Mycoplasma bovis is a significant problem on UK beef and dairy farms; having risen to an endemic level it is cited as the most common pathogen in respiratory disease diagnoses. The AHDB estimates pneumonia costs UK farmers £50m/year.

The disease is difficult to treat – but fortunately, there is already one vaccine available in the UK and Ireland, and another is expected to hit the market next year. "M. bovis is a particularly challenging disease to manage," says vet Graeme Fowlie, director of Meadows Vets near Aberdeen. It usually presents as pneumonia, particularly in calves, but is also a significant cause of septic arthritis, otitis and mastitis. It has no cell wall, so does not respond to penicillin and cephalosporin antibiotics, making prevention a much better option than cure.

Since 2019, farmers have had access to a three-strain inactivated single-shot vaccine through the Cascade system (prescription only). Mr Fowlie has conducted several trials on this vaccine, one of which showed that it reduced weaned calf mortality from 5.8% to just 0.5%. Over the same time, mortality on the unvaccinated control farms increased from 7.6% to 9.6%. Other trials have shown vaccination reduced lung lesion scores by 56-64%, alongside a significant reduction in clinical arthritis.

From next year there will be a new live, single strain vaccine available. So what's the difference between the two? "Immunity needs to be targeted," explains Mr Fowlie. "The M. bovis bacterium can alter its surface proteins, making it harder for the immune system to recognise it. Having three strains in a vaccine provides a broader range of protection against the different pathogenic strains circulating."

An advantage to the live vaccine is that it can be given to calves from seven days old, with a booster 21 days later, and the onset of immunity 12 days after that. The inactivated vaccine is just one shot and recommended to be given from 60 days old – although it has been proven in a farm trial that careful use from four weeks of age can be successful. Full immunity is provided five weeks after vaccination. It has also shown in farm trials to be safe to use in in-calf cows, who will pass on the immunity to their calf via colostrum.

"The biggest drawback to the live vaccine is that you can't treat calves with the most effective antibiotics against M. bovis for 15 days before and after each jab, because they will kill the vaccine," says Mr Fowlie. "That's a long period of no treatment, and a killed live vaccine can't perform nearly as well." Using a live vaccine also carries a small – but real – risk of spreading the actual infection. "One in 700 calves got arthritis from the vaccine in trials."

In farm trials run by Mr Fowlie, comparing three groups of calves of different ages arriving at a rearing farm in a late and wet 2023, the vast majority of calves needed treatment for pneumonia, and many needed more than one treatment. "Under these circumstances you'd want access to a broad choice of therapy, including antibiotics to use – but the live vaccine would really narrow down that choice," he explains. "In my view, that makes the inactivated, single-shot vaccine a far better option."

Of course, vaccination isn't the only tool in kit – it's also important that farmers adopt stringent biosecurity standards. This means buying animals from as few sources as possible, and perhaps using an antibody test to check if stock are carriers before arriving on-farm. "Good ventilation in housing, with minimum stress at difficult times like weaning, will also help reduce the risk of disease," says Mr Fowlie. "Always follow up with your vet for accurate diagnosis if you're not getting a response to control measures."

· For further information contact Graeme on 01651 872481 or email thevets@meadowsvets.co.uk