Mycoplasma bovis - for veterinarians

Jersey cows


Mycoplasma bovis - information for veterinarians


 

Mycoplasma bovis (M. bovis) is a bacterium which can a range of conditions in cattle - including mastitis that doesn’t respond to treatment, pneumonia, arthritis, and late-term abortions.

M. bovis is an Unwanted Organism under the Biosecurity Act 1993.

M. bovis was first identified in New Zealand in July 2017, following collaboration between veterinarians and farm staff seeking to understand an unusual pattern of disease. This is the first time M. bovis has been found in New Zealand.

In May 2018, MPI announced the Government, dairy and beef industries had agreed to eradicate M. bovis from New Zealand.

The New Zealand Veterinary Association (NZVA) is not directly involved in the Government's M. bovis eradication programme. We do however act as a liaison between the Ministry for Primary Industries (MPI) and NZVA member veterinarians.

Veterinarians provide essential support to New Zealand farmers as the rural sector continues its Mycoplasma bovis  eradication. Veterinarians are highly valued and skilled on-farm animal health advisors.

For the latest updates on M. bovis, visit the MPI website and subscribe to the weekly MPI Mycoplasma bovis stakeholder update.

If you have any concerns about your animals, contact your veterinarian as soon as possible for advice, or call the Ministry for Primary Industries on 0800 80 99 66

Below you will find:

Frequently asked questions

So far, the most common presenting signs of M. bovis infection in New Zealand cattle have been clinical mastitis (with poor response to treatment) and arthritis. However, other clinical presentations may include pneumonia, otitis media, late-term abortion and conjunctivitis.

Latency and sub-clinical disease are two of the most challenging problems with M. bovis. During active infection, cattle may be entirely sub-clinical (shedding and bacteraemic but appear completely healthy) or they may have clinically evident disease.

Clinical disease and shedding may be triggered by increased stress such as calving.

More information is available on the MPI website.

The greatest risk for spread of M. bovis is movement of infected cattle.

Infection is transmitted between cattle in close contact with each other - generally prolonged or repeated contact with infected animals is required. Transmission of disease by running different lines of stock through yards and races is extremely unlikely, unless bodily secretions remain in significant amounts, and contain an infective dose which then contacts a susceptible animal's mucosa.

Feeding of infected raw milk to calves is also a known risk factor and is one of the two highest risks factors for spread.

M. bovis may also be spread on equipment used between farms. Because milk may contain M. bovis, milking equipment is particularly important to clean and disinfect if the equipment is shared between properties or herds.

Contaminated mud or faeces from infected animals also has the potential to spread disease, however it is a much lower risk. Given the bacteria is fragile outside of its host, cleaning and disinfection, and ultraviolet light all render the bacteria non-infective reasonably easily. M. bovis does not survive in soil for a long period.

Remember most disinfectants do not function in the presence of organic matter - cleaning is required prior to disinfection, and replenishing disinfection solutions contaminated with organic matter is required to ensure efficacy. Contact time is also critical for efficacy.

For adult cattle, spread through feed is not a significant risk. Feeding calves unpasteurised milk infected with M. bovis is a cause of spread in countries where this disease is established. Properly made silage with a pH < 4.5 that is wrapped correctly, is not considered a significant risk for transmission of Mycoplasma bovis. Silage can be tested to ensure it has reached this standard.

Although it is very rare for M. bovis to infect animals other than cattle (and American bison), other animals may carry the bacteria and in theory could pass this on to a susceptible cattle beast. The significance of this is unknown as a route of disease transfer. Where possible, it is prudent to keep infected cattle isolated from all other species.

MPI recently made some changes to on-farm animal sampling, and interpretation of these test results. You can read more about these changes in this update from Biosecurity NZ.

In addition to animal testing, the M. bovis Programme is also undertaking continuous bulk tank milk surveillance testing. You can read more about this surveillance in a recent update sent to NZVA members.

MPI presented a webinar to NZVA members in August 2019 where changes to testing were discussed. The slides for the presentation are available here, and MPI's answers to the questions posed by attendees can be found here.

Further information is available on the MPI website.

Currently, the only commercially available test for M. bovis which veterinarians can use in New Zealand is PCR.

The NZVA has several concerns relating to use and interpretation of the current tests and considers that the limitations of commercial testing for Mycoplasma bovis are not sufficiently understood by potential end-users.

Therefore, the NZVA does not support the use of commercial testing for detection of M. bovis in individual animals and discourage veterinarians from using them.

