With an estimated cost of $150 million a year on herd health, the hit is about $4000 a farm every year through ill thrift, diminished production, calf deformities and abortions.
The BVD Free Challenge was launched at the start of the year to prompt farmers and vets to take disease control measures to help determine how much more productive herds would if the disease was eliminated.
The data would also help provide a business case to present to the industry on a national approach to control the disease.
Different stages of the competition include completing a survey that includes farmers’ and vets’ views on preferred national control measures, submitting a BVD plan for the farm and proving livestock have been tested.
Some cattle get only a transient infection, from animal to animal contact, and recover after three weeks.
But the most damage is done by persistently infected animals contracting the disease as embryos. They shed millions of BVD virus particles and continue to spread the disease from birth until death or removal from the herd.
Vaccination before mating can eliminate the risk of permanently infected animals being born and transient BVD being contracted. Bulk milk tests can determine herd infection in dairy cows while blood tests are done for beef cattle.
But BVD Free team leader, Massey University senior lecturer in veterinary epidemiology, Dr Carolyn Gates said getting farmers to enter a competition offering a $4000 prize has been tough.
So far 126 vets have entered but farmer numbers are expected to be even less.
“And remember, this is in a country where we have about 12,000 dairy farms and over 20,000 sheep and beef properties so it is a small proportion.”
Gates said the campaign has had a tougher road given Mycoplasma bovis has proved to be a major preoccupation for disease control.
M bovis also has the luxury of an $800m-plus mega budget pulling in resources and political attention unlike any other since Psa in 2010.
Nationally, there has been greater progress on BVD control in the dairy sector than the cattle sector, with about 65% of commercial dairy herds doing screening tests every year compared to less than 5% of beef herds.
“This is partly because you can screen dairy cows through a bulk milk screening test whereas beef herds need to have blood or tissue samples collected from every individual breeding cow.”
Gates acknowledged the irony that BVD has a known and significant economic impact on cattle herds as her programme operates in the shadow of an eradication programme for a disease with little data on its actual financial impact.
“NZ herds seem to be responding somewhat differently from herds overseas that contract M bovis. We do not seem to be seeing the same levels of mastitis and ill calves as reported in other countries.”
Meantime, she and fellow researchers are collating data that indicates the $150m a year estimate of BVD’s impact is likely to increase.
In terms of eradicating BVD, NZ authorities might do well to look offshore at the contrast between trying to eradicate M bovis versus BVD.
While M bovis eradication has proven problematic with most countries choosing to live with it, BVD has been successfully eradicated from Scandinavia and Germany.
Scotland is also aiming to eliminate it, reducing it from prevalence in 40% of herds to only 10% in six years.
In NZ two thirds of beef herds and a third of dairy herds are actively infected with BVD.
But despite its prevalence here it could theoretically be eliminated by Christmas if the country made a concerted effort.
Wholesale vaccination of breeding cows before mating would eliminate the risk of persistently infected calves being born next year while blood and milk tests would quickly identify any existing infected animals.
“With M bovis, infected cattle shed low numbers of bacteria.”
But a BVD animal oozes virus particles form every pore.
“That is bad news from a disease transmission perspective but great news from a diagnostic perspective.”
She suspects the case for BVD control will err on voluntary approaches but the upside of M bovis is that infrastructure to manage a database on infected animals is in place through Nait.
Gates said the BVD Free competition deadline is being extended to encourage more farmers and vets to enter.
“There are already a lot of farmers and vets doing great work towards voluntarily controlling BVD in herds and we want to help support them.”
