Mycoplasma infections in cattle

What are Mycoplasma?

Mycoplasma are small bacteria. There are over 125 different types, and several that are found on cattle. They are different to most other bacteria because they don’t have a cell wall around them. ‘Mycoplasma bovis’ is the most common type that can be associated with disease in cattle in the UK.

We have known about Mycoplasma bovis infections in cattle in the UK since the mid-seventies, so it is not really a ‘new’ disease; farmers, vets and scientists have been working with it for years. Despite this, we are still learning about exactly how and when it causes disease, and how best to prevent and treat it.

What problems do Mycoplasma cause?

Like many other bacteria, Mycoplasma can be present in cows without causing any disease at all. When they do cause disease, it can be because the cow’s animals immune system is not working well, the animals’ environment is poor or because the type of Mycoplasma is very aggressive.

In cattle, the major diseases that Mycoplasma can contribute to are pneumonia and mastitis. Occasionally they can contribute to other problems too, including ear infections, eye infections and joint infections.

There are many other bacteria and viruses that can also contribute to all of these problems, and it is difficult to be able to diagnose when exactly Mycoplasma are involved. When they are involved they can also be difficult to treat.

What makes Mycoplasma difficult to diagnose and treat?

Mycoplasma are difficult to grow in the laboratory. Most bacteria will grow in about 24 hours, but Mycoplasma can take up to a week. They can also be ‘masked’ by other bacteria that grow more quickly in the lab. These challenges mean they are difficult to study and learn about in the laboratory too.

Modern tests, like PCR, can help with these problems, as they don’t need to wait for the bacteria to grow. However, as Mycoplasma don’t always cause disease, when you find them you can’t always be sure they are causing a problem.

With regard to treatment, lots of antibiotics work by attacking the cell wall around bacteria. However, as Mycoplasma don’t have a cell wall, these type of antibiotics don’t work. Even when an effective antibiotic is used, animals can still respond poorly. This may be because there is too much tissue damage already done or there is co-infection with other bugs (like viruses). In some instances, the Mycoplasma can evade even effective antibiotics.

Can I stop Mycoplasma getting into my herd?

Not always, but It is a very good idea to try. Mycoplasma don’t live for long away from carrier animals, and so most spread between herds occurs by moving stock. In simple terms, the more animals you bring into your herd, the more likely you are to bring Mycoplasma in with them.

Try to minimise stock purchases and movement to only those that are absolutely essential to your business. If you do need to buy in animals, ask your vet to help with planning to reduce some of the risk. There is no legal requirement, but blood tests are available that can help to identify potential carrier animals. For testing to reduce the risk, you need to be able to turn away animals that test-positive, so planning where and when they are tested is essential.

Other basic biosecurity measures, like maintaining fencing that prevents nose to nose contact at farm boundaries, will also help to reduce the risk.

What should be done to control Mycoplasma on my farm?

Most dairy farms probably don’t need a specific Mycoplasma control plan. Instead, focus on reducing the major disease problems that Mycoplasma can contribute to; pneumonia and mastitis. For both of these diseases, the environment and management of the farm can have as much influence as the specific bacteria, viruses or Mycoplasma that ‘cause’ them.

All farms are different, so regular discussions and reviews with your own herd-health vet are essential. Your vet can advise on both environment and management, and any appropriate diagnostic testing needed for monitoring. There are no commercial vaccines for Mycoplasma in the UK, so husbandry is even more important in prevention.

For pneumonia, focus on improving air quality and reducing stress (like mixing, handling and uncomfortable accommodation). Include young-stock diets when planning nutrition to make sure they have the nutrients to grow and maintain immune function. Working on these will help to control all causes of pneumonia, not just Mycoplasma.

For mastitis, Mycoplasma are generally considered a ‘contagious’ type of bacteria, that will spread from cow to cow in the parlour. Creating a milking routine to minimise cow to cow spread is the aim, and again this will control much more than just Mycoplasma. In some cases, if Mycoplasma become established as a major cause of mastitis, more specific controls (like segregation or culling of carrier cows) cows can be required.

Tim Geraghty, Veterninary Centre Manager, SAC Consulting