Mycoplasma bovis (M. bovis) is a major cause of pneumonia, mastitis and other production-sapping symptoms, and is extremely difficult to treat. So how can farmers tackle it?
UK Veterinary Investigation Diagnosis Analysis data shows a sharp rise in M. bovis diagnoses since 2013, to the level that it is now endemic in the British dairy herd. But as it cannot be treated by many common antibiotics, how can producers get on top of it?
The first step, according to Emmie Bland, director at Beacon Farm Vets, Lancashire, is to adopt stringent biosecurity.
This includes keeping a closed herd or testing purchased stock, not mixing ages, keeping calves in small groups, disinfecting feed equipment, reducing stress and ensuring good ventilation in livestock buildings.
She says: "Feeding unpasteurised whole milk is a key route of infection, as cows can be carriers without showing symptoms. Often, producers will feed powdered milk to heifers and whole milk to bulls, but once a calf is infected, the disease will easily spread."
Mrs Bland suggests using bulk milk PCR tests to ascertain the level of infection within a dairy herd, or blood tests for purchased stock. But what are the symptoms to look out for?
Common signs include pneumonia, contagious mastitis, swollen joints and middle-ear disease, and the disease is notoriously difficult to treat with common antibiotics, she adds.
She says: "If you feel you have done everything you can and you are still not winning, you need a vaccine to help you. Often, it will tip the balance in your favour."
Until recently, the only available vaccine was an autogenous one, produced specifically for an individual farm. This requires a sample to be taken from a sick animal, which is grown into a culture.
After the culture is grown, the isolate is cloned to purity so different strains can be identified, says Dr Tim Wallis, managing director at Ridgeway Biologicals. A straightforward test costs about £250.
If one strain is identified, it will be used to create a single-strain vaccine, whereas where multiple strains are present, they will be used to create a multi-strain vaccine.
Dr Wallis says: "It takes about two weeks to get a pure isolate, then we are able to supply the vaccine onto farm within eight to 10 weeks."
All vaccines are subjected to standard testing to ensure purity, sterility and inactivation, and then must be tested on-farm before they can be widely used.
He says: "You must inject a double dose into a minimum of five animals and check them daily for a week for reactions. This includes monitoring temperatures every day."
After the initial week-long test, this must then be repeated for another week, says Dr Wallis.
He says: "If the vaccine is to be used on calves, it must be tested on calves. If it is to be used on pregnant cows, it must be tested on pregnant cows."
Ridgeway made its first M. bovis vaccine in 2016 and vets are now requesting them more widely.
Ruth Fraser, a vet at Strathspey veterinary practice, Morayshire, used an autogenous vaccine on calves last year.
She says: "The farmer felt there was definitely an improvement in pneumonia, although there are other respiratory issues on-farm and he is now vaccinating for other pathogens too.
"But it can be expensive to culture M. bovis. It took us four oral-nasal swabs and several post-mortems."
However, farmers and vets now have another option to autogenous vaccines: an imported multi-strain M. bovis vaccine from the US, which can be prescribed in the UK under the Cascade system.
Mrs Bland says: "I am really interested in the imported vaccine, partly because of the convenience of having something on the shelf rather than waiting for months.
"Studies show it is reducing the incidence and severity of symptoms in the US by about half, and as a one-dose shot, it will be cheaper than an autogenous vaccine.
"We are yet to see any trials results in the UK, but based on the US studies, it should give a return on investment of more than 700%. But neither the imported or autogenous vaccine are the only answer to M. bovis.
"The farm on which we have used an autogenous vaccine has seen a huge improvement, but we have also instigated significant management changes at the same time. You cannot rely on vaccinating without implementing the other biosecurity measures."
Graham Fowlie, director of Meadows Vets, assisted in securing the licence to import the vaccine, via Kernfarm, and has also set up the UK's first on-farm study to establish its effectiveness.
He says: "M. bovis is a bacterium which does not have a cell wall, which makes it extremely difficult to treat, as many antibiotics work by attacking the cell wall.
"The disease is often well advanced by the time it is picked up, so prevention is definitely better than cure, and will help to reduce antibiotic use on-farm.
"As a vet, it is frustrating not being able to prevent the most common cause of pneumonia, despite utilising extensive vaccines for other diseases.
"I am extremely hopeful this new vaccine will be the answer that I, and lots of farmers, are looking for."
*For more information, contact Graeme Fowlie at Meadows Vets on 01651 872 481, or email [email protected]
