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Bovine Viral Diarrhea |
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Table of Contents
1. What
is BVD? 2. What
diseases does BVD virus cause? 4. Is
BVD virus the only cause of these diseases? 6. Are
there "New" BVD viruses? 7. How
does BVD virus come onto a farm? 10. Does
BVD virus cause long term contamination on a farm or in a barn? 12. Will
you need to use special sanitation procedures against BVD? 13. Will
BVD virus infect humans or other animals? 14. How
can herds protect themselves? 15. What
protection can you expect ? 16. What
should producers do after a BVD outbreak? What is BVD?
Bovine viral diarrhea (BVD) is the name of a group of diseases in
cattle all caused by the BVD virus. Similar but different viruses cause
Border disease in sheep and Hog cholera in pigs. BVD was first recognised in In | Top
of Page | What diseases does BVD virus cause?
BVD virus causes different
diseases depending on which cattle it infects. The most severe problems occur
when pregnant cows and heifers are infected. When this happens, the virus can
cause breeding problems with irregular heats. Sometimes it causes abortion,
premature births or the birth of weak or stunted calves. Sometimes calves are
born which look healthy but are carriers of BVD virus. These calves will be
carriers for the rest of their lives. If the BVD virus infects
calves, open heifers and open cows, it usually doesn't make these animals
very sick. Even if an animal does not become sick from the BVD virus, the
virus can temporarily damage the immune system. Infected animals are more
likely to have other diseases like pneumonia. Most cattle recover from BVD
but sometimes the infection is so severe that cattle will die. One type of
severe disease is called acute BVD. Cattle with acute BVD go off feed, have a
high fever and diarrhea. They may also have sores
in their mouths. | Top
of Page | What
is mucosal disease?
Mucosal disease is one
disease caused by BVD virus that occurs only under special circumstances.
Cattle with mucosal disease have high fever, diarrhea
that often contains blood and sores in the mouth. All cattle with mucosal
disease will die from it, usually within a few days although some can live
for weeks. Mucosal disease is special because only cattle that were infected
with BVD virus before they were born will get it. Cattle that get mucosal
disease are also carriers of BVD virus and have been carriers since they were
born. These carriers are important in spreading BVD virus within and between
farms. | Top
of Page | Is BVD virus the only cause of these diseases?
Almost all the diseases
caused by BVD virus also have other causes. Laboratory tests are needed to be
sure that BVD is causing the problem. If BVD is suspected, it is important to
select the correct samples to send to the laboratory to make the
diagnosis. | Top
of Page | Are
all BVD viruses the same?
There are many strains of
BVD virus. Some of the strains have names like NADL, Singer and | Top
of Page | Are
there "new" BVD viruses?
There are slight
differences between some "new" BVD viruses and the BVD viruses that
have been around before. This means that the "new" BVD viruses are
different from the BVD viruses that are in the vaccines. The differences are
small enough that the vaccines currently available are still effective. The
most important thing to remember is that a vaccine must be used properly to
be effective. The "new" BVD
viruses causing problems in | Top
of Page | How does BVD virus come onto a farm?
BVD virus is usually
brought onto farms by carriers. BVD virus also can be brought onto a farm is
by an animal that isn't a carrier but has recently become infected with the
virus. These animals haven't had a chance to get sick or might not even get
sick but will pass the virus to other cattle they contact. | Top
of Page | What are
carriers?
Carriers are cattle that
were infected with BVD virus before they were born. They must have been
infected in the first 125 to 150 days of pregnancy to be born a carrier.
These cattle don't look sick when they are born but have BVD virus in their
blood, nasal mucus, saliva, manure and urine. These carriers can live for
years without becoming sick from BVD but most die of mucosal disease before
they are 2 years old. Carriers are important because they pass the virus
along to other cattle. Another way to describe these carriers is to say that
they are persistently infected (PI). | Top
of Page | How is
BVD spread?
Once the BVD virus comes
onto a farm, it usually spreads by contact between cattle. Generally, cattle
must be close enough to have nose to nose contact to spread the virus.
Because there is virus in nasal mucus and saliva, articles like unwashed feed
pails or nipples can also spread the virus. BVD is also present in the urine
and manure of infected calves and might also serve to spread the virus. | Top
of Page | Does BVD virus cause long term contamination on a farm or in a barn?
Not likely, the BVD virus
does not survive well away from cattle. Hog cholera, a virus that is very
similar to BVD can only survive for about 2 weeks in feces
and dies more quickly in other fluids. | Top
of Page | Can BVD
be treated?
There is no cure for BVD
but some animals will survive the infection. Treatment can be useful to
reduce the impact of complications like pneumonia. There is no way to cure carriers, they will always be infected with the BVD
virus. | Top
of Page | If you have BVD in my herd, is there anything you can do to control
the spread?
If you can, you should
isolate animals with symptoms of BVD as well as any animals in direct contact
with them. This will help limit spread to other cattle. You should handle
infected cattle last. Be especially careful to handle pregnant cows and
heifers before caring for sick animals. Cleaning and sanitizing may also help
prevent spread. | Top
of Page | Will you need to use special sanitation procedures against BVD?
The BVD virus is killed by
disinfectants. Routine cleaning and power washing or disinfection will kill
the BVD virus. Sanitation can be combined with an "all-in, all-out"
to eradicate BVD in pens. Any new virus must be brought onto the farm by
carriers or recently infected calves. | Top
of Page | Will BVD virus infect humans or other animals?
