B V D


A  scary disease, lurking on most farms today - is it on yours? and how can we avoid it?

 

BVD – Bovine Viral Diarrhoea.

What is it? The Wikipedia description is.

Bovine Viral Diarrhea (BVD) or Bovine Viral Diarrhoea (UK English), and previously referred to as Bovine Virus Diarrhoea (BVD), is a significant economic disease of cattle which is endemic in the majority of countries throughout the world.

  • It is one of the most important diseases of cattle in NZ (including TB)
  • It is a wasting disease, a reproductive disease, a disease that cost’s the life of many calf’s
  • It cost’s our Beef industry 10’s of million per annum
  • It cost’s our Dairy Industry 100’s of million per annum
  • And yet as a country we still are only in the infant stages of recognising this as a serious endemic issue.
  • The most recent information is that more than half of beef farms, and a quarter to a third of dairy farms would have active infection. Also 90% to 95% of dairy farms have animals that have been exposed at some point in their lives (there is at the time of this article no data for Beef Farms – and certainly nothing for the small block ‘lifestyle farmer”).

 

So how does BVD affect?

It can affect cattle of all age groups. It Transiently infects (TI) or Persistently Infects (PI). Symptoms include Diarrhoea, weakened immunity, low growth rates to respiratory disease, congenital defects, increased death rates in foetus causing abortion and worst of all Persistently Infects.

This is neither a nice nor selective disease.

Most yearling or older animals that are Transiently infected (TI) do not show outward signs of infection.  Their immune system will be suppressed though and will be more likely to experience other infections and they may be more severe.  The reproductive effects are also an issue that’s not always immediately obvious.

Persistently Infected (PI) animals have about a 50% per year death rate because of increased risk of illness.  They can affect growth and health of any other cattle on the property, and are a risk to your neighbours cattle.  You really Don’t want a PI animal.

In pregnant cows BVD can cause reproductive disorders, abortions and congenital defects.  It can create Persistently Infective (PI) calves in foetus up to 4 months’ gestation (however the mother develops natural immunity). 

PI Calves spread large amounts of BVD virus and have a crucial role in its spread.  They are in effect a lifelong mass spreader of the disease.

BVD can affect other species like pigs, sheep and alpacas, but the role of these other species in the spread of infection is unclear

So how does BVD in cattle spread?

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  1. Transiently Infected.  These are animals that may experience respiratory, intestinal, or reproductive effects but become immune after a few weeks. In other words, this is like chicken pox, that can make us sick but passes, and we remain immune for years.

 

  1. Persistently infected.  If a cow is “Transiently” infected during the first 4 months of gestation the calf can then become Persistently Infected (PI). And a PI Calf will always produce PI Progeny. 

 

This means that the PI calf will constantly pass this pathogen to ALL herd mates during its lifetime. This then exposes all pregnant heifers / cows within the herd to this disease, thus in turn may then create more PI (Persistently Infected) progeny, or in the later stages of gestation both congenital defects or death. These new PI (Persistently infected) progeny (Heifer or Bull) then in their turn infect many more animals in the herd.  This means if Mum is a PI and progeny is PI the disease then spreads rapidly.

 

So imagine if you will someone feeding out 2 chickens – a handful of grain feed out for a few days is the Transient spread. And an entire bucket’s worth of grain thrown daily, for the same 2 chickens for their entire life is the equivalent of a PI spread

How does this affect the lifestyle block owner that doesn’t breed? - bearing in mind that BVD control is still in its infancy in New Zealand.

For the small block owner, owning a couple of “forever home”- lawn mowers, BVD should not be a problem – your breeder may have supplied you with a BVD Negative cert before delivery.  Any good breeder should be able to provide you with this, by knowing that your pet moos are BVD Negative you know that you are not possibly spreading BVD to your neighbours animals.

