Thursday, November 30, 2023

New Canterbury property confirmed to have Mycoplasma bovis

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Strain of infection identified as the original detected in New Zealand.
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A dairy farm in Canterbury has been confirmed infected with Mycoplasma bovis this week after it was first identified by standard Bulk Tank Milk background screening.

The find follows several months of no infection and testing has identified the strain is ST-21, the strain originally detected on a South Canterbury farm in 2017.

Deputy Director General Biosecurity NZ Stuart Anderson said the ST-21 strain is significant at this point in the eradication programme.

The new infected property has not previously been infected. 

“It is connected to the old strain as that means it is likely connected historically to an infected property.

“We don’t know yet, we are working through that and still to figure that out.”

The property is situated in a pocket of dairy farms.

“It is surrounded by dairy farms so there will be a number of farms to test, including animal movements, that could be 10 farms.

“We expect the number of notice of directions (NoDs) will increase over the next few weeks.”     

The M bovis Programme is working with the farmer on a plan to depopulate 1000 cows while also undertaking tracing of animal movements on and off the farm.

“This work will help identify the likely source of the infection and any other farms it may have moved to,” Anderson said.

In September 2022, a new strain of M bovis was identified on a dairy farm in Mid Canterbury, which has now been depopulated, cleaned, disinfected, and all movement restrictions lifted. 

Imported semen is considered the most likely source of introduction of this new strain.

“We are pretty certain that new strain was localised and contained to just the one property which is now cleared.”   

The new infection does not affect development of the proposed National Pest Management Plan to manage M bovis over the next few years. 

“Since the disease was first identified in July 2017, we have learned a lot about how best to control and remove infection from the NZ cattle population. 

“We have much more information on historic cattle movements in NZ and our processes and tools have matured over time,” M bovis programme director Simon Andrew said. 

At a cost so far of more than $650 million, 280 farms depopulated and some 2800 farms subjected to movement controls over the past six years, Andrew said the contribution the farming community has made cannot be underestimated.

The programme is jointly funded by government, 68%, and DairyNZ and B+LNZ, 32%.

The budget for the 10-year programme, which started in July 2018, is $870m.

To protect the work and progress to date the programme undertakes assurance activities to provide complete confidence that no infection has been left behind.

“This will ensure that our statement of absence from NZ stands up to scrutiny so everyone can be confident in the eradication declaration.”

MPI is undertaking case reviews of historic M bovis infection with the additional information now available.

Animal movement records have improved greatly since July 2017 and the earlier years of the M boviseradication effort, providing more insights about historic cattle movements in NZ.

This additional information, combined with the new improved tracing tools developed by the programme, means there is more information on how confirmed infected properties may or may not have been linked; the possible infection risk period; any cattle that may have been on a confirmed property within its highest risk period; additional cattle movements on and off infected properties, and where to focus disease control activities.

Andrew said in the majority of cases the reviews will be able to rely on the information already at hand to close off any potential risk identified with no further action required.

In a small number of cases, it may be necessary to contact farmers who have previously been involved in the programme, and their trading partners, to determine if any action is required to provide total confidence that infection is not present.

“We will only contact you if we cannot identify another way to be sure that risk has been addressed.”

Looking ahead the risk of transmission via semen is considered very low, especially following the introduction of the new Import Health Standard (IHS) in May 2022.

But low risk is not the same as no risk, Andrew said.

As a precaution farmers are encouraged to: use semen imported under the current IHS; farmers planning to use bovine semen that was imported into NZ before May 2022 should check with their supplier to discuss whether that semen has been treated with the Certified Semen Services Minimum Requirements for Disease Control of Semen Produced for AI (CSS) protocol or has been tested for Mbovis.

Importers of bovine semen are working with the M bovis programme to bring all imported semen currently in stock to an equivalent level of protection as the new IHS.

Bulls that have been in contact with infected cows and then moved to another herd are a risk for the spread of M bovis. 

To avoid this risk bulls should arrive properly identified and with their movement history details. 

Farmers can have their say on the proposed plan for the next phase of eradication can do so on the MPI website

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