The presence of Mycoplasma bovis in non-milk samples in dairy farms positive for M. bovis in bulk tank milk: indication for future prevention

Abstract

　In order to identify the within-farm prevalence of Mycoplasma bovis, we investigated 10 farms that were positive for M. bovis in bulk tank milk. We collected nasal swabs from calves and pneumonia cows and vaginal swabs from postpartum cows and interviewed farms regarding the onset of pneumonia and milk infection. When M. bovis was detected from nasal or vaginal swabs, pulsed-field gel electrophoresis （PFGE） was performed to determine the epidemiological association with M. bovis detected in the milk. In 4 of the 10 farms investigated, M. bovis was detected in milk but not from nasal or vaginal swabs. Since pregnant cows were introduced from markets into these farms, these cows were suspected of being a source of infection. In the remaining 6 farms, M. bovis was detected from nasal swabs of calves or cows or from vaginal swabs of postpartum cows. Their PFGE patterns were consistent with those of milk samples at each farm. These results suggest that milk infection with M. bovis can occur not only by introduced cows, but also through the lochia in postpartum cows as well as calves and cows with pneumonia in the farm. It is important to take appropriate measures to prevent transmission through these animals.