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The following information
relates to BVDV (Bovine Virus Diarrhea Virus) in camelids. There is
documentation of infection of alpacas resulting in reproductive loss and
illness. It behooves any camelid owner or caretaker to be familiar with
this emerging disease. The cattle industry has been battling BVDV for
decades. Perhaps with unity and dedication we can curtail the disease in
our industry.
In regards to questions about BVDV testing for AOBA shows: demonstration
of a negative BVDV viral state can be done with either the polymerase
chain reaction (PCR) test or the virus isolation/identification (VI)
test on whole blood. A negative result to either test will be accepted
at AOBA show check in. Your local state animal diagnostic laboratory may
prefer one test over another. The blood is submitted through the owner's
local veterinarian in a purple top non-clotting (EDTA) tube with the
animal's ARI number, owner name and animal name on the label. Have your
veterinarian check with the diagnostic laboratory for the proper
amount of blood needed for testing and any specific procedures that the
testing laboratory may require. The sample should be sent overnight
delivery.
Abstract: Bovine Viral Diarrhea Virus (BVDV) has recently been
recognized as a source of disease in alpacas. As of this writing (Feb 1,
2006), there are at least 40 persistently infected (PI) alpacas
currently identified in North America. One PI alpaca is nearly three
years old and appears completely healthy. PI animals propagate further
infection. To control the emerging problem, PI animals must first be
identified and then permanently removed from the herd. BVDV can be
rapidly spread by PIs. The disease could be brought back to the farm by
an infected alpaca. If that animal is pregnant there is a possibility
she could then deliver another new PI cria thereby propagating the
disease. Testing and eliminating all alpacas for active BVDV before show
entry will make a tested show safer for all participants. Testing will
therefore significantly decrease both the incidence and spread of BVDV.
The combination of show testing, on-farm biosecurity measures, on-farm
herd testing and careful attention taking animals from one farm to
another should reduce the incidence of BVDV in the North American alpaca
herd.
BVDV - Overview, Testing and Recommendations
Overview: Bovine Viral Diarrhea Virus (BVDV) is currently a rare
alpaca disease. There is clear evidence indicating that the disease has
been present in the North American alpaca herd since at least 2001 and
likely originated from BVDV infected cows. Recent testing of a small
fraction of the national herd has revealed at least 40 persistently
infected (PI) alpacas. Ongoing research and testing is being funded by
the Alpaca Research Foundation (ARF) to determine the prevalence of BVDV
in our national herd. This virus has potential to spread within the
alpaca industry under specific circumstances. The Alpaca Research
Foundation, together with the Alpaca Owner Breeders Association (AOBA),
is providing this information to alpaca breeders so that informed
decisions can be made in consultation with their veterinarian. These
include recommendations on education, testing, bio-security and
management. We feel certain these are the keys to prevent and then to
control this disease in our alpaca industry.
Clinical Information: Healthy alpacas can get the virus from
infected alpacas and cows. This virus is fought off by that alpaca's
immune system, is acute (short lived), and results in an increase in the
ability of that alpaca's antibodies to neutralize the virus. Potential
symptoms in an alpaca infected with BVDV include, but are not limited
to, a mild fever, decreased appetite and rarely diarrhea, but animals
may show no symptoms.
The BVDV infection in a pregnant alpaca can be a completely different
matter. The infected pregnant dam acts just as described above -
virtually no symptoms and no consequences to her. However, the
consequences of infection on the developing fetus can be serious. These
range from no effect to abortion to birth of a persistently infected
(PI) cria. This PI state results because the fetal immune system accepts
the virus as its own. The fetus is unable to fight the virus and never
develops antibodies to that strain of virus for its entire life.
However, some PI crias grow to adulthood with no signs of any clinical
disease. Note that a PI animal does not get the infection outside the
womb. The only way to become a PI alpaca is viral exposure in utero
(before birth).
Understand that not every "poor doer", small or aborted fetus has BVDV
infection or is a PI. The reason PI animals are such a problem is that
they shed huge quantities of infectious virus through respiration and
all body fluids into the environment every day with some of them looking
and acting perfectly normal.
The reason for these drastic measures is that the unrecognized PI alpaca
can spread this disease in the North American alpaca herd. Since there
is no treatment for BVDV infection, the PI animal must be identified and
then euthanized or completely quarantined.
To protect our alpaca population from PI animals, we recommend the
following testing protocols. These will also be posted on the ARF and
AOBA websites.
Testing Protocols
Introduction: The following testing protocols are recommended to
identify Bovine Viral Diarrhea Virus (BVDV) infection in alpacas. BVDV
is a newly recognized disease in alpacas that can cause abortions and
viral persistent infections (PI). It has the potential to spread from
farm to farm via poor bio-security, commingling of animals at sales or
shows and through transport of PI animals for breeding, sales or other
reasons. Therefore, education, bio-security and early detection are
critically important.
