Student Case Presentation
Duration of viremia and positive PCR testing post vaccination with Pyramid® 5 or Express® FP 5
| Date/Time: |
9/12/2024 07
|
| Presenter: |
Kailey Wichman |
| Veterinary School: |
WI |
Abstract:
Historically, diagnosticians have voiced concerns over potential testing interference created by modified-live viral (MLV) vaccines for bovine respiratory disease (BRD). The objective of this study was to determine if vaccination with a MLV respiratory vaccine would result in viral detection by PCR or viral isolation.
This study utilized thirty individually housed, clinically healthy, BVD negative Holstein calves on a commercial dairy 27 to 31 days of age on the day of vaccination. Calves were equally distributed among three treatment groups: vaccination with Pyramid 5®, vaccination with Express FP 5®, and no vaccination. The study was conducted in two cohorts enrolled ten days apart. Each cohort contained one vaccine group and 5 control calves. Animals in the same treatment group were housed in adjacent hutches and each treatment group was separated by at least three hutches to minimize risk of viral dissemination.
Immediately prior to treatment administration and for 21 days following vaccination administration, whole blood, serum, and deep nasopharyngeal swabs were collected on a set schedule checking for the presence of viral shedding. All diagnostic testing was conducted at Iowa State University’s Veterinary Diagnostic Laboratory. PCR tests results were considered negative with a Ct >= 35.
PCR results were negative at all time points indicating no viral shedding occurred in the respiratory tract or hematogenously. Serology demonstrated antibody titers consistent with passive transfer of maternal immunity but did not identify a later peak in response due to vaccination. This study concluded that serology testing will only detect natural antibody presence 21 days post vaccination. Neither whole blood PCR testing nor deep nasopharyngeal PCR will yield false positive results for IBR, BVD-1, BVD-2, or BRSV after SQ vaccination with Pyramid 5® or Express FP 5® in thirty-day aged calves given adequate colostrum.