BVD virus does not cause
disease in humans. BVD virus can infect sheep and wild ruminants including
white-tailed deer and bison. | Top
of Page | How can herds protect themselves from BVD?
Producers can effectively
increase the resistance of their herd and reduce the risk of exposing their
herd to BVD. Producers can: 1. Prevent the introduction of
infected animals by:
o
bringing
in only animals from uninfected herds; o
bringing
in only animals from herds with a known effective vaccination program; o
avoiding
the purchase of animals from sales barns; o
testing
new animals for persistent infection in advance of introduction; and o
isolating new animals for 30 days before allowing contact with
animals on-farm. 2. Increase the resistance of the herd
to BVD by: o
vaccinating
strategically as directed by the herd veterinarian and the product label; o
maximizing
colostrum consumption by newborn calves; and o
reducing stress on cattle caused by other diseases, poor
nutrition, uncomfortable housing or poor air quality. 3. Decrease exposure to BVD by: o
preventing
manure contamination of hair coat, feed and water; o
housing
baby calves in individual calf hutches; and o
isolating sick animals. Vaccination for BVD is an important
component of a BVD prevention program. | Top
of Page | What protection can you expect from BVD vaccines?
Vaccination does not
provide complete protection against BVD. Vaccination will protect most cattle
from becoming sick but some vaccinated cattle may get sick. When they do get
sick, vaccination appears to protect them from getting so sick that they die.
Vaccination provides some protection against infection of the fetus in pregnant cattle. Pregnant cattle may abort even
if they are vaccinated but it appears that vaccination reduces number of
cattle that will abort. Vaccinated cattle may still become infected with BVD
virus and pass it to the other cattle even if they don't get sick themselves. | Top
of Page | What should producers do after a BVD outbreak?
After an outbreak of BVD,
producers must continue to be watchful to make sure that BVD does not become
a chronic problem on the farm. Here are some points that producers should
know about: Vaccination: Your vaccination program
is the best protection that you can give cattle against BVD. Cattle that have
been infected with BVD do not have long lasting immunity. So it is important
that producers all cattle and keep booster vaccinations up to date. Use
vaccines according to the recommendations on the label unless your
veterinarian makes different recommendations. Calves, heifers and cows that
have not been vaccinated before will need a double vaccination the first time
they are vaccinated with a killed vaccine. Selling cattle from
your herd: There are no regulations
to stop producers from selling cattle during an outbreak of BVD. To prevent
the spread of BVD to other farms, we recommend that no cattle or calves
should be sold other than to slaughter until at least 3 weeks after the last
animal is seen to be sick. You may wish to advise prospective purchasers that
an outbreak of BVD has occurred. We also recommend that if you sell heifers
or cows that were pregnant during the outbreak, advise
the buyer to test the calves when they are born to see if they are BVD
carriers. If a calf is a carrier, it should be slaughtered. Abortions after a BVD
outbreak: Producers who have
outbreaks of BVD can expect abortions to occur several weeks after the last
cattle are seen to be sick. The BVD virus can cause abortion by killing the fetus when pregnant cows or heifers are infected. The fetus is not expelled immediately after it dies. It often
takes several weeks before the abortion occurs. Carriers and BVD virus. Any cows or heifers that
were pregnant for less 5 months when they were infected
with BVD virus may give birth to a calf that is a carrier of BVD virus. If
these carrier calves stay in the herd you may have long term problems with
BVD. We advise producers to test calves as they are born to identify any
carriers. The test to identify
carriers is a blood test. You should arrange for testing through your
veterinarian. Your veterinarian will help determine who should be tested. You
should expect to start testing all calves born about 3 months after the date
you saw the first animal sick from BVD. You should continue to test all
calves until 9 months after the date you saw the last animal on your farm
sick from BVD. Keep these calves away from pregnant cows and heifers until
you know the result of the blood test. There is no way to
"cure" a carrier. Any calf that is a carrier when it is born, will always be a carrier. If you find that a calf is
a carrier, we recommend that it be slaughtered. You should not sell a carrier
other than to slaughter. Bringing new cattle
into your herd: Even if you have
vaccinated your herd, you should be cautious about bringing new cattle onto
your farm. Try to arrange that purchased animals are vaccinated or boosted
before they come to your farm. Vaccinated cattle are resistant to getting
BVD, but they may still be able to carry BVD for a short time (from a few
days to a few weeks) and can probably pass it to other cattle. This means
that even vaccinated cattle could bring BVD (and other diseases) into your
herd. It is best to quarantine
any new cattle by keeping them separate from your own cattle for about 3
weeks. To prevent spread of BVD, the quarantine pen should be located so your
cattle cannot touch the quarantined animal. They should not share waters or
feeders either. Be careful that manure is not transferred from pen to pen on
feed or water buckets or manure forks. After a BVD outbreak, the
BVD virus can continue to cause disease problems. To reduce the chances of
ongoing BVD problems, we recommend that producers maintain a good vaccination
program. Producers should also test calves that are born after the outbreak
to make sure that none are carriers that could keep BVD in the herd.
Producers should always be cautious when selling or purchasing cattle. | Top
of Page | For more information: |
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