Frequently Asked Questions
What is the Uncertainty Gap™?
What is the diagnostic gap?
What’s the difference between acute/transient infection and persistent infection?
What are false negatives/false positives?
What causes false negatives/false positives?
What does overpooling mean?
What does CT value mean?
What are internal controls and why are they necessary?
What is the Uncertainty Gap™? 
BVD is a complex and devastating disease. Most diagnostic tools on the market today are tedious to use, prone to errors, and lack the assurance and thoroughness that vigilant eradication demands. Without accurate detection, the industry is left to cope with an uncertainty gap.
BoVir® closes this Uncertainty Gap™ by addressing the four greatest needs to assure reliable results in routine high-throughput screening:
- Unparalleled Easy-to-Use Testing Protocol. Fast and simple sample preparation helps eliminate probabilities for human error
- Sensitivity and Specificity for Superior Results. Proprietary molecular assay design provides unparalleled diagnostic performance for eliminating false positives and false negatives
- Unsurpassed Early Detection. Newborn calves detectable as early as one day old versus up to 120 days with other testing methods
- Diverse Genotype and Strain Detection. Its effectiveness is validated by European governmental reference labs for its ability to detect all 68 referenced strains of BVDV, including atypical European and North American strains, such as the HOBI and the H138 strains
What is the diagnostic gap?
In a pregnant cow, BVDV can be transplacentally transmitted to the fetus, which can result in the birth of a persistently infected (PI) calf. Moreover, when a mother cow has experienced BVDV infection, antibodies against the virus are present in her colostrum.
During lactation, the newborn calf consumes colostrum that contains maternal antibodies, possibly against BVDV. These antibodies will mask the virus and lead to a reduced virus titer in blood of the calf creating what’s referred to as a diagnostic gap—the window of time in which the virus remains hidden. This gap makes it difficult to detect the virus in a calf during its first 120 days.
Highly sensitive, BoVir® closes this diagnostic gap by detecting viruses even within the very first days of birth despite maternal antibodies that may mask the infection.
What’s the difference between acute/transient infection and persistent infection?
There are two types of BVDV infection—Persistent Infection (PI) or transient infection
Transient infections cause adult animal acute diarrhea, high fever, epithelial lesions, anorexia, and suppressed immunity. As a result, a cow’s health will be weakened leaving it vulnerable to secondary infections and greater problems including scours, pneumonia, lost milk production, and deformed or stillborn calves.
By contrast, PI animals often have no clinical appearance of infection and cannot be easily detected. They are lifetime carriers of the virus and can quickly infect herd mates, as well as introduce the disease to other herds. PIs receive exposure to the virus in utero. The calf is infectious from birth, shedding several billion viral particles a day and infecting other cattle immediately.
Some estimates are that 70-90 percent of all BVDV infections are PI, leaving most cases of BVDV perilously undetected.
BoVir® accurately identifies and differentiates both persistent infection and transient infection when using blood as the sample type. When using ear notch samples, BoVir® detects PI animals only.
What are false negatives/false positives?
Some diagnostic tests fail to provide accurate results. Consequently, test outcomes may show a sample as being negative, or free from BVDV when in fact, it is positive for the virus (a false negative).
Likewise, a test may indicate that a sample is positive for the virus, when in actuality it is negative (a false positive).
Why do false negatives or false positives ocurr?
Many factors can contribute to both false negatives and false positives results.
False Negatives – poor assay sensitivity, assay not broadly reactive to detect all known strains, inhibition of PCR reaction that is not monitored by an internal control, testing samples from animals within the diagnostic gap with assays showing inferior sensitivity, overpooling of samples, human error, improper instrument performance, deviations from approved assay protocols, etc.
False Positives – lack of assay specificity, cross contamination, human error, etc.
What does overpooling mean?
Pooling refers to the collection of multiple samples to represent one sample of weighted value. Pooling samples for diagnostic testing can be an efficient, practical, and economical approach to detection, but only when it’s performed according to scientifically approved protocols.
According to extensive evaluation studies using samples from experimentally and naturally infected cattle, it was determined that in the case of BVDV testing, the proper pooling protocol is 10 samples. Anything above 10 samples is considered overpooling and will produce inaccurate test results.
What does CT value mean?
CT value stands for Cycle Threshold value. At its simplest, the CT value represents the first cycle during testing in which a detection occurs. Low CT values indicate a test’s ability to detect positives early in the diagnostic process, or sooner than those of higher CT values.
More technically, the threshold is the numerical value assigned for each run of a test. Each threshold value reflects a statistically significant point above an established baseline. The CT value represents the PCR cycle number, or point at which a diagnostic tool first detects a noticeable increase in fluorescence above a baseline signal.
When testing identical samples with two separate real time PCR assays the one with the lower CT value would represent the most sensitive assay.
When testing pooled PI positive ear notch samples BoVir® detects 95 percent (normal range) with a CT value in the range of 23 – 28. When testing pooled PI positive blood samples Bovir® detects 95 percent (normal range) with a CT value in the range of 17 – 25.
The remaining 5 percent positives are all detected in ear notches with a maximum CT value of 32 and in blood with 28. Further analysis revealed that the causative strains were specific low virulent strains.
What are internal controls and why are they necessary?
In scientific experiments, internal amplification controls (a.k.a. internal controls) are used to eliminate alternate explanations for outcomes and validate the integrity of the results. In a diagnostic test, an internal control is an unaltered result used as a standard against which actual results are compared. Having an internal control helps to eliminate errors and bias, and ensures that the test is working as expected.
“The European Standardization Committee, in collaboration with International Standard Organization (ISO), has proposed a general guideline for PCR testing that requires the presence of Internal Amplification Control in the reaction mixture.”
All AnDiaTec tests, including BoVir®, are performed using internal controls for optimum accuracy.
