RECOMMENDATIONS FOR TESTING FOR BOVINE VIRAL DIARRHEA VIRUS IN ALPACAS AND LLAMAS
Dr. Susy Carman DVM PhD
1
2005/07/04
With the recent discovery that bovine viral diarrhea virus (BVDV) can cause abortions and persistent
infection in alpacas, there has been a request for a testing protocol to identify BVDV infection in alpaca.
The following general recommendations are from Dr. Susy Carman DVM PhD, a veterinary virologist at
the Animal Health Lab, University of Guelph, Ontario.
BVDV and persistent infection is a newly recognized disease in alpaca. So far only one persistently
infected alpaca cria has been studied. The following BVDV testing strategies for alpaca are based on
comparative medicine and derived from those currently used for cattle. These recommendations may
need to be refined as more is learned about BVDV in alpaca.
· All aborted and stillborn fetuses, cria that die, and any unexplained deaths should be
autopsied by your veterinarian so that samples of tissue can be sent to a veterinary diagnostic
lab to be tested for disease agents, including BVDV. Low birth weight cria, poor doing cria, very
premature cria, and alpacas with unexplained illness should be tested for BVDV (blood test – see
below).
· If BVDV is identified from any submission, then the herd should be strategically tested (BVDV
herd screening) to see if there is a persistently infected (PI) animal still present in the herd as the
source of the infection. For BVDV herd screening every animal in the herd should be evaluated
for the virus in some way. If the entire herd cannot be tested due to economic reasons, it is more
important to test all animals under 2 years of age and reproductively active females.
· To test live animals over 12 weeks of age for BVDV send serum (blood test) for PCR or antigen
ELISA or virus isolation.
· To test live animals under 12 weeks of age for BVDV send serum (blood test) for PCR. Maternal
antibody in these young animals will interfere with other tests.
· Your veterinarian should contact the veterinary diagnostic laboratory in your area to find out
which tests are offered for the detection of BVDV in cattle. The same tests can be used to detect
BVDV in alpaca. Some veterinarians and laboratories prefer to use skin tests for BVDV detection.
· If the first blood test in a live animal is positive for BVDV, this may only represent an acute
infection. A second blood sample must be collected three weeks later and tested to confirm that the
animal is indeed persistently infected. This second test is essential, for the animal will be
euthanized on the basis of this testing. Since testing methodologies are not perfect, inconclusive
test results can occur. In these cases ask that a different test be used on the same sample to confirm
the result or submit a new sample.
· Any pregnant females who may have been exposed to BVDV during their pregnancy should
have their cria tested for BVDV soon after birth using serum . BVDV was isolated from the
placenta of the one persistently infected cria studied.
· To determine if your herd has been infected in the past you may wish to test serum from adults
for antibodies to BVDV type 1 and BVDV type 2.
· To evaluate as to whether a pregnant female may have been exposed to BVDV at another farm
in early pregnancy , use serum to test for antibodies to both BVDV type 1 and BVDV type 2. If the
tests for antibody are negative, it is unlikely the dam is carrying a PI fetus. In cattle, persistent
infection has been reported to occur in bovine fetuses infected between 18 and 125 days of
2
gestation. If the alpaca dam has antibodies, she may not be carrying a PI fetus if she was infected
pre-pregnancy or at the end of pregnancy. Since you do not know when the dam was infected you
may want to quarantine the dam before delivery in case she does deliver a PI cria, and plan to test
the cria soon after birth.
· It is possible for PI cattle to live and reproduce. If a PI cow has a calf, the calf will always be
PI. If a calf is negative for the virus, its mother is never persistently infected. For herd testing, if
you have many females with their cria, you might try to use this information and strategically bleed
and test only cria. If the cria is negative, the dam will also be negative. Adults not represented by
cria would need to be individually tested. However if you test only cria, and if a cria is positive, you
would have to pay for another veterinary visit to draw blood from the dam. Depending on the herd
size, it may be more cost effective to have blood taken from both dams and cria at the initial visit.
The serum from dams could be held by your veterinarian and submitted to the laboratory for testing
following the return of any positive results for cria.
· If you receive a positive BVDV report, it is essential that you discuss this with your
veterinarian to determine if any follow-up testing is needed and contact any farms that may have
had contact with your animals so that they can take action to limit the spread of BVDV.
· If your veterinarian recommends that you vaccinate for BVDV use only a killed vaccine until more
is known about BVDV in alpacas and llamas.
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