How can we, as lifestyle / small block herd breeders prevent BVD? – once again, bearing in mind that BVD control is still in its infancy in New Zealand

Whether you produce 1 calf per year or 100 calves’ per year you really need to have a look at your farm’s Biosecurity.  The following links are for 2 different biosecurity questionnaire’s.  These have been set up for vets to make farm assessments and put BVD management plans in place, but they are not hard to follow and I would encourage everyone to at least have a look, it will give you a better understanding on just how easily BVD can be spread. 

http://www.controlbvd.org.nz/sites/default/files/domain-23/tooklit/BVD_SC_Toolkit_09_BeefAppendix1.pdf

http://www.controlbvd.org.nz/sites/default/files/domain-23/tooklit/BVD_SC_Toolkit_10_BeefAppendix2.pdf

As a breeder you can and should test for BVD.  Test all stock leaving to give your clients peace of mind and request all stock coming on have BVD Negative certification from a qualified source (farmer Joe telling you it’s all good is not a qualified source unless he can produce the paperwork to support his claim)

For a start BVD testing is not actually that complicated.  You do not need a vet to do blood samples if you have a tissue punch gun, LIC (Livestock Improvement Corporation) have a product available for this http://www.lic.co.nz/lic_GeneMark_Punch.cfm This is easy to use, sealed (so no cross contamination) and the same gun and tissue tubes can be used for DNA testing.  We personally send our BVD tests to GeneMark which is part of LIC and our DNA tissue samples, we send to Genome / AgResearch).

For all Breeders supplying – a reputable breeder should always supply a copy of the BVD results, for any animal being purchased, and actually advise purchasers about BVD in general no matter what the breed the client may end up with.  The more we discuss this disease, the more aware everyone becomes, the more chance we have of eliminating BVD in the future.

If you are looking at breeding, ensure your own stock are all BVD negative, check if your neighbours cattle on the boundary have been BVD tested – remember this is also an airborne pathogen.  For us as a small block we ensure all our breeding stock are kept well away from any neighbouring boundary lines that may have suspect cattle, prior to and during initial 4 months of gestation.

Sharing Yards is something that seems to be the Kiwi way – not all lifestyle blocks have the facilities and portable yards are not cheap.  The BVD virus is pretty fragile so it doesn’t survive well in the environment.  It can survive up to about 3 weeks in slurry at very low temperatures, but only around 3 hours on a very hot day.  Unless the temperatures are close to freezing, a week would usually be enough time for the contamination to degrade.  So if you do share yards with farmer Joe down the road, and you are sceptical about his BVD controls than be aware of when his stock has been in the yards, and look at vaccination

What does a “BVD Negative” Result mean?

“Negative BVD Antigen ELISA Result A single, once-in-a-lifetime, negative BVD Antigen ELISA result is sufficient to confirm that the animal is not a BVD carrier or PI (i.e. not persistently infected with BVD). If the animal becomes acutely infected in future, it will rapidly develop immunity and rid itself of the virus. In pregnant cows however, acute or transient infection (TI) may cause reproduction failure or PI calf”

Vaccination

Heifers / Cows

You can vaccinate yearly to prevent BVD, but some of these vaccine’s only prevent the symptoms in the animal vaccinated, these vaccine’s cannot prevent foetal infection, meaning PI progeny are still produced.  The only way to protect against this is to vaccinate with a vaccine for “prevention of transplacental infection” another words a BVD foetal protection vaccine, this is the only way to stop a foetus being infected hence stopping the spread of BVD.

The cost of vaccination (from the 3 vets I spoke to), is anywhere from $7.50 - $23.00 per dose (you would need to discuss this with you vet) and would also include a vet callout fee if you are not able to do the vaccination yourself.  For the initial vaccination you need to give one dose and then another 4 weeks later (this should be done a few weeks prior to mating to ensure the most optimisation from the vaccine).  Then a yearly booster done (again preferably a few weeks prior to mating), to ensure protection. 

The vaccination can be injected either Subcutaneous (under the skin) or Intramuscular (into the muscle)

If you are showing it pays to vaccinate, for your own peace of mind.  I sincerely doubt that every bovine at every A&P show has been tested negative for BVD.  If your Woolly Moo (or any moo) has not been tested and vaccinated and is not immune, then it may be able to spread infection if it is exposed

Bulls

Your bull should also be vaccinated, A few breeders / small block holders share bulls, so once again all herds that the bull visits (including his own herd) should be tested.  Vaccinate your big boy.  A BVD infection (TI) in a bull can render him infertile for at least 3 months, and he can shed the virus in his semen for a while also – thus creating the possibility of PI offspring. Not only has this the potential health problems, it can end up costing you financially as well.

