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How do you know the
cattle you just purchased won’t bring along an infectious
hitchhiker, like BVD or Johne’s? Using quarantine areas is one
way, in some situations, to mitigate that risk. The trick is
knowing when and how.
When a new cow is
added to the herd, there might be a little scuffling until the
order of social dominance is reestablished. But one thing her
pasture-mates shouldn’t have to fight is exposure to harmful
pathogens the new gal could be shedding in her urine, feces or
nasal secretions, though she doesn’t look one bit sick.
Quarantining her
for a period for time may be one way to protect your herd
against any disease that might be secretly incubating inside
her. But it’s not always the right thing to do. Whether or not
to isolate any newly purchased animals depends on the age or
class of animal, ranch or area of origin, diseases that are
probable, the balance between cost of treatment vs. cost of
prevention and other factors.
There is no simple
answer for every situation, which is one reason that many
producers don’t get it right, according to experts in
biosecurity.
Dr. Michael
Sanderson, DVM, of Kansas State University is one of several
folks who helped put together a great resource on all facets of
biosecurity for producers on the web at
www.farmandranchbiosecurity.com. The website is a cooperative
effort between the University of Nebraska, Iowa State University
and Kansas State University.
“One of the things
that I’ve seen in talking to producers, and in the survey work
that we’ve done, is that producers don’t seem to understand when
they ought to quarantine and how long it has to be,” he
explains. “Veterinarians don’t always understand it either.
Sometimes, they’re doing stuff that isn’t going to accomplish
their goals.
“For example, in
the NAHMS (National Animal Health Monitoring System) BEEF 97
survey, producers weren’t testing for brucellosis. They were
more likely to quarantine them, and quarantine isn’t an
effective method for controlling this risk of introducing
brucellosis to the herd unless you’re also testing. The cows
don’t look like there’s anything wrong with them and in 30 days
of quarantine, you’re not going to see any clinical signs.”
Sanderson
encourages producers to sit down with their veterinarian, go
through their individual risk factors and better understand what
diseases their cattle may be susceptible to, how these diseases
are transmitted, how long the pathogens that cause them survive
in the environment and how long cattle are preclinical.
“It’s a complex
enough of an issue that you can’t just make a set of rules that
this is what everybody should do,” he says. “It depends on the
individual ranch.”
However, with that
proviso in mind, there are some general guidelines that can help
guide your thought process in working out the complexities of
quarantine use in your own operation. And while it may seem like
a hassle now, don’t underestimate how costly some of these
diseases can be.
Several studies
about the cost of disease are cited on the website. For example,
“Losses from trichomoniasis (trich) and campylbacteriosis (vibrio)
have reduced calving rates by 30 percent to 50 percent before
detection and have resulted in average losses over $150 per beef
cow unit.” Ouch!
When Quarantine is Useful
“The philosophy behind quarantine is based on if cattle come in
and they appear to be healthy, but they are infected, they’re
just not showing any clinical symptoms, then they are going
through an incubation period,” explains Dr. Buddy Faries, DVM,
of Texas A&M University. “All infectious agents that enter
cattle’s bodies, no matter what route – by horsefly bite or
needle or inhaled or ingested – those germs don’t show any
symptoms immediately whether they are viruses or bacteria.
“There is a period of time that they have to invade the tissues
and multiply before they reach a certain stage where they can
produce a disease,” he says. “That length of incubation period
is all over the board, depending in the disease agent. If it’s a
respiratory virus, that may exhibit itself as a clinical sign in
just a few days or a week.
“But many of the
bacterial diseases like leptospirosis, it may be 30 or 40 days
before they’re showing clinical signs. Another thing is if
they’re going to break with a disease, they break in that
quarantine area and the only cattle exposed are the others in
that confined area.”
So, if the disease
you’re concerned about has a short incubation, like IBR
(Infectious Bovine Rhinotracheitis) in stocker calves, keeping
them isolated for a short time might be appropriate from a
health standpoint, (assuming they might otherwise have some type
of contact with the breeding herd) though it may or may not make
sense from an economic perspective.
However, if you’re
wary about any of your new replacement heifers being
persistently infected with BVD (Bovine Viral Diarrhea),
quarantine would not be effective – at least not unless you
tested those animals while they were isolated.
The same goes for
new herd bulls in that combining testing with quarantine is the
appropriate action. Unless they are virgin bulls, testing for
venereal diseases like trich is extremely important, as is
waiting for the test results before turning them out with the
cows.
On the other hand,
testing is not a simple cure-all either.
