Beating Bovis

By: Neil Warnock

The government has announced that they intend to attempt eradication of Mycoplasma Bovis. Although the disease is not zoonotic (in other words, it cannot be transmitted from animals to humans), it’s detrimental to animal welfare and hurts milk production. Hence, the big drive to eradicate it. Dairy farmers will receive instructions from their milk companies in the coming weeks as to their testing regimes, but smallholders and lifestylers will need to play a part as well. As a smallholder, what steps can you take to maximise the chances of keeping the disease off your property?

Good biosecurity is an easy start. Buckets of disinfectant set up for contractors to wash themselves before they come on to the farm is easily implemented. If you rear calves, contaminated milk is one of the biggest contributors to the spread of the disease.  M. Bovis causes mastitis in cows, which is usually treated with antibiotics. After a cow has been treated with antibiotics, her milk is unfit for consumption. This milk is meant to be dumped, as it contains sub-optimal levels of antibiotics and can contribute to antibiotic resistance developing when fed to other animals. The milk also contains the pathogens which have caused the mastitis, therefore it can potentially contain M. Bovis. However, the economics of farming over the last 30 years have meant that this milk is often fed to replacement calves or is sold to other farming enterprises. Unfortunately, this process has been very effective at spreading M. Bovis. The pathogen excreted in the milk of one cow, can be fed to large numbers of calves causing multiple new infections. The process of feeding waste milk to calves needs to stop if we are to limit further spread of the disease. It is safest to use milk powder rather than buy fresh milk from dairy farms.

The National Animal Identity Tracking (NAIT) system has come under a lot of scrutiny during the outbreak. The sale of young calves to friends or neighbours without NAIT recordings has been a pretty common part of New Zealand rural trading for the last 50 years. Unfortunately, this has made tracking the spread of the disease difficult. It is imperative going forward that all cattle sales or movements are recorded – regardless of the age of the calf or the type of transaction. It will mean that any future disease outbreaks can be traced rapidly back to the point of origin and the disease tracked more effectively.

Lastly, if you are concerned that you may have the disease on your property, don’t bury your head in the sand. Most of the conditions that M. Bovis causes (mastitis, pneumonia, abortions, arthritis) have more common causes, which can be identified with appropriate testing. The Ministry of Primary Industries is only alerted if an animal tests positive, so you are not going to have any movements suspended unless we confirm a diagnosis. It is better to get any suspect animals inspected rather than continue as normal and risk exacerbating the spread of disease.

Neil Warnock, Wellsford Vet Clinic


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