These alpaca BVDV testing recommendations are based on comparative
medicine, are derived from those currently used for cattle, but with
regard to alpacas are currently incomplete. The ELISA using serum or
skin biopsies for use in alpacas appear to be unreliable at this time.
Research is ongoing. Consult with your veterinarian and note that
updates will be appearing on the ARF and AOBA websites.
Because every state laboratory has different sample requirements, it is
critical that you work with your local veterinarian to insure that
samples are submitted properly.
1) Appropriate on going farm bio-security has been and will continue to
be an important tool that owner's can use to prevent BVDV from getting
onto the farm. Quarantine all alpacas that come to the farm or return
from another untested location (shows, breedings, etc.) for a minimum of
thirty days. Test all existing and new alpacas before they come to the
farm for BVDV with a viral whole blood test. Add a clause to all
contracts that provides for testing and full refund if the alpaca is PI.
2) There are three excellent and widely accepted BVDV tests: the
polymerase chain reaction (PCR) test, the virus isolation/identification
(VI) test and the IHC (immunohistochemistry) test. Blood for either the
PCR or VI test can be collected in an EDTA (purple/lavender top) tube. A
negative blood viral test would indicate that the alpaca is not PI for
the life of that animal when run at a laboratory experienced with alpaca
BVDV testing. A negative IHC test also rules out a PI status.
3) All aborted and stillborn fetuses, crias that die, and any
unexplained deaths should be necropsied by a veterinarian or sent intact
to your state veterinary diagnostic laboratory. Tissue samples and blood
can be sent to this diagnostic lab and tested for disease agents,
including BVDV. Low birth weight crias, poor doing crias, "failure to
thrive", very premature crias, and alpacas with unexplained illness
should be tested for BVDV.
4) If BVDV is identified from any blood/tissue submission, then the herd
could be strategically tested (BVDV herd screening) to see if there is a
persistently infected (PI) animal present in the herd as the source of
the infection.
Your veterinarian should contact a veterinary diagnostic laboratory
which is experienced with BVDV testing in alpacas to find out
which viral tests are offered for the detection of BVDV.
Some diagnostic laboratories have viral testing preferences using PCR
vs. VI (virus isolation) testing on whole blood. With proper
blood submission, both tests are valid for the detection of active viral
infection in alpacas.
Evaluation of tests:
-
PI animals can live,
reproduce and appear healthy in every way.
-
Any pregnant females
who may have been exposed to BVDV during their pregnancy should have
their crias tested for BVDV soon after birth using a whole blood
viral test or IHC test. Until results are known, these animals
should be quarantined. The only valid tests for these crias (up to 3
months) is a viral blood test done on the blood "buffy coat" (PCR or
VI submitted in an EDTA tube) or IHC on a biopsy.
5) If the test in a live
animal is positive for BVDV, this may only represent an acute (short
lived) viral infection. A second sample must be collected three to four
weeks later and tested to confirm that the animal is or is not
persistently infected. A negative viral result on the second test shows
the animal was simply exposed to BVDV and fought the infection.
Quarantine after a second positive whole blood PCR or VI (virus
isolation), or IHC, is very important. This requires veterinary
consultation to determine the need for further testing or possible
euthanasia.
The serum neutralization test may be used to demonstrate antibodies
to the virus, indicating exposure to the virus. After doing viral
testing, use the serum neutralization (SN) test as a subsequent
screening tool to evaluate if any alpaca may have ever been exposed to
BVDV. Note that this test is NOT useful to detect PI animals.
6) If you receive any
positive BVDV report (viral or SN test), it is essential that you
discuss this with your veterinarian. Determine the necessary
follow-up testing and contact any farms that may have had contact with
your animals so that they can take action to limit the spread of BVDV.
Conclusion: In summary, although presently rare, BVDV is a
potential threat to the alpaca industry. It is imperative that all
alpaca owners become familiar with BVDV terminology/science, the
potential for animal losses, prevention of viral contamination and
testing procedures to identify infected carrier animals (PI) as well as
identification of exposed, but non-infectious alpacas.
NOTE: Testing for PI status need only be done once in the life of the
animal as PI animals can only develop from fetal infection.
The following websites have additional information on BVDV, testing and
terminology:
www.vetmed.wsu.edu/depts_waddl/bvdcamelids.asp
www.alpacaresearchfoundation.org
ARF has immediately funded research to provide new information about
BVDV in alpacas and will announce results on their website as they are
available. ARF will also be in close contact with AOBA and will be
sponsoring the first annual Special Lecture which this year will be
presented by Dr. Ed Dubovi on BVDV at the AOBA National Conference
(Louisville, KY; May 18, 2006) regarding ongoing research, testing and
results.
Source: Karen Baum, DVM;
lildoc@mindspring.com
February
4, 2006 [Version]
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