WORDS: Tim Fulton

A critical cog in the drive to eradicate Mycoplasma bovis is the use of NAIT to find ‘trace’ infections.

MPI describes M bovis traces as identified events of interest, or connections to an infected farm or a property likely to be infected.

When a farmer was first contacted by MPI they were asked if they had specific animals on the farm at that moment. The stock were found on the farm by scanning the animals with a wand or looking at their visual tag.

This may be done by the farmer or by staff working on the M bovis programme at the time of sample collection.

There were times when animals were not located at the property that MPI expected them to be on, based on NAIT records or other information, an MPI spokesperson said.

It happened “from time to time for a variety of reasons, it is not always a compliance issue”.

“When this happens we will ask farmers to clarify where the animals may be and ask them to update their NAIT records. The additional information is then followed up, and if necessary further investigation carried out, until the animals can be located.

“Every farm is treated on its merits and we make decisions based on the information the farmer supplies as evidence that specific animals are (or are not) located on their farm.”

Field staff may do a census of the property if it was believed that a trace was still on the property, but not identifiable due to an ear tag falling out. In that case, all untagged animals may be treated as potential traces, the spokesperson said.

“If the animal is believed to be on another property or has already been sent to the meat works, we will follow up on this information and ask the destination location to provide evidence that the animal has been received. This process is repeated until we can be assured that the animal has been located or accounted for.”

Essentially, animal tracing was following business relationships “and therefore we are able to use historic information as potential leads to find animals of interest”.

The spokesperson said MPI accepted this could be extremely time consuming and may cause significant disruption to farming. Farmers with accurate and complete records found the process much less disruptive – and the eradication programme relied on these farmers to give tracing and surveillance staff accurate information on their animal movement.

At January 18 MPI had recorded 29,690 trace animals on its database. More than 50,000 animals had been culled at December 2018 however it was not possible for MPI to say how many trace animals were still alive at that point.

“Because Mycoplasma bovis is spread so easily via cow-to-cow contact, if there is one confirmed infected cattle the whole herd is considered infected. We do not collate this information, only the total number of cattle which have been culled as part of the Mycoplasma bovis programme.”

In response to a request under the Official Information Act, MPI reported the total cull at December 2018 was 52,112.

Since the decision to eradicate M bovis was announced in May 2018, there had been a significant increase in funding allocated to the programme.

“Our resources have grown and, as we’ve learned more about the disease, our processes have become more streamlined and efficient. This has resulted in the number of identified events of interest growing significantly from May 2018.”

The number of “identified events of interest” was always growing, however, the rate at which it grows could fluctuate.

A number of factors contributed to this including, for example, the rising number of staff dedicated to tracing, improved process, the number of farms with low NAIT compliance and the time it took to trace animal movements.

Meanwhile the number of beef farms with links to infected properties had grown and there were fewer animal movements from beef farms.

The number of recorded animal movements had grown since the decision to pursue eradication was made. This meant MPI could more easily trace animals connected to infected properties, the spokesperson said.