|
|
|
|
Animal Health Diagnostic Center - News
 |
|
Alpaca BVDV Testing
September 2006 Update
Ed Dubovi, Director of Virology
Animal Health Diagnostic Center, College of Veterinary Medicine, Cornell University
|
| |
Recent reports on the existence of BVDV persistently infected (PI) alpacas has generated considerable interest in testing animals to assess their status. We have initiated a testing program that depends on the specific needs of the owner and the degree of risk he/she wishes to assume. The AHDC offers a choice of BVDV tests that can be helpful in detecting BVDV infections in alpacas. For a summary of these, see the table displayed below.
To detect exposure to BVDV, serum neutralization (SN) is the appropriate test. A positive value on a single serum sample simply indicates previous infection or vaccination. It is not able to identity the timeframe. Testing on paired samples may determine whether the exposure has been recent. Owners, working with their clinicians, may want to consider SN testing on pregnant females to assess the potential for an infected fetus. A negative value on a single serum sample can indicate no previous exposure to infection. However, caution is indicated, as a persistently infected animal will not produce antibodies against the virus and will also test negative by SN. Show and breeding facility administrators will generally want to incorporate BVD PCR or virus isolation into their biosecurity testing requirements and should be consulting with a veterinarian who understands the epidemiology of BVDV.
To detect a persistently infected animal, we are not recommending the antigen-capture ELISA (ACE) test using serum. We have seen false negatives with this test. The ACE test using skin biopsies does give positive test results. However, the response is much less in alpacas than in cattle, so we have concerns about the potential for missing a positive animal. Virus isolation, regardless of the animal's age, is considered to be the gold standard for detecting persistently infected animals. For animals up to 60 days of age, the required sample is whole blood (EDTA); for older animals, serum, plasma, or whole blood are appropriate.
Persistent infections can also be detected using the BVDV PCR test, which we believe to be an acceptable alternative to the virus isolation test. These results are completed sooner than virus isolation, and with pooling are more cost-effective. When pooling BVDV PCR, we pool up to 5 samples for alpacas, except for crias up to 60 days of age. Blood must be submitted on individual animals, and animal birth dates must be listed on the submission form. For crias up to 60 days of age, we are only pooling two samples, and whole blood must be submitted, because samples are processed differently than older animals. We are unable to pool samples of the young crias up to 60 days of age with any animals over 60 days of age, including their own dams. We are also not able to pool samples from different owners or submissions. Ideally, we would also like samples to be grouped sequentially by age on the submission form. Please understand that we are trying to provide the most economical, yet reliable, testing as possible and that, if new information regarding the behavior of BVDV in alpacas emerges, our test recommendations or strategies may be changed.
Examples: If samples from both a cria and its dam are submitted, two PCR assays will be performed and the submitter will be billed for two PCR tests. If samples from up to 5 animals over 60 days of age are submitted, all from the same owner, a single PCR assay will be performed as a pooled sample and the submitter will be billed for only one PCR test. Likewise, if samples from 3 crias under 61 days of age and 2 adult animals are submitted, 3 PCR assays will be performed and charged. There may be occasional buyers or shows that demand individual testing of animals. Please indicate on paperwork if individual testing is required.
|
| |
| Summary of BVDV Testing for Alpacas |
Type of
Infection |
Recommended
Testing |
Sample
Requirements |
Test
Fee |
Test Result can
determine. . . |
to detect
exposure |
BVDV SN |
single |
$13.75 |
previous infection or vaccination |
| paired |
$27.50 |
to determine if exposure is recent |
| for persistently infected (PI) animals |
BVDV Whole Blood
Virus Isolation |
whole blood required for animals up to 60 days of age; this test can be performed on whole blood sample of any age animal |
$26.25 |
PI or acute
infection |
| BVDV Serum Virus Isolation |
for animals 61 days of age and older,
serum can be tested by virus isolation |
$21.00 |
PI or acute
infection |
BVDV PCR:
- individual animal
- pooling for only two samples from animals up to 60 days of age, whole blood only
- pooling up to 5 animals, 61 days of age or older (for pooling, EDTA blood, plasma, or serum only) |
1) whole blood required for animals up to 60 days of age
2) EDTA blood, plasma, or serum (min. 2 ml) for animals 61 days of age and older
3) tissue, post mortem or abortion samples (min 5g)
(Please submit sequentially by age) |
$36.75 per animal or per pool |
PI or acute infection |
|
|
