Successful BVDV Prevention Strategies Focus on Type 1b
DULUTH, Ga. (July 28, 2020) — Thirty years ago, the majority of bovine viral diarrhea virus (BVDV) cases were caused by Type 1a. Now Type 1b has emerged as the most prevalent subgenotype of BVDV in the United States, accounting for roughly 70% of reported cases.1,2
One reason for the shift is that viruses often mutate to escape detection by the animal’s immune system. But some experts theorize that Type 1b may have gained dominance by taking advantage of gaps in protection left by vaccines that haven’t adequately stimulated immunity against this ever-increasing disease threat.
Once the virus
gains a foothold in an operation, animals that are persistently infected (PI)
with BVDV Type 1b expose susceptible cattle to the virus, and are considered to
be a primary source for maintaining BVDV infections in cattle herds.
a cow-calf, stocker or feedlot operation, when your cattle are exposed to BVDV,
I would say the odds are three to one they’re going to be exposed to Type 1b,”
said John Davidson, DVM, DABVP, senior associate director of beef professional
veterinary services, Boehringer Ingelheim. “If you’re a betting person and you
take those odds, you’ll want to make sure your vaccine program lines up against
In addition to
an effective vaccination program, sound prevention strategies frequently
utilize herd surveillance for PI cattle and strict biosecurity measures to
prevent BVDV from damaging the herd.
Herd surveillance for PI cattle
are the cornerstone of any herd health program, but they’re especially
important for identifying potential BVDV issues. “When you start with excellent
records, and you recognize changes in reproductive performance, productivity or
unexplained illness rates, you can begin to piece together a possible
explanation,” advised Dr. Davidson.
problem that could be related to BVDV should trigger surveillance testing. In
large operations, veterinarians may start with pooled ear notches or blood
samples, which can help determine if BVDV is part of the issue. Any pools with
positive results are followed up with individual tests to identify PI calves.
All bulls, replacement heifers and dams of PI calves should be tested as well,
and positives should be culled or isolated from the rest of the herd.
Biosecurity to minimize exposure
At the cow-calf
level, it’s important to minimize exposure of cows and heifers to calves of
unknown PI status. “I’ve seen numerous instances where an operation might have
cattle with an unknown history on one side of a common fence line and
vulnerable pregnant cows on the other, not aware that fence line contact
between pregnant cows and PI calves was what eventually led to more BVDV PI
cattle,” said Dr. Davidson.
It’s a numbers
game. For operations that buy cattle from unknown sources, the odds are good
there will be PI calves present. Infected calves can shed large amounts of
virus, exposing other cattle at the local livestock market and on the trailer
ride to the stocker or feedlot. On arrival, infected animals can leave virus
around the feed bunk, in the water trough and through the chute during
That’s why it’s
important to quarantine new additions to the herd. “It’s a good idea to keep
them in their own group for 14 to 21 days, test their BVDV status, monitor them
for disease and make sure they’re vaccinated before moving those cattle out
into the general population,” Dr. Davidson added.
Establish a sound vaccination program
Dr. Davidson, BVDV PI calves are preventable. “This is truly one of those
diseases we can impact through selection of the right vaccine and giving it at
the right time,” he explained. Producers should work with their veterinarians
to choose the right vaccines for the unique disease threats on their
recommends vaccinating cows with a modified-live virus BVDV vaccine pre-breeding.
“It’s important to identify vaccines that have the PI prevention claims clearly
indicated on the label,” he said. “Even further, make sure those package
inserts also include language about the efficacy of those vaccines against the
most common subtype of BVDV, which is Type 1b.”
cows against BVDV helps protect their health and reproductive efficiency, and
enables them to deliver healthier, PI-free calves. That same pre-breeding
vaccine also helps them produce antibody-rich colostrum, to protect calves from
BVDV for several weeks to a few months. “If a calf is born with sufficient
colostrum intake from a well-vaccinated cow or heifer, producers can then
vaccinate that calf at around 30 days of age with a modified-live virus vaccine that includes
antigens for BVDV,” noted Dr. Davidson.
Avoid the commodity mentality
“If we’re going
to utilize health programs to minimize disease and reduce our reliance on
antibiotics to treat disease, it’s vitally important that producers and their
veterinarians understand that all modified-live virus vaccines are not equal in
preventing BVDV PI calves,” stressed Dr. Davidson.
A recent study,
in fact, showed that different BVDV vaccines vary in their ability to stimulate
a protective immune response against the virus.1 The scientists
compared six different BVDV vaccines, including five modified-live virus
vaccines and one killed vaccine. After administering the vaccines, researchers
evaluated the effect the vaccines had on the calves’ immune response by
measuring antibodies to BVDV subtypes including Type 1b, currently the most
prevalent strain in the United States.
determined that heifers required a BVDV Type 1b antibody titer of 128 or higher
at the time of exposure to BVDV Type 1b PI cattle to be protected against fetal
infection.3 In order for an animal to be considered protected from,
or immune to, the BVD virus, the vaccine must stimulate the production of a
certain level, or titer, of antibodies.
In other words,
even if heifers had received a BVDV vaccine, if it didn’t stimulate an antibody
titer of at least 128, some cattle could still be vulnerable to fetal
infection. This was especially true for heifers with titers of 64 or fewer.
The Singer strain
The study found
that two modified-live virus vaccines containing the BVDV Type 1a Singer strain
induced higher levels of Type 1a and Type 1b antibodies than BVDV vaccines
containing different Type 1 strains. It also resulted in a greater number of
calves with BVDV Type 1b titers of 128 or higher, potentially providing greater
protection against today’s most common BVDV subtype.
“One of the
most compelling parts of this research is the fact that only two
vaccines were consistently able to hit that minimum-threshold titer of 128,
while the others were not,” reported Dr. Davidson. He credits the Singer strain
for that difference. “Compared to other BVDV vaccine strains, the Singer strain
has demonstrated an ability to traffic through the animal tissues, exposing the
vaccine virus to more immune tissue,” he added.4
“It’s really about awareness of the true threats, the economically important diseases in the industry, and finding the vaccines that best line up against those,” Dr. Davidson concluded.
Source: Boehringer Ingelheim Animal Health