Molecular epidemiology of mycoplasma mastitis outbreak

Objectives of this research were: 1) determine the association between mycoplasma mastitis and colonization of mycoplasma organisms at body sites of asymptomatic carriers; 2) determine whether concentration of milk via centrifugation prior to conventional culture could increase the ability to detect Mycoplasma spp.; 3) determine factors associated with the clearance of mycoplasma mastitis from a dairy herd; and 4) determine the effect of segregation of mycoplasma mastitis cows into a hospital pen on incidence rate and transmission of the disease in a commercial dairy herd. Colonization of the mastitis outbreak mycoplasma strain at accessible mucosal surfaces of cows and replacements was concurrent with the start of the outbreak, in a dairy herd. However, isolation of Mycoplasma bovis of any strain type from these mucosal surfaces did not appear to precede mastitis. The ability to detect Mycoplasma spp. in milk samples was enhanced using centrifugation followed by resuspension in a reduced volume of fluid before agar plating. Detection of Mycoplasma spp. after centrifugation and resuspension was improved and appeared to be best when the concentration was at, or below, the minimum concentration for detection using standard direct culture techniques. Culling of mycoplasma mastitis cows did not have a significant effect on time to clearance of mycoplasma mastitis in outbreak herds. Fifty percent of herds cleared the disease within 1 month without culling the mycoplasma mastitis cows, while an equal number of herds did not preferentially cull cows and had similar times to clearance of this disease. The segregation of Mycoplasma bovis mastitis cows in a hospital pen was associated with a higher risk of Mycoplasma bovis mastitis incidence in an outbreak herd. Every episode of mycoplasma mastitis transmission in the hospital pen corresponded to the introduction of a Mycoplasma bovis mastitis cows from the milking pens and only one strain caused mycoplasma mastitis and other mycoplasma diseases. Evidence indicates that Mycoplasma bovis mastitis cows from milking pens were the source of transmission of the disease in the hospital pen suggesting that the hospital pen appeared to be a risk factor for transmission Mycoplasma bovis mastitis