How does the vaccination work?

To understand how the vaccine works we need to first understand how the BVD Virus works.  After the body of a ruminate animal is first exposed to BVD it takes the immune system several weeks to produce enough antibodies to kill off the virus and clear the infection.  In the meantime, the virus can do damage, get into the foetus and basically run rampant.

To give a ruminate animal a shot of straight virus would be potentially very damaging, the vaccine needs to be not only effective but safe as well. So in New Zealand the vaccines for BVD are made up of killed virus that cannot cause infection, but still allow the immune system to recognise parts of the virus. Over several weeks, the immune system builds the antibodies required to fight off live BVD virus.”

 

After vaccination, the body remembers the virus and can very quickly turn on the production of antibodies.  In turn if contracted, the virus can barely start an infection before the antibodies jump on it and snuff it out.

The initial vaccine requires one dose that is similar to an introduction if you like to let the body know it’s there, then 4 weeks later a second “booster” is given to get the immune system excited enough about BVD to be on the alert for the next year.

Because there is no actual infection with the vaccine, the immune system doesn’t get as excited as it would with an actual BVD infection and so the protection only lasts for 6 – 12 months before the body forgets about it.  This is why there is the need to give a booster vaccine yearly to remind the body about BVD and therefore be ready to produce antibodies when needed.

The BVD vaccine is safe for pregnant animals, but it’s better to have the protection there before they become pregnant.  There is also no problem vaccinating a cow with calf at foot.

Anyone considering vaccination should consult with your veterinarian to get the best possible plan put in place.

So what has this meant for Woolly Manor Moos?

The common term used I was hearing was “test and eradicate” – pretty simple really - and for us was very, very scary when we first started out with a BVD program some years ago.  We are not a big Beef or Dairy farmer that knows their animals as 127 or 935, ours have names!  I spend time daily brushing or talking to Piper, Sir Walter, Cadbury Pebbles or any of the others within our herd. 

We have tested and our herd contains no PI’s. We test and have done for several years, ALL our progeny.  If they don’t test NEGATIVE (which means they neither have BVD or are a PI) before leaving – they don’t leave.  We provide this certificate along with the AHB / Nait forms to ALL clients.  Any animals coming onto the property are also tested prior to arrival, if this is not achievable then those animals are held in quarantine until we have completed testing, and I will re-iterate, we only continue with BVD Negative stock.

Show animals are vaccinated, and BVD is discussed with all clients to make them aware of how potentially damaging this disease can be, and to help make clients aware of farm biosecurity.

BVD has become endemic in many cattle populations worldwide but it can be managed successfully.  Many countries have now successfully eradicated or are in the process. Norway, Sweden, Finland, Denmark, Switzerland, Austria and Germany have virtually eliminated infection.

So I will say for anyone buying in Highlands, or any cattle for that matter, request a BVD NEGATIVE certificate from a recognised tester.

This is a simple procedure that can help stop the spread of disease, undue suffering to animals and gives you peace of mind that the ani-moo you’ve just purchased (whether pet, lawnmower or producer) is in good health at the time of testing.

So however you farm please help to eradicate this disease, or in the very least stop the spread.  Either test your animals before they leave and give your client peace of mind, test before new stock arrive and vaccinate if applicable – giving yourself and your herd peace of mind.

MSD has a great Video that also helps explain BVD  http://www.bvd.co.nz

 

And the following link is for the New Zealand Veterinary Association BVD steering committee http://www.controlbvd.org.nz which is keen to get the message out to farmers. Whilst most of the information has been focussed on vets / for vets the Toolkit on the website has a lot of useful information.

I would like to thank Andrew Weir from the New Zealand Veterinary Association BVD Steering committee for all the excellent information, and putting up with my endless questions and emails.  I had a good understanding of BVD, but have learnt so much.