The current media spin around the distribution of M Bovis infected herds in New Zealand and the origins of these infections is very misleading and potentially very damaging to the beef industry and in particular those in the seedstock industry.
There are recent reports that currently there are more beef farms infected than dairy farm infections. This contention is very concerning as to date the only infections in beef herds are believed to be in trading herds where imported dairy sourced animals have tested positive. These have also all been identified through trace forward pathways from infected dairy farms.
Currently there are NO known infected beef breeding herds or cow/calf operations without links to infected dairy farms. We also believe that there is no reported evidence of infection spreading to beef breeding cows or other base stock on these so called infected beef farms.This is of course not to say there are not infected beef breeding herds but there appears to be no evidence of this to date.
The highly significant feature of this information is that most of these infected dairy animals that have moved onto beef fattening farms were likely infected by being fed M Bovis contaminated milk from affected dairy cows on the dairy farm of origin rather than from direct contact.The practice of feeding mastitic milk to young calves on dairy farms appears likely to be the most effective way of spreading this disease.
The limited evidence to date so far also is highly suggestive that the disease entered New Zealand through legitimately imported European frozen germplasm and this may never be confirmed. DNA sequencing is highly suggestive that the M Bovis strain is of European origin. The infected farms also seem to be predominantly Holstein based. Historically, MPI have been warned of such risks by the germplasm industry but were ignored.
The risks associated with germlasm and M Bovis have always been there and certainly with embryos, there was never any requirement by MPI or their predecessors to test donor cows for Bovis. There is also evidence for M Bovis transmission in frozen bovine semen.
There is also some quite compelling anecdotal information that M Bovis has been in this country for much longer than the date MPI are touting but their apparent reluctance to backtrace is of concern, especially to those owners of herds that have been killed or will be killed before a definitive date and method of entry is identified.
The fact that the TAG group of advisors to MPI over the M Bovis incursion was split on the decision to manage or eradicate should be very concerning to New Zealand farmers given the lack of really conclusive information relating to this disease which is prevalent worldwide.
If it transpires that legitimate germplasm imports are implicated as the source of the M Bovis incursion, then that opens a minefield for NZ agriculture in general. Historically MAF were warned about weaknesses in their oversight of biosecurity related to germplasm and other imports (palm kernal, pig diseases, PSA to name a few) but political pressure from both within NZ and our trading partners has taken precedence in decision making around risk to our economy. We are seeing the terrible economic and social consequences which are surely unpalatable.
Is it time our whole biosecurity risk analysis process was overhauled, especially now that industry has been dragged into paying for these horrific incursions as they occur ?. If it is ever proven that legitimately imported germplasm is the incursion pathway,then the question that is surely raised is whether unwitting beef and dairy farmers should be expected to help foot the bill for the cleanup.
VETERINARIAN, DIRECTOR ADVANCED GENETICS LTD.
DIRECTOR, FOSSIL CREEK ANGUS LTD, OTAGO.