“BVD is one of
those diseases where quarantine is valuable, because we have a
good test that we can run during that time and know the outcome
for that cow or calf before we introduce them to the resident
herd,” explains Sanderson. “That said, it also matters what
class of cattle you’re talking about whether it’s justified to
test them.”
The accuracy of the
test for each disease is something you certainly need to discuss
with your vet.
On his web presentation,Sanderson says, “We do have a test for
trichamoniasis. It works best on bulls; it actually works less
well on cows. But the sensitivity is about 70 percent. So, if
you lined up 100 positive bulls and cultured them all, you’d get
30 false negatives. So on a one-time run through, trich testing
is not ideal.”
A word about
vaccinations, This vet says they do their job, some more so than
others, but they can also be easily overwhelmed.
“Producers
generally look at vaccinations as sort of the magic bullet. ‘If
we just vaccinate, things will go away.’ And in reality, that’s
not the case,” says Sanderson. He uses the trich vaccine as an
example. “That data would suggest that it does blunt the effect
of an outbreak…. But it will not stop or prevent an outbreak.”
The next question
is, if the disease you’re trying to evade does merit the use of
a quarantine period, whether you test or not, how long should
you keep the new animal(s) apart from the herd?
A Matter of Time
Faries says there is a lack of clinical studies to determine
proper quarantine times for each infectious disease, but he can
give you a range based on experience and practicality.
“It’s been recommended (to quarantine new purchases) anywhere
from two weeks to two months,” he explains. “The longer they
stay quarantined, maybe the safer the producer is to determine
if there’s a problem or not. But two weeks could be ideal for a
particular set of cattle coming in. If I buy some cattle from
you private treaty and I know your place, I may feel comfortable
with one or two weeks.
“But if I buy mixed
cattle from sale barns and order buyers, there’s probably going
to be some transmission going on,” Faries says. “If the cattle
are coming in from some country where there’s some lepto
exposure, I probably need to hold them 30 or 40 days. Then you
get some longstanding bacteria, like anaplasmosis, where the
incubation period could be up to 60 days. However, the mechanics
of holding cattle for two months gets to be extreme.”
For his part,
Sanderson says, “If you’re going to use quarantine alone, it
probably needs to be 30 days to make sure whatever disease they
might have, they’re going to get over it before you introduce
them to the resident herd. Thirty days is a nice round number,
some people use 21 days, and in most cases that’s probably okay.
“For diseases like
Johne’s, salmonella and lepto, where we may not see clinical
signs, there’s no length of quarantine – except permanent – that
would prevent the rest of the herd from being exposed.”
That brings us to
the question of where to locate your quarantine areas if you
need them.
Location,
Location, Location
Drainage is a big concern to Sanderson. “With lepto, for
example, it’s not just a matter of nose-to-nose or aerosol
contact, but also drainage. It lives in stagnant water. If your
quarantine pen drains into your calving pen, that’s a bad thing.
If we can avoid standing water, lepto isn’t going to survive
very long. Good drainage is a wonderful thing. You need to think
for each particular disease, what are the issues, where do we
need to stop transmission, how is it transmitted?”
Along with paying
attention to drainage, fenceline contact is another factor to
consider when assigning pens or pastures. It doesn’t do much
good to quarantine if the isolated animals can rub noses with
vulnerable neighbors.
Of course you can
do all the right things to prevent diseases from being spread
but there are things you can’t exert much control over, like the
neighbor’s dog coming over and leaving behind some neospora or
the other neighbor’s bull jumping the fence and sharing
something nasty.
Then there is the environment that cow-calf operations exist in
where you have wide open spaces for the most part, and your
cattle aren’t the only inhabitants. Wildlife on your place can
also be a disease reservoir for things like lepto, neospora,
salmonella, coccidiosis, etc.
Even flies and
other biting insects can spread disease. So fly control and
other wildlife population management tools can compliment your
other biosecurity measures. Also, some of these diseases (e.
coli, salmonella, brucellosis, etc.) can also affect your
employees and family members if you’re not careful. Even using
banked colostrum, especially from dairies, carries a risk of
disease with it.
Keeping the Area
Clean
If you’re using quarantine areas, another factor to consider is
what needs to be done if any of the isolated animals do break
with a disease. Once the animal is removed from the area, are
there contamination issues to deal with before a new set of
cattle occupies the pen or pasture?
Some pathogens can live in the ground or water or even on
squeeze chutes and other equipment for a period of time, some
longer than others. So, these experts say you need to have a
rotation schedule for your quarantine areas to give those
pathogens time to die out.
