Effects of ear-notch sample handling on reliability of antigen-capture enzyme-linked immunosorbent assay testing for bovine viral diarrhea virus.

Abstract

Antigen-capture enzyme-linked immunosorbent assay (ACE) testing of skin samples obtained by ear-notching is commonly used to detect animals persistently infected (PI) with bovine viral diarrhea virus (BVDV). At times practitioners may not have access to phosphate buffered saline (PBS) solution for specimen storage as suggested by the ACE kit manufacturer. The first objective of this study was to observe the effects of storing ear-notch samples in varying amounts of PBS on ACE results. The second objective was to observe the effects of delayed time before the ear-notch sample was placed in PBS on the ACE results. Using virus isolation and immunohistochemistry, nine PI-positive and eight PI-negative calves were identified to obtain ear notch biopsies for the study. The amount of PBS used to store both positive and negative ear-notch samples was varied (1, 2, 4, 6, 8 and 10 mL) in the first trial. In the second trial, the addition of PBS to both positive and negative samples was delayed post-collection; phosphate buffered saline was added to ear-notch samples at 0, 1, 2, 4, 8, 12 and 24 hours post-collection. Following sampling and application of treatments, all samples were tested in duplicate for BVDV antigen following the guidelines of the ACE kit manufacturer. Although the S/P ratios were different among treatment groups in both studies (P<0.05), neither varying the amount of PBS added to the sample vial nor delaying the addition of PBS to the sample affected the outcome when testing positive or negative samples.