Vets urged to help in fight against deadly disease

With a dramatic increase in the identification of the bacteria Mycoplasma bovis associated with cases of pneumonia, lameness and mastitis in both diary and suckler herds around the country, vets should consider this diagnosis, especially in difficult-totreat cases or where infections continued to recur.

That was the message at meetings in Perth and Kelso recently by the SRUC’S Colin Mason, manager of the disease surveillance centre at Dumfries, who said that while Mycoplasma bovis had first been identified in the 1970’s and had only rarely been implicated in disease outbreaks, things had changed markedly in recent years.

“Over the past three years there has been a marked increase in the identification of Mycoplasma bovis where tests have been conducted,” said Mason – who indicated that while no exact figures were available, it was probably present in almost half of calf pneumonia cases where tests were carried out.

He said that although mycoplasma was a bacterium, it lacked cell walls and could re-arrange its surface lipoproteins:

“Not only do these factors make it difficult to

0 Dairy herds are at increasing risk from Mycoplasma bovis treat with many of the widely-used antibiotics such as penicillin, but it also means that it can partially evade the animal’s immune system.”

And with no vaccine registered for use against the infection in the UK and only a limited number of antimicrobials effective against an outbreak, it could be difficult to control: “While outbreaks of pneumonia in claves are seldom simple – often involving a predisposing factor resulting in an initial viral attack which could later be compounded by a bacterial infection, Mycoplasma could come in as an exacerbating factor at any of these stages.”

He said that Mycoplasma bovis was often seen in chronic outbreaks where there was high morbidity but low mortality – and especially where there was a degree of facial paralysis and head tilt in calves associated with inner ear infection by the bug.

Although early prophylactic treatment with effective antibiotics could help keep the disease out, Mason was wary of such an approach:

“As far as prevention is concerned we have to walk the tightrope between preserving antimicrobial efficacy and animal welfare.”

Healsoindicatedthatspecially prepared vaccines isolated from the strain infecting the farm could produce good responses – but warned that this was neither cheap nor straightforward and emphasised that the possible downsides of such a n approach should be explained to a farmer before this route was embarked upon.