title: Epidemiologic study of intramammary infections with Staphylococcus aureus during a control program in nine commercial dairy herds.
abstract: OBJECTIVE
  To determine the epidemiologic pattern of intramammary infections (IMIs) with Staphylococcus aureus during implementation of a control program in 9 commercial dairy herds.
  
  
  METHODS
  Cohort study.
  
  
  METHODS
  1,651 lactating cows and 53,098 quarter milk samples.
  
  
  METHODS
  Nine herds located in different regions of Italy were enrolled. Control of S. aureus infections followed the general principles of contagious mastitis control and was based on precise diagnostic procedures and strict control and segregation of infected cows. All lactating cows in each herd were tested, and those free of S. aureus IMI were enrolled as the cohorts. Further additions to the cohort group were cows and heifers free of S. aureus IMI, as determined from aseptically collected milk samples taken approximately 7 and 14 days after calving.
  
  
  RESULTS
  After the ninth month of the program, incidence decreased to < 2 new IMIs/100 cow-months in 7 of the herds. At the end of the study, 8 of 9 herds had an incidence of < or = 1 new IMI/100 cow-months. Heifers were most at risk of developing an IMI.
  
  
  CONCLUSIONS
  Results suggest that control of S. aureus IMIs can be achieved by use of a control program based on segregation and use of hygienic and therapeutic protocols. Analysis of incidence and identification of risk factors in a herd could avoid the possible shortcomings of the program, maximizing the probability of success.
authors.affiliation: Dipartimento Patologia Animale, Igiene e Sanità Pubblica Veterinaria, Sezione di Malattie Infettive, Università degli Studi di Milano, Via Celoria 10, 20133 Milano, Italy.
authors.forename: Alfonso
authors.initials: A
authors.lastname: Zecconi
authors.forename: Renata
authors.initials: R
authors.lastname: Piccinini
authors.forename: Larry K
authors.initials: LK
authors.lastname: Fox
mesh_terms: D000818:Animals; D002417:Cattle; D015331:Cohort Studies; D003612:Dairying / Q000379:methods; D005260:Female; D006920:Hygiene; D015994:Incidence; D017053:Infection Control; D007558:Italy / Q000453:epidemiology; D007774:Lactation; D008321:Mammary Glands, Animal / Q000382:microbiology; D008414:Mastitis, Bovine / Q000453:epidemiology* / Q000517:prevention & control; D012307:Risk Factors; D012621:Seasons; D013203:Staphylococcal Infections / Q000453:epidemiology / Q000517:prevention & control / Q000662:veterinary*; D013211:Staphylococcus aureus / Q000472:pathogenicity