While M. bovis and Covid-19 may be competing for farmers’ attention this winter, another equally infectious disease that has lurked in
the background for years poses at least as big a threat to farm profitability and livestock health.
Bovine Viral Diarrhea (BVD) is estimated to be costing the New Zealand dairy industry at least $150 million a year in
animal health costs and lost production, yet experts agree with a focused campaign it could potentially be eliminated in
a matter of months, not years.
Greg Chambers, Zoetis veterinary operations manager has been working closely with vets and farmers this year to help
raise the profile and understanding of BVD.
He says despite what farmers may often think, BVD is both contagious and common among dairy herds.
“It is far from being random or rare. But often BVD is mainly a subclinical disease, and its symptoms get lost amid the
usual health outcomes farmers see quite regularly within their herd.
“These can include immune suppression causing more infectious disease, early embryonic death, abortion, elevated somatic
cell counts, birth defects – all can appear random, but can actually all be tied back to BVD, such is the wide range of
conditions it can create.”
But despite being such an insidious background disease, BVD can be controlled with a few steps revolving around testing,
culling, vaccination and farm biosecurity.
Testing for BVD is a well-established practice in New Zealand dairy herds. Bulk milk sampling provides a good pathway
for vets and farmers to determine its presence, then commence identifying and culling individual infected herd members.
“Testing and culling to get a clear result is good. But often no further action is taken once that is achieved, and only
when the next BVD-infected animal is detected is the disease addressed again.
“It is a bit like using your smoke detector to tell you your house is on fire- by the time that alarm has gone off the
fire has got hold and the damage is already done.”
He has been focusing on reinforcing the need for farmers to build biosecurity and vaccination into their animal health
plans to prevent the test going positive.
“As a farmer, you really need to use the twin tools of vaccination and good farm biosecurity to keep BVD out, otherwise
your efforts are going to be constantly eroded with it returning- it’s like trying to build a sandcastle when the tide
is coming in.”
Vaccination wraps a layer of insurance around the herd’s health.
“It’s really like investing to fireproof the building, to stop fire taking hold again and the alarm going off again.”
Research looking over the past decade at BVD infections indicates over time more and more herds that may have contracted
BVD and been cleared become naïve to the disease, and once again are susceptible.
“We have had infected herds drop from about 15% to 5% in only a few years, which is good. But it also means without
vaccination those herds are sitting ducks for becoming susceptible again.”
Amid heightened concerns over M. bovis, more farmers have been careful about where they send young stock, and many also vaccinate that stock against BVD.
“But while protecting your young stock is worthwhile, focusing on your breeding herd is probably even more important.
“It is from them you get your Persistently Infected (PI) calves, from where it can spread quickly.”
Timely BVD vaccination of cows prior to mating will ensure no PI calves are born that spring, helping break a cycle of
Both the symptoms and the $150 million cost to the dairy sector of BVD are difficult for affected farmers to identify.
“The cost of at least $150 million is an average of $32 a cow a year, but it can seem to be a zero-cost disease if you
are just interpreting the many different symptoms as unrelated health issues in the herd.”
The per head cost of BVD far outstrips the cost to vaccinate, and Chambers says vaccination could play an invaluable
role in helping New Zealand eradicate the disease.
“If as a country we can deal to Covid-19, and as an industry deal to both M. bovis and BVD, it will do much for New Zealand’s biosecurity standing and enhance the dairy sector’s profitability.”