Characterisation of the course of Mycoplasma bovis infection in naturally infected dairy herds

Mycoplasma bovis causes bovine respiratory disease, mastitis, arthritis and otitis. The importance of M. bovis has escalated because of recent outbreaks and introductions into countries previously free of M. bovis. We characterized the course of M. bovis infection on 19 recently infected dairy farms over 24 months. Our objective was to identify diagnostic tools to assess the efficacy of control measures to assess low risk infection status on M. bovis infected farms. PCR assays and culture were used to detect M. bovis, and in-house and BioX ELISAs were used to follow antibody responses. Cows and young stock were sampled on four separate occasions, and clinical cases were sampled when they arose. On 17 farms, a few cases of clinical mastitis were detected, mostly within the first eight weeks after the index case. Antibodies detected by in-house ELISA persisted in the serum of cows at least for 1.5 years on all farms, regardless of the M. bovis infection status or signs of clinical disease or subclinical mastitis on the farm. Six out of 19 farms became low risk as the infection was resolved. Our results suggest that, for biosecurity purposes, regular monitoring should be conducted on herds by screening for M. bovis in samples from cows with clinical mastitis and calves with pneumonia, in conjunction with testing young stock by screening longitudinally collected nasal swabs for M. bovis and sequential serum samples for antibody against recombinant antigen.Peer reviewe

Application of an indirect MilA ELISA for the detection of Mycoplasma bovis antibodies in bovine milk

The objective of this study was to detect Mycoplasma bovis specific antibodies using a recently reported MilA ELISA with the aim to detect M. bovis antibodies in milk. An indirect ELISA, based on a recombinant fragment of the Mycoplasma immunogenic lipase A (MilA) protein, was conducted on 291 milk samples for the detection of M. bovis antibodies. Samples were also tested with conventional Mycoplasma culture and M. bovis PCR. Samples were collected from individual cows from 2 commercial dairy herds in South Australia. Of 291 samples tested, 68 (23.4%) were detected positive for M. bovis antibodies, 150 (51.5%) were positive for M. bovis in PCR and 166 (57.0%) in bacterial culture. These results indicate that MilA indirect ELISA can be utilized for the detection of M. bovis antibodies in milk