Mycoplasma and Biosecurity

What is Mycoplasma Bovis
Minimising Mycoplasma Bovis risk for calves
Testing for Mycoplasma Bovis
Service bulls and Mycoplasma - the risks

What is Mycoplasma?

Mycoplasma bovis is a bacterial disease that typically affects both adult dairy cattle and calves. It does not infect humans and poses no risk to food safety. Mycoplasma was first detected in a small number of New Zealand herds on the South Island in July 2017. Currently 38 farms are known to be infected including a number in the North Island. All farms identified to date are linked by animal movements.

What symptoms are typically seen with infected animals?

In adult cows symptoms include:
  • Mastitis that is often poorly responsive to treatment and in multiple quarters
  • Diffuse swelling of the joints/legs with associated lameness
  • Pneumonia
  • Abortion
In calves symptoms include:
  • Acute and severe pneumonia
  • Diffuse swelling of the joints/legs with associated lameness
  • Head tilt caused by an inner ear infection
  • Conjunctivitis
Clinical disease may be seen in an individual animal or in a large percentage of a group of animals. It is not uncommon to see symptoms in cows (like mastitis as described) in conjunction with affected calves.
However not all animals or herds with mycoplasma may show clinical signs of disease. A silent ‘carrier’ state may exist, with clinical disease occurring weeks or months after introduction to a herd.

How is Mycoplasma diagnosed?

Mycoplasma is difficult to grow hence specific microbiological techniques are required.
An alternative testing system, known as PCR, which relies on the detection of the bacterial DNA has been widely used by MPI in the current outbreak. However animals that are truly infected may test negative, and bulk milk may test negative even though a herd is infected, particularly where the infected animals are showing clinical signs and have been removed form supply.

Your Vet is your first point of contact, should you suspect Mycoplasma is present in your herd. They can guide a herd through the required steps to rule out, or confirm, this type of diagnosis. Currently if the disease is confirmed government veterinary involvement will occur.

What are the best, immediate steps for prevention?

Cattle movement onto farm is the greatest risk for introduction of mycoplasma. Currently all known farms in New Zealand with mycoplasma are under movement control (that is they can’t sell cattle), so the risk should be small. Any activity which co-mingles your livestock with cattle from other farms increases the risk of exposure.
Other, best practice, control points involve standard biosecurity measures such as thorough washing of boots, protective clothing and gear after contact with cattle when shifting activities between cattle age groups on a single farm or shifting activities between farms.

If you have any questions or concerns about your stock, please contact your lead Anexa Vet, we're here to help.

Dairy NZ Downloadable Files

Not sure what to be looking for in your cows and calves? Wondering how you can effectively clean your gear or are you wanting a checklist of what you can do to protect your farm - Check out these downloadable pdfs from DairyNZ

Minimising Mycoplasma risk for calves

It is very difficult in most NZ calf rearing systems to completely eliminate the risk of Mycoplasma transmission. However, the below 5 steps can minimise the risk of introducing this disease. Recall that a major risk factor for spread of Mycoplasma bovis from one herd to another is introduction of stock, or raw milk, between herds.

Step 1: If calves have to be purchased, take steps to ascertain the level of mastitis, joint related lameness and respiratory disease (cows and calves) in the herd of origin. Where possible, limit the number of herds that calves are sourced from.

Step 2: When purchased calves first arrive on your farm, quarantine them for at least one week and practice good surveillance for conditions associated with Mycoplasma infection (swollen joints, head tilt, pneumonia). If you are suspicious of these conditions seek veterinary advice.

Step 3: Make sure that all purchased calves have accurate NAIT and ASD records with matching ear tags.

Step 4: Where possible, use calf milk replacer as a low risk alternative to whole milk or the higher risk option of treated cow waste milk. If whole milk is to be used, consider purchasing a pasteurising unit as this will significantly lower the pathogen load in the milk and will not affect immunoglobulin levels in colostrum. An alternative to pasteurisation (but not a replacement for) is acidification of the milk with citric acid. This process may interfere with immunoglobulin viability in colostrum. A fact sheet on the acidification process is signposted below.

Step 5: Practice excellent hygiene around the calf rearing area. Consider the use of a human foot bath, dedicated protective clothing for the calf areas and disinfection of feeding utensils between calves. Sick calves should be isolated and treated appropriately.

Testing for Mycoplasma Bovis

There are two types of tests that have been developed for detection of this infection in cattle. The first is a PCR test which attempts to identify the presence of the M. bovis bacteria by the DNA of the bacteria. The second test type is an ELISA which looks for the presence of an antibody response to the bacteria in an infected animal. They work in fundamentally different ways. The PCR is generally used on whole milk or nasal secretions, while the ELISA is a blood test typically. Neither test is perfect at identifying infection – in fact, they are tests with only average performance and this is due to the nature of the infection. Mycoplasma bovis is very good at establishing a subclinical infection with a low level immune response making detection with both tests challenging.

Testing for M. bovis has now become available at commercial labs other than those run by MPI. If a sample returns a positive test, the commercial lab is obligated to forward the results and sample onto MPI as is standard for an exotic disease organism. If you are contemplating testing animals for M. bovis (eg testing introduced herd bulls) it is important that you contact your Anexa FVC veterinarian for further advice on the number of animals required for testing and what this means for interpreting any results. It may also be a timely opportunity to conduct a Biosecurity Risk Assessment with your herd vet. This process takes around an hour and is highly useful at identifying risk factors for multiple diseases we are wishing to minimise or prevent.

Service bulls and Mycoplasma - the risks

Animal movements are one of the key risk factors for the introduction of Mycoplasma bovis in dairy and beef farms. Most farms we service either purchase or lease bulls for a portion of their mating period. Mycoplasma can be spread through infected semen during natural mating, so the risk is real.

There are a number of things you can do to reduce the risk of introduction of M. Bovis via bulls to your herd. When buying bulls, you need to do your homework.

Firstly you need a full history of any bulls to be purchased including their electronic identification numbers, NAIT locations for all movements of these animals, and disease history for the herds and grazing blocks from which these animals have been purchased.

Purchasing bulls from a closed beef farm, particularly beef units that use AB rather than natural service bulls for mating may reduce the risk of infection substantially.

Risk is increased where bulls are purchased from sales yards or youngstock units where animals from multiple sources are reared together, particularly where waste milk has been purchased to rear these bulls. Non-virgin bulls also carry a higher risk, as they have been used previously on other farms before coming to your property.

Testing is available but there are severe limitations around the test. A positive bull may not be shedding the bacterium at the time of testing, so no test can prove freedom from disease. Testing should only be done at the mob/herd level and is not recommended once the bulls are dispatched to the farms.

The lowest risk bulls are from single ‘closed’ herds with minimal history of lameness, mastitis or calfhood disease. As per our normal recommendations, virgin bulls are best and BVD status must be known from a negative blood test result and vaccination is crucial.

On arrival the bulls should be held separately from the main herd for a minimum of seven days, during that time you should assess the health and lameness status of the bull before mixing with the herd. If you have any concerns about the bulls, contact your Vet.
Creating a biosecurity plan for a farm