Bovine Viral Diarrhea Virus (BVDV) is one of several worldwide pestiviruses known to infect domestic and wild ruminants, camelids, and swine. As with most viral infections, there is a wide range of signs, from inapparent infections to diarrhea, respiratory tract disease, hemorrhage, abortions (pregnancy loss), birth defects, and death.
Acute infection
Bovine viral diarrhea refers to a mild disease caused by a BVD virus infection in immunocompetent cattle. In general, animals develop acute BVD 10-12 days after initial infection. Since BVDV infects white blood cells, whole blood (buffy coat) is the sample of choice for isolation of BVDV from clinically ill animals.
Persistent infection
BVDV can lead to a persistent infection in a calf infected during a certain time (40-120 days) in gestation. If infected prior to the complete development of the fetal immune system, the virus will not be recognized as foreign and tolerance occurs. After birth, the calf will shed virus and infect other animals in the herd. Sometimes these calves look sick, but they can also look healthy, thereby making it impossible to visually identify these animals.
Can alpacas or llamas get BVDV?
Research has shown that llamas and alpacas can be infected with BVDV and develop clinical signs. There have also been reports of persistent infections in crias. In cattle, persistent infected calves are one of the primary sources of transmitting the infection to other animals. Likewise, persistently infected crias are the primary source of herd infection in camelids. Since alpacas and llamas travel all over North America for shows, breeding, etc., lapses in biosecurity could permit a persistent infected cria to infect other animals and herds.
Can camelids like alpacas and llamas be tested for BVDV?
The Washington Animal Disease Diagnostic Laboratory (WADDL) and Washington State University Veterinary Teaching Hospital recommend testing alpacas and llamas. The tests below are based on the most current information available and may change as research is completed. Herds should be examined on a case-by-case basis, as testing may not be warranted in some situations.
Herd screening
Submit whole blood samples (purple top tube, PTT, whole blood in EDTA, and red top tube, RTT, serum) individually identified to WADDL on multiple animal ID form.
WADDL will test PTT sample for BVDV by PCR. Up to 12 samples can be pooled and tested, which may reduce testing costs. If needed, individual samples from positive pools would be retested to identify individual positive animals within the pool.
- Negative results (BVDV not detected) = no BVD infection
- Positive results (BVDV detected) = persistent OR transient BVD infection suspected
Definitive diagnosis of persistent infection requires submission of another blood sample (PTT) from an individual positive sample to be collected in 3-4 weeks and re-tested.
Serum samples (RTT) can be used to check for BVDV antibody to determine prior infection through serologic testing.
If unable to test entire herd, test all juveniles less than 2 years old and breeding males and females. Diagnosis of BVDV persistent infection would require 2 whole blood samples collected 3-4 weeks apart.
New arrivals to a herd
Quarantine for minimum of 30 days. Quarantining is not only important to allow screening for BVDV but also for other infections. Herd biosecurity is important to protect your herd from diseases that new animals may carry. For animals that will be remaining on your property, a minimum 30-day quarantine is recommended before introducing to your herd.
- Negative results (BVDV not detected) = no BVD infection
- Positive results (BVDV detected) = persistent OR transient BVD infection suspected
- Remain in quarantine until retested in 3-4 weeks
- Negative re-test = most likely a transient infection
- Positive re-test = persistent infection suspected
- Remain in quarantine until retested in 3-4 weeks
A negative-tested dam can be returned to the herd, but it is recommended to quarantine just before delivery until newborn cria is tested with PCR and identified as BVD infected or not.
Other recommended tests
Necropsy and submit fixed and fresh tissues to test from all aborted and stillborn crias, and from crias or adults with unexplained deaths. Submit whole blood (PTT) and serum (RTT) from the dam as well.
In addition to performing an abortion panel, it is a good opportunity to evaluate the herd’s trace mineral status, such as selenium and copper.
What are some possible clinical signs of BVDV seen in alpacas and llamas?
Typical signs of BVDV in alpacas and llamas include fever, oral ulcers, anorexia, diarrhea, abortion, ill-thrift, and birth defects.
How is BVDV transmitted?
The most efficient method of BVDV transmission in camelids is considered to be by aerosol. Transmission in cattle has been primarily by ingestion or inhalation of the virus. The virus can be detected in all body secretions and excretions (respiratory and oral secretions, urine, milk, semen, and feces). Transplacental (dam to fetus) transmission also occurs. Transmission is similar in other susceptible species, including alpacas and llamas.
What species can transmit BVDV?
Virus can spread between domestic ruminants (cattle, sheep, goats), camelids, and wildlife (deer, elk, etc).
Is there a vaccine available for alpacas and llamas?
Currently, there is no BVDV vaccine licensed for use in camelids. There are several vaccines available for use in cattle. The vaccines do not prevent infection but reduce the clinical disease effects. At this time, it is not recommended to vaccinate camelids until more is understood about the virus. Unwarranted vaccination can interfere with diagnostic testing and the capability to identify truly infected animals.
Can BVDV infections be prevented?
BVDV infections are dose-related (virus challenge load), therefore, prevention is critical. Maintaining a closed herd, implementing strict biosecurity protocols for all incoming animals (recommended not just for reducing BVDV infections but others, like coronavirus), and periodic screening of open herds can reduce the occurrence.
What diagnostic techniques are currently recommended for alpacas and llamas?
Types of tests available
- Polymerase chain reaction (PCR) – nucleic acid detection, very sensitive. Will detect persistent as well as acute (transient) infections. Diagnostic method of choice because of good sensitivity.
- Antigen-enzyme-linked immunosorbent assay (Ag-ELISA) – antigen detection; validation of this test has not been established in camelids but is being evaluated.
- Serology (serum neutralization) – antibody detection, a single test indicates prior infection, but not active infection. Testing acute and convalescent samples and showing a four-fold increase in antibody titer indicates active infection. False negatives may occur if sample taken soon after an infection (prior to development of an immune response), or in animals less than 3 months of age when maternal, colostrum derived, antibodies interfere with the test.
- Skin biopsy with immunohistochemistry (IHC) – antigen detection; results are not conclusive in camelids.
- Virus isolation – Detects live virus in blood and tissues. May be required for virus typing.
Testing strategies
- Acute infection: BVDV acute infection can be diagnosed by virus isolation, polymerase chain reaction (PCR), or serology. Virus detection must be done in the first 3-10 days after infection. A whole blood sample is the best sample for BVDV detection by PCR or virus isolation. Paired acute and convalescent samples collected 3-4 weeks apart are required to identify four-fold increase in serum antibody titers following recovery from clinical illness.
- Persistent Infection: Definitive diagnosis of persistent infection in camelids cannot be based upon testing done at a single time point. Detection of BVDV persistent infection requires showing virus is present in a particular animal over time (the infection persists). Although the BVDV antigen ELISA test done at a single time point is used to detect BVDV persistent infection in cattle, whether or not similar interpretation of the test in camelids is accurate is not known. Therefore, persistent infections in camelids should be determined by detecting virus (by PCR or virus isolation) in sequential samples collected 3-4 weeks apart.
Contact the consulting microbiologist at WADDL at 509-335-9696 with any questions.
Who can I contact for more information about BVDV?
WADDL and WSU-VTH veterinarians who can assist you: