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M. bovis-caused mastitis: Prevention is crucial


Treatment for Mycoplasma bovis-caused mastitis is disappointing at best. Prevention is key.


BY MELANIE EPP


Dr Colin Mason, a veterinarian with SRUC Veter- inary Services in the UK.


ing. M. bovis causes a range of clinical presentations but M. bovis mastitis is particularly disastrous because successful treatment options are extremely limited. For this reason, pre- vention is crucial. Dr Colin Mason, a veterinarian with SRUC Veterinary Services in the UK, spoke on the subject at the British Mastitis Conference, which took place in Worcester in November 2019. First recognised as a bovine pathogen in 1961, Mycoplasma bovis was first discovered in the UK in the mid-1970s, and


M


ycoplasma bovis continues to make headlines around the world, especially in New Zealand where officials continue efforts to eradicate the bovine pathogen through widespread cull-


more recently in New Zealand in 2017. In UK dairy herds, M. bovis most commonly causes pneumonia, arthritis and kera- toconjunctivitis, among other diseases. Less commonly, M. bovis causes mastitis. In fact, Dr Mason estimates that mastitis diagnoses are about one-tenth of pneumonia diagnoses in the UK. Note that this is not a statistically significant sample. “It might be that if you went and surveyed, you might get a different answer, but I don’t think it will change that much,” he said. Regardless, since mastitis treatment is ineffective and out- breaks often end in significant herd loss, its mere mention raises alarm bells. Outbreaks can be quite devastating, said Dr Mason. When they do occur, they generally come in the form of pneumo- nia, arthritis and mastitis together. On an individual farm, when outbreaks do occur they can be nasty and costly. “In large outbreaks, cows will be culled and will die, there will be a significant impact in terms of cell count, and a significant im- pact in terms of clinical mastitis,” he said. “We do get these large outbreaks periodically, but frankly, they’re not that common.”


Transmission and treatment Mycoplasma bovis is transmitted in a number of ways. It can be transferred via direct udder and teat contact through the milking machine. It can also be transmitted via direct contact, which means hands and tools pose a risk if they are not properly disinfected. Another means of spread is airborne transmission, which in- creases risk significantly in large and expanding herds, espe- cially where cows are in close contact with one another. According to diagnostic research, some of the organism’s characteristics directly impact antibiotic treatment choices. Due to cell structure and because the organism does not syn- thesise folic acid, some antibiotics are completely ineffective. Some of the antibiotics that do control M. bovis are consid- ered High Priority Critically Important Antibiotics (HPCIAs), which poses obvious challenges. Even more concerning, a 2014 study comparing antibiotic sensitivity for M. bovis isolates suggests resistance could be developing.


Prevention strategies While there is not a lot of evidence-based information related to the transmission of M. bovis in the UK, Dr Mason said there


6 ▶DAIRY GLOBAL | Volume 7, No. 1, 2020


PHOTO: DR COLIN MASON


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