There are more than 120 known mycoplasma bacteria species – but one in particular mycoplasma bovis, is the most significant mycoplasma pathogen for the UK cattle population.
Species of mycoplasma are a family of bacteria which do not have a cell wall, which means antibiotic treatments such as penicillin, which work to break down the cell wall, are not effective in treating the disease.
As well as this, the pathogen has the ability to change its surface proteins to disguise itself, thus avoiding the triggering of the animal’s immune response.
They are also able to produce a sugar biofilm which allows it to hide from immune response and antibiotic treatment.
Over recent years, the Animal and Plant Health Agency has reported a gradual increase in the number of submissions linked to mycoplasma, although it is unclear whether this is due to an increase in disease prevalence or an increase in awareness of the disease by both farmers and vets.
According to Dr Tim Potter, youngstock consultant at Westpoint Farm Vets, Horsham, the increase in reported cases could also be down to changes in management practices, such as commercial calf rearing units, bringing calves from large numbers of farms to be reared on one holding.
“It is a melting pot for potential disease outbreaks,” he says.
However, Dr Potter explains it is difficult to know the full extent of the disease.
He says: “We do not know what the herd level is in the UK, mainly because the disease is difficult to diagnose.
“And is not always routinely tested for on farm.”
Infection with M.bovis is associated with a number of different symptoms and can cause multiple problems in some animals, while other animals exhibit no symptoms at all.
Dr Potter says: “There is a real spectrum of disease.
“Apparently healthy animals may be carrying mycoplasma, but it may not be causing clinical disease.”
Pneumonia is the most common presentation associated with mycoplasma infection, most commonly seen in youngstock.
“The pneumonia does not always respond well to treatment and the condition can become chronic,” says Dr Potter.
THE post mortem usually shows consolidated lungs and the level of damage makes the poor response to treatment understandable.
It is usually hard to say how long the calf has been suffering with the disease before its death but, eventually, the lung capacity is no longer sufficient to sustain the calf.
Dr Potter says inner ear infections are common in young calves, with symptoms such as droopy ears and head tilts. In more severe cases there may be discharge resulting from an ear drum rupture and, again, calves do not always respond well to treatment.
In older cattle, arthritis and mastitis are the most common symptoms, which are often less commonly diagnosed.
Cattle are often seen with swollen, hot joints and lameness which can affect one or more joints. Mastitis caused by the M.bovis pathogen behaves in the same way as a contagious mastitis pathogen and is spread during milking most commonly.
It is difficult to culture M.bovis bacteria, so it is not routinely picked up in bacteriology for mastitis, but it does not mean it is not there.
Specific testing using techniques such as PCR need to be carried out.
HAVING in place a strict biosecurity protocol is one way to avoid bring the disease on to your farm, however the most likely way for M. bovis to occur is through bought-in stock.
Dr Potter says: “If you do not have the disease, avoid buying stock in. Running a closed herd is a good starting point.”
Pre-movement diagnostic testing may be an option if buying cattle in is a necessity, however this is not always 100 per cent accurate and an animal could still be carrying the disease. So it is also important to ask the farmer the mycoplasma status of their herd before buying.
“In the dairy herd the main time when infection occurs is from dam to calf, so a key method of control is to break the cycle at calving, ensuring calving pens are hygienic,” says Dr Potter.
It is also important to ensure calf sheds are thoroughly cleaned between each batch of calves.
Dr Potter says: “Most commercially available disinfectants will kill the pathogen, but the cleaning process needs to be very deep and thorough, as they create a biofilm which they use to protect themselves from chemicals.”
Mycoplasma is spread via respiratory secretions, so it is important to clean all equipment calves may have come into contact with.
“Calves lick everything so buckets, teats and even gates need to be thoroughly cleaned, it is not just a case of mucking out and disinfecting the concrete,” he adds.
Calves should be moved out of calving areas as soon as possible after birth, in order to minimise potential points of contact between calf and pathogen.
One of the main routes of transmission is through milk from infected animals. To avoid this, either feed powdered milk, or ensure any colostrum or whole milk is pasteurised before feeding, as this kills the bacteria.
“Early identification of the disease is key. Get on top of it as soon as possible, it spreads very rapidly. If an infected animal enters a group it will take just days to spread through the whole group.”
In adult cattle, the most common symptom is mastitis so good parlour hygiene is vital and most standard teat disinfectants will be effective in killing the pathogen.
Dr Potter says: “Treat it as a contagious problem, as you would staphylococcus aureus mastitis, practise good hygiene and cull cows which are persistently infected.”
There is difficulty in diagnosing the disease at herd level and eradication can be difficult.
Dr Potter says: “Some cows shed, some do not, some show infection, some do not, the disease never manifests in the same way in every animal.”
There is currently no commercially available vaccine for M.bovis, but some herds which are badly affected have recently started using autogenous vaccines, which are vaccines made specifically from the bacteria isolated on that farm.
Dr Potter advises working closely with your vet to determine the best course of treatment and management.
Treatment will involve the use of antimicrobials, so it is important the correct products are selected and that they are being used with care in the correct way.