Update of BVDV (Bovine Virus Diarrhea Virus) in Camelids
by Karen Baum, DVM

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

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.

• Submit blood for SN analysis (red topped clot tube) to test for antibodies to BVDV. If the SN test for antibody is negative or low, further testing is required and a veterinarian should be consulted. Recall that the PI alpaca may have no or few antibodies.

6) If you receive any positive BVDV report (viral or SN test), it is essential that you discuss this with your veterinarian. Determinethe 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.