Read more about these concerns in the Position statement: Commercial testing for Mycoplasma bovis

The NZVA's advice is not to sign documents with any such declarations.

Please do not sign anything you are unsure about. If you are presented with a certificate to sign and you are unsure about its integrity, please stop and get advice.

This includes certifying that a herd is free from a specific disease.

A key role for veterinarians is to educate farmers about risk factors that make them vulnerable to M. bovis. This conversation will flow out of the risk assessment as farmers are made aware of what their on-farm risk behaviours and practices.

An online tool for assessment of M. bovis risk (the Dairy Risk Assessment tool, developed by XLVets) has been distributed by the NZVA. This tool is designed for use by veterinarians in consultation with their dairy farming clients, and generates a risk 'score' based on farm management practices known to be a risk for spread of M. bovis. Veterinarians are then able to give specific advice to help farmers reduce their risk. Find out more on our website at https://www.nzva.org.nz/page/dra.

While the key risk factors have been well publicised by MPI and the industry, it is useful for veterinarians to reinforce them when talking with farmers.

Key points for discussion on minimising M. bovis risk

Animal movements

Farmers should limit cattle movements onto their farms and avoid contact with neighbouring animals. Double-fencing all boundaries and ensuring they are stock-proof, is a sensible pre-caution. Accurate NAIT is required, and animal movement history should be considered before new stock is introduced. See above for more information.

Transportation of infected cattle remains the greatest risk of disease spread, but the contaminated trucks are also present a small risk regarding spread of disease. Disinfection is only effective in the absence of organic matter. Therefore, reducing risk is a two-step process - first thorough cleaning, then disinfection.

The most important thing to do is hose all the mud, faeces and urine out of the trucks and let all surfaces dry. Sunlight and desiccation destroy Mycoplasmas, so with good cleaning, drying and then disinfection there is little chance Mycoplasma bacteria will survive.

Ideally, trucks should be thoroughly cleaned between loads from different farms, particularly those under legal notice. Multiple consignments on one truck should to be avoided. It is not necessary to clean between loads from the same farm.

Farmers should be instructed to minimise the number of trucks used to cart stock. For example, using one truck all day for one property rather than 5 trucks over a couple of hours, and then going to the next farm. Trucks should then clean and disinfect before the next property.

Feeding raw milk

Milk from infected cows that is fed to calves is the other key risk factor in transmission of M. bovis. NZVA advocates for no between-farm milk movements. This is key to reducing transmission of M. bovis because milk movement is not currently recorded in New Zealand, and therefore presents a real challenge in the response tracing.

Ideally farmers would only feed milk from their own farm to their own calves.

However, if milk is transported between farms the NZVA strongly recommends milk movements are always linked to calf movement between the same farms - in other words, calf NAIT tracing will be a proxy for waste milk tracing (which is currently unregulated and untraced) and the risk profile for farms would be the same.

Introduction of milk from outside sources should be considered very carefully - cows shed M. bovis intermittently, so prior bulk milk results are not a robust way to gauge a farm's status, and even less so a cow's individual status. Shedding is more likely at times of stress (i.e. during transition).

Pet days

With the above in mind, calf days do present some challenge - on first principles, they involve movement of animals and this should be carefully considered prior to being undertaken.

In a low-risk area, risk of disease transfer at a pet day is probably very low with appropriate management. In the hot spots, careful consideration would be prudent. During the current eradication phase, NZVA advocates calves are not taken to pet days.

Further information on pet day biosecurity can be found on the MPI website.

Muddy tracks and trucks

Disinfectants won't work through dirt - it is necessary to remove all organic matter from gear and vehicles BEFORE attempting disinfection. Once items are clean, using a disinfectant is only useful if mixed correctly and correct contact time is achieved. With some disinfectants, this may be up to 10 minutes.

Cleanliness and good hygiene practices are good general biosecurity tools with which all farmers should engage, and veterinarians should encourage and drive these conversations.

Further information on farm biosecurity can be found on the MPI website, the DairyNZ website and the Beef+Lamb New Zealand website.

Technical information for veterinarians

Mycoplasma bovis - Ministry for Primary Industries website. Status reports, guidance for farmers and farming communities, reports and notices issued by MPI.

2019 changes to on-farm sampling and ELISA interpretation.

2019 update on bulk tank milk testing.

Slides from MPI webinar on M. bovis Programme testing.

MPI answers to NZVA member technical questions.

Position statement: Commercial testing for Mycoplasma bovis.