Bovine herpesvirus 1: within-herd seroprevalence and antibody levels in bulk-tank milk

Abstract

The aim of the present study was to establish a relationship between the results obtained with the enzyme-linked immunosorbent assay (ELISA) technique for antibodies (against bovine herpesvirus 1) in serum and those in milk at the herd level. For this purpose, 275 samples of bulk-tank milk were analysed with glycoprotein E (gE) antibody ELISA and 207 more were analysed with glycoprotein B (gB) antibody ELISA (482 in total). All of these samples came from dairy herds whose seroprevalence was also evaluated. The results of this study were then used to analyse the sensitivity of the bulk-tankmilk test in detecting herds with a high risk of active infection (>60% seroprevalence) and its specificity in detecting those with few (<20%) or no seropositive animals. In regard to the reference test (results in blood serum), the sensitivity of the bulk-tankmilk test in detecting herds with >60% seropositive animals was 100% for both gE and gB ELISAs. The specificity figures, for gE and gB ELISAs, respectively, were 88.4% and 99.1% for infection-free herds and 72.6% and 96% for herds with <20% seroprevalence. In a quantitative approach, Pearson's correlation coefficients, reported as a measure of linear association between herd seroprevalences and transformed optical density values recorded in bulk-tank milk, were -0.63 for gE ELISA and 0.67 for gB ELISA.

Serological testing of an equal-volume milk sample – a new method to estimate the seroprevalence of small ruminant lentivirus infection?

“…Therefore, the relationship between OD EVMS and EVMS %POS could not be described using a single function for the entire range of values of EVMS %POS (0% to 100%). Interestingly, a similar phenomenon could be noticed after careful inspection of scatter plots presented in many previous studies on BTM in bovine viral infections [34,[36][37][38][39]. In these studies, exponential, square root, and logarithmic functions were used to link the two variables in the whole range of their possible values.…”

“…This concept is very tempting as practical benefits from quantitative evaluation of a herd status based on testing only one sample are undeniable. Hope for this has encouraged many scientific teams to attain this goal by testing a BTM sample [34][35][36][37][38][39]. However, despite significant correlations and R 2 ranging from 0.7 to 0.85 a considerable spread of OD values from the regression line could be observed in all these studies.…”

“…The intensity of color reaction in ELISA performed on BTM sample, both raw and corrected optical density (OD), is known to correlate with the within-herd prevalence of infections in lactating individuals. As a consequence, quantitative ELISA results obtained on BTM samples have been used to estimate the within-herd prevalence of infections with bovine viral diarrhea virus (BVDV) [34,35], bovine herpesvirus type 1 (BHV-1) [36][37][38], bovine leukemia virus (BLV) [39], and F. hepatica infection in cattle [23,24], and T. gondii infection in goats [30]. However, the contribution of individual animals to the seroreactivity of a BTM sample depends on the volume of milk they yield and the concentration of antibodies in individual milk samples.…”