title: Outbreak of mastitis caused by one strain of Staphylococcus aureus in a closed dairy herd.
abstract: The Washington State University dairy experienced an outbreak of intramammary infections (IMI) caused by Staphylococcus aureus during autumn 1993 through summer 1995. The outbreak was believed to be a result of transmission of 1 strain of S aureus in a herd that historically had excellent control of contagious mastitis. Control practices included strict hygiene at time of milking and preferential culling of cows infected with S aureus. Mastitis caused by Streptococcus agalactiae was not found in this herd. Despite excellent control practices, the strain of S aureus caused a new infection rate of approximately 3% of the herd per month. Moreover, a second strain of S aureus, isolated from a cow with mastitis, was introduced into the herd experimentally, and it failed to transmit disease. The outbreak of S aureus mastitis in this herd was eventually controlled by maintaining a program of strict milking time hygiene, by intensifying the program of preferentially culling infected cows, and by segregating cows with S aureus IMI in a separate pen and milking these infected cows last.
authors.affiliation: Department of Veterinary Clinical Sciences, College of Veterinary Medicine, Washington State University, Pullman 99164-6610, USA.
authors.forename: T H
authors.initials: TH
authors.lastname: Smith
authors.forename: L K
authors.initials: LK
authors.lastname: Fox
authors.forename: J R
authors.initials: JR
authors.lastname: Middleton
mesh_terms: D000818:Animals; D015373:Bacterial Typing Techniques / Q000662:veterinary; D002417:Cattle; D004196:Disease Outbreaks / Q000662:veterinary*; D005260:Female; D015994:Incidence; D008414:Mastitis, Bovine / Q000453:epidemiology* / Q000382:microbiology; D015995:Prevalence; D013203:Staphylococcal Infections / Q000453:epidemiology / Q000382:microbiology / Q000662:veterinary*; D013211:Staphylococcus aureus / Q000145:classification*; D014861:Washington / Q000453:epidemiology