Mycoplasma bovis bigger issue than thought, research shows

A costly bug affecting dairy and beef cattle is more widespread than previously thought, a vet-led farm project has concluded.

However, bulk milk serology testing could be an easy way to monitor dairy herds.

The 41-farm study across the UK found 18 farms tested positive for Mycoplasma bovis (M. bovis), which causes pneumonia, mastitis, sore and swollen joints and otitis, and can be fatal.

See also: How a dairy farm is controlling mycoplasma using vaccination

Graeme Fowlie, director of Meadows Vets, Aberdeenshire, and lead vet on the project, said M. bovis was found in England, Scotland, Northern Ireland and Wales in beef and dairy herds during the study.

“For a few years, I have suspected that M. bovis is more prevalent than expected,” said Mr Fowlie. “And from working with vets across the country taking part in the surveillance programme, it’s become clear that that is the case.”

Mr Fowlie was instrumental in making a multi-strain vaccine for M. bovis available in the UK under the cascade system in 2019.

Test evaluation

The project evaluated three testing methods, which were:

• Polymerase chain reaction (PCR): This looks for the bacterial DNA in swab samples, lung tissue, milk, or joint fluid.
• Antibody test in milk: This is useful for screening exposed lactating animals that are showing an antibody response to the bacteria
• Antibody test in blood serum: This has wider use in cattle that are showing an antibody response

Identifying M. bovis has historically been challenging, said Mr Fowlie. Vets found it hard to culture it in laboratories from post-mortem samples, often because dead calves had been treated with antibiotics before they died.

Findings

The study found:

• Bulk milk PCR testing did not appear to be particularly sensitive. A total of 11 PCR samples came back negative
• Blood serology and bulk milk serology were more useful and returned fewer false negatives than bulk milk PCR
• 25 herds were screened via blood tests, of which 52% were positive, 20% were inconclusive and 28% were negative

“One of the biggest problems with M. bovis is that it’s very hard to treat – it doesn’t respond to many common antibiotics, so prevention is much better than cure,” said Mr Fowlie.

“That means screening herds via blood or bulk milk serology testing, and PCR testing of sick animals or post-mortem samples to confirm the presence of the disease initially and having confidence in those results.”

Ben Pedley, farm clinical director at Willows Farm Vets, Cheshire, said: “In the past two years we have found M. bovis on several farms after PCR testing of lung samples taken post-mortem from pneumonia cases.

“Since diagnosing the infection, calf pneumonia on these units has been greatly reduced via management changes including specific vaccination programmes for Mycoplasma.”

An extension of the survey has just been announced for this winter. Vets and farmers concerned about M.bovis in their herds are encouraged to get in touch with Mr Folie at Meadows Vets to discuss subsidised testing.