“We might disinfect
some equipment, chutes, dehorners nose tongs, that type of
thing,” says Faries. “But if the environment is contaminated,
there’s not much you can do with it. We don’t have anything
chemical-wise that we could spread as a disinfectant. The normal
recommendation is to rest that area for 30 days, though any day
rested is a benefit compared to an animal handling facility that
is used every day.
“Hopefully, we
would have some dry weather and lots of sun,” he adds. “If that
area is grassy, they can mow it and have more exposure to
sunlight. If we had sick cattle in there, the topsoil can be
removed with a blade and then replace the topsoil. Especially
with a hospital holding area, the area should be built so that
you can get in there with a tractor and blade between cattle.”
In terms of diseases that can cause an environmental
contamination problem, this list would include Johne’s,
leptospirosis and the gastrointestinal bugs like salmonella, e.
Coli and coccidiosis, plus the clostridium group.
“Type B and C
clostridium hit in calves under 30 days of age; type D can be
any age,” explains Faries. “Here is a group with clostridium in
your pen and those formed spores go in the ground. Now you bring
in other cattle and they swallow these blackleg-type spores and
instead of causing blackleg they cause blackgut.
“If one of them
died of blackleg in the pen, you could get further contamination
from dragging him around and spreading discharge or the buzzards
opening him up or just decomposing. Any of those clostridium
would contaminate the soil,” he says.
“But you’ve got
other diarrhea caused by viruses, like rotavirus or coronavirus,
and those don’t live very long in the environment. However if
the holding area becomes contaminated, from germs in the urine
or feces, and other cattle follow right after the sick ones, the
viruses may live long enough that the next group is exposed.
“It’s a good matter
of practice to rotate and rest your quarantine area whether
animals got sick in it or not,” says Faries. “Also, it’s a
mistake to go into your quarantine area and then your other pens
or traps without disinfecting your clothing and boots. You could
carry something out of there. You might even want to disinfect
your trailer between loads, too.”
Analyzing the
Costs
Of course, just to make things even more complicated, what makes
sense from strictly a health standpoint may not necessarily add
up on the financial side. Dr. John Lawrence, associate professor
in agricultural economics at Iowa State University, has an
excellent presentation of the economics of disease at
www.farmandranchbiosecurity.com .
For example, he
discusses the concept of marginal analysis for disease
prevention:
“What is the value of an additional intervention versus its
cost? The optimal is when the last dollar of prevention just
pays for itself…. The trouble is where do you draw the line? If
I get a benefit to cost ratio of 20, where every dollar I spend
on cost I get $20 back, sure I’m going to do it. What about 10
or 5 or 1?”
In addition to the
cost of disease, there is also the cost of biosecurity to
consider, which may include not only investments in equipment or
space but also the cost of management – setting up protocol and
following it – and the cost of limiting your choices from a
supplier standpoint.
“If you say you’re
only going to buy bulls from a herd that has been Johne’s tested
and guaranteed free, you may have only a handful of herds to
pick from. What are you giving up in genetic progress because of
that tradeoff?” Lawrence asks.
“We really deal in
an issue of tradeoffs. It’s not an all or nothing type game.
Cases like FMD, maybe zero tolerance at any cost is the approach
we want to take. But for a lot of other diseases, zero tolerance
may be very costly to achieve,” he points out.
So, balancing the
cost of preventing a disease against the cost of treating the
disease if you get it is one way to think about it. Such as, is
the cost of quarantining those new cows more or less than the
cost of treating some of the herd if they get exposed to a
respiratory disease? Or BVD? Obviously, those two situations
would have very different answers.
“If (preventing the
disease) is highly costly and the treatment is extremely
effective, we’re going to treat,” says Lawrence. “But if it’s
highly costly and the treatment is not very effective, that’s
one you might want to think about preventing in the first place.
Or if the cost (of the disease) is low enough, you simply live
with it.
“What are the
variables? It’s the exercise of how you think through it,” he
adds.
Sanderson says we
don’t always know what the most cost-effective program is, but
emphasizes you can’t spend more on the biosecurity program,
including quarantine areas, than you save by having it in the
first place.
“We need to decide
what the real risks are,” he says. “We need better data in some
areas to know what the real risks are, so that we can target our
biosecurity efforts and dollars in the right area.”
Editor’s note: By the end of summer, check out the Kansas State
University College of Veterinary Medicine website at
www.vet.ksu.edu for a risk analysis tool that will help
producers assess their risk of BVD and the most cost-effective
option to control that risk. When this program is up, it will be
the culmination of two years research by one of Sanderson’s grad
students. |
