Q&A: What you need to know about Mycoplasma bovis in cattle

Mycoplasma bovis (or M bovis) is a bacterial disease found in dairy and beef cattle. It can lead to serious illness in cattle affecting health and production.

Farmers whose herds have been affected have reported issues with lameness, unexplained death, low yields and poor fertility. (See Wake-up call as disease costs dairy farmer £1m.)

There is currently no treatment for the disease and although some of the conditions it causes can be treated, an infected animal will always be a carrier.

The best way to control the disease is by avoiding transmission in the first place. To do that it is important to recognise the symptoms quickly.

See also: Farmer speaks of his hell at losing herd to Mycoplasma bovis

What are mycoplasmas?

Mycoplasmas are very small bacteria that belong to the class Mollicutes (meaning soft skin). More than 12 different mycoplasmas and related species occur in cattle, but few result in disease.

Mycoplasmas are totally dependent on the animals they infect to provide the nutrients they require.

Why are they a problem?

M bovis causes the most concern to UK farmers because it can be difficult to treat. The organism has a number of defence mechanisms, which include:

  • The lack of the cell wall, so that certain widely used antibiotics are not effective.
  • An ability to change the surface proteins so it can evade the cow’s immune response.
  • An ability to produce a sugar matrix (biofilm) so that it can temporarily hide from both the immune system and antibiotic treatment.

What diseases does M bovis cause?

M bovis causes several diseases in cattle.

The most common is respiratory disease in calves, and less commonly ear infections (otitis media) resulting in head tilt.

In older animals, it can also cause arthritis, untreatable mastitis and pneumonia, eye infections and abortion.

How is it transmitted?

By close and repeated contact over short distances; untreated infected milk can also be a source of infection to calves.

Transmission of M bovis “within cow” is thought to be possible both from the udder to other organs and vice versa.

In situations when herds have concurrent problems (other diseases such as salmonellosis or BVD) or very poor nutrition/environments, mycoplasma species outbreaks can be severe both in terms of numbers of cows affected and severity of clinical signs.

How can you diagnose?

Diagnosis used to rely on selective culture media and prolonged incubation. Growth usually becomes apparent in a few days but in some cases it can take up to 21 days.

Techniques based on polymerase chain reaction are also available, but most commercial kits are designed to detect only M bovis.

Specialist laboratories use the PCR/DGGE method, which can detect and identify mycoplasma species, including mixed mycoplasma infections, in one test.

Bulk tank culture and PCR have been advocated as ways of monitoring and screening herds for the presence of M bovis mastitis. However, successful bulk tank culture relies on a clean milking routine.

Serology is an established method of detecting disease in a herd and can provide evidence of infection.

How can you prevent it?

The largest risk is considered to be from the purchase of cows or heifers clinically or sub-clinically infected with M bovis.

Make sure you get a detailed history, purchase from low somatic cell count herds and screen the herd from which animals have been purchased or from individuals quarantined before joining the main herd.

Maintaining a strictly closed-herd policy is the best method to minimise the risk.

Feeding of waste milk to calves is not recommended where Mycoplasma bovis has been diagnosed.

Although no commercial vaccines are licensed in Europe for M bovis, the Animal and Plant Health Agency (Apha) and other companies are licensed to produce an autogenous vaccine.

Source: Apha