.forename: B A
authors.initials: BA
authors.lastname: Mallard
authors.forename: J H
authors.initials: JH
authors.lastname: Lumsden
authors.forename: P C
authors.initials: PC
authors.lastname: Dick
authors.forename: G H
authors.initials: GH
authors.lastname: Vessie
authors.forename: M E
authors.initials: ME
authors.lastname: Kehrli
mesh_terms: D000483:Alleles; D000818:Animals; D002417:Cattle; D002448:Cell Adhesion; D002452:Cell Count; D004198:Disease Susceptibility / Q000662:veterinary; D005260:Female; D015395:Histocompatibility Antigens Class I / Q000235:genetics; D007774:Lactation; D007962:Leukocytes / Q000502:physiology; D008414:Mastitis, Bovine / Q000276:immunology*; D008892:Milk / Q000166:cytology / Q000382:microbiology; D011247:Pregnancy; D012307:Risk Factors; D013203:Staphylococcal Infections / Q000276:immunology / Q000662:veterinary*; D014810:Vitamin E / Q000097:blood
chemical_list: D015395:Histocompatibility Antigens Class I; D014810:Vitamin E