These are words to strike fear into the heart of many farmers. However, as lifestyle farmers, there are far fewer risks for you and your cattle than there are for many commercial dairy farmers. Big commercial farms are certainly being hit hardest. So what does this outbreak mean to us as lifestyle farmers?
We hope this article will help clarify the situation.
If you haven't bought adult cattle, calves, or raw milk onto your farm in the last 3 years, it is extremely unlikely that your cattle are infected. If you had bought cattle from a confirmed or suspected infected property it’s likely that by now you will have been contacted by MPI, who are tracing the movement of all cattle from known infected properties as part of an eradication programme.
Most of the cases so far have been on commercial dairy farms, but beef properties and other properties have been confirmed as infected. At this stage, it appears the disease has been spread from farm to farm by the movement of infected cattle (i.e. cattle that carry the bacteria in their body), but overseas, feeding of raw milk to calves is a known risk for the spread of Mycoplasma bovis. The disease is spread between animals within a farm by direct contact between cattle, or from cows to calves in milk. It isn’t spread by wind and there’s a much lower risk of spread by dirty stock trucks, clothes, or equipment.
Surveillance to date suggests the disease is not widespread within the national cattle population and appears to be limited to a network of farms connected by cattle movements. Given this position and the potential impact the disease could have in New Zealand, the government decided to pursue phased eradication – announced in May 2018.
Other livestock species are considered to be at low risk for spreading the disease. Mycoplasma bovis poses almost no health risk to other farm animals, or to humans, as it is host-adapted to cattle. The bacteria do not survive for long outside their cattle host, however, any object such as AI gear or equipment contaminated with milk could theoretically transfer bacteria.
One of the largest challenges for eradication is that Mycoplasma bovis is difficult to detect in cattle that are infected with the bacterium but not showing signs of disease. Testing is being performed on blood and milk samples, and swabs taken from the tonsils. These are being carried out by MPI on all cattle thought to have been in contact with infected cattle. As well as this, extensive screening tests are being carried out on bulk milk samples from dairy farms across the country. Because it’s hard to identify cattle with Mycoplasma bovis, it follows that determining a herd is free is not easy.
MPI has strict movement controls in place to stop the disease from spreading further than it already has. When the infection is detected, the only way to eliminate it from the herd is to cull all the cattle (because tests are not guaranteed to find all infected individual animals). This is of course hugely distressing to the farmers whose apparently healthy productive cows are sent for slaughter. They need our support.
In most western countries, Mycoplasma bovis infections are well established. New Zealand cattle have only recently become infected and the disease is not widespread, and MPI considers that eradication is achievable. If we are successful, we would be the first country in the world to achieve eradication. While the effort will be expensive and laborious, MPI considers it would be well worthwhile.
- unusual mastitis in cattle that doesn't respond to treatment
- arthritis in cows and calves
- late-term abortion
- pneumonia in calves
- conjunctivitis in calves
- signs of ear infection in calves - droopy ears, head tilting, discharge from the ear
Testing for m.bovis
There are two tests:
- ELISA - a blood test that shows antibodies
- PCR - test on milk and swabs which detects the presence of the bacteria
The problem is that m. bovis hides in the immune system and may only be able to be found when the animal is actively shedding. Infected animals tested in a normal pastoral environment may test negative but when stressed - by weather, change of environment, transportation etc they may start showing symptoms and test positive.
This means that multiple tests must be done multiple times over an extended period before a definitive answer is found. Even then it's not always possible to be 100% certain.
So far the evidence from both here and overseas shows that the most common way in which m. bovis is spread is by prolonged animal contact or calves drinking milk from infected cows. There is no evidence so far of over-the-fence contagion without substantial animal contact. The spread in NZ has been within herds and via stock movements from one farm to another.
The bacteria does not persist in the soil for long and MPI believes that letting infected properties lie fallow for 60 days after the stock have been culled will prevent the chance of re-infection. Urine and faeces are not regarded as significant vectors but see good practice below.
It is technically possible for Mycoplasma bovis to be transferred to some other animals, including pigs, sheep, and goats. However, it is extremely rare because it can only be spread to them by feeding them raw milk from an infected cow. No transmission of the disease back to cattle has ever been recorded. Other hosts are considered to be a dead-end infection and are not important in the ongoing spread of the disease.
Nose-to-nose contact with your neighbours’ stock should be prevented as Mycoplasma bovis is spread through direct contact between animals. This can be achieved by creating buffer zones using electric outrigger fencing or a separate electric fence two metres back from the boundary.
If you are buying in cattle stock
Make sure the stock is healthy - use MPI's checklist here.
Quarantine stock on arrival for a week to see if they develop symptoms. This is not just m. bovis it's good practice to avoid infecting your farm with other of diseases.
Take sensible biosecurity measures.
Thorough farm hygiene can reduce the risk of the disease entering your farm. Make sure that footwear, protective clothing, and equipment that has been in contact with animals on other farms is not used on your farm, or is properly cleaned and disinfected before use.
Second-hand equipment that has been in contact with animals, especially bodily fluids, presents a higher risk of transmission and should be cleaned and disinfected prior to use.
Vehicles coming on and off your farm should be confined to the main access track. Use your own vehicles to transport visitors around your farm.
Cleaning and disinfection
This is a two-step process. Disinfectants won’t work through dirt, so it is important to remove all visible dirt and dung from gear and vehicles that have been in contact with the stock.
Once items are clean, use a disinfectant. It’s best to leave disinfectant on items for a few minutes – ten minutes is best.
Suitable disinfectants are: 1% Virkon (made by mixing 50gstandard sachet) Virkon with 5 litres water), 0.2% citric acid (made by mixing 1 tsp of citric acid with 1 litre of water), Trigene, or any appropriate disinfectant used to the manufacturer’s instructions.
Provide a foot bath with disinfectant and a scrubbing brush for visitors to clean their boots when they come on and off the property.
Have clean hot water and soap available so visitors can effectively clean their hands and any equipment that they need to take off-farm (e.g. vet’s equipment).
If your livestock shows any symptoms of m. bovis then talk to your vet or contact MPI directly.
Overall - the message is that it should be safe to buy and sell cattle with farms that are not under any form of control. But be sensible.
Make sure all cattle comply with NAIT regulations and register all stock movements on NAIT within 48 hours.
For more information check out MPI mycoplasma bovis.
What can you do?
If you suspect you have cattle that could have the disease contact your veterinarian.
Don’t bring any cattle onto your property unless you can be sure they have not come from an infected farm.
Don't buy milk from other farms – use milk powder for calves if possible.
If you have to use raw milk, buy it from the same farm as where your calves are sourced. Milk isn’t traced nor is its movement regulated in New Zealand. Given milk’s potential to spread Mycoplasma bovis, it is necessary to be able to trace milk – calves are traced via NAIT and so if milk is purchased from the same farms, the calves become a proxy for the milk if tracing is required.
Raw milk is best treated to reduce the risk of disease – talk to your vet if you intend to purchase raw milk.
Ensure your cattle have NAIT tags and their records are up to date.
Keep stock separate from your neighbours – consider double fencing the boundary, and have stock proof fences.
There is a great deal more information about Mycoplasma bovis on MPI’s website: https://www.mpi.govt.nz/protection-and-response/mycoplasma-bovis/
We would like to thank the NZVA for their assistance in writing this article