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Mycoplasma Mastitis Huge Threat in UK & EU

28 November 2018

Mycoplasma bovis is an ongoing threat to dairy and beef herds in the UK and Europe, infecting cows not only with mastitis, but manifesting itself in joints or the middle ear and also infecting calves, according to Colin Lindsay, practicing veterinarian, at the international meeting of the National Mastitis Council in Milan, Italy.

"Mycoplasma bovis (M. bovis) is a huge challenge in the UK and Europe for a variety of reasons. In the UK, it would qualify as endemic in dairy and beef units because it's so widespread, and in parts of Europe, it's widespread as well. The problem is deciding the significance of any disease outbreak," said Dr. Lindsay, who is also a veterinary consultant in the UK and Europe. 

The disease has a variety of manifestations. Typically in calves, M. bovis primarily presents itself as pneumonia but can also be seen as arthritis or otitis media, which is an infection in the middle ear  identified by a calf's head tilting. In adult cows, severe outbreaks of polyarthritis are not uncommon, and these animals are extremely hard to treat, he said.

"It's very topical with the situation in New Zealand, where the working hypothesis is that we have a new introduction of M. bovis to that country," he said. "In that situation, you're getting rapid spread or has been spread, you're going to get significant clinical signs, and it's going to have a huge impact. Whereas in the UK, we have an endemic situation, so it tends to grumble on and give you subclinical and subproduction issues."

Diagnostics Role in Identifying M. bovis

Diagnosing M. bovis is very difficult partly due to the fact that it is a very delicate organism. Any delay getting milk samples to the lab can result in a high false-negative rate. Previous treatment with antibiotic, which is usually the case, will also suppress any growth and result in a high false-negative rate.

"In our practice, we normally use mycoplasma transfer medium. If you don't have the right medium to get M. bovis to the lab quickly, you're going to compromise growth," he noted. "Then the lab has to know what it's looking for. You can't just use a standard culture technique. Sometimes you have to [incubate] for 21 days, so it is a problem to diagnose with culture."

Historically, serology has been available from a diagnostic standpoint, but because M. bovis is endemic on the UK, Dr. Lindsay explained that testing of any production units would come back positive. However, with PCR testing, it's a real game-changer in helping veterinarians get a handle on M. bovis, offering a faster, easier solution compared to culture

"With PCR, just understand that if you get a positive, you have to link that up with your clinical disease. So you have to have the disease syndrome and the positive diagnosis, then link them both together. That's when you're confident," said Dr. Lindsay.

Treatment Options

Mycoplasmas don't have a cell wall which automatically rules out many of the antibiotic options, because antibiotics work by attacking the cell wall. If an organism doesn't have a cell wall, they are resistant to antibiotic treatment.

"So it's difficult to diagnose; it's difficult to isolate. Then once you do have a diagnosis, it can be very, very difficult to treat," he said. "If you have an early diagnosis, you're actually better to slaughter the animals."

Transmission and Risk Factors

"The organism itself mainly is direct transmission from animal to animal. Nasal secretions would be the main way or coughing," he noted. "Once it's in the host animal, the problem is that it can change its antigenic type, so once the animal starts to mount an immune response against the mycoplasma, it can flip its characteristics and the immune system has to start over again. They can produce biofilms, and the organism can hide within that biofilm."

Within large or expanding herds, one of the biggest issues is asymptomatic carriers. The key risk factor for M. bovis is bringing new cattle into the herd.

"They may look healthy, but they're going to be asymptomatic, and then you can get a disease episode," he noted. "It's a major challenge for the livestock industry."

 

Sarah Mikesell, Senior Editor

Sarah Mikesell, Senior Editor



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