November 2025
Practical Uses of Bovine Genetic Sequencing at KVDL
By Gregg A. Hanzlicek, DVM, PhD, PAS
There are times in bovine abortion, neonatal diarrhea, and respiratory disease workups when positive viral PCR results are reported, and the follow-up questions are: “Is this virus due to a natural infection or could it be vaccine virus?” or How closely related is our vaccine strain to the strain our herd is infected with?”
For multiple viruses, KVDL ‘s Next Generation Sequencing Section can differentiate vaccine strain from field strain in diagnostic samples. These include, BVDV, IBR, BRSV, BCoV, and Rotavirus. We have genetically sequenced these viruses from all available commercial bovine modified live vaccines and have added their genetic genome into our library. This allows us to sequence the sample virus and compare the sample genetic genome with the cataloged vaccine virus sequences.
An example of how this test can be used is when IBR is found in an aborted fetus. Over the last seven years, IBR (BHV-1) has been found in 5% to 20% of the KVDL diagnosed bovine abortion workups.
In some of these cases a modified live IBR containing vaccine was administered to late- term pregnant cows. To use these vaccines in pregnant animals the label requirement states these animals must have received the same vaccine (or other labeled vaccine) within the previous 12 months. In some cases, this requirement was not met. KVDL has not sequenced all of these cases, but of those we have, the virus found in the fetus was the vaccine strain and the abortion was associated with vaccine label directions not being followed.
Another example of the practical use of this new technology concerns vaccine selection. It is known that genetic similarity between field and vaccine strain is necessary for vaccines to be effective. When a field strain has been identified through sequencing in a diagnostic submission, KVDL will also report the vaccine ((vaccine name(s)) that is most closely related to the sample strain. This information can be used to help select the vaccine that will hopefully provide the most protection for that operation in the future.
A Summary of Some Uses of Genetic Sequencing
- Differentiate between vaccine and sample strain to determine if a herd health issue is due to field strain infection.
- Compare sample strain to commercial vaccine strains to assist with vaccine selection
- Opportunity to choose varied genetic strains from multiple samples for incorporation into broad genetic spectrum autogenous vaccines