The Ministry for Primary Industries (MPI) is welcoming a huge drop in the number of farms under active surveillance for Mycoplasma bovis.
Recent reports say more beef than dairy farms are infected, a worry because to date the only infections in beef herds are believed to be in trading herds where imported dairy sourced animals have tested positive. These also have all been identified via 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 know of no reported evidence of infection spreading to beef breeding cows or other base stock on these allegedly infected beef farms.This is not to say no beef breeding herds are infected, just that no evidence of this has been seen to date.
Most of the infected dairy animals that were 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 is likely the most effective way of spreading this disease.
The limited evidence to date so far also is highly suggestive that the disease entered NZ in 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 mostly Holstein based. Historically, MPI has 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 M. bovis. There is also evidence for M. bovis transmission in frozen bovine semen.
Compelling anecdotal information suggests M. bovis has been in NZ much longer than the date MPI is touting but its apparent reluctance to backtrace is of concern, especially to the owners of herds now killed or to 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 concern NZ farmers given the lack of conclusive information relating to this disease which is prevalent worldwide.
If it turns out 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 was warned about weaknesses in its oversight of biosecurity related to germplasm and other imports but political pressure from within NZ and our trading partners has taken precedence in decisionmaking on risk to our economy.
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.
• Neil Sanderson is a veterinarian and director of Advanced Genetics Ltd and director of Fossil Creek Angus Ltd, Otago.