International proficiency trial for bovine viral diarrhea virus (BVDV) antibody detection: limitations of milk serology

Table 1 Sample panel sent to the participants of the interlaboratory proficiency trial for BVDV serology

sample ID	material	sample status	NT titer (of corresponding sera for milk)
01/21	serum	BVDV antibody-positive, anti-BVDV-2, after infection	Fig. 2, 180 against BVDV-1, 1812 against BVDV-2, 11 against BDV
02/21	serum	BVDV antibody-negative	Fig. 2, < 5 against BVDV-1, BVDV-2 and BDV
03/21	serum	BVDV antibody-positive, anti-BVDV-1, animal immunized with inactivated vaccine	Fig. 2, 572 against BVDV-1, 90 against BVDV-2, 23 against BDV
04/21	serum	BVDV antibody-negative	Fig. 2, < 5 against BVDV-1, BVDV-2 and BDV
05/21	serum	BDV antibody-positive, after infection	Fig. 2, 143 against BVDV-1, 9 against BVDV-2, 720 against BDV
06/21	milk	pooled sample, 4 seropositive animals + 4 negative milk samples	226, 160, 160, 113
07/21	milk	pooled sample, 2 seropositive animals + 8 negative milk samples	1280, 40
08/21	milk	pooled sample, 4 seropositive animals + 4 negative milk samples	57, 40, 28, 14
09/21	milk	BVDV antibody-negative	n.a.
10/21	milk	pooled sample, 2 seropositive animals + 8 negative milk samples	80, 80

Legend: Sample identifier, material and sample status are given. The serum samples 01/21 to 05/21 were tested by the participants by microneutralization tests against BVDV and BDV, the resulting neutralizing (NT) titers from the author’s laboratory are indicated in the table and the titers measured in all participating laboratories are shown in Fig. 2. For the milk samples 06/21 to 10/21, the corresponding sera were tested against BVDV-1 isolate NADL and the resulting titers are given. For the samples 06/21, 07/21, 08/21 and 10/21 only the titers of the seropositive samples are indicated. n.a. – not available

ISSN: